Outcomes and access to angiography following non-ST-segment elevation acute coronary syndromes in patients who present to rural or urban hospitals: ANZACS-QI 72
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In Aotearoa New Zealand, patients who present with non-ST-segment elevation acute coronary syndrome (NSTEACS, which comprises non-ST-segment elevation myocardial infarction [NSTEMI] and unstable angina [UA]) will initially access one of three groups of hospitals: urban hospitals with routine access to percutaneous intervention (PCI), urban hospitals without routine access to PCI and rural hospitals (which also do not have routine access to PCI).[[1]] Australasian consensus guidelines recommend that most patients with NSTEACS, especially those at high or intermediate risk of mortality, receive “an invasive strategy of angiography with coronary revascularisation” within 72 hours.[[2]]
There are nine urban hospitals in New Zealand that have routine access to PCI. Hospitals that don’t have routine PCI capabilities typically have catchments that include smaller regional or rural areas. Compared with major urban areas, these smaller catchments include a higher proportion of Māori, who have poorer cardiovascular outcomes than NZ Europeans.[[3,4]] Rural hospitals are typically staffed by generalist doctors and nursing teams, have fewer resources and are at a distance from urban hospitals with specialists or associated services (40 minutes to 4 hours by road from urban hospitals with routine access to PCI).[[5]] Patients with NSTEACS who present to urban hospitals without routine access to PCI may be cared for by cardiology specialists or general physicians.
Stable patients who present with NSTEACS to hospitals without routine access to PCI will receive initial treatment and if clinically stable, are usually admitted to that hospital while awaiting transfer for angiography. Unstable patients or patients at rural hospitals with fewer resources may require early transfer to a larger hospital. For rural hospitals whose primary referral hospital does not have PCI capabilities, patients may undergo several transfers to receive definitive treatment.
The aim of this study was to determine if there were differences in invasive angiography performed and clinical outcomes, including mortality, associated with the category of hospital of presentation (rural hospitals or urban hospitals with or without routine access to PCI) for patients with NSTEACS.
Methods
All first admissions for patients aged 20 years or older with NSTEACS between 1 January 2014 and 31 December 2017 to a publicly funded New Zealand hospital were included in the study.
Registries
The All New Zealand Acute Coronary Syndrome Quality Improvement (ANZACS-QI) programme is a clinically led initiative. Its primary aim is to “support appropriate, evidence-based management of ACS… regardless of age, sex, ethnicity, socioeconomic status, or rural or city dwelling”.[[6]]
This study used the ANZACS-QI programme’s ACS Routine Information cohort, which incorporates the Ministry of Health’s National Minimum Dataset for Hospital Admissions (NMDS) and the National Mortality Collection, which are linked using the patient’s encrypted national health index (NHI). The NMDS includes information for all public hospital admissions (including all hospitals considered in this study) and the mortality collection contains information regarding deaths. All New Zealand residents aged 20 years or older who are admitted to hospital with a primary or secondary ICD-10 code consistent with ACS (I20.0, I21.x, I22.x) are included in this cohort.[[6]] The mortality collection contained all deaths until 31 December 2018, which was at least 1 year after the last admission to hospital.
Hospitals of presentation
Hospitals were identified using the facility code assigned by the New Zealand Ministry of Health – Manatū Hauora (Table 1) and divided into three urban-rural hospital categories:
1. Urban hospitals with routine access to PCI (urban hospitals with PCI),
2. Urban hospitals without routine access to PCI (urban hospitals without PCI) and
3. Rural hospitals.
Three hospitals did not easily fit within these categories. Tauranga and Nelson have PCI-capable angiography suites but do not have reliable after-hours access to these. They were considered urban hospitals with PCI for the purposes of this analysis, as there would be few exceptions to not being able to offer PCI for patients with NSTEACS within 3 days. Greymouth Hospital was considered a rural hospital due to its distance from and the logistical challenges associated with accessing a hospital with PCI, in addition to an increasingly rural generalist workforce.[[7]] These groupings are consistent with previous studies.[[1]]
Patients were assigned to the first hospital of presentation. To account for the movement of patients with NSTEACS between hospitals to receive PCI or other investigations or treatments, admissions were bundled into group inter-hospital transfers as part of the same episode of care.[[1,8]]
View Tables 1–3 and Figures 1–3.
Data collected
Age, sex, prioritised ethnicity (using the New Zealand Ministry of Health’s protocols),[[6]] NZ Deprivation Index 2013 (NZDep2013) deciles, admission to hospital with either MI or heart failure in the last 5 years, non-cardiac Charlson Comorbidity Index score and type of NSTEACS (NSTEMI or UA) were collected from the ACS Routine Information cohort for the patient’s first ACS admission. The Charlson Comorbidity Index is a method of predicting mortality by weighting comorbid conditions and is widely used in health research.[[9]] The non-cardiac Charlson score excludes congestive heart failure.[[1,9]]
Outcome measures
The following outcome measures were considered: 30-day and 1-year all-cause mortality; angiography performed within 30 days and 1 year; and readmission to hospital within 1 year with heart failure, major adverse cardiac event (MACE) or major bleeding. MACE was defined as: acute myocardial infarction, cardiac arrest, cardiogenic shock, ventricular arrythmia (ventricular tachycardia or fibrillation), high-grade atrioventricular block requiring intervention or emergency coronary revascularisation. To determine 2-year all-cause mortality, only patients with at least 2 years of follow-up were considered.
All definitions and ICD-10 codes are shown in Appendix 1.
Statistical analysis
Data were summarised using mean and standard deviation (SD) for continuous data and frequency and percentage for categorical data in total and by category of hospital.
Logistic regression, modelled separately for each outcome, was used to estimate odds ratios (OR) with 95% confidence intervals (95% CI) comparing urban hospitals without access to PCI and rural hospitals to urban hospitals with access to PCI (the reference group).
Unadjusted mortality comparing the hospital types was visualised using Kaplan–Meier curves. Cox proportional hazard ratios were then used to estimate hazard ratios (HR), with 95% confidence intervals, comparing hospital type. All patients were followed for at least 1 year after admission and patients were “right-censored” if they had not died by the end of the study period.
For all outcome measures, the following variables were considered as potential confounders within the models: sex, ethnicity, age, type of NSTEACS, prior heart failure, prior acute myocardial infarction, socio-economic deprivation and non-cardiac Charlson score. For the mortality- and readmission-related outcomes, the variable angiography performed within 1 year was considered a potential confounder. Additionally, readmission to hospital with MACE, major bleeding or heart failure within 1 year were considered for mortality related outcome measures.
The linearity for any continuous variable was assessed and complex associations were dealt with by categorising the variable. Age was categorised into the following groups: 20–44 years, 45–59 years, 60–69 years, 70–89 years and 90+ years. Backwards elimination was used to reduce the number of variables in the models; however, important confounders were retained regardless of significance. Likelihood ratio tests were used to assess the significance of each variable (p<0.05) in the model. Only a priori interactions (age, ethnicity and socioeconomic deprivation) were investigated.
Data manipulation, analysis and visualisation were done in the open-access R statistical programming language (version 4.1.1) using the R-Studio integrated data environment (IDE) (22.02.3 Boston, MA).[[10]]
Ethics
ANZACS-QI is part of the Auckland University-based Vascular Informatics Using Epidemiology and the Web (VIEW) study. The VIEW study was approved by the Northern Region Ethics Committee in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries. There are annual approvals by the National Multi-Region Ethics Committee since 2007 (MEC07/10/EXP).[[6]]
Funding
This study was supported by a University of Otago Early Career Clinician Start-up grant.
Results
There were 42,923 patients with a diagnosis of NSTEACS who presented to New Zealand public hospitals between 2014 and 2017. Table 2 describes the characteristics of the included patients. Most patients (62.4%) presented to urban hospitals with access to PCI, nearly a third (29.1%) to urban hospitals without PCI and 8.4% to rural hospitals. Compared to patients who presented to urban hospitals with PCI, a higher percentage of patients who presented to urban hospitals without PCI and rural hospitals were Māori (8.1%, 15.8% and 14% respectively) and lived in the most deprived quintile (24.1%, 33.9% and 28.3%). Patients were followed for a median of 3.2 years (interquartile range 1.8 to 4.8), with 40,272 (93.8%) followed for at least 2 years.
Table 3 presents the number, percentage, unadjusted and adjusted odds ratios (OR) for each outcome grouped by hospital type. Adjusted OR are shown in Figure 1. Compared to patients presenting to urban hospitals with PCI, those who present to rural hospitals had lower odds of receiving angiography within 30 days (0.76, 95% CI: 0.70 to 0.83) and 1 year (OR 0.82, 95% CI: 0.75 to 0.90), as well as increased odds of death at 2 years (OR 1.16, 95% CI: 1.05 to 1.29) but not at 30 days or 1 year. Urban hospitals without PCI similarly had reduced odds of receiving angiography at 30 days (OR 0.70, 95% CI: 0.66 to 0.73) and 1 year (OR 0.75, 95% CI: 0.71 to 0.79) but no increase in the odds of dying. There was, however, a small increase in the odds of readmission with MACE within 1 year of admission (OR 1.10, 95% CI: 1.03 to 1.16). Full model outputs are included as Appendix 2.
Figure 2 shows the unadjusted Kaplan–Meier survival curve for mortality over the 6 years of the study and demonstrates that survival for patients who presented to rural compared with urban hospitals (with or without PCI) was reduced from 1 year following admission. There was weak evidence of increased adjusted risk of dying for patients who presented to rural hospitals (hazard ratio (HR) 1.06, 95% CI: 1.00 to 1.13), as shown in Figure 3. Unadjusted HR are presented in Appendix 3. Adjusting for hospital category, Māori (HR 1.34, 95% CI: 1.27 to 1.43) and Pasifika (1.17, 95% CI: 1.07 to 1.27) had increased risk of dying compared with European/Other.
Model diagnostics
For all models, age had a non-linear association with the outcome so was modelled categorically. There were no important interactions identified. The proportional hazards assumption was violated for some variables in the Cox proportional hazards model, however, graphical inspection of the scaled Schoenfeld residuals showed that this was due to very small departures from proportional hazards being shown as “significant” due to the large sample size.[[11]] Including these as stratified variables in the model did not change model interpretation (Appendix 4).
Discussion
This nationwide study describes the outcomes for patients who presented to public hospitals in New Zealand with NSTEACS based on the type of available specialist and interventional resources of the hospital that the patient first presented to. The main findings were that patients presenting to rural hospitals and urban hospitals without access to PCI were less likely to receive angiography at both 30 days (OR 0.75 and 0.82 respectively) and 1 year (0.70 and 0.76 respectively, however, there is no difference in mortality at 30 days or 1 year. Patients that presented to rural hospitals had slightly higher odds of dying at 2 years (OR 1.16) compared to patients that presented to urban hospitals. Patients that presented to urban hospitals without access to PCI were more likely to be readmitted with a MACE within 1 year of admission (OR 1.10) compared to the other two hospital types.
Angiography performed
That patients who presented to hospitals without access to PCI (both urban and rural) were less likely to receive angiography, which is consistent with other studies for patients who presented to the same hospital groupings with ST-segment elevation myocardial infarction (STEMI).[[1]] These patients had not only reduced access to angiography during the index admission, but the time to angiography was significantly longer.[[1]] The finding is also consistent with previous Australian and New Zealand studies of all ACS events, where “smaller” or non-urban hospitals had reduced rates of angiography and PCI.[[8,12,13]]
This is especially problematic in New Zealand given the higher percentage of Māori who present to rural hospitals and urban hospitals without access to PCI. It is well established that Māori patients with ACS have been shown to have reduced access to angiography and revascularisation and subsequently have poorer outcomes. The geographic inequities in access to optimal care that we have identified compound these inequities resulting from historical and ongoing colonisation and racism.[[14,15]]
Mortality
Similar to a recent study that found no difference in mortality for patients with STEMI that present to New Zealand rural and urban hospitals without PCI,[[1]] reassuringly there were few differences found in the mortality between the three groups of hospitals included in this study. Historically, differences in mortality have been large, with up to a 300% increase in the odds of dying for patients that presented to an urban hospital without PCI compared with a hospital that had within the same district.[[16]] Since this time, reflective of increased risk reduction measures,[[6,17]] as well as improved access to interventional practice and development of regional networks, the incidence, prevalence, hospitalisation and mortality rates from ischaemic heart disease in New Zealand have decreased. Although, as it is with our data, for Māori and Pasifika these remain disproportionately high.[[4,17]] International rural mortality rates following acute coronary syndrome vary according to the definition of “rural” that is used.[[13,18–20]] Mortality rates for Indigenous peoples from other countries are consistently higher than non-Indigenous peoples.[[21]]
However, this study did demonstrate a small increase in 2-year mortality following admission for patients who present to rural hospitals compared to both types of urban hospitals. We are unaware of any recent New Zealand-based studies that have demonstrated a mortality difference between urban hospitals with PCI and hospitals without PCI, and none that differentiate rural from urban hospitals.
The reason for the small difference in delayed mortality demonstrated for rural hospitals in this study is not known but does not appear to be related to reduced access to angiography. Patients that present to urban hospitals without PCI have similar odds of angiography being performed as rural hospitals but do not demonstrate the same increase in 2-year mortality. Possible explanations include reduced access to primary care, secondary prevention and cardiac rehabilitation.
Secondary prevention therapies are considered critically important and are strongly recommended in all international guidelines, with emphasis on cardiac rehabilitation and the prescription of evidence-based therapies: anti-platelet therapy, statins, beta-blockers and renin-angiotensin antagonists.[[2,22]]
In New Zealand, there is evidence of reduced prescribing of these evidence-based therapies for NSTEACS in patients who are Māori or Pasifika, female, present to hospitals outside main centres[[1]] and live in the most deprived areas.[[23,24]] Our results showed that compared with major urban hospitals, a higher percentage of patients that present to rural hospitals were Māori and live in more deprived areas. Therefore, a reduction in the prescription and maintenance of appropriate secondary prevention medicine may account for some of the increased risk of 2-year mortality.
Referral to cardiac rehabilitation services has been shown to reduce future cardiac events, and death, following an admission with IHD.[[12]] Within New Zealand, patient referral and attendance of cardiac rehabilitation services are well below international standards in many regions, but there is yet to be analysis based on the geographic location of the patient.[[25,26]] There is clear evidence internationally that access to all phases of cardiac rehabilitation is reduced for patients that live in rural and remote areas.[[27–29]] The reliance on group sessions in central locations reported in the New Zealand literature may mean that rural residents find it difficult to access cardiac rehabilitation sessions, representing a potential gap in the system and missed opportunities for evidence-based care.[[26]]
Strengths and limitations
This study is the first to differentiate patients with NSTEACS that present to New Zealand rural hospitals, as opposed to any hospital without PCI routinely available. A key strength of this study is the ability to identify all patients with NSTEACS diagnosis codes admitted to New Zealand public hospitals and follow these patients using linked national mortality and hospitalisation datasets to ascertain investigations and outcomes that occurred after the admission. This linkage is not possible in many countries on a national scale.[[17]]
The major limitation is that the cohort of patients that present to rural hospitals may not represent those that live in rural places. Approximately 19% of the New Zealand population live in rural areas,[[3]] but only 8% of the cohort that was admitted with NSTEACS presented to a rural hospital. This finding may be attributed to rural patients living closer to an urban hospital, patient preference or ambulance service destination policies.[[1,30]] A study using the geographic location of the patient is planned to understand the effect of rurality on the outcomes of NSTEACS as well as explore differences between rural Māori and non-Māori peoples.
A further limitation is that apart from angiography, the investigations and treatments that occurred during or after the NSTEACS admission were not considered. This includes revascularisation procedures, and these will be examined in more detail using the ANZACS-QI CathPCI cohort.[[6]] Additionally, inconsistency in the clinical coding, particularly in rural hospitals where anecdotally this task is frequently performed by clinicians or clerical staff without formal training, may have influenced the results. It was not possible to differentiate between type 1 and type 2 acute myocardial infarction (AMI) from the available data.
Patients who received investigations in private facilities, underwent CT coronary angiography instead of invasive angiography, died prior to reaching hospital or who received treatment or died overseas were unable to be accounted for. This may differ between urban and rural areas.
Implications
The ability to track mortality and access to interventions over time is an important function in registries such as ANZACS-QI, especially for rural populations. In New Zealand, health outcome data are routinely reported by regions, usually encompassing rural and urban areas. This can miss urban-rural variation, which can be larger than the variation between regions.[[3]]
The large improvement seen in the care for patients with NSTEACS is largely attributable to the success of ANZACS-QI and the implementation and monitoring of targeted policy and procedures by PCI centres to ensure that the wider population they serve has equitable access to services.[[6]] While mortality is similar across the three groups of hospitals, this study demonstrates that equitable access to angiography is still not being achieved for patients initially admitted to rural and urban hospitals without PCI. Improving complex inter-hospital transfer policies should be a priority as Te Whatu Ora and Te Aka Whai Ora become more established.
The factors that contribute to the higher rate of delayed mortality for those who present to rural hospitals and for Māori should be identified and eliminated. This may include improving access to and ongoing use of proven secondary prevention therapies.
Conclusion
This study has demonstrated that patients presenting to rural or urban hospitals without PCI are less likely to receive angiography. Reassuringly there were no increased odds of 30-day or 1-year mortality, but patients who initially present to rural hospitals do have a small increase in the odds of dying that becomes apparent at 2-years post admission. There is a higher risk of mortality for Māori and Pasifika. This may reflect poorer access to evidence-based cardiac rehabilitation and secondary prevention.
View Appendices.
Summary
Abstract
Aim
This study’s aim was to identify differences in invasive angiography performed and health outcomes for patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) presenting to either i) a rural hospital, or an urban hospital ii) with or iii) without routine access to percutaneous intervention (PCI) in New Zealand.
Method
Patients with NSTEACS between 1 January 2014 and 31 December 2017 were included. Logistic regression was used to model each of the outcome measures: angiography performed within 1 year; 30-day, 1-year and 2-year all-cause mortality; and readmission within 1 year of presentation with either heart failure, a major adverse cardiac event or major bleeding.
Results
There were 42,923 patients included. Compared to urban hospitals with access to PCI, the odds of a patient receiving an angiogram were reduced for rural and urban hospitals without routine access to PCI (odds ratio [OR] 0.82 and 0.75) respectively. There was a small increase in the odds of dying at 2 years (OR 1.16), but not 30 days or 1 year for patients presenting to a rural hospital.
Conclusion
Patients who present to hospitals without PCI are less likely to receive angiography. Reassuringly there is no difference in mortality, except at 2 years, for patients that present to rural hospitals.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Lee S, Miller R, Lee M, White H, Kerr A. Outcomes after ST-elevation myocardial infarction presentation to hospitals with or without a routine primary percutaneous coronary intervention service (ANZACS-QI 46). N Z Med J. 2020;133(1524):64-81.
2) Chew DP, Scott IA, Cullen L, French JK, Briffa TG, Tideman PA, Woodruffe S, Kerr A, Branagan M, Aylward PE; NHFA/CSANZ ACS Guideline 2016 Executive Working Group:. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand: Australian Clinical Guidelines for the Management of Acute Coronary Syndromes 2016. Heart Lung Circ. 2016;25(9):895-951. doi: 10.1016/j.hlc.2016.06.789.
3) Whitehead J, Davie G, de Graaf B, Crengle S, Fearnley D, Smith M, Lawrenson R, Nixon G. Defining rural in Aotearoa New Zealand: a novel geographic classification for health purposes. N Z Med J. 2022;135(1559):24-40.
4) Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, Sundborn G, Kerr AJ. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018;131(1478):21-31.
5) Blattner K, Miller R, Lawrence-Lodge R, Nixon G, McHugh P, Pirini J. New Zealand's vocational Rural Hospital Medicine Training Programme: the first ten years. N Z Med J. 2021;134(1529):57-68.
6) Kerr A, Williams MJ, White H, Doughty R, Nunn C, Devlin G, Grey C, Lee M, Flynn C, Rhodes M, Sutherland K, Wells S, Jackson R, Stewart R. The All New Zealand Acute Coronary Syndrome Quality Improvement Programme: Implementation, Methodology and Cohorts (ANZACS-QI 9). N Z Med J. 2016;129(1439):23-36.
7) Marshall B, Aileone L. COVID-19 pandemic and rural generalism: the West Coast's rural workforce solution. N Z Med J. 2020;133(1514):90-92.
8) Ellis C, Gamble G, Devlin G, Elliott J, Hamer A, Williams M, Matsis P, Troughton R, Ranasinghe I, French J, Brieger D, Chew D, White H; New Zealand Acute Coronary Syndromes (NZACS) SNAPSHOT Audit Group. The management of acute coronary syndrome patients across New Zealand in 2012: results of a third comprehensive nationwide audit and observations of current interventional care. N Z Med J. 2013;126(1387):36-68.
9) Quan H, Li B, Couris CM, Fushimi K, Graham P, Hider P, Januel JM, Sundararajan V. Updating and validating the Charlson comorbidity index and score for risk adjustment in hospital discharge abstracts using data from 6 countries. Am J Epidemiol. 2011;173(6):676-82. doi: 10.1093/aje/kwq433.
10) R Core Team. R: A Language and Environment for Statistical Computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2019. Available from: https://www.R-project.org/.
11) Vittinghoff E, Glidden DV, Shiboski SC, McCulloch CE. Regression Methods in Biostatistics [Internet]. Boston, MA: Springer US; 2012 [cited 2022 Sep 1]. (Statistics for Biology and Health).
12) Chew DP, French J, Briffa TG, Hammett CJ, Ellis CJ, Ranasinghe I, Aliprandi-Costa BJ, Astley CM, Turnbull FM, Lefkovits J, Redfern J, Carr B, Gamble GD, Lintern KJ, Howell TE, Parker H, Tavella R, Bloomer SG, Hyun KK, Brieger DB. Acute coronary syndrome care across Australia and New Zealand: the SNAPSHOT ACS study. Med J Aust. 2013;199(3):185-91. doi: 10.5694/mja12.11854.
13) Alston L, Peterson KL, Jacobs JP, Allender S, Nichols M. Quantifying the role of modifiable risk factors in the differences in cardiovascular disease mortality rates between metropolitan and rural populations in Australia: a macrosimulation modelling study. BMJ Open. 2017;7:e018307. doi: 10.1136/bmjopen-2017-018307.
14) Curtis E, Harwood M, Riddell T, Robson B, Harris R, Mills C, Reid P. Access and society as determinants of ischaemic heart disease in indigenous populations. Heart Lung Circ. 2010 May-Jun;19(5-6):316-24. doi: 10.1016/j.hlc.2010.04.129. Epub 2010 May 4.
15) Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, Exeter DJ, Kerr AJ. Ethnic Differences in Coronary Revascularisation following an Acute Coronary Syndrome in New Zealand: A National Data-linkage Study (ANZACS-QI 12). Heart Lung Circ. 2016;25(8):820-8. doi: 10.1016/j.hlc.2016.03.004.
16) Tang EW, Wong CK, Herbison P. Community hospital versus tertiary hospital comparison in the treatment and outcome of patients with acute coronary syndrome: a New Zealand experience. N Z Med J. 2006;119(1238):U2078.
17) Grey C, Jackson R, Wells S, Wu B, Pujades-Rodriguez M, Schmidt M, Selak V, Kerr AJ. Both incidence and prevalence of ischaemic heart disease are declining in parallel: a national data-linkage study in New Zealand (ANZACS-QI 52). Eur J Prev Cardiol. 2022;29(2):321-327. doi: 10.1093/eurjpc/zwaa120.
18) Tideman P, Taylor AW, Janus E, Philpot B, Clark R, Peach E, Laatikainen T, Vartiainen E, Tirimacco R, Montgomerie A, Grant J, Versace V, Dunbar JA. A comparison of Australian rural and metropolitan cardiovascular risk and mortality: the Greater Green Triangle and North West Adelaide population surveys. BMJ Open. 2013;3(8):e003203. doi: 10.1136/bmjopen-2013-003203.
19) Bechtold D, Salvatierra GG, Bulley E, Cypro A, Daratha KB. Geographic Variation in Treatment and Outcomes Among Patients With AMI: Investigating Urban-Rural Differences Among Hospitalized Patients. J Rural Health. 2017;33(2):158-166. doi: 10.1111/jrh.12165.
20) Cai M, Liu E, Tao H, Qian Z, Lin X, Cheng Z. Does Level of Hospital Matter? A Study of Mortality of Acute Myocardial Infarction Patients in Shanxi, China. Am J Med Qual. 2018;33(2):185-192. doi: 10.1177/1062860617708608.
21) Brown A. Acute coronary syndromes in indigenous Australians: opportunities for improving outcomes across the continuum of care. Heart Lung Circ. 2010 May-Jun;19(5-6):325-36. doi: 10.1016/j.hlc.2010.02.011.
22) Roffi M, Patrono C, Collet JP, Mueller C, Valgimigli M, Andreotti F, Bax JJ, Borger MA, Brotons C, Chew DP, Gencer B, Hasenfuss G, Kjeldsen K, Lancellotti P, Landmesser U, Mehilli J, Mukherjee D, Storey RF, Windecker S; ESC Scientific Document Group. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: Task Force for the Management of Acute Coronary Syndromes in Patients Presenting without Persistent ST-Segment Elevation of the European Society of Cardiology (ESC). Eur Heart J. 2016;37(3):267-315. doi: 10.1093/eurheartj/ehv320.
23) Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, Harrison J, Riddell T, Kerr A. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014;100(10):770-4. doi: 10.1136/heartjnl-2013-304960.
24) Kerr AJ, Turaga M, Grey C, Lee M, McLachlan A, Devlin G. Initiation and maintenance of statins and aspirin after acute coronary syndromes (ANZACS-QI 11). J Prim Health Care. 2016;8(3):238-249. doi: 10.1071/HC16013.
25) Benatar J, Langdana F, Doolan-Noble F, McLachlan A. Cardiac rehabilitation in New Zealand-moving forward. N Z Med J. 2016;129(1435):68-74.
26) Kira G, Doolan-Noble F, Humphreys G, Williams G, O'Shaughnessy H, Devlin G. A national survey of cardiac rehabilitation services in New Zealand: 2015. N Z Med J. 2016;129(1435):50-8.
27) Field PE, Franklin RC, Barker RN, Ring I, Leggat PA. Cardiac rehabilitation services for people in rural and remote areas: an integrative literature review. Rural Remote Health. 2018;18(4):4738. doi: 10.22605/RRH4738.
28) Field P, Franklin RC, Barker R, Ring I, Leggat P, Canuto K. Importance of cardiac rehabilitation in rural and remote areas of Australia. Aust J Rural Health. 2022;30(2):149-163. Doi: 10.1111/ajr.
29) Thompson SC, Nedkoff L, Katzenellenbogen J, Hussain MA, Sanfilippo F. Challenges in Managing Acute Cardiovascular Diseases and Follow Up Care in Rural Areas: A Narrative Review. Int J Environ Res Public Health. 2019;16(24):5126. doi: 10.3390/ijerph16245126.12818.
30) Liao BY, Lee MAW, Dicker B, Todd VF, Stewart R, Poppe K, Kerr A. Prehospital identification of ST-segment elevation myocardial infarction and mortality (ANZACS-QI 61). Open Heart. 2022;9(1):e001868. doi: 10.1136/openhrt-2021-001868.
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Outcomes and access to angiography following non-ST-segment elevation acute coronary syndromes in patients who present to rural or urban hospitals: ANZACS-QI 72
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In Aotearoa New Zealand, patients who present with non-ST-segment elevation acute coronary syndrome (NSTEACS, which comprises non-ST-segment elevation myocardial infarction [NSTEMI] and unstable angina [UA]) will initially access one of three groups of hospitals: urban hospitals with routine access to percutaneous intervention (PCI), urban hospitals without routine access to PCI and rural hospitals (which also do not have routine access to PCI).[[1]] Australasian consensus guidelines recommend that most patients with NSTEACS, especially those at high or intermediate risk of mortality, receive “an invasive strategy of angiography with coronary revascularisation” within 72 hours.[[2]]
There are nine urban hospitals in New Zealand that have routine access to PCI. Hospitals that don’t have routine PCI capabilities typically have catchments that include smaller regional or rural areas. Compared with major urban areas, these smaller catchments include a higher proportion of Māori, who have poorer cardiovascular outcomes than NZ Europeans.[[3,4]] Rural hospitals are typically staffed by generalist doctors and nursing teams, have fewer resources and are at a distance from urban hospitals with specialists or associated services (40 minutes to 4 hours by road from urban hospitals with routine access to PCI).[[5]] Patients with NSTEACS who present to urban hospitals without routine access to PCI may be cared for by cardiology specialists or general physicians.
Stable patients who present with NSTEACS to hospitals without routine access to PCI will receive initial treatment and if clinically stable, are usually admitted to that hospital while awaiting transfer for angiography. Unstable patients or patients at rural hospitals with fewer resources may require early transfer to a larger hospital. For rural hospitals whose primary referral hospital does not have PCI capabilities, patients may undergo several transfers to receive definitive treatment.
The aim of this study was to determine if there were differences in invasive angiography performed and clinical outcomes, including mortality, associated with the category of hospital of presentation (rural hospitals or urban hospitals with or without routine access to PCI) for patients with NSTEACS.
Methods
All first admissions for patients aged 20 years or older with NSTEACS between 1 January 2014 and 31 December 2017 to a publicly funded New Zealand hospital were included in the study.
Registries
The All New Zealand Acute Coronary Syndrome Quality Improvement (ANZACS-QI) programme is a clinically led initiative. Its primary aim is to “support appropriate, evidence-based management of ACS… regardless of age, sex, ethnicity, socioeconomic status, or rural or city dwelling”.[[6]]
This study used the ANZACS-QI programme’s ACS Routine Information cohort, which incorporates the Ministry of Health’s National Minimum Dataset for Hospital Admissions (NMDS) and the National Mortality Collection, which are linked using the patient’s encrypted national health index (NHI). The NMDS includes information for all public hospital admissions (including all hospitals considered in this study) and the mortality collection contains information regarding deaths. All New Zealand residents aged 20 years or older who are admitted to hospital with a primary or secondary ICD-10 code consistent with ACS (I20.0, I21.x, I22.x) are included in this cohort.[[6]] The mortality collection contained all deaths until 31 December 2018, which was at least 1 year after the last admission to hospital.
Hospitals of presentation
Hospitals were identified using the facility code assigned by the New Zealand Ministry of Health – Manatū Hauora (Table 1) and divided into three urban-rural hospital categories:
1. Urban hospitals with routine access to PCI (urban hospitals with PCI),
2. Urban hospitals without routine access to PCI (urban hospitals without PCI) and
3. Rural hospitals.
Three hospitals did not easily fit within these categories. Tauranga and Nelson have PCI-capable angiography suites but do not have reliable after-hours access to these. They were considered urban hospitals with PCI for the purposes of this analysis, as there would be few exceptions to not being able to offer PCI for patients with NSTEACS within 3 days. Greymouth Hospital was considered a rural hospital due to its distance from and the logistical challenges associated with accessing a hospital with PCI, in addition to an increasingly rural generalist workforce.[[7]] These groupings are consistent with previous studies.[[1]]
Patients were assigned to the first hospital of presentation. To account for the movement of patients with NSTEACS between hospitals to receive PCI or other investigations or treatments, admissions were bundled into group inter-hospital transfers as part of the same episode of care.[[1,8]]
View Tables 1–3 and Figures 1–3.
Data collected
Age, sex, prioritised ethnicity (using the New Zealand Ministry of Health’s protocols),[[6]] NZ Deprivation Index 2013 (NZDep2013) deciles, admission to hospital with either MI or heart failure in the last 5 years, non-cardiac Charlson Comorbidity Index score and type of NSTEACS (NSTEMI or UA) were collected from the ACS Routine Information cohort for the patient’s first ACS admission. The Charlson Comorbidity Index is a method of predicting mortality by weighting comorbid conditions and is widely used in health research.[[9]] The non-cardiac Charlson score excludes congestive heart failure.[[1,9]]
Outcome measures
The following outcome measures were considered: 30-day and 1-year all-cause mortality; angiography performed within 30 days and 1 year; and readmission to hospital within 1 year with heart failure, major adverse cardiac event (MACE) or major bleeding. MACE was defined as: acute myocardial infarction, cardiac arrest, cardiogenic shock, ventricular arrythmia (ventricular tachycardia or fibrillation), high-grade atrioventricular block requiring intervention or emergency coronary revascularisation. To determine 2-year all-cause mortality, only patients with at least 2 years of follow-up were considered.
All definitions and ICD-10 codes are shown in Appendix 1.
Statistical analysis
Data were summarised using mean and standard deviation (SD) for continuous data and frequency and percentage for categorical data in total and by category of hospital.
Logistic regression, modelled separately for each outcome, was used to estimate odds ratios (OR) with 95% confidence intervals (95% CI) comparing urban hospitals without access to PCI and rural hospitals to urban hospitals with access to PCI (the reference group).
Unadjusted mortality comparing the hospital types was visualised using Kaplan–Meier curves. Cox proportional hazard ratios were then used to estimate hazard ratios (HR), with 95% confidence intervals, comparing hospital type. All patients were followed for at least 1 year after admission and patients were “right-censored” if they had not died by the end of the study period.
For all outcome measures, the following variables were considered as potential confounders within the models: sex, ethnicity, age, type of NSTEACS, prior heart failure, prior acute myocardial infarction, socio-economic deprivation and non-cardiac Charlson score. For the mortality- and readmission-related outcomes, the variable angiography performed within 1 year was considered a potential confounder. Additionally, readmission to hospital with MACE, major bleeding or heart failure within 1 year were considered for mortality related outcome measures.
The linearity for any continuous variable was assessed and complex associations were dealt with by categorising the variable. Age was categorised into the following groups: 20–44 years, 45–59 years, 60–69 years, 70–89 years and 90+ years. Backwards elimination was used to reduce the number of variables in the models; however, important confounders were retained regardless of significance. Likelihood ratio tests were used to assess the significance of each variable (p<0.05) in the model. Only a priori interactions (age, ethnicity and socioeconomic deprivation) were investigated.
Data manipulation, analysis and visualisation were done in the open-access R statistical programming language (version 4.1.1) using the R-Studio integrated data environment (IDE) (22.02.3 Boston, MA).[[10]]
Ethics
ANZACS-QI is part of the Auckland University-based Vascular Informatics Using Epidemiology and the Web (VIEW) study. The VIEW study was approved by the Northern Region Ethics Committee in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries. There are annual approvals by the National Multi-Region Ethics Committee since 2007 (MEC07/10/EXP).[[6]]
Funding
This study was supported by a University of Otago Early Career Clinician Start-up grant.
Results
There were 42,923 patients with a diagnosis of NSTEACS who presented to New Zealand public hospitals between 2014 and 2017. Table 2 describes the characteristics of the included patients. Most patients (62.4%) presented to urban hospitals with access to PCI, nearly a third (29.1%) to urban hospitals without PCI and 8.4% to rural hospitals. Compared to patients who presented to urban hospitals with PCI, a higher percentage of patients who presented to urban hospitals without PCI and rural hospitals were Māori (8.1%, 15.8% and 14% respectively) and lived in the most deprived quintile (24.1%, 33.9% and 28.3%). Patients were followed for a median of 3.2 years (interquartile range 1.8 to 4.8), with 40,272 (93.8%) followed for at least 2 years.
Table 3 presents the number, percentage, unadjusted and adjusted odds ratios (OR) for each outcome grouped by hospital type. Adjusted OR are shown in Figure 1. Compared to patients presenting to urban hospitals with PCI, those who present to rural hospitals had lower odds of receiving angiography within 30 days (0.76, 95% CI: 0.70 to 0.83) and 1 year (OR 0.82, 95% CI: 0.75 to 0.90), as well as increased odds of death at 2 years (OR 1.16, 95% CI: 1.05 to 1.29) but not at 30 days or 1 year. Urban hospitals without PCI similarly had reduced odds of receiving angiography at 30 days (OR 0.70, 95% CI: 0.66 to 0.73) and 1 year (OR 0.75, 95% CI: 0.71 to 0.79) but no increase in the odds of dying. There was, however, a small increase in the odds of readmission with MACE within 1 year of admission (OR 1.10, 95% CI: 1.03 to 1.16). Full model outputs are included as Appendix 2.
Figure 2 shows the unadjusted Kaplan–Meier survival curve for mortality over the 6 years of the study and demonstrates that survival for patients who presented to rural compared with urban hospitals (with or without PCI) was reduced from 1 year following admission. There was weak evidence of increased adjusted risk of dying for patients who presented to rural hospitals (hazard ratio (HR) 1.06, 95% CI: 1.00 to 1.13), as shown in Figure 3. Unadjusted HR are presented in Appendix 3. Adjusting for hospital category, Māori (HR 1.34, 95% CI: 1.27 to 1.43) and Pasifika (1.17, 95% CI: 1.07 to 1.27) had increased risk of dying compared with European/Other.
Model diagnostics
For all models, age had a non-linear association with the outcome so was modelled categorically. There were no important interactions identified. The proportional hazards assumption was violated for some variables in the Cox proportional hazards model, however, graphical inspection of the scaled Schoenfeld residuals showed that this was due to very small departures from proportional hazards being shown as “significant” due to the large sample size.[[11]] Including these as stratified variables in the model did not change model interpretation (Appendix 4).
Discussion
This nationwide study describes the outcomes for patients who presented to public hospitals in New Zealand with NSTEACS based on the type of available specialist and interventional resources of the hospital that the patient first presented to. The main findings were that patients presenting to rural hospitals and urban hospitals without access to PCI were less likely to receive angiography at both 30 days (OR 0.75 and 0.82 respectively) and 1 year (0.70 and 0.76 respectively, however, there is no difference in mortality at 30 days or 1 year. Patients that presented to rural hospitals had slightly higher odds of dying at 2 years (OR 1.16) compared to patients that presented to urban hospitals. Patients that presented to urban hospitals without access to PCI were more likely to be readmitted with a MACE within 1 year of admission (OR 1.10) compared to the other two hospital types.
Angiography performed
That patients who presented to hospitals without access to PCI (both urban and rural) were less likely to receive angiography, which is consistent with other studies for patients who presented to the same hospital groupings with ST-segment elevation myocardial infarction (STEMI).[[1]] These patients had not only reduced access to angiography during the index admission, but the time to angiography was significantly longer.[[1]] The finding is also consistent with previous Australian and New Zealand studies of all ACS events, where “smaller” or non-urban hospitals had reduced rates of angiography and PCI.[[8,12,13]]
This is especially problematic in New Zealand given the higher percentage of Māori who present to rural hospitals and urban hospitals without access to PCI. It is well established that Māori patients with ACS have been shown to have reduced access to angiography and revascularisation and subsequently have poorer outcomes. The geographic inequities in access to optimal care that we have identified compound these inequities resulting from historical and ongoing colonisation and racism.[[14,15]]
Mortality
Similar to a recent study that found no difference in mortality for patients with STEMI that present to New Zealand rural and urban hospitals without PCI,[[1]] reassuringly there were few differences found in the mortality between the three groups of hospitals included in this study. Historically, differences in mortality have been large, with up to a 300% increase in the odds of dying for patients that presented to an urban hospital without PCI compared with a hospital that had within the same district.[[16]] Since this time, reflective of increased risk reduction measures,[[6,17]] as well as improved access to interventional practice and development of regional networks, the incidence, prevalence, hospitalisation and mortality rates from ischaemic heart disease in New Zealand have decreased. Although, as it is with our data, for Māori and Pasifika these remain disproportionately high.[[4,17]] International rural mortality rates following acute coronary syndrome vary according to the definition of “rural” that is used.[[13,18–20]] Mortality rates for Indigenous peoples from other countries are consistently higher than non-Indigenous peoples.[[21]]
However, this study did demonstrate a small increase in 2-year mortality following admission for patients who present to rural hospitals compared to both types of urban hospitals. We are unaware of any recent New Zealand-based studies that have demonstrated a mortality difference between urban hospitals with PCI and hospitals without PCI, and none that differentiate rural from urban hospitals.
The reason for the small difference in delayed mortality demonstrated for rural hospitals in this study is not known but does not appear to be related to reduced access to angiography. Patients that present to urban hospitals without PCI have similar odds of angiography being performed as rural hospitals but do not demonstrate the same increase in 2-year mortality. Possible explanations include reduced access to primary care, secondary prevention and cardiac rehabilitation.
Secondary prevention therapies are considered critically important and are strongly recommended in all international guidelines, with emphasis on cardiac rehabilitation and the prescription of evidence-based therapies: anti-platelet therapy, statins, beta-blockers and renin-angiotensin antagonists.[[2,22]]
In New Zealand, there is evidence of reduced prescribing of these evidence-based therapies for NSTEACS in patients who are Māori or Pasifika, female, present to hospitals outside main centres[[1]] and live in the most deprived areas.[[23,24]] Our results showed that compared with major urban hospitals, a higher percentage of patients that present to rural hospitals were Māori and live in more deprived areas. Therefore, a reduction in the prescription and maintenance of appropriate secondary prevention medicine may account for some of the increased risk of 2-year mortality.
Referral to cardiac rehabilitation services has been shown to reduce future cardiac events, and death, following an admission with IHD.[[12]] Within New Zealand, patient referral and attendance of cardiac rehabilitation services are well below international standards in many regions, but there is yet to be analysis based on the geographic location of the patient.[[25,26]] There is clear evidence internationally that access to all phases of cardiac rehabilitation is reduced for patients that live in rural and remote areas.[[27–29]] The reliance on group sessions in central locations reported in the New Zealand literature may mean that rural residents find it difficult to access cardiac rehabilitation sessions, representing a potential gap in the system and missed opportunities for evidence-based care.[[26]]
Strengths and limitations
This study is the first to differentiate patients with NSTEACS that present to New Zealand rural hospitals, as opposed to any hospital without PCI routinely available. A key strength of this study is the ability to identify all patients with NSTEACS diagnosis codes admitted to New Zealand public hospitals and follow these patients using linked national mortality and hospitalisation datasets to ascertain investigations and outcomes that occurred after the admission. This linkage is not possible in many countries on a national scale.[[17]]
The major limitation is that the cohort of patients that present to rural hospitals may not represent those that live in rural places. Approximately 19% of the New Zealand population live in rural areas,[[3]] but only 8% of the cohort that was admitted with NSTEACS presented to a rural hospital. This finding may be attributed to rural patients living closer to an urban hospital, patient preference or ambulance service destination policies.[[1,30]] A study using the geographic location of the patient is planned to understand the effect of rurality on the outcomes of NSTEACS as well as explore differences between rural Māori and non-Māori peoples.
A further limitation is that apart from angiography, the investigations and treatments that occurred during or after the NSTEACS admission were not considered. This includes revascularisation procedures, and these will be examined in more detail using the ANZACS-QI CathPCI cohort.[[6]] Additionally, inconsistency in the clinical coding, particularly in rural hospitals where anecdotally this task is frequently performed by clinicians or clerical staff without formal training, may have influenced the results. It was not possible to differentiate between type 1 and type 2 acute myocardial infarction (AMI) from the available data.
Patients who received investigations in private facilities, underwent CT coronary angiography instead of invasive angiography, died prior to reaching hospital or who received treatment or died overseas were unable to be accounted for. This may differ between urban and rural areas.
Implications
The ability to track mortality and access to interventions over time is an important function in registries such as ANZACS-QI, especially for rural populations. In New Zealand, health outcome data are routinely reported by regions, usually encompassing rural and urban areas. This can miss urban-rural variation, which can be larger than the variation between regions.[[3]]
The large improvement seen in the care for patients with NSTEACS is largely attributable to the success of ANZACS-QI and the implementation and monitoring of targeted policy and procedures by PCI centres to ensure that the wider population they serve has equitable access to services.[[6]] While mortality is similar across the three groups of hospitals, this study demonstrates that equitable access to angiography is still not being achieved for patients initially admitted to rural and urban hospitals without PCI. Improving complex inter-hospital transfer policies should be a priority as Te Whatu Ora and Te Aka Whai Ora become more established.
The factors that contribute to the higher rate of delayed mortality for those who present to rural hospitals and for Māori should be identified and eliminated. This may include improving access to and ongoing use of proven secondary prevention therapies.
Conclusion
This study has demonstrated that patients presenting to rural or urban hospitals without PCI are less likely to receive angiography. Reassuringly there were no increased odds of 30-day or 1-year mortality, but patients who initially present to rural hospitals do have a small increase in the odds of dying that becomes apparent at 2-years post admission. There is a higher risk of mortality for Māori and Pasifika. This may reflect poorer access to evidence-based cardiac rehabilitation and secondary prevention.
View Appendices.
Summary
Abstract
Aim
This study’s aim was to identify differences in invasive angiography performed and health outcomes for patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) presenting to either i) a rural hospital, or an urban hospital ii) with or iii) without routine access to percutaneous intervention (PCI) in New Zealand.
Method
Patients with NSTEACS between 1 January 2014 and 31 December 2017 were included. Logistic regression was used to model each of the outcome measures: angiography performed within 1 year; 30-day, 1-year and 2-year all-cause mortality; and readmission within 1 year of presentation with either heart failure, a major adverse cardiac event or major bleeding.
Results
There were 42,923 patients included. Compared to urban hospitals with access to PCI, the odds of a patient receiving an angiogram were reduced for rural and urban hospitals without routine access to PCI (odds ratio [OR] 0.82 and 0.75) respectively. There was a small increase in the odds of dying at 2 years (OR 1.16), but not 30 days or 1 year for patients presenting to a rural hospital.
Conclusion
Patients who present to hospitals without PCI are less likely to receive angiography. Reassuringly there is no difference in mortality, except at 2 years, for patients that present to rural hospitals.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Lee S, Miller R, Lee M, White H, Kerr A. Outcomes after ST-elevation myocardial infarction presentation to hospitals with or without a routine primary percutaneous coronary intervention service (ANZACS-QI 46). N Z Med J. 2020;133(1524):64-81.
2) Chew DP, Scott IA, Cullen L, French JK, Briffa TG, Tideman PA, Woodruffe S, Kerr A, Branagan M, Aylward PE; NHFA/CSANZ ACS Guideline 2016 Executive Working Group:. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand: Australian Clinical Guidelines for the Management of Acute Coronary Syndromes 2016. Heart Lung Circ. 2016;25(9):895-951. doi: 10.1016/j.hlc.2016.06.789.
3) Whitehead J, Davie G, de Graaf B, Crengle S, Fearnley D, Smith M, Lawrenson R, Nixon G. Defining rural in Aotearoa New Zealand: a novel geographic classification for health purposes. N Z Med J. 2022;135(1559):24-40.
4) Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, Sundborn G, Kerr AJ. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018;131(1478):21-31.
5) Blattner K, Miller R, Lawrence-Lodge R, Nixon G, McHugh P, Pirini J. New Zealand's vocational Rural Hospital Medicine Training Programme: the first ten years. N Z Med J. 2021;134(1529):57-68.
6) Kerr A, Williams MJ, White H, Doughty R, Nunn C, Devlin G, Grey C, Lee M, Flynn C, Rhodes M, Sutherland K, Wells S, Jackson R, Stewart R. The All New Zealand Acute Coronary Syndrome Quality Improvement Programme: Implementation, Methodology and Cohorts (ANZACS-QI 9). N Z Med J. 2016;129(1439):23-36.
7) Marshall B, Aileone L. COVID-19 pandemic and rural generalism: the West Coast's rural workforce solution. N Z Med J. 2020;133(1514):90-92.
8) Ellis C, Gamble G, Devlin G, Elliott J, Hamer A, Williams M, Matsis P, Troughton R, Ranasinghe I, French J, Brieger D, Chew D, White H; New Zealand Acute Coronary Syndromes (NZACS) SNAPSHOT Audit Group. The management of acute coronary syndrome patients across New Zealand in 2012: results of a third comprehensive nationwide audit and observations of current interventional care. N Z Med J. 2013;126(1387):36-68.
9) Quan H, Li B, Couris CM, Fushimi K, Graham P, Hider P, Januel JM, Sundararajan V. Updating and validating the Charlson comorbidity index and score for risk adjustment in hospital discharge abstracts using data from 6 countries. Am J Epidemiol. 2011;173(6):676-82. doi: 10.1093/aje/kwq433.
10) R Core Team. R: A Language and Environment for Statistical Computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2019. Available from: https://www.R-project.org/.
11) Vittinghoff E, Glidden DV, Shiboski SC, McCulloch CE. Regression Methods in Biostatistics [Internet]. Boston, MA: Springer US; 2012 [cited 2022 Sep 1]. (Statistics for Biology and Health).
12) Chew DP, French J, Briffa TG, Hammett CJ, Ellis CJ, Ranasinghe I, Aliprandi-Costa BJ, Astley CM, Turnbull FM, Lefkovits J, Redfern J, Carr B, Gamble GD, Lintern KJ, Howell TE, Parker H, Tavella R, Bloomer SG, Hyun KK, Brieger DB. Acute coronary syndrome care across Australia and New Zealand: the SNAPSHOT ACS study. Med J Aust. 2013;199(3):185-91. doi: 10.5694/mja12.11854.
13) Alston L, Peterson KL, Jacobs JP, Allender S, Nichols M. Quantifying the role of modifiable risk factors in the differences in cardiovascular disease mortality rates between metropolitan and rural populations in Australia: a macrosimulation modelling study. BMJ Open. 2017;7:e018307. doi: 10.1136/bmjopen-2017-018307.
14) Curtis E, Harwood M, Riddell T, Robson B, Harris R, Mills C, Reid P. Access and society as determinants of ischaemic heart disease in indigenous populations. Heart Lung Circ. 2010 May-Jun;19(5-6):316-24. doi: 10.1016/j.hlc.2010.04.129. Epub 2010 May 4.
15) Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, Exeter DJ, Kerr AJ. Ethnic Differences in Coronary Revascularisation following an Acute Coronary Syndrome in New Zealand: A National Data-linkage Study (ANZACS-QI 12). Heart Lung Circ. 2016;25(8):820-8. doi: 10.1016/j.hlc.2016.03.004.
16) Tang EW, Wong CK, Herbison P. Community hospital versus tertiary hospital comparison in the treatment and outcome of patients with acute coronary syndrome: a New Zealand experience. N Z Med J. 2006;119(1238):U2078.
17) Grey C, Jackson R, Wells S, Wu B, Pujades-Rodriguez M, Schmidt M, Selak V, Kerr AJ. Both incidence and prevalence of ischaemic heart disease are declining in parallel: a national data-linkage study in New Zealand (ANZACS-QI 52). Eur J Prev Cardiol. 2022;29(2):321-327. doi: 10.1093/eurjpc/zwaa120.
18) Tideman P, Taylor AW, Janus E, Philpot B, Clark R, Peach E, Laatikainen T, Vartiainen E, Tirimacco R, Montgomerie A, Grant J, Versace V, Dunbar JA. A comparison of Australian rural and metropolitan cardiovascular risk and mortality: the Greater Green Triangle and North West Adelaide population surveys. BMJ Open. 2013;3(8):e003203. doi: 10.1136/bmjopen-2013-003203.
19) Bechtold D, Salvatierra GG, Bulley E, Cypro A, Daratha KB. Geographic Variation in Treatment and Outcomes Among Patients With AMI: Investigating Urban-Rural Differences Among Hospitalized Patients. J Rural Health. 2017;33(2):158-166. doi: 10.1111/jrh.12165.
20) Cai M, Liu E, Tao H, Qian Z, Lin X, Cheng Z. Does Level of Hospital Matter? A Study of Mortality of Acute Myocardial Infarction Patients in Shanxi, China. Am J Med Qual. 2018;33(2):185-192. doi: 10.1177/1062860617708608.
21) Brown A. Acute coronary syndromes in indigenous Australians: opportunities for improving outcomes across the continuum of care. Heart Lung Circ. 2010 May-Jun;19(5-6):325-36. doi: 10.1016/j.hlc.2010.02.011.
22) Roffi M, Patrono C, Collet JP, Mueller C, Valgimigli M, Andreotti F, Bax JJ, Borger MA, Brotons C, Chew DP, Gencer B, Hasenfuss G, Kjeldsen K, Lancellotti P, Landmesser U, Mehilli J, Mukherjee D, Storey RF, Windecker S; ESC Scientific Document Group. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: Task Force for the Management of Acute Coronary Syndromes in Patients Presenting without Persistent ST-Segment Elevation of the European Society of Cardiology (ESC). Eur Heart J. 2016;37(3):267-315. doi: 10.1093/eurheartj/ehv320.
23) Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, Harrison J, Riddell T, Kerr A. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014;100(10):770-4. doi: 10.1136/heartjnl-2013-304960.
24) Kerr AJ, Turaga M, Grey C, Lee M, McLachlan A, Devlin G. Initiation and maintenance of statins and aspirin after acute coronary syndromes (ANZACS-QI 11). J Prim Health Care. 2016;8(3):238-249. doi: 10.1071/HC16013.
25) Benatar J, Langdana F, Doolan-Noble F, McLachlan A. Cardiac rehabilitation in New Zealand-moving forward. N Z Med J. 2016;129(1435):68-74.
26) Kira G, Doolan-Noble F, Humphreys G, Williams G, O'Shaughnessy H, Devlin G. A national survey of cardiac rehabilitation services in New Zealand: 2015. N Z Med J. 2016;129(1435):50-8.
27) Field PE, Franklin RC, Barker RN, Ring I, Leggat PA. Cardiac rehabilitation services for people in rural and remote areas: an integrative literature review. Rural Remote Health. 2018;18(4):4738. doi: 10.22605/RRH4738.
28) Field P, Franklin RC, Barker R, Ring I, Leggat P, Canuto K. Importance of cardiac rehabilitation in rural and remote areas of Australia. Aust J Rural Health. 2022;30(2):149-163. Doi: 10.1111/ajr.
29) Thompson SC, Nedkoff L, Katzenellenbogen J, Hussain MA, Sanfilippo F. Challenges in Managing Acute Cardiovascular Diseases and Follow Up Care in Rural Areas: A Narrative Review. Int J Environ Res Public Health. 2019;16(24):5126. doi: 10.3390/ijerph16245126.12818.
30) Liao BY, Lee MAW, Dicker B, Todd VF, Stewart R, Poppe K, Kerr A. Prehospital identification of ST-segment elevation myocardial infarction and mortality (ANZACS-QI 61). Open Heart. 2022;9(1):e001868. doi: 10.1136/openhrt-2021-001868.
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Outcomes and access to angiography following non-ST-segment elevation acute coronary syndromes in patients who present to rural or urban hospitals: ANZACS-QI 72
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In Aotearoa New Zealand, patients who present with non-ST-segment elevation acute coronary syndrome (NSTEACS, which comprises non-ST-segment elevation myocardial infarction [NSTEMI] and unstable angina [UA]) will initially access one of three groups of hospitals: urban hospitals with routine access to percutaneous intervention (PCI), urban hospitals without routine access to PCI and rural hospitals (which also do not have routine access to PCI).[[1]] Australasian consensus guidelines recommend that most patients with NSTEACS, especially those at high or intermediate risk of mortality, receive “an invasive strategy of angiography with coronary revascularisation” within 72 hours.[[2]]
There are nine urban hospitals in New Zealand that have routine access to PCI. Hospitals that don’t have routine PCI capabilities typically have catchments that include smaller regional or rural areas. Compared with major urban areas, these smaller catchments include a higher proportion of Māori, who have poorer cardiovascular outcomes than NZ Europeans.[[3,4]] Rural hospitals are typically staffed by generalist doctors and nursing teams, have fewer resources and are at a distance from urban hospitals with specialists or associated services (40 minutes to 4 hours by road from urban hospitals with routine access to PCI).[[5]] Patients with NSTEACS who present to urban hospitals without routine access to PCI may be cared for by cardiology specialists or general physicians.
Stable patients who present with NSTEACS to hospitals without routine access to PCI will receive initial treatment and if clinically stable, are usually admitted to that hospital while awaiting transfer for angiography. Unstable patients or patients at rural hospitals with fewer resources may require early transfer to a larger hospital. For rural hospitals whose primary referral hospital does not have PCI capabilities, patients may undergo several transfers to receive definitive treatment.
The aim of this study was to determine if there were differences in invasive angiography performed and clinical outcomes, including mortality, associated with the category of hospital of presentation (rural hospitals or urban hospitals with or without routine access to PCI) for patients with NSTEACS.
Methods
All first admissions for patients aged 20 years or older with NSTEACS between 1 January 2014 and 31 December 2017 to a publicly funded New Zealand hospital were included in the study.
Registries
The All New Zealand Acute Coronary Syndrome Quality Improvement (ANZACS-QI) programme is a clinically led initiative. Its primary aim is to “support appropriate, evidence-based management of ACS… regardless of age, sex, ethnicity, socioeconomic status, or rural or city dwelling”.[[6]]
This study used the ANZACS-QI programme’s ACS Routine Information cohort, which incorporates the Ministry of Health’s National Minimum Dataset for Hospital Admissions (NMDS) and the National Mortality Collection, which are linked using the patient’s encrypted national health index (NHI). The NMDS includes information for all public hospital admissions (including all hospitals considered in this study) and the mortality collection contains information regarding deaths. All New Zealand residents aged 20 years or older who are admitted to hospital with a primary or secondary ICD-10 code consistent with ACS (I20.0, I21.x, I22.x) are included in this cohort.[[6]] The mortality collection contained all deaths until 31 December 2018, which was at least 1 year after the last admission to hospital.
Hospitals of presentation
Hospitals were identified using the facility code assigned by the New Zealand Ministry of Health – Manatū Hauora (Table 1) and divided into three urban-rural hospital categories:
1. Urban hospitals with routine access to PCI (urban hospitals with PCI),
2. Urban hospitals without routine access to PCI (urban hospitals without PCI) and
3. Rural hospitals.
Three hospitals did not easily fit within these categories. Tauranga and Nelson have PCI-capable angiography suites but do not have reliable after-hours access to these. They were considered urban hospitals with PCI for the purposes of this analysis, as there would be few exceptions to not being able to offer PCI for patients with NSTEACS within 3 days. Greymouth Hospital was considered a rural hospital due to its distance from and the logistical challenges associated with accessing a hospital with PCI, in addition to an increasingly rural generalist workforce.[[7]] These groupings are consistent with previous studies.[[1]]
Patients were assigned to the first hospital of presentation. To account for the movement of patients with NSTEACS between hospitals to receive PCI or other investigations or treatments, admissions were bundled into group inter-hospital transfers as part of the same episode of care.[[1,8]]
View Tables 1–3 and Figures 1–3.
Data collected
Age, sex, prioritised ethnicity (using the New Zealand Ministry of Health’s protocols),[[6]] NZ Deprivation Index 2013 (NZDep2013) deciles, admission to hospital with either MI or heart failure in the last 5 years, non-cardiac Charlson Comorbidity Index score and type of NSTEACS (NSTEMI or UA) were collected from the ACS Routine Information cohort for the patient’s first ACS admission. The Charlson Comorbidity Index is a method of predicting mortality by weighting comorbid conditions and is widely used in health research.[[9]] The non-cardiac Charlson score excludes congestive heart failure.[[1,9]]
Outcome measures
The following outcome measures were considered: 30-day and 1-year all-cause mortality; angiography performed within 30 days and 1 year; and readmission to hospital within 1 year with heart failure, major adverse cardiac event (MACE) or major bleeding. MACE was defined as: acute myocardial infarction, cardiac arrest, cardiogenic shock, ventricular arrythmia (ventricular tachycardia or fibrillation), high-grade atrioventricular block requiring intervention or emergency coronary revascularisation. To determine 2-year all-cause mortality, only patients with at least 2 years of follow-up were considered.
All definitions and ICD-10 codes are shown in Appendix 1.
Statistical analysis
Data were summarised using mean and standard deviation (SD) for continuous data and frequency and percentage for categorical data in total and by category of hospital.
Logistic regression, modelled separately for each outcome, was used to estimate odds ratios (OR) with 95% confidence intervals (95% CI) comparing urban hospitals without access to PCI and rural hospitals to urban hospitals with access to PCI (the reference group).
Unadjusted mortality comparing the hospital types was visualised using Kaplan–Meier curves. Cox proportional hazard ratios were then used to estimate hazard ratios (HR), with 95% confidence intervals, comparing hospital type. All patients were followed for at least 1 year after admission and patients were “right-censored” if they had not died by the end of the study period.
For all outcome measures, the following variables were considered as potential confounders within the models: sex, ethnicity, age, type of NSTEACS, prior heart failure, prior acute myocardial infarction, socio-economic deprivation and non-cardiac Charlson score. For the mortality- and readmission-related outcomes, the variable angiography performed within 1 year was considered a potential confounder. Additionally, readmission to hospital with MACE, major bleeding or heart failure within 1 year were considered for mortality related outcome measures.
The linearity for any continuous variable was assessed and complex associations were dealt with by categorising the variable. Age was categorised into the following groups: 20–44 years, 45–59 years, 60–69 years, 70–89 years and 90+ years. Backwards elimination was used to reduce the number of variables in the models; however, important confounders were retained regardless of significance. Likelihood ratio tests were used to assess the significance of each variable (p<0.05) in the model. Only a priori interactions (age, ethnicity and socioeconomic deprivation) were investigated.
Data manipulation, analysis and visualisation were done in the open-access R statistical programming language (version 4.1.1) using the R-Studio integrated data environment (IDE) (22.02.3 Boston, MA).[[10]]
Ethics
ANZACS-QI is part of the Auckland University-based Vascular Informatics Using Epidemiology and the Web (VIEW) study. The VIEW study was approved by the Northern Region Ethics Committee in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries. There are annual approvals by the National Multi-Region Ethics Committee since 2007 (MEC07/10/EXP).[[6]]
Funding
This study was supported by a University of Otago Early Career Clinician Start-up grant.
Results
There were 42,923 patients with a diagnosis of NSTEACS who presented to New Zealand public hospitals between 2014 and 2017. Table 2 describes the characteristics of the included patients. Most patients (62.4%) presented to urban hospitals with access to PCI, nearly a third (29.1%) to urban hospitals without PCI and 8.4% to rural hospitals. Compared to patients who presented to urban hospitals with PCI, a higher percentage of patients who presented to urban hospitals without PCI and rural hospitals were Māori (8.1%, 15.8% and 14% respectively) and lived in the most deprived quintile (24.1%, 33.9% and 28.3%). Patients were followed for a median of 3.2 years (interquartile range 1.8 to 4.8), with 40,272 (93.8%) followed for at least 2 years.
Table 3 presents the number, percentage, unadjusted and adjusted odds ratios (OR) for each outcome grouped by hospital type. Adjusted OR are shown in Figure 1. Compared to patients presenting to urban hospitals with PCI, those who present to rural hospitals had lower odds of receiving angiography within 30 days (0.76, 95% CI: 0.70 to 0.83) and 1 year (OR 0.82, 95% CI: 0.75 to 0.90), as well as increased odds of death at 2 years (OR 1.16, 95% CI: 1.05 to 1.29) but not at 30 days or 1 year. Urban hospitals without PCI similarly had reduced odds of receiving angiography at 30 days (OR 0.70, 95% CI: 0.66 to 0.73) and 1 year (OR 0.75, 95% CI: 0.71 to 0.79) but no increase in the odds of dying. There was, however, a small increase in the odds of readmission with MACE within 1 year of admission (OR 1.10, 95% CI: 1.03 to 1.16). Full model outputs are included as Appendix 2.
Figure 2 shows the unadjusted Kaplan–Meier survival curve for mortality over the 6 years of the study and demonstrates that survival for patients who presented to rural compared with urban hospitals (with or without PCI) was reduced from 1 year following admission. There was weak evidence of increased adjusted risk of dying for patients who presented to rural hospitals (hazard ratio (HR) 1.06, 95% CI: 1.00 to 1.13), as shown in Figure 3. Unadjusted HR are presented in Appendix 3. Adjusting for hospital category, Māori (HR 1.34, 95% CI: 1.27 to 1.43) and Pasifika (1.17, 95% CI: 1.07 to 1.27) had increased risk of dying compared with European/Other.
Model diagnostics
For all models, age had a non-linear association with the outcome so was modelled categorically. There were no important interactions identified. The proportional hazards assumption was violated for some variables in the Cox proportional hazards model, however, graphical inspection of the scaled Schoenfeld residuals showed that this was due to very small departures from proportional hazards being shown as “significant” due to the large sample size.[[11]] Including these as stratified variables in the model did not change model interpretation (Appendix 4).
Discussion
This nationwide study describes the outcomes for patients who presented to public hospitals in New Zealand with NSTEACS based on the type of available specialist and interventional resources of the hospital that the patient first presented to. The main findings were that patients presenting to rural hospitals and urban hospitals without access to PCI were less likely to receive angiography at both 30 days (OR 0.75 and 0.82 respectively) and 1 year (0.70 and 0.76 respectively, however, there is no difference in mortality at 30 days or 1 year. Patients that presented to rural hospitals had slightly higher odds of dying at 2 years (OR 1.16) compared to patients that presented to urban hospitals. Patients that presented to urban hospitals without access to PCI were more likely to be readmitted with a MACE within 1 year of admission (OR 1.10) compared to the other two hospital types.
Angiography performed
That patients who presented to hospitals without access to PCI (both urban and rural) were less likely to receive angiography, which is consistent with other studies for patients who presented to the same hospital groupings with ST-segment elevation myocardial infarction (STEMI).[[1]] These patients had not only reduced access to angiography during the index admission, but the time to angiography was significantly longer.[[1]] The finding is also consistent with previous Australian and New Zealand studies of all ACS events, where “smaller” or non-urban hospitals had reduced rates of angiography and PCI.[[8,12,13]]
This is especially problematic in New Zealand given the higher percentage of Māori who present to rural hospitals and urban hospitals without access to PCI. It is well established that Māori patients with ACS have been shown to have reduced access to angiography and revascularisation and subsequently have poorer outcomes. The geographic inequities in access to optimal care that we have identified compound these inequities resulting from historical and ongoing colonisation and racism.[[14,15]]
Mortality
Similar to a recent study that found no difference in mortality for patients with STEMI that present to New Zealand rural and urban hospitals without PCI,[[1]] reassuringly there were few differences found in the mortality between the three groups of hospitals included in this study. Historically, differences in mortality have been large, with up to a 300% increase in the odds of dying for patients that presented to an urban hospital without PCI compared with a hospital that had within the same district.[[16]] Since this time, reflective of increased risk reduction measures,[[6,17]] as well as improved access to interventional practice and development of regional networks, the incidence, prevalence, hospitalisation and mortality rates from ischaemic heart disease in New Zealand have decreased. Although, as it is with our data, for Māori and Pasifika these remain disproportionately high.[[4,17]] International rural mortality rates following acute coronary syndrome vary according to the definition of “rural” that is used.[[13,18–20]] Mortality rates for Indigenous peoples from other countries are consistently higher than non-Indigenous peoples.[[21]]
However, this study did demonstrate a small increase in 2-year mortality following admission for patients who present to rural hospitals compared to both types of urban hospitals. We are unaware of any recent New Zealand-based studies that have demonstrated a mortality difference between urban hospitals with PCI and hospitals without PCI, and none that differentiate rural from urban hospitals.
The reason for the small difference in delayed mortality demonstrated for rural hospitals in this study is not known but does not appear to be related to reduced access to angiography. Patients that present to urban hospitals without PCI have similar odds of angiography being performed as rural hospitals but do not demonstrate the same increase in 2-year mortality. Possible explanations include reduced access to primary care, secondary prevention and cardiac rehabilitation.
Secondary prevention therapies are considered critically important and are strongly recommended in all international guidelines, with emphasis on cardiac rehabilitation and the prescription of evidence-based therapies: anti-platelet therapy, statins, beta-blockers and renin-angiotensin antagonists.[[2,22]]
In New Zealand, there is evidence of reduced prescribing of these evidence-based therapies for NSTEACS in patients who are Māori or Pasifika, female, present to hospitals outside main centres[[1]] and live in the most deprived areas.[[23,24]] Our results showed that compared with major urban hospitals, a higher percentage of patients that present to rural hospitals were Māori and live in more deprived areas. Therefore, a reduction in the prescription and maintenance of appropriate secondary prevention medicine may account for some of the increased risk of 2-year mortality.
Referral to cardiac rehabilitation services has been shown to reduce future cardiac events, and death, following an admission with IHD.[[12]] Within New Zealand, patient referral and attendance of cardiac rehabilitation services are well below international standards in many regions, but there is yet to be analysis based on the geographic location of the patient.[[25,26]] There is clear evidence internationally that access to all phases of cardiac rehabilitation is reduced for patients that live in rural and remote areas.[[27–29]] The reliance on group sessions in central locations reported in the New Zealand literature may mean that rural residents find it difficult to access cardiac rehabilitation sessions, representing a potential gap in the system and missed opportunities for evidence-based care.[[26]]
Strengths and limitations
This study is the first to differentiate patients with NSTEACS that present to New Zealand rural hospitals, as opposed to any hospital without PCI routinely available. A key strength of this study is the ability to identify all patients with NSTEACS diagnosis codes admitted to New Zealand public hospitals and follow these patients using linked national mortality and hospitalisation datasets to ascertain investigations and outcomes that occurred after the admission. This linkage is not possible in many countries on a national scale.[[17]]
The major limitation is that the cohort of patients that present to rural hospitals may not represent those that live in rural places. Approximately 19% of the New Zealand population live in rural areas,[[3]] but only 8% of the cohort that was admitted with NSTEACS presented to a rural hospital. This finding may be attributed to rural patients living closer to an urban hospital, patient preference or ambulance service destination policies.[[1,30]] A study using the geographic location of the patient is planned to understand the effect of rurality on the outcomes of NSTEACS as well as explore differences between rural Māori and non-Māori peoples.
A further limitation is that apart from angiography, the investigations and treatments that occurred during or after the NSTEACS admission were not considered. This includes revascularisation procedures, and these will be examined in more detail using the ANZACS-QI CathPCI cohort.[[6]] Additionally, inconsistency in the clinical coding, particularly in rural hospitals where anecdotally this task is frequently performed by clinicians or clerical staff without formal training, may have influenced the results. It was not possible to differentiate between type 1 and type 2 acute myocardial infarction (AMI) from the available data.
Patients who received investigations in private facilities, underwent CT coronary angiography instead of invasive angiography, died prior to reaching hospital or who received treatment or died overseas were unable to be accounted for. This may differ between urban and rural areas.
Implications
The ability to track mortality and access to interventions over time is an important function in registries such as ANZACS-QI, especially for rural populations. In New Zealand, health outcome data are routinely reported by regions, usually encompassing rural and urban areas. This can miss urban-rural variation, which can be larger than the variation between regions.[[3]]
The large improvement seen in the care for patients with NSTEACS is largely attributable to the success of ANZACS-QI and the implementation and monitoring of targeted policy and procedures by PCI centres to ensure that the wider population they serve has equitable access to services.[[6]] While mortality is similar across the three groups of hospitals, this study demonstrates that equitable access to angiography is still not being achieved for patients initially admitted to rural and urban hospitals without PCI. Improving complex inter-hospital transfer policies should be a priority as Te Whatu Ora and Te Aka Whai Ora become more established.
The factors that contribute to the higher rate of delayed mortality for those who present to rural hospitals and for Māori should be identified and eliminated. This may include improving access to and ongoing use of proven secondary prevention therapies.
Conclusion
This study has demonstrated that patients presenting to rural or urban hospitals without PCI are less likely to receive angiography. Reassuringly there were no increased odds of 30-day or 1-year mortality, but patients who initially present to rural hospitals do have a small increase in the odds of dying that becomes apparent at 2-years post admission. There is a higher risk of mortality for Māori and Pasifika. This may reflect poorer access to evidence-based cardiac rehabilitation and secondary prevention.
View Appendices.
Summary
Abstract
Aim
This study’s aim was to identify differences in invasive angiography performed and health outcomes for patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) presenting to either i) a rural hospital, or an urban hospital ii) with or iii) without routine access to percutaneous intervention (PCI) in New Zealand.
Method
Patients with NSTEACS between 1 January 2014 and 31 December 2017 were included. Logistic regression was used to model each of the outcome measures: angiography performed within 1 year; 30-day, 1-year and 2-year all-cause mortality; and readmission within 1 year of presentation with either heart failure, a major adverse cardiac event or major bleeding.
Results
There were 42,923 patients included. Compared to urban hospitals with access to PCI, the odds of a patient receiving an angiogram were reduced for rural and urban hospitals without routine access to PCI (odds ratio [OR] 0.82 and 0.75) respectively. There was a small increase in the odds of dying at 2 years (OR 1.16), but not 30 days or 1 year for patients presenting to a rural hospital.
Conclusion
Patients who present to hospitals without PCI are less likely to receive angiography. Reassuringly there is no difference in mortality, except at 2 years, for patients that present to rural hospitals.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Lee S, Miller R, Lee M, White H, Kerr A. Outcomes after ST-elevation myocardial infarction presentation to hospitals with or without a routine primary percutaneous coronary intervention service (ANZACS-QI 46). N Z Med J. 2020;133(1524):64-81.
2) Chew DP, Scott IA, Cullen L, French JK, Briffa TG, Tideman PA, Woodruffe S, Kerr A, Branagan M, Aylward PE; NHFA/CSANZ ACS Guideline 2016 Executive Working Group:. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand: Australian Clinical Guidelines for the Management of Acute Coronary Syndromes 2016. Heart Lung Circ. 2016;25(9):895-951. doi: 10.1016/j.hlc.2016.06.789.
3) Whitehead J, Davie G, de Graaf B, Crengle S, Fearnley D, Smith M, Lawrenson R, Nixon G. Defining rural in Aotearoa New Zealand: a novel geographic classification for health purposes. N Z Med J. 2022;135(1559):24-40.
4) Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, Sundborn G, Kerr AJ. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018;131(1478):21-31.
5) Blattner K, Miller R, Lawrence-Lodge R, Nixon G, McHugh P, Pirini J. New Zealand's vocational Rural Hospital Medicine Training Programme: the first ten years. N Z Med J. 2021;134(1529):57-68.
6) Kerr A, Williams MJ, White H, Doughty R, Nunn C, Devlin G, Grey C, Lee M, Flynn C, Rhodes M, Sutherland K, Wells S, Jackson R, Stewart R. The All New Zealand Acute Coronary Syndrome Quality Improvement Programme: Implementation, Methodology and Cohorts (ANZACS-QI 9). N Z Med J. 2016;129(1439):23-36.
7) Marshall B, Aileone L. COVID-19 pandemic and rural generalism: the West Coast's rural workforce solution. N Z Med J. 2020;133(1514):90-92.
8) Ellis C, Gamble G, Devlin G, Elliott J, Hamer A, Williams M, Matsis P, Troughton R, Ranasinghe I, French J, Brieger D, Chew D, White H; New Zealand Acute Coronary Syndromes (NZACS) SNAPSHOT Audit Group. The management of acute coronary syndrome patients across New Zealand in 2012: results of a third comprehensive nationwide audit and observations of current interventional care. N Z Med J. 2013;126(1387):36-68.
9) Quan H, Li B, Couris CM, Fushimi K, Graham P, Hider P, Januel JM, Sundararajan V. Updating and validating the Charlson comorbidity index and score for risk adjustment in hospital discharge abstracts using data from 6 countries. Am J Epidemiol. 2011;173(6):676-82. doi: 10.1093/aje/kwq433.
10) R Core Team. R: A Language and Environment for Statistical Computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2019. Available from: https://www.R-project.org/.
11) Vittinghoff E, Glidden DV, Shiboski SC, McCulloch CE. Regression Methods in Biostatistics [Internet]. Boston, MA: Springer US; 2012 [cited 2022 Sep 1]. (Statistics for Biology and Health).
12) Chew DP, French J, Briffa TG, Hammett CJ, Ellis CJ, Ranasinghe I, Aliprandi-Costa BJ, Astley CM, Turnbull FM, Lefkovits J, Redfern J, Carr B, Gamble GD, Lintern KJ, Howell TE, Parker H, Tavella R, Bloomer SG, Hyun KK, Brieger DB. Acute coronary syndrome care across Australia and New Zealand: the SNAPSHOT ACS study. Med J Aust. 2013;199(3):185-91. doi: 10.5694/mja12.11854.
13) Alston L, Peterson KL, Jacobs JP, Allender S, Nichols M. Quantifying the role of modifiable risk factors in the differences in cardiovascular disease mortality rates between metropolitan and rural populations in Australia: a macrosimulation modelling study. BMJ Open. 2017;7:e018307. doi: 10.1136/bmjopen-2017-018307.
14) Curtis E, Harwood M, Riddell T, Robson B, Harris R, Mills C, Reid P. Access and society as determinants of ischaemic heart disease in indigenous populations. Heart Lung Circ. 2010 May-Jun;19(5-6):316-24. doi: 10.1016/j.hlc.2010.04.129. Epub 2010 May 4.
15) Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, Exeter DJ, Kerr AJ. Ethnic Differences in Coronary Revascularisation following an Acute Coronary Syndrome in New Zealand: A National Data-linkage Study (ANZACS-QI 12). Heart Lung Circ. 2016;25(8):820-8. doi: 10.1016/j.hlc.2016.03.004.
16) Tang EW, Wong CK, Herbison P. Community hospital versus tertiary hospital comparison in the treatment and outcome of patients with acute coronary syndrome: a New Zealand experience. N Z Med J. 2006;119(1238):U2078.
17) Grey C, Jackson R, Wells S, Wu B, Pujades-Rodriguez M, Schmidt M, Selak V, Kerr AJ. Both incidence and prevalence of ischaemic heart disease are declining in parallel: a national data-linkage study in New Zealand (ANZACS-QI 52). Eur J Prev Cardiol. 2022;29(2):321-327. doi: 10.1093/eurjpc/zwaa120.
18) Tideman P, Taylor AW, Janus E, Philpot B, Clark R, Peach E, Laatikainen T, Vartiainen E, Tirimacco R, Montgomerie A, Grant J, Versace V, Dunbar JA. A comparison of Australian rural and metropolitan cardiovascular risk and mortality: the Greater Green Triangle and North West Adelaide population surveys. BMJ Open. 2013;3(8):e003203. doi: 10.1136/bmjopen-2013-003203.
19) Bechtold D, Salvatierra GG, Bulley E, Cypro A, Daratha KB. Geographic Variation in Treatment and Outcomes Among Patients With AMI: Investigating Urban-Rural Differences Among Hospitalized Patients. J Rural Health. 2017;33(2):158-166. doi: 10.1111/jrh.12165.
20) Cai M, Liu E, Tao H, Qian Z, Lin X, Cheng Z. Does Level of Hospital Matter? A Study of Mortality of Acute Myocardial Infarction Patients in Shanxi, China. Am J Med Qual. 2018;33(2):185-192. doi: 10.1177/1062860617708608.
21) Brown A. Acute coronary syndromes in indigenous Australians: opportunities for improving outcomes across the continuum of care. Heart Lung Circ. 2010 May-Jun;19(5-6):325-36. doi: 10.1016/j.hlc.2010.02.011.
22) Roffi M, Patrono C, Collet JP, Mueller C, Valgimigli M, Andreotti F, Bax JJ, Borger MA, Brotons C, Chew DP, Gencer B, Hasenfuss G, Kjeldsen K, Lancellotti P, Landmesser U, Mehilli J, Mukherjee D, Storey RF, Windecker S; ESC Scientific Document Group. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: Task Force for the Management of Acute Coronary Syndromes in Patients Presenting without Persistent ST-Segment Elevation of the European Society of Cardiology (ESC). Eur Heart J. 2016;37(3):267-315. doi: 10.1093/eurheartj/ehv320.
23) Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, Harrison J, Riddell T, Kerr A. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014;100(10):770-4. doi: 10.1136/heartjnl-2013-304960.
24) Kerr AJ, Turaga M, Grey C, Lee M, McLachlan A, Devlin G. Initiation and maintenance of statins and aspirin after acute coronary syndromes (ANZACS-QI 11). J Prim Health Care. 2016;8(3):238-249. doi: 10.1071/HC16013.
25) Benatar J, Langdana F, Doolan-Noble F, McLachlan A. Cardiac rehabilitation in New Zealand-moving forward. N Z Med J. 2016;129(1435):68-74.
26) Kira G, Doolan-Noble F, Humphreys G, Williams G, O'Shaughnessy H, Devlin G. A national survey of cardiac rehabilitation services in New Zealand: 2015. N Z Med J. 2016;129(1435):50-8.
27) Field PE, Franklin RC, Barker RN, Ring I, Leggat PA. Cardiac rehabilitation services for people in rural and remote areas: an integrative literature review. Rural Remote Health. 2018;18(4):4738. doi: 10.22605/RRH4738.
28) Field P, Franklin RC, Barker R, Ring I, Leggat P, Canuto K. Importance of cardiac rehabilitation in rural and remote areas of Australia. Aust J Rural Health. 2022;30(2):149-163. Doi: 10.1111/ajr.
29) Thompson SC, Nedkoff L, Katzenellenbogen J, Hussain MA, Sanfilippo F. Challenges in Managing Acute Cardiovascular Diseases and Follow Up Care in Rural Areas: A Narrative Review. Int J Environ Res Public Health. 2019;16(24):5126. doi: 10.3390/ijerph16245126.12818.
30) Liao BY, Lee MAW, Dicker B, Todd VF, Stewart R, Poppe K, Kerr A. Prehospital identification of ST-segment elevation myocardial infarction and mortality (ANZACS-QI 61). Open Heart. 2022;9(1):e001868. doi: 10.1136/openhrt-2021-001868.
Contact diana@nzma.org.nz
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Outcomes and access to angiography following non-ST-segment elevation acute coronary syndromes in patients who present to rural or urban hospitals: ANZACS-QI 72
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In Aotearoa New Zealand, patients who present with non-ST-segment elevation acute coronary syndrome (NSTEACS, which comprises non-ST-segment elevation myocardial infarction [NSTEMI] and unstable angina [UA]) will initially access one of three groups of hospitals: urban hospitals with routine access to percutaneous intervention (PCI), urban hospitals without routine access to PCI and rural hospitals (which also do not have routine access to PCI).[[1]] Australasian consensus guidelines recommend that most patients with NSTEACS, especially those at high or intermediate risk of mortality, receive “an invasive strategy of angiography with coronary revascularisation” within 72 hours.[[2]]
There are nine urban hospitals in New Zealand that have routine access to PCI. Hospitals that don’t have routine PCI capabilities typically have catchments that include smaller regional or rural areas. Compared with major urban areas, these smaller catchments include a higher proportion of Māori, who have poorer cardiovascular outcomes than NZ Europeans.[[3,4]] Rural hospitals are typically staffed by generalist doctors and nursing teams, have fewer resources and are at a distance from urban hospitals with specialists or associated services (40 minutes to 4 hours by road from urban hospitals with routine access to PCI).[[5]] Patients with NSTEACS who present to urban hospitals without routine access to PCI may be cared for by cardiology specialists or general physicians.
Stable patients who present with NSTEACS to hospitals without routine access to PCI will receive initial treatment and if clinically stable, are usually admitted to that hospital while awaiting transfer for angiography. Unstable patients or patients at rural hospitals with fewer resources may require early transfer to a larger hospital. For rural hospitals whose primary referral hospital does not have PCI capabilities, patients may undergo several transfers to receive definitive treatment.
The aim of this study was to determine if there were differences in invasive angiography performed and clinical outcomes, including mortality, associated with the category of hospital of presentation (rural hospitals or urban hospitals with or without routine access to PCI) for patients with NSTEACS.
Methods
All first admissions for patients aged 20 years or older with NSTEACS between 1 January 2014 and 31 December 2017 to a publicly funded New Zealand hospital were included in the study.
Registries
The All New Zealand Acute Coronary Syndrome Quality Improvement (ANZACS-QI) programme is a clinically led initiative. Its primary aim is to “support appropriate, evidence-based management of ACS… regardless of age, sex, ethnicity, socioeconomic status, or rural or city dwelling”.[[6]]
This study used the ANZACS-QI programme’s ACS Routine Information cohort, which incorporates the Ministry of Health’s National Minimum Dataset for Hospital Admissions (NMDS) and the National Mortality Collection, which are linked using the patient’s encrypted national health index (NHI). The NMDS includes information for all public hospital admissions (including all hospitals considered in this study) and the mortality collection contains information regarding deaths. All New Zealand residents aged 20 years or older who are admitted to hospital with a primary or secondary ICD-10 code consistent with ACS (I20.0, I21.x, I22.x) are included in this cohort.[[6]] The mortality collection contained all deaths until 31 December 2018, which was at least 1 year after the last admission to hospital.
Hospitals of presentation
Hospitals were identified using the facility code assigned by the New Zealand Ministry of Health – Manatū Hauora (Table 1) and divided into three urban-rural hospital categories:
1. Urban hospitals with routine access to PCI (urban hospitals with PCI),
2. Urban hospitals without routine access to PCI (urban hospitals without PCI) and
3. Rural hospitals.
Three hospitals did not easily fit within these categories. Tauranga and Nelson have PCI-capable angiography suites but do not have reliable after-hours access to these. They were considered urban hospitals with PCI for the purposes of this analysis, as there would be few exceptions to not being able to offer PCI for patients with NSTEACS within 3 days. Greymouth Hospital was considered a rural hospital due to its distance from and the logistical challenges associated with accessing a hospital with PCI, in addition to an increasingly rural generalist workforce.[[7]] These groupings are consistent with previous studies.[[1]]
Patients were assigned to the first hospital of presentation. To account for the movement of patients with NSTEACS between hospitals to receive PCI or other investigations or treatments, admissions were bundled into group inter-hospital transfers as part of the same episode of care.[[1,8]]
View Tables 1–3 and Figures 1–3.
Data collected
Age, sex, prioritised ethnicity (using the New Zealand Ministry of Health’s protocols),[[6]] NZ Deprivation Index 2013 (NZDep2013) deciles, admission to hospital with either MI or heart failure in the last 5 years, non-cardiac Charlson Comorbidity Index score and type of NSTEACS (NSTEMI or UA) were collected from the ACS Routine Information cohort for the patient’s first ACS admission. The Charlson Comorbidity Index is a method of predicting mortality by weighting comorbid conditions and is widely used in health research.[[9]] The non-cardiac Charlson score excludes congestive heart failure.[[1,9]]
Outcome measures
The following outcome measures were considered: 30-day and 1-year all-cause mortality; angiography performed within 30 days and 1 year; and readmission to hospital within 1 year with heart failure, major adverse cardiac event (MACE) or major bleeding. MACE was defined as: acute myocardial infarction, cardiac arrest, cardiogenic shock, ventricular arrythmia (ventricular tachycardia or fibrillation), high-grade atrioventricular block requiring intervention or emergency coronary revascularisation. To determine 2-year all-cause mortality, only patients with at least 2 years of follow-up were considered.
All definitions and ICD-10 codes are shown in Appendix 1.
Statistical analysis
Data were summarised using mean and standard deviation (SD) for continuous data and frequency and percentage for categorical data in total and by category of hospital.
Logistic regression, modelled separately for each outcome, was used to estimate odds ratios (OR) with 95% confidence intervals (95% CI) comparing urban hospitals without access to PCI and rural hospitals to urban hospitals with access to PCI (the reference group).
Unadjusted mortality comparing the hospital types was visualised using Kaplan–Meier curves. Cox proportional hazard ratios were then used to estimate hazard ratios (HR), with 95% confidence intervals, comparing hospital type. All patients were followed for at least 1 year after admission and patients were “right-censored” if they had not died by the end of the study period.
For all outcome measures, the following variables were considered as potential confounders within the models: sex, ethnicity, age, type of NSTEACS, prior heart failure, prior acute myocardial infarction, socio-economic deprivation and non-cardiac Charlson score. For the mortality- and readmission-related outcomes, the variable angiography performed within 1 year was considered a potential confounder. Additionally, readmission to hospital with MACE, major bleeding or heart failure within 1 year were considered for mortality related outcome measures.
The linearity for any continuous variable was assessed and complex associations were dealt with by categorising the variable. Age was categorised into the following groups: 20–44 years, 45–59 years, 60–69 years, 70–89 years and 90+ years. Backwards elimination was used to reduce the number of variables in the models; however, important confounders were retained regardless of significance. Likelihood ratio tests were used to assess the significance of each variable (p<0.05) in the model. Only a priori interactions (age, ethnicity and socioeconomic deprivation) were investigated.
Data manipulation, analysis and visualisation were done in the open-access R statistical programming language (version 4.1.1) using the R-Studio integrated data environment (IDE) (22.02.3 Boston, MA).[[10]]
Ethics
ANZACS-QI is part of the Auckland University-based Vascular Informatics Using Epidemiology and the Web (VIEW) study. The VIEW study was approved by the Northern Region Ethics Committee in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries. There are annual approvals by the National Multi-Region Ethics Committee since 2007 (MEC07/10/EXP).[[6]]
Funding
This study was supported by a University of Otago Early Career Clinician Start-up grant.
Results
There were 42,923 patients with a diagnosis of NSTEACS who presented to New Zealand public hospitals between 2014 and 2017. Table 2 describes the characteristics of the included patients. Most patients (62.4%) presented to urban hospitals with access to PCI, nearly a third (29.1%) to urban hospitals without PCI and 8.4% to rural hospitals. Compared to patients who presented to urban hospitals with PCI, a higher percentage of patients who presented to urban hospitals without PCI and rural hospitals were Māori (8.1%, 15.8% and 14% respectively) and lived in the most deprived quintile (24.1%, 33.9% and 28.3%). Patients were followed for a median of 3.2 years (interquartile range 1.8 to 4.8), with 40,272 (93.8%) followed for at least 2 years.
Table 3 presents the number, percentage, unadjusted and adjusted odds ratios (OR) for each outcome grouped by hospital type. Adjusted OR are shown in Figure 1. Compared to patients presenting to urban hospitals with PCI, those who present to rural hospitals had lower odds of receiving angiography within 30 days (0.76, 95% CI: 0.70 to 0.83) and 1 year (OR 0.82, 95% CI: 0.75 to 0.90), as well as increased odds of death at 2 years (OR 1.16, 95% CI: 1.05 to 1.29) but not at 30 days or 1 year. Urban hospitals without PCI similarly had reduced odds of receiving angiography at 30 days (OR 0.70, 95% CI: 0.66 to 0.73) and 1 year (OR 0.75, 95% CI: 0.71 to 0.79) but no increase in the odds of dying. There was, however, a small increase in the odds of readmission with MACE within 1 year of admission (OR 1.10, 95% CI: 1.03 to 1.16). Full model outputs are included as Appendix 2.
Figure 2 shows the unadjusted Kaplan–Meier survival curve for mortality over the 6 years of the study and demonstrates that survival for patients who presented to rural compared with urban hospitals (with or without PCI) was reduced from 1 year following admission. There was weak evidence of increased adjusted risk of dying for patients who presented to rural hospitals (hazard ratio (HR) 1.06, 95% CI: 1.00 to 1.13), as shown in Figure 3. Unadjusted HR are presented in Appendix 3. Adjusting for hospital category, Māori (HR 1.34, 95% CI: 1.27 to 1.43) and Pasifika (1.17, 95% CI: 1.07 to 1.27) had increased risk of dying compared with European/Other.
Model diagnostics
For all models, age had a non-linear association with the outcome so was modelled categorically. There were no important interactions identified. The proportional hazards assumption was violated for some variables in the Cox proportional hazards model, however, graphical inspection of the scaled Schoenfeld residuals showed that this was due to very small departures from proportional hazards being shown as “significant” due to the large sample size.[[11]] Including these as stratified variables in the model did not change model interpretation (Appendix 4).
Discussion
This nationwide study describes the outcomes for patients who presented to public hospitals in New Zealand with NSTEACS based on the type of available specialist and interventional resources of the hospital that the patient first presented to. The main findings were that patients presenting to rural hospitals and urban hospitals without access to PCI were less likely to receive angiography at both 30 days (OR 0.75 and 0.82 respectively) and 1 year (0.70 and 0.76 respectively, however, there is no difference in mortality at 30 days or 1 year. Patients that presented to rural hospitals had slightly higher odds of dying at 2 years (OR 1.16) compared to patients that presented to urban hospitals. Patients that presented to urban hospitals without access to PCI were more likely to be readmitted with a MACE within 1 year of admission (OR 1.10) compared to the other two hospital types.
Angiography performed
That patients who presented to hospitals without access to PCI (both urban and rural) were less likely to receive angiography, which is consistent with other studies for patients who presented to the same hospital groupings with ST-segment elevation myocardial infarction (STEMI).[[1]] These patients had not only reduced access to angiography during the index admission, but the time to angiography was significantly longer.[[1]] The finding is also consistent with previous Australian and New Zealand studies of all ACS events, where “smaller” or non-urban hospitals had reduced rates of angiography and PCI.[[8,12,13]]
This is especially problematic in New Zealand given the higher percentage of Māori who present to rural hospitals and urban hospitals without access to PCI. It is well established that Māori patients with ACS have been shown to have reduced access to angiography and revascularisation and subsequently have poorer outcomes. The geographic inequities in access to optimal care that we have identified compound these inequities resulting from historical and ongoing colonisation and racism.[[14,15]]
Mortality
Similar to a recent study that found no difference in mortality for patients with STEMI that present to New Zealand rural and urban hospitals without PCI,[[1]] reassuringly there were few differences found in the mortality between the three groups of hospitals included in this study. Historically, differences in mortality have been large, with up to a 300% increase in the odds of dying for patients that presented to an urban hospital without PCI compared with a hospital that had within the same district.[[16]] Since this time, reflective of increased risk reduction measures,[[6,17]] as well as improved access to interventional practice and development of regional networks, the incidence, prevalence, hospitalisation and mortality rates from ischaemic heart disease in New Zealand have decreased. Although, as it is with our data, for Māori and Pasifika these remain disproportionately high.[[4,17]] International rural mortality rates following acute coronary syndrome vary according to the definition of “rural” that is used.[[13,18–20]] Mortality rates for Indigenous peoples from other countries are consistently higher than non-Indigenous peoples.[[21]]
However, this study did demonstrate a small increase in 2-year mortality following admission for patients who present to rural hospitals compared to both types of urban hospitals. We are unaware of any recent New Zealand-based studies that have demonstrated a mortality difference between urban hospitals with PCI and hospitals without PCI, and none that differentiate rural from urban hospitals.
The reason for the small difference in delayed mortality demonstrated for rural hospitals in this study is not known but does not appear to be related to reduced access to angiography. Patients that present to urban hospitals without PCI have similar odds of angiography being performed as rural hospitals but do not demonstrate the same increase in 2-year mortality. Possible explanations include reduced access to primary care, secondary prevention and cardiac rehabilitation.
Secondary prevention therapies are considered critically important and are strongly recommended in all international guidelines, with emphasis on cardiac rehabilitation and the prescription of evidence-based therapies: anti-platelet therapy, statins, beta-blockers and renin-angiotensin antagonists.[[2,22]]
In New Zealand, there is evidence of reduced prescribing of these evidence-based therapies for NSTEACS in patients who are Māori or Pasifika, female, present to hospitals outside main centres[[1]] and live in the most deprived areas.[[23,24]] Our results showed that compared with major urban hospitals, a higher percentage of patients that present to rural hospitals were Māori and live in more deprived areas. Therefore, a reduction in the prescription and maintenance of appropriate secondary prevention medicine may account for some of the increased risk of 2-year mortality.
Referral to cardiac rehabilitation services has been shown to reduce future cardiac events, and death, following an admission with IHD.[[12]] Within New Zealand, patient referral and attendance of cardiac rehabilitation services are well below international standards in many regions, but there is yet to be analysis based on the geographic location of the patient.[[25,26]] There is clear evidence internationally that access to all phases of cardiac rehabilitation is reduced for patients that live in rural and remote areas.[[27–29]] The reliance on group sessions in central locations reported in the New Zealand literature may mean that rural residents find it difficult to access cardiac rehabilitation sessions, representing a potential gap in the system and missed opportunities for evidence-based care.[[26]]
Strengths and limitations
This study is the first to differentiate patients with NSTEACS that present to New Zealand rural hospitals, as opposed to any hospital without PCI routinely available. A key strength of this study is the ability to identify all patients with NSTEACS diagnosis codes admitted to New Zealand public hospitals and follow these patients using linked national mortality and hospitalisation datasets to ascertain investigations and outcomes that occurred after the admission. This linkage is not possible in many countries on a national scale.[[17]]
The major limitation is that the cohort of patients that present to rural hospitals may not represent those that live in rural places. Approximately 19% of the New Zealand population live in rural areas,[[3]] but only 8% of the cohort that was admitted with NSTEACS presented to a rural hospital. This finding may be attributed to rural patients living closer to an urban hospital, patient preference or ambulance service destination policies.[[1,30]] A study using the geographic location of the patient is planned to understand the effect of rurality on the outcomes of NSTEACS as well as explore differences between rural Māori and non-Māori peoples.
A further limitation is that apart from angiography, the investigations and treatments that occurred during or after the NSTEACS admission were not considered. This includes revascularisation procedures, and these will be examined in more detail using the ANZACS-QI CathPCI cohort.[[6]] Additionally, inconsistency in the clinical coding, particularly in rural hospitals where anecdotally this task is frequently performed by clinicians or clerical staff without formal training, may have influenced the results. It was not possible to differentiate between type 1 and type 2 acute myocardial infarction (AMI) from the available data.
Patients who received investigations in private facilities, underwent CT coronary angiography instead of invasive angiography, died prior to reaching hospital or who received treatment or died overseas were unable to be accounted for. This may differ between urban and rural areas.
Implications
The ability to track mortality and access to interventions over time is an important function in registries such as ANZACS-QI, especially for rural populations. In New Zealand, health outcome data are routinely reported by regions, usually encompassing rural and urban areas. This can miss urban-rural variation, which can be larger than the variation between regions.[[3]]
The large improvement seen in the care for patients with NSTEACS is largely attributable to the success of ANZACS-QI and the implementation and monitoring of targeted policy and procedures by PCI centres to ensure that the wider population they serve has equitable access to services.[[6]] While mortality is similar across the three groups of hospitals, this study demonstrates that equitable access to angiography is still not being achieved for patients initially admitted to rural and urban hospitals without PCI. Improving complex inter-hospital transfer policies should be a priority as Te Whatu Ora and Te Aka Whai Ora become more established.
The factors that contribute to the higher rate of delayed mortality for those who present to rural hospitals and for Māori should be identified and eliminated. This may include improving access to and ongoing use of proven secondary prevention therapies.
Conclusion
This study has demonstrated that patients presenting to rural or urban hospitals without PCI are less likely to receive angiography. Reassuringly there were no increased odds of 30-day or 1-year mortality, but patients who initially present to rural hospitals do have a small increase in the odds of dying that becomes apparent at 2-years post admission. There is a higher risk of mortality for Māori and Pasifika. This may reflect poorer access to evidence-based cardiac rehabilitation and secondary prevention.
View Appendices.
Summary
Abstract
Aim
This study’s aim was to identify differences in invasive angiography performed and health outcomes for patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) presenting to either i) a rural hospital, or an urban hospital ii) with or iii) without routine access to percutaneous intervention (PCI) in New Zealand.
Method
Patients with NSTEACS between 1 January 2014 and 31 December 2017 were included. Logistic regression was used to model each of the outcome measures: angiography performed within 1 year; 30-day, 1-year and 2-year all-cause mortality; and readmission within 1 year of presentation with either heart failure, a major adverse cardiac event or major bleeding.
Results
There were 42,923 patients included. Compared to urban hospitals with access to PCI, the odds of a patient receiving an angiogram were reduced for rural and urban hospitals without routine access to PCI (odds ratio [OR] 0.82 and 0.75) respectively. There was a small increase in the odds of dying at 2 years (OR 1.16), but not 30 days or 1 year for patients presenting to a rural hospital.
Conclusion
Patients who present to hospitals without PCI are less likely to receive angiography. Reassuringly there is no difference in mortality, except at 2 years, for patients that present to rural hospitals.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
1) Lee S, Miller R, Lee M, White H, Kerr A. Outcomes after ST-elevation myocardial infarction presentation to hospitals with or without a routine primary percutaneous coronary intervention service (ANZACS-QI 46). N Z Med J. 2020;133(1524):64-81.
2) Chew DP, Scott IA, Cullen L, French JK, Briffa TG, Tideman PA, Woodruffe S, Kerr A, Branagan M, Aylward PE; NHFA/CSANZ ACS Guideline 2016 Executive Working Group:. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand: Australian Clinical Guidelines for the Management of Acute Coronary Syndromes 2016. Heart Lung Circ. 2016;25(9):895-951. doi: 10.1016/j.hlc.2016.06.789.
3) Whitehead J, Davie G, de Graaf B, Crengle S, Fearnley D, Smith M, Lawrenson R, Nixon G. Defining rural in Aotearoa New Zealand: a novel geographic classification for health purposes. N Z Med J. 2022;135(1559):24-40.
4) Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, Sundborn G, Kerr AJ. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018;131(1478):21-31.
5) Blattner K, Miller R, Lawrence-Lodge R, Nixon G, McHugh P, Pirini J. New Zealand's vocational Rural Hospital Medicine Training Programme: the first ten years. N Z Med J. 2021;134(1529):57-68.
6) Kerr A, Williams MJ, White H, Doughty R, Nunn C, Devlin G, Grey C, Lee M, Flynn C, Rhodes M, Sutherland K, Wells S, Jackson R, Stewart R. The All New Zealand Acute Coronary Syndrome Quality Improvement Programme: Implementation, Methodology and Cohorts (ANZACS-QI 9). N Z Med J. 2016;129(1439):23-36.
7) Marshall B, Aileone L. COVID-19 pandemic and rural generalism: the West Coast's rural workforce solution. N Z Med J. 2020;133(1514):90-92.
8) Ellis C, Gamble G, Devlin G, Elliott J, Hamer A, Williams M, Matsis P, Troughton R, Ranasinghe I, French J, Brieger D, Chew D, White H; New Zealand Acute Coronary Syndromes (NZACS) SNAPSHOT Audit Group. The management of acute coronary syndrome patients across New Zealand in 2012: results of a third comprehensive nationwide audit and observations of current interventional care. N Z Med J. 2013;126(1387):36-68.
9) Quan H, Li B, Couris CM, Fushimi K, Graham P, Hider P, Januel JM, Sundararajan V. Updating and validating the Charlson comorbidity index and score for risk adjustment in hospital discharge abstracts using data from 6 countries. Am J Epidemiol. 2011;173(6):676-82. doi: 10.1093/aje/kwq433.
10) R Core Team. R: A Language and Environment for Statistical Computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2019. Available from: https://www.R-project.org/.
11) Vittinghoff E, Glidden DV, Shiboski SC, McCulloch CE. Regression Methods in Biostatistics [Internet]. Boston, MA: Springer US; 2012 [cited 2022 Sep 1]. (Statistics for Biology and Health).
12) Chew DP, French J, Briffa TG, Hammett CJ, Ellis CJ, Ranasinghe I, Aliprandi-Costa BJ, Astley CM, Turnbull FM, Lefkovits J, Redfern J, Carr B, Gamble GD, Lintern KJ, Howell TE, Parker H, Tavella R, Bloomer SG, Hyun KK, Brieger DB. Acute coronary syndrome care across Australia and New Zealand: the SNAPSHOT ACS study. Med J Aust. 2013;199(3):185-91. doi: 10.5694/mja12.11854.
13) Alston L, Peterson KL, Jacobs JP, Allender S, Nichols M. Quantifying the role of modifiable risk factors in the differences in cardiovascular disease mortality rates between metropolitan and rural populations in Australia: a macrosimulation modelling study. BMJ Open. 2017;7:e018307. doi: 10.1136/bmjopen-2017-018307.
14) Curtis E, Harwood M, Riddell T, Robson B, Harris R, Mills C, Reid P. Access and society as determinants of ischaemic heart disease in indigenous populations. Heart Lung Circ. 2010 May-Jun;19(5-6):316-24. doi: 10.1016/j.hlc.2010.04.129. Epub 2010 May 4.
15) Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, Exeter DJ, Kerr AJ. Ethnic Differences in Coronary Revascularisation following an Acute Coronary Syndrome in New Zealand: A National Data-linkage Study (ANZACS-QI 12). Heart Lung Circ. 2016;25(8):820-8. doi: 10.1016/j.hlc.2016.03.004.
16) Tang EW, Wong CK, Herbison P. Community hospital versus tertiary hospital comparison in the treatment and outcome of patients with acute coronary syndrome: a New Zealand experience. N Z Med J. 2006;119(1238):U2078.
17) Grey C, Jackson R, Wells S, Wu B, Pujades-Rodriguez M, Schmidt M, Selak V, Kerr AJ. Both incidence and prevalence of ischaemic heart disease are declining in parallel: a national data-linkage study in New Zealand (ANZACS-QI 52). Eur J Prev Cardiol. 2022;29(2):321-327. doi: 10.1093/eurjpc/zwaa120.
18) Tideman P, Taylor AW, Janus E, Philpot B, Clark R, Peach E, Laatikainen T, Vartiainen E, Tirimacco R, Montgomerie A, Grant J, Versace V, Dunbar JA. A comparison of Australian rural and metropolitan cardiovascular risk and mortality: the Greater Green Triangle and North West Adelaide population surveys. BMJ Open. 2013;3(8):e003203. doi: 10.1136/bmjopen-2013-003203.
19) Bechtold D, Salvatierra GG, Bulley E, Cypro A, Daratha KB. Geographic Variation in Treatment and Outcomes Among Patients With AMI: Investigating Urban-Rural Differences Among Hospitalized Patients. J Rural Health. 2017;33(2):158-166. doi: 10.1111/jrh.12165.
20) Cai M, Liu E, Tao H, Qian Z, Lin X, Cheng Z. Does Level of Hospital Matter? A Study of Mortality of Acute Myocardial Infarction Patients in Shanxi, China. Am J Med Qual. 2018;33(2):185-192. doi: 10.1177/1062860617708608.
21) Brown A. Acute coronary syndromes in indigenous Australians: opportunities for improving outcomes across the continuum of care. Heart Lung Circ. 2010 May-Jun;19(5-6):325-36. doi: 10.1016/j.hlc.2010.02.011.
22) Roffi M, Patrono C, Collet JP, Mueller C, Valgimigli M, Andreotti F, Bax JJ, Borger MA, Brotons C, Chew DP, Gencer B, Hasenfuss G, Kjeldsen K, Lancellotti P, Landmesser U, Mehilli J, Mukherjee D, Storey RF, Windecker S; ESC Scientific Document Group. 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation: Task Force for the Management of Acute Coronary Syndromes in Patients Presenting without Persistent ST-Segment Elevation of the European Society of Cardiology (ESC). Eur Heart J. 2016;37(3):267-315. doi: 10.1093/eurheartj/ehv320.
23) Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, Harrison J, Riddell T, Kerr A. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014;100(10):770-4. doi: 10.1136/heartjnl-2013-304960.
24) Kerr AJ, Turaga M, Grey C, Lee M, McLachlan A, Devlin G. Initiation and maintenance of statins and aspirin after acute coronary syndromes (ANZACS-QI 11). J Prim Health Care. 2016;8(3):238-249. doi: 10.1071/HC16013.
25) Benatar J, Langdana F, Doolan-Noble F, McLachlan A. Cardiac rehabilitation in New Zealand-moving forward. N Z Med J. 2016;129(1435):68-74.
26) Kira G, Doolan-Noble F, Humphreys G, Williams G, O'Shaughnessy H, Devlin G. A national survey of cardiac rehabilitation services in New Zealand: 2015. N Z Med J. 2016;129(1435):50-8.
27) Field PE, Franklin RC, Barker RN, Ring I, Leggat PA. Cardiac rehabilitation services for people in rural and remote areas: an integrative literature review. Rural Remote Health. 2018;18(4):4738. doi: 10.22605/RRH4738.
28) Field P, Franklin RC, Barker R, Ring I, Leggat P, Canuto K. Importance of cardiac rehabilitation in rural and remote areas of Australia. Aust J Rural Health. 2022;30(2):149-163. Doi: 10.1111/ajr.
29) Thompson SC, Nedkoff L, Katzenellenbogen J, Hussain MA, Sanfilippo F. Challenges in Managing Acute Cardiovascular Diseases and Follow Up Care in Rural Areas: A Narrative Review. Int J Environ Res Public Health. 2019;16(24):5126. doi: 10.3390/ijerph16245126.12818.
30) Liao BY, Lee MAW, Dicker B, Todd VF, Stewart R, Poppe K, Kerr A. Prehospital identification of ST-segment elevation myocardial infarction and mortality (ANZACS-QI 61). Open Heart. 2022;9(1):e001868. doi: 10.1136/openhrt-2021-001868.
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Outcomes and access to angiography following non-ST-segment elevation acute coronary syndromes in patients who present to rural or urban hospitals: ANZACS-QI 72
In Aotearoa New Zealand, patients who present with non-ST-segment elevation acute coronary syndrome (NSTEACS, which comprises non-ST-segment elevation myocardial infarction [NSTEMI] and unstable angina [UA]) will initially access one of three groups of hospitals: urban hospitals with routine access to percutaneous intervention (PCI), urban hospitals without routine access to PCI and rural hospitals (which also do not have routine access to PCI).
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