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Variation in implantable cardioverter defibrillator (ICD) implant rates by ethnic groups have been identified in the United States and the United Kingdom, with African American and South Asian patients being less likely to receive an ICD compared to White patients.[[1–4]] However, there is limited information on ethnic disparity in ICD implant rates elsewhere. In New Zealand, there is variation in cardiovascular and non-cardiovascular risk factors, investigation, management and outcomes by ethnicity.[[5–19]] ICD implant rates for Māori, Pacific, Asian and New Zealand Europeans have been reported for a single year,[[20]] but whether the reported trend has persisted over a longer time-period is unclear. The main ethnic groups in New Zealand also have differing age structures,[[21]] but the age-specific ICD implant rates by ethnicity are unknown.

The rate of ICD implants has increased globally in recent years.[[22]] In patients with heart failure with reduced ejection fraction ICDs have an important role in the prevention of sudden cardiac death,[[23–26]] in addition to risk factor modification and pharmacological treatment. In New Zealand, ICDs are indicated for primary prevention of sudden cardiac death in patients <75 years old with symptomatic heart failure with reduced ejection fraction, and for the secondary prevention of sudden cardiac death in patients who have survived a cardiac arrest.[[26]] ICD implant rates in New Zealand have increased significantly over the past decade,[[27]] with substantial regional variation.[[28]] This paper aims to provide an analysis of trends in new ICD implants in New Zealand by ethnicity over the past 15 years.

Methodology

All patients who received a new ICD implant, including cardiac resynchronisation therapy defibrillators, between 1 January 2005 to 31 December 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. The Dataset does not include procedures from private hospitals, but ICD implants were rarely performed in the private sector over the study period, as device costs were not covered by health insurance providers in New Zealand. ICD implants were identified using specific codes from the Australian Classification of Health Interventions (ACHI), which were issued as part of the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD10-AM) procedure coding[[29]] (Supplementary Table 1). Specific prioritisation and categorisation rules were applied using a previously validated methodology, which had an excellent ability to capture all permanent pacemaker (PPM) and ICD implants nationally, differentiate between PPM and ICD implants and distinguish between new and replacement procedures.[[30]] Replacement ICD procedures were excluded from this analysis.

Self-identified ethnicity is routinely recorded in all national health databases in New Zealand following a standardised protocol. For patients with multiple ethnic groups recorded, a modified prioritisation of the Ministry of Health’s Ethnicity Data Protocols was used to assign each individual to one ethnic group.[[31]] Prioritisation was performed in the following order: Māori, Pacific (Tokelauan, Fijian, Niuean, Tongan, Cook Island Māori, Samoan, Other Pacific), Asian (Indian, Southeast Asian, Chinese, Other Asian) and European/Other (Middle Eastern, Latin American, African, Other Ethnicity, Other European and New Zealand European). The sole exception were Fijian Indian patients, who were categorised as Indian (in the Asian group) rather than Pacific, as a previous local study demonstrated that these patients have cardiovascular risk profiles that are more similar to Indians than other Pacific groups.[[32]] As Europeans represent >90% of the European/Other group, this group is referred to as “European” in the rest of this paper. Over the study period, the proportion of the population the main ethnic groups were as follows: Māori: 15.7%, Pacific: 6.4%, Asian: 11.8%, European: 66.1%.[[21]]

Statistical analysis

Implant rates per million population by ethnicity were calculated using the number of new ICD implants as the numerator and the estimated population of New Zealand for each year as the denominator.[[21]] The estimated population of New Zealand by ethnicity (the denominator) is prioritised in the same method as described above. These data are available in the 2018 New Zealand Population Projections from Stats NZ.[[21]] Age-specific rates for the age groups <40, 40–69, 70–79 and ≥80 years by ethnicity were calculated. Due to low implant volumes in some age groups, age-specific rates were also combined for the three years at the beginning and the end of the study period (2005–2007 and 2017–2019) to facilitate comparisons. Implant rates per million population were age-standardised using the direct method with the European Standard Population.[[33]] Trend analysis of age-standardised implant rates was performed using a “joinpoint” regression model, to accommodate non-linear trends over time.[[34]] The process fits the simplest model that the data allow and tests whether one or more joinpoints, which indicate a change in slope of the trend, are statistically significant. Annual percentage changes in trend were calculated. Version 4.7.0.0 of the Joinpoint Regression Program was used.[[35]] Other analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).

Ethics

This is a sub-study of ANZACS-QI, which is part of the wider Vascular Informatics using Epidemiology and the Web (VIEW) programme. The VIEW programme was approved by the Northern Region Ethics Committee Y in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries, and with annual approvals by the National Multi-region Ethics Committee since 2007 (MEC07/19/EXP).

Results

A total of 5,514 new ICDs were implanted between 2005 and 2019. New ICD implant rates increased by 137% over the 15-year period, from 41.4 per million in 2005 to 98.2 per million in 2019, an average increase of 5.4% per year (95% confidence interval (CI): 4.7–6.1%, p<0.01).

Age-specific trends by ethnicity

In all age groups <80 years, Māori and Pacific people had higher implant rates through most of the study period. Asians consistently had the lowest new ICD implant rates across all age groups, with the lowest rate in patients <40 years. Māori and Pacific people in the 40–59 years and 60–69 years age groups had substantially higher age-specific implant rates compared to Europeans and Asians (Figure 1, Supplementary Figure 1). Of note, at the beginning of the study there were no implants in Pacific people over 70 or Māori and Asians over 80. However, new ICD implants in octogenarians across all ethnicities represented only 2.4% of all new ICD implants over the study period (Supplementary Tables 2 and 3).

Figure 1: Age-specific new ICD implant rate per million population by ethnicity and age groups from 2005–2007 to 2017–2019. Age group ≥80 years not included as they accounted for only 2.4% of all new ICD implants.

Trends in age-standardised new ICD implant rates by ethnicity

Between 2005 to 2019, the highest age-standardised new ICD implant rates were among Māori, followed by Pacific, Europeans and Asians. In 2005, age-standardised new ICD implant rates were higher in Māori and Pacific people than Europeans. Since 2005, the largest increase in new ICD implant rates was seen in Pacific patients at 8.9% per year (95% CI: 6.1–11.7%, p<0.01). New ICD implant rates increased by 4.7% per year (95% CI: 2.2–7.2%, p<0.01) in Māori and increased by 4.3% per year (95% CI: 1.3–7.4%, p<0.01) in Asians. In Europeans, new ICD implant rates initially increased by 10.3% per year (95% CI: 17.1–13.6%, p <0.01) between 2005 to 2012, but then plateaued at -0.4% per year (95% CI: -2.6–1.9%, p=0.71) between 2012 to 2019. By 2019, the age-standardised new ICD implant rate in Māori and Pacific people were approximately double that of Europeans and three- to four-fold higher than Asians (Figure 2).

Figure 2: Trends in age-standardised new implantable cardioverter defibrillator implant rates per million population by ethnicity. Solid trend lines indicate statistically significant changes and dotted trend lines indicate non-statistically significant changes. APC, annual percentage change; CI, confidence interval.

Discussion

This is the first nationwide description of ICD implant trends by ethnicity in New Zealand over an extended time-period. In 2005 the age-standardised implant rates for Māori were higher than for Europeans, but implant rates among Pacific people were similar to those for Europeans. By 2019, implant rates in Europeans had plateaued, but implant rates for both Māori and Pacific people continued to increase and diverge from Europeans, resulting in Māori and Pacific people having more than twice the implant rates of Europeans.

Wilson et al have previously shown that Māori patients had a higher crude ICD implant rate compared to Europeans in 2010, but the crude implant rates in Pacific patients lagged behind Europeans despite their known higher incidence of ischaemic heart disease.[[20]] We have shown that, although the age-standardised ICD implant rates plateaued in European patients in recent years, rates have continued to increase for both Māori and Pacific people.

Are ICD implant rates in New Zealand equitable?

In New Zealand, there is evidence of inequitable distribution of risk factors, investigation, management and outcomes for both cardiac and non-cardiac disease.[[5–19]] Although we have reported higher and increasing rates of ICD implantation in Māori and Pacific people relative to Europeans, a key question arising from this work is what the ideal rate of ICD implants should be if clinical guidelines for implantation were strictly adhered to.[[23–26]] Any gap between the ideal rate and observed rates may be attributable to unwarranted variation and therefore evidence of inequitable treatment. In this study we cannot give a definitive answer to this question as a full clinical description of the populations eligible to receive an ICD is not available.

We recently performed an analysis using national administrative datasets, which found that the rates of incident heart failure are two-fold higher in Māori and Pacific patients compared with Europeans (Chan et al, submitted for publication). This confirms other data demonstrating that Māori and Pacific had higher rates of prior heart failure and heart failure hospitalisation compared to Europeans.[[5,11,36]] We also know that, compared with Europeans, the age-standardised burdens of hospitalisation or death due to ischaemic heart disease for Māori and Pacific people were two-fold greater in 2014–2015, and that the case fatality for acute coronary syndromes in 2014–2017 was two- to three-fold higher.[[11,12]] The at least two-fold incidence and mortality of both heart failure and ischaemic heart disease for Māori and Pacific people relative to Europeans is consistent with the higher ICD implant rates observed in this study. However, further work is required to determine whether implant rates are high enough.

In recent years, the age-standardised ICD implant rates in European patients in New Zealand have plateaued. At the same time, there has been a decline in hospitalisations and deaths due to ischaemic heart disease and heart failure [[12]] (Chan et al, submitted for publication). However, this does not take into consideration changes in clinical guidelines for ICD implantation in recent years, level of adherence to clinical guidelines, changes in rates of investigation and risk factor management. Further work is therefore needed to determine whether the appropriate implant rates have been achieved.

Interestingly, our study showed that Asians (including Indians) had substantially lower ICD implant rates compared to other ethnicities, even though Indians have among the highest rates of cardiovascular disease and diabetes in New Zealand.[[5,11]] Due to the small number of ICD implants in Asians, we did not separate Indian and non-Indian Asians in this analysis. Previous research has shown that both Indian and non-Indian Asians had higher overall coronary revascularisation rates in addition to the lowest all-cause mortality after a myocardial infarction compared to other ethnicities.[[9,11,12]] Thus, the favourable cardiovascular outcomes and likely lower incidence of ischaemic cardiomyopathy in Asians may partially explain the lower rates of ICD implants in this ethnic group.

Ethnic variation in ischaemic heart disease and implantable cardioverter defibrillator implants internationally

Ethnic variation in ICD implants has been reported internationally, but data are predominantly limited to the United Kingdom and the United States and only a small number of ethnicities were compared. In the United States, studies from the late 1990s and early 2000s showed that African American patients were less likely to receive ICD implants compared to White patients, irrespective of primary prevention or secondary prevention indications.[[37,38]] However, this disparity may have narrowed in recent years.[[39]] Previous studies have also reported that African American patients were less likely to receive coronary angiography and coronary revascularisation than White patients.[[40]] Mistry et al reported lower ICD implant rates in South Asian patients compared to White patients, despite a higher burden of coronary artery disease.[[4]] In these international studies, poor communication, system-wide failures to address health literacy, a lack of acknowledgement of cultural beliefs and language barriers were hypothesised as reasons for disparity in ICD implant rates.[[2,4]] However, in the United States’ Get With The Guidelines – Heart Failure Program, there was still disparity in the rate of ICD use by ethnicity, even among patients who received counselling for ICD therapy.[[41]]

To ensure equitable treatment and to improve cardiovascular outcomes for Māori and Pacific patients, it is imperative that unwarranted ethnic differences at every stage of the management of cardiovascular disease, particularly for ischaemic heart disease and heart failure, is addressed: from risk-factor modification to treatment with pharmacologic therapy and coronary procedures, and finally with fair and appropriate patient selection for ICD implants. To achieve this, health services must, among other things, recognise the importance of effective communication, continuity of care and integrated models of care that respect and are aligned with the values of diverse communities.

Limitations

This study is a descriptive analysis of ICD implant rates by ethnicity in New Zealand. It has been reported in the context of inequities of underlying disease burden at a population level. However, a detailed patient-level investigation of clinical, geographical or socioeconomic factors that may have impacted on implant rates is beyond the scope of this study.

Self-identified ethnicity may differ between national health databases and the national census. This study uses data from Stats NZ only, but trends in self-identified ethnicity over time is unknown.

Although there have been significant changes in population within each age band as well as age structure by ethnicity over the study period, the calculation of age-specific and age-standardised rates take these changes into account and minimise errors in comparison of implant rates between ethnicities.

Additionally, ICD implants for primary vs secondary prevention indications could not be reliably differentiated in the national level data.

Conclusion

There is marked ethnic variation in ICD implant rates in New Zealand. Implant rates have increased in non-European ethnic groups but have plateaued in European patients in the past seven years. The higher implant rates among Māori and Pacific people parallel known differences between ethnic groups in rates of underlying cardiac disease. The more rapid increase in implant rates in these groups may be due to a greater clinical need or more equitable treatment over time. However, further research at an individual patient level is needed to determine whether implant rates are high enough to represent equity in patient selection for ICD implant.

Supplementary Material

  • Supplementary Table 1: ICD10-AM codes for permanent pacemaker (PPM) and implantable cardioverter defibrillator (ICD) implants. If codes for ICD and PPM were both present in a single episode of care (EoC), this was categorised as an ICD implant. When codes for a new and replacement procedure were both present in a single EoC, it was categorised as a replacement procedure if replacement codes were present on the same day or earlier than the dates of the new procedure codes. Conversely, if replacement codes were one day or more after the date of new procedure codes, the procedure was categorised as a new implant. View Supplementary Table 1.
  • Supplementary Table 2: Number of implantable cardioverter defibrillator implants by ethnicity and age-groups. View Supplementary Table 2.
  • Supplementary Table 3: Age-specific new ICD implant rate per million population by ethnicity and age groups from 2005-2007 to 2017-2019. *European ethnicity includes European/other after ethnic group prioritisation for Māori, Pacific and Asian ethnicities. CI, confidence interval; ICD, implantable cardioverter defibrillator. View Supplementary Table 3.
  • Supplementary Figure 1: Trends in new ICD implant rates by ethnicity and age groups. Excludes replacement procedures. ICD, implantable cardioverter defibrillator. View Supplementary Figure 1.

Summary

There is marked ethnic variation in implantable cardioverter defibrillator (ICD) implant rates in New Zealand. The highest implant rates were among Māori, followed by Pacific, European/Other and Asian ethnicities. Implant rates have increased significantly among Pacific, Māori and Asian ethnic groups but have plateaued in European patients in the past seven years. The more rapid increase in implant rates in these groups may be due to a greater clinical need or more equitable treatment over time. However, further research at an individual patient level is needed to determine whether implant rates are high enough to represent equity in patient selection for ICD implant.

Abstract

Aim

Ethnic variation in implantable cardioverter defibrillator (ICD) implant rates have been reported internationally but have not previously been examined in New Zealand. This study examined trends in new ICD implants by ethnicity over an extended period.

Method

All patients who received a new ICD implant between 2005 and 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. Ethnicity was classified using the following standard prioritisation: Māori, Pacific, Asian and European/Other. New ICD implant rates were analysed by ethnicity and age groups.

Results

A total of 5,514 new ICDs were implanted. New ICD implant rates increased from 41.4/million in 2005 to 98.2/million in 2019, an average increase of 5.4%/year (p<0.01). The highest age-standardised implant rates were among Māori, followed by Pacific, European/Other and Asian ethnicities. The largest increase was seen in Pacific people at 8.9%/year (p <0.01), followed by Māori and Asian people at 4.7%/year and 4.3%/year respectively (both p<0.01). In European/Other patients, ICD implant rates increased by 10.3%/year (p<0.01) between 2005 to 2012, then plateaued at -0.4%/year (p=0.71) between 2012 to 2019. By 2019, the age-standardised implant rates in Māori and Pacific people were two-fold higher than European/Others.

Conclusion

There is marked ethnic variation in ICD implant rates in New Zealand. The higher implant rates in Māori and Pacific parallel known ethnic differences in rates of underlying cardiac disease. The more rapid increase in implant rates in these ethnic groups may represent more equitable treatment over time.

Author Information

Fang Shawn Foo: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Department of Cardiology, North Shore Hospital, Auckland, New Zealand. Mildred Lee: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Katrina K Poppe: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; Department of Medicine, University of Auckland, New Zealand. Corina Grey: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Geoffrey C Clare: Department of Cardiology, Christchurch Hospital, Christchurch, New Zealand; University of Otago, Christchurch, New Zealand. Martin K. Stiles: Waikato Clinical School, Faculty of Medical and Health Sciences, University of Auckland; Department of Cardiology, Waikato Hospital, Hamilton, New Zealand. David Heaven: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Department of Cardiology, Auckland City Hospital, Auckland, New Zealand. Matthew Webber: Department of Cardiology, Wellington Hospital, Wellington, New Zealand. Matire Harwood: Department of General Practice & Primary Health Care, School of Population Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. Rod Jackson: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Andrew J Kerr: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; Department of Medicine, University of Auckland, New Zealand.

Acknowledgements

ANZACS-QI programme implementation, coordination and analysis: The ANZACS-QI registry software was developed and supported by Enigma Solutions. Programme implementation is coordinated by the National Institute for Health Innovation (NIHI) at the University of Auckland. The ANZACS-QI programme is funded by the New Zealand Ministry of Health and governance is from the ANZACS-QI Governance group. Access to the New Zealand National Administrative Health datasets is governed by the University of Auckland Health Research funded Vascular risk Informatics using Epidemiology & the Web (VIEW) investigators. We acknowledge all the New Zealand cardiologists, physicians, nursing staff and radiographers who have supported and contributed to ANZACS-QI.

Correspondence

Dr Fang Shawn Foo, Department of Cardiology, Middlemore Hospital, Private Bag 93311, Otahuhu, Auckland, New Zealand, +649 2760061 (phone), +649 2709746 (fax)

Correspondence Email

shawnfoo@icloud.com

Competing Interests

Dr Katrina Poppe receives funding from the Heart Foundation of New Zealand – senior fellowship; and the Health Research Council – programme grant.

1. Hernandez AF, Fonarow GC, Liang L, Al-Khatib SM, Curtis LH, LaBresh KA, et al. Sex and Racial Differences in the Use of Implantable Cardioverter-Defibrillators Among Patients Hospitalized With Heart Failure. JAMA. 2007 Oct 3;298(13):1525-32.

2. Gauri AJ, Davis A, Hong T, Burke MC, Knight BP. Disparities in the Use of Primary Prevention and Defibrillator Therapy Among Blacks and Women. Am J Med. 2006 Feb 1;119(2):167.e17-167.e21.

3. Thomas KL, Al-Khatib SM, Kelsey RC, Bush H, Brosius L, Velazquez EJ, et al. Racial Disparity in the Utilization of Implantable-Cardioverter Defibrillators Among Patients With Prior Myocardial Infarction and an Ejection Fraction of. Am J Cardiol. 2007;100(6):924-9.

4. Mistry A, Vali Z, Sidhu B, Budgeon C, Yuyun MF, Pooranachandran V, et al. Disparity in implantable cardioverter defibrillator therapy among minority South Asians in the United Kingdom. Heart. 2020 May 1;106(9):671-6.

5. Selak V, Poppe K, Grey C, Mehta S, Winter-Smith J, Jackson R, et al. Ethnic differences in cardiovascular risk profiles among 475,241 adults in primary care in Aotearoa, New Zealand. N Z Med J. 2020;133(1521).

6. Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, et al. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014 May;100(10):770-4.

7. 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 Sep;8(3):238-49.

8. Kerr A, Lee M, Grey C, Pegg T, Fisher N, White H, et al. Acute reperfusion for ST-elevation myocardial infarction in New Zealand (2015-2017): patient and system delay (ANZACS-QI 29). N Z Med J. 2019 Jul;132(1498):41-59.

9. Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, et al. 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 Aug;25(8):820-8.

10. Sandiford P, El-Jack SS, Scott AG, Crengle SM, Bramley DM. Different Needs or Treated Differently? Understanding Ethnic Inequalities in Coronary Revascularisation Rates. Heart Lung Circ. 2015;24(10):960-8.

11. Mazengarb J, Grey C, Lee M, Poppe K, Mehta S, Harwood M, et al. Inequity in one-year mortality after first myocardial infarction in Māori and Pacific patients: how much is associated with differences in modifiable clinical risk factors? (ANZACS-QI 49). N Z Med J. 2020 Sep;133(1521):40-54.

12. Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, et al. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018 Jul;131(1478):21-31.

13. Disney G, Teng A, Atkinson J, Wilson N, Blakely T. Changing ethnic inequalities in mortality in New Zealand over 30years: Linked cohort studies with 68.9 million person-years of follow-up. Popul Health Metr. 2017 Dec 26;15(1):15.

14. Teng AM, Atkinson J, Disney G, Wilson N, Sarfati D, McLeod M, et al. Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up. BMC Cancer. 2016 Sep;16(1):755.

15. Tobias M, Blakely T, Matheson D, Rasanathan K, Atkinson J. Changing trends in indigenous inequalities in mortality: lessons from New Zealand. Int J Epidemiol. 2009 Dec;38(6):1711-22.

16. Hobbs M, Ahuriri-Driscoll A, Schluter PJ. Ethnic differences in mortality and hospital admission in a New Zealand population with type 2 diabetes. Lancet Glob Heal. 2021 Feb 1;9(2):e102-3.

17. Yu D, Zhao Z, Osuagwu UL, Pickering K, Baker J, Cutfield R, et al. Ethnic differences in mortality and hospital admission rates between Māori, Pacific, and European New Zealanders with type 2 diabetes between 1994 and 2018: a retrospective, population-based, longitudinal cohort study. Lancet Glob Heal. 2021 Feb;9(2):e209-17.

18. Cunningham R, Shaw C, Blakely T, Atkinson J, Sarfati D. Ethnic and socioeconomic trends in breast cancer incidence in New Zealand. BMC Cancer. 2010;10(1):674.

19. Blakely T, Shaw C, Atkinson J, Tobias M, Bastiampillai N, Sloane K, et al. Cancer Trends: Trends in Cancer Incidence by Ethnic and Socioeconomic Group, New Zealand 1981–2004. Wellingt Univ Otago Minist Heal. 2010.

20. Wilson D, Harding SA, Melton I, Lever NA, Stiles MK, Boddington D, et al. Geographic, Ethnic and Socioeconomic Factors Influencing Access to Implantable Cardioverter Defibrillators (ICDs) in New Zealand. Heart Lung Circ. 2012;21(9):576-81.

21. Statistics New Zealand [Internet]. Projected New Zealand Population. 2019.

22. Raatikainen MJP, Arnar DO, Merkely B, Nielsen JC, Hindricks G, Heidbuchel H, et al. A Decade of Information on the Use of Cardiac Implantable Electronic Devices and Interventional Electrophysiological Procedures in the European Society of Cardiology Countries: 2017 Report from the European Heart Rhythm Association. Europace. 2017;19(2):ii1-90.

23. Al-Khatib SM, Stevenson WG, Ackerman MJ, Bryant WJ, Callans DJ, Curtis AB, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: Executive summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Gui. Heart Rhythm. 2018 Oct 1;15(10):e190-252.

24. Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JGF, Coats AJS, et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J. 2016 Jul 14;37(27):2129-200.

25. Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE, Drazner MH, et al. 2013 ACCF/AHA Guideline for the Management of Heart Failure. J Am Coll Cardiol. 2013;62(16):e147-239.

26. Smith W. New Zealand primary implantable cardioverter defibrillator implantation and biventricular pacing guidelines. N Z Med J. 2010;123(1309):86-96.

27. Foo FS, Stiles MK, Lee M, Looi K-L, Clare GC, Webber M, et al. Ten year trends in cardiac implantable electronic devices in New Zealand: a national data linkage study (ANZACS-QI 51). Intern Med J. 2020 Oct 17.

28. Foo FS, Poppe KK, Lee M, Clare GC, Stiles MK, Looi K-L, et al. Regional variation in cardiac implantable electronic device implants trends in New Zealand over the past decade (ANZACS-QI 54). Intern Med J. 2020 Dec.

29. Ministry of Health [Internet]. National Minimum Dataset (Hospital Inpatient Events). Data Mart - Data Dictionary. Version 7.8.  2016.

30. Foo FS, Lee M, Larsen P, Heaven D, Lever N, Sinclair S, et al. Completeness of ANZACS-QI Cardiac Implanted DEVICE Registry and agreement with national datasets: ANZACS-QI 30. N Z Med J. 2019 Aug 16;132(1500):40-9.

31. Health Information Standards Organisation. HISO 10001:2017. Ethnicity Data Protocols. Minist Heal. 2017.

32. Grey C, Wells S, Riddell T, Pylypchuk R, Marshall R, Drury P, et al. A comparative analysis of cardiovascular disease risk profiles of five Pacific ethnic groups assessed in New Zealand primary care practice: PREDICT CVD-13. N Z Med J. 2010 Nov;123(1325):41-52.

33. Eurostat European Commission [Internet]. Revision of the European Standard Population. Report of Eurostat’s task force. 2013.

34. Kim HJ, Fay MP, Feuer EJ, Midthune DN. Permutation tests for joinpoint regression with applications to cancer rates. Stat Med. 2000 Feb 15;19(3):335-51.

35. Joinpoint Regression Program, Version 4.8.0.1 - April 2020. Statistical Methodology and Applications Branch, Surveillance Research Program, National Cancer Institute.

36. Ministry of Health. 2015. Tatau Kahukura: Māori Health Chart Book 2015 (3rd edition). Wellington: Ministry of Health.

37. Voigt A, Ezzeddine R, Barrington W, Obiaha-Ngwu O, Ganz LI, London B, et al. Utilization of implantable cardioverter-defibrillators in survivors of cardiac arrest in the United States from 1996 to 2001. J Am Coll Cardiol. 2004 Aug;44(4):855-8.

38. Groeneveld PW, Heidenreich PA, Garber AM. Trends in implantable cardioverter-defibrillator racial disparity: the importance of geography. J Am Coll Cardiol. 2005 Jan;45(1):72-8.

39. Patel NJ, Edla S, Deshmukh A, Nalluri N, Patel N, Agnihotri K, et al. Gender, Racial, and Health Insurance Differences in the Trend of Implantable Cardioverter-Defibrillator (ICD) Utilization: A United States Experience Over the Last Decade. Clin Cardiol. 2016 Feb;39(2):63-71.

40. Vaccarino V, Rathore SS, Wenger NK, Frederick PD, Abramson JL, Barron H V, et al. Sex and racial differences in the management of acute myocardial infarction, 1994 through 2002. N Engl J Med. 2005 Aug;353(7):671-82.

41. Hess PL, Hernandez AF, Bhatt DL, Hellkamp AS, Yancy CW, Schwamm LH, et al. Sex and Race/Ethnicity Differences in Implantable Cardioverter-Defibrillator Counseling and Use Among Patients Hospitalized With Heart Failure: Findings from the Get With The Guidelines-Heart Failure Program. Circulation. 2016 Aug 16;134(7):517-26.

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Variation in implantable cardioverter defibrillator (ICD) implant rates by ethnic groups have been identified in the United States and the United Kingdom, with African American and South Asian patients being less likely to receive an ICD compared to White patients.[[1–4]] However, there is limited information on ethnic disparity in ICD implant rates elsewhere. In New Zealand, there is variation in cardiovascular and non-cardiovascular risk factors, investigation, management and outcomes by ethnicity.[[5–19]] ICD implant rates for Māori, Pacific, Asian and New Zealand Europeans have been reported for a single year,[[20]] but whether the reported trend has persisted over a longer time-period is unclear. The main ethnic groups in New Zealand also have differing age structures,[[21]] but the age-specific ICD implant rates by ethnicity are unknown.

The rate of ICD implants has increased globally in recent years.[[22]] In patients with heart failure with reduced ejection fraction ICDs have an important role in the prevention of sudden cardiac death,[[23–26]] in addition to risk factor modification and pharmacological treatment. In New Zealand, ICDs are indicated for primary prevention of sudden cardiac death in patients <75 years old with symptomatic heart failure with reduced ejection fraction, and for the secondary prevention of sudden cardiac death in patients who have survived a cardiac arrest.[[26]] ICD implant rates in New Zealand have increased significantly over the past decade,[[27]] with substantial regional variation.[[28]] This paper aims to provide an analysis of trends in new ICD implants in New Zealand by ethnicity over the past 15 years.

Methodology

All patients who received a new ICD implant, including cardiac resynchronisation therapy defibrillators, between 1 January 2005 to 31 December 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. The Dataset does not include procedures from private hospitals, but ICD implants were rarely performed in the private sector over the study period, as device costs were not covered by health insurance providers in New Zealand. ICD implants were identified using specific codes from the Australian Classification of Health Interventions (ACHI), which were issued as part of the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD10-AM) procedure coding[[29]] (Supplementary Table 1). Specific prioritisation and categorisation rules were applied using a previously validated methodology, which had an excellent ability to capture all permanent pacemaker (PPM) and ICD implants nationally, differentiate between PPM and ICD implants and distinguish between new and replacement procedures.[[30]] Replacement ICD procedures were excluded from this analysis.

Self-identified ethnicity is routinely recorded in all national health databases in New Zealand following a standardised protocol. For patients with multiple ethnic groups recorded, a modified prioritisation of the Ministry of Health’s Ethnicity Data Protocols was used to assign each individual to one ethnic group.[[31]] Prioritisation was performed in the following order: Māori, Pacific (Tokelauan, Fijian, Niuean, Tongan, Cook Island Māori, Samoan, Other Pacific), Asian (Indian, Southeast Asian, Chinese, Other Asian) and European/Other (Middle Eastern, Latin American, African, Other Ethnicity, Other European and New Zealand European). The sole exception were Fijian Indian patients, who were categorised as Indian (in the Asian group) rather than Pacific, as a previous local study demonstrated that these patients have cardiovascular risk profiles that are more similar to Indians than other Pacific groups.[[32]] As Europeans represent >90% of the European/Other group, this group is referred to as “European” in the rest of this paper. Over the study period, the proportion of the population the main ethnic groups were as follows: Māori: 15.7%, Pacific: 6.4%, Asian: 11.8%, European: 66.1%.[[21]]

Statistical analysis

Implant rates per million population by ethnicity were calculated using the number of new ICD implants as the numerator and the estimated population of New Zealand for each year as the denominator.[[21]] The estimated population of New Zealand by ethnicity (the denominator) is prioritised in the same method as described above. These data are available in the 2018 New Zealand Population Projections from Stats NZ.[[21]] Age-specific rates for the age groups <40, 40–69, 70–79 and ≥80 years by ethnicity were calculated. Due to low implant volumes in some age groups, age-specific rates were also combined for the three years at the beginning and the end of the study period (2005–2007 and 2017–2019) to facilitate comparisons. Implant rates per million population were age-standardised using the direct method with the European Standard Population.[[33]] Trend analysis of age-standardised implant rates was performed using a “joinpoint” regression model, to accommodate non-linear trends over time.[[34]] The process fits the simplest model that the data allow and tests whether one or more joinpoints, which indicate a change in slope of the trend, are statistically significant. Annual percentage changes in trend were calculated. Version 4.7.0.0 of the Joinpoint Regression Program was used.[[35]] Other analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).

Ethics

This is a sub-study of ANZACS-QI, which is part of the wider Vascular Informatics using Epidemiology and the Web (VIEW) programme. The VIEW programme was approved by the Northern Region Ethics Committee Y in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries, and with annual approvals by the National Multi-region Ethics Committee since 2007 (MEC07/19/EXP).

Results

A total of 5,514 new ICDs were implanted between 2005 and 2019. New ICD implant rates increased by 137% over the 15-year period, from 41.4 per million in 2005 to 98.2 per million in 2019, an average increase of 5.4% per year (95% confidence interval (CI): 4.7–6.1%, p<0.01).

Age-specific trends by ethnicity

In all age groups <80 years, Māori and Pacific people had higher implant rates through most of the study period. Asians consistently had the lowest new ICD implant rates across all age groups, with the lowest rate in patients <40 years. Māori and Pacific people in the 40–59 years and 60–69 years age groups had substantially higher age-specific implant rates compared to Europeans and Asians (Figure 1, Supplementary Figure 1). Of note, at the beginning of the study there were no implants in Pacific people over 70 or Māori and Asians over 80. However, new ICD implants in octogenarians across all ethnicities represented only 2.4% of all new ICD implants over the study period (Supplementary Tables 2 and 3).

Figure 1: Age-specific new ICD implant rate per million population by ethnicity and age groups from 2005–2007 to 2017–2019. Age group ≥80 years not included as they accounted for only 2.4% of all new ICD implants.

Trends in age-standardised new ICD implant rates by ethnicity

Between 2005 to 2019, the highest age-standardised new ICD implant rates were among Māori, followed by Pacific, Europeans and Asians. In 2005, age-standardised new ICD implant rates were higher in Māori and Pacific people than Europeans. Since 2005, the largest increase in new ICD implant rates was seen in Pacific patients at 8.9% per year (95% CI: 6.1–11.7%, p<0.01). New ICD implant rates increased by 4.7% per year (95% CI: 2.2–7.2%, p<0.01) in Māori and increased by 4.3% per year (95% CI: 1.3–7.4%, p<0.01) in Asians. In Europeans, new ICD implant rates initially increased by 10.3% per year (95% CI: 17.1–13.6%, p <0.01) between 2005 to 2012, but then plateaued at -0.4% per year (95% CI: -2.6–1.9%, p=0.71) between 2012 to 2019. By 2019, the age-standardised new ICD implant rate in Māori and Pacific people were approximately double that of Europeans and three- to four-fold higher than Asians (Figure 2).

Figure 2: Trends in age-standardised new implantable cardioverter defibrillator implant rates per million population by ethnicity. Solid trend lines indicate statistically significant changes and dotted trend lines indicate non-statistically significant changes. APC, annual percentage change; CI, confidence interval.

Discussion

This is the first nationwide description of ICD implant trends by ethnicity in New Zealand over an extended time-period. In 2005 the age-standardised implant rates for Māori were higher than for Europeans, but implant rates among Pacific people were similar to those for Europeans. By 2019, implant rates in Europeans had plateaued, but implant rates for both Māori and Pacific people continued to increase and diverge from Europeans, resulting in Māori and Pacific people having more than twice the implant rates of Europeans.

Wilson et al have previously shown that Māori patients had a higher crude ICD implant rate compared to Europeans in 2010, but the crude implant rates in Pacific patients lagged behind Europeans despite their known higher incidence of ischaemic heart disease.[[20]] We have shown that, although the age-standardised ICD implant rates plateaued in European patients in recent years, rates have continued to increase for both Māori and Pacific people.

Are ICD implant rates in New Zealand equitable?

In New Zealand, there is evidence of inequitable distribution of risk factors, investigation, management and outcomes for both cardiac and non-cardiac disease.[[5–19]] Although we have reported higher and increasing rates of ICD implantation in Māori and Pacific people relative to Europeans, a key question arising from this work is what the ideal rate of ICD implants should be if clinical guidelines for implantation were strictly adhered to.[[23–26]] Any gap between the ideal rate and observed rates may be attributable to unwarranted variation and therefore evidence of inequitable treatment. In this study we cannot give a definitive answer to this question as a full clinical description of the populations eligible to receive an ICD is not available.

We recently performed an analysis using national administrative datasets, which found that the rates of incident heart failure are two-fold higher in Māori and Pacific patients compared with Europeans (Chan et al, submitted for publication). This confirms other data demonstrating that Māori and Pacific had higher rates of prior heart failure and heart failure hospitalisation compared to Europeans.[[5,11,36]] We also know that, compared with Europeans, the age-standardised burdens of hospitalisation or death due to ischaemic heart disease for Māori and Pacific people were two-fold greater in 2014–2015, and that the case fatality for acute coronary syndromes in 2014–2017 was two- to three-fold higher.[[11,12]] The at least two-fold incidence and mortality of both heart failure and ischaemic heart disease for Māori and Pacific people relative to Europeans is consistent with the higher ICD implant rates observed in this study. However, further work is required to determine whether implant rates are high enough.

In recent years, the age-standardised ICD implant rates in European patients in New Zealand have plateaued. At the same time, there has been a decline in hospitalisations and deaths due to ischaemic heart disease and heart failure [[12]] (Chan et al, submitted for publication). However, this does not take into consideration changes in clinical guidelines for ICD implantation in recent years, level of adherence to clinical guidelines, changes in rates of investigation and risk factor management. Further work is therefore needed to determine whether the appropriate implant rates have been achieved.

Interestingly, our study showed that Asians (including Indians) had substantially lower ICD implant rates compared to other ethnicities, even though Indians have among the highest rates of cardiovascular disease and diabetes in New Zealand.[[5,11]] Due to the small number of ICD implants in Asians, we did not separate Indian and non-Indian Asians in this analysis. Previous research has shown that both Indian and non-Indian Asians had higher overall coronary revascularisation rates in addition to the lowest all-cause mortality after a myocardial infarction compared to other ethnicities.[[9,11,12]] Thus, the favourable cardiovascular outcomes and likely lower incidence of ischaemic cardiomyopathy in Asians may partially explain the lower rates of ICD implants in this ethnic group.

Ethnic variation in ischaemic heart disease and implantable cardioverter defibrillator implants internationally

Ethnic variation in ICD implants has been reported internationally, but data are predominantly limited to the United Kingdom and the United States and only a small number of ethnicities were compared. In the United States, studies from the late 1990s and early 2000s showed that African American patients were less likely to receive ICD implants compared to White patients, irrespective of primary prevention or secondary prevention indications.[[37,38]] However, this disparity may have narrowed in recent years.[[39]] Previous studies have also reported that African American patients were less likely to receive coronary angiography and coronary revascularisation than White patients.[[40]] Mistry et al reported lower ICD implant rates in South Asian patients compared to White patients, despite a higher burden of coronary artery disease.[[4]] In these international studies, poor communication, system-wide failures to address health literacy, a lack of acknowledgement of cultural beliefs and language barriers were hypothesised as reasons for disparity in ICD implant rates.[[2,4]] However, in the United States’ Get With The Guidelines – Heart Failure Program, there was still disparity in the rate of ICD use by ethnicity, even among patients who received counselling for ICD therapy.[[41]]

To ensure equitable treatment and to improve cardiovascular outcomes for Māori and Pacific patients, it is imperative that unwarranted ethnic differences at every stage of the management of cardiovascular disease, particularly for ischaemic heart disease and heart failure, is addressed: from risk-factor modification to treatment with pharmacologic therapy and coronary procedures, and finally with fair and appropriate patient selection for ICD implants. To achieve this, health services must, among other things, recognise the importance of effective communication, continuity of care and integrated models of care that respect and are aligned with the values of diverse communities.

Limitations

This study is a descriptive analysis of ICD implant rates by ethnicity in New Zealand. It has been reported in the context of inequities of underlying disease burden at a population level. However, a detailed patient-level investigation of clinical, geographical or socioeconomic factors that may have impacted on implant rates is beyond the scope of this study.

Self-identified ethnicity may differ between national health databases and the national census. This study uses data from Stats NZ only, but trends in self-identified ethnicity over time is unknown.

Although there have been significant changes in population within each age band as well as age structure by ethnicity over the study period, the calculation of age-specific and age-standardised rates take these changes into account and minimise errors in comparison of implant rates between ethnicities.

Additionally, ICD implants for primary vs secondary prevention indications could not be reliably differentiated in the national level data.

Conclusion

There is marked ethnic variation in ICD implant rates in New Zealand. Implant rates have increased in non-European ethnic groups but have plateaued in European patients in the past seven years. The higher implant rates among Māori and Pacific people parallel known differences between ethnic groups in rates of underlying cardiac disease. The more rapid increase in implant rates in these groups may be due to a greater clinical need or more equitable treatment over time. However, further research at an individual patient level is needed to determine whether implant rates are high enough to represent equity in patient selection for ICD implant.

Supplementary Material

  • Supplementary Table 1: ICD10-AM codes for permanent pacemaker (PPM) and implantable cardioverter defibrillator (ICD) implants. If codes for ICD and PPM were both present in a single episode of care (EoC), this was categorised as an ICD implant. When codes for a new and replacement procedure were both present in a single EoC, it was categorised as a replacement procedure if replacement codes were present on the same day or earlier than the dates of the new procedure codes. Conversely, if replacement codes were one day or more after the date of new procedure codes, the procedure was categorised as a new implant. View Supplementary Table 1.
  • Supplementary Table 2: Number of implantable cardioverter defibrillator implants by ethnicity and age-groups. View Supplementary Table 2.
  • Supplementary Table 3: Age-specific new ICD implant rate per million population by ethnicity and age groups from 2005-2007 to 2017-2019. *European ethnicity includes European/other after ethnic group prioritisation for Māori, Pacific and Asian ethnicities. CI, confidence interval; ICD, implantable cardioverter defibrillator. View Supplementary Table 3.
  • Supplementary Figure 1: Trends in new ICD implant rates by ethnicity and age groups. Excludes replacement procedures. ICD, implantable cardioverter defibrillator. View Supplementary Figure 1.

Summary

There is marked ethnic variation in implantable cardioverter defibrillator (ICD) implant rates in New Zealand. The highest implant rates were among Māori, followed by Pacific, European/Other and Asian ethnicities. Implant rates have increased significantly among Pacific, Māori and Asian ethnic groups but have plateaued in European patients in the past seven years. The more rapid increase in implant rates in these groups may be due to a greater clinical need or more equitable treatment over time. However, further research at an individual patient level is needed to determine whether implant rates are high enough to represent equity in patient selection for ICD implant.

Abstract

Aim

Ethnic variation in implantable cardioverter defibrillator (ICD) implant rates have been reported internationally but have not previously been examined in New Zealand. This study examined trends in new ICD implants by ethnicity over an extended period.

Method

All patients who received a new ICD implant between 2005 and 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. Ethnicity was classified using the following standard prioritisation: Māori, Pacific, Asian and European/Other. New ICD implant rates were analysed by ethnicity and age groups.

Results

A total of 5,514 new ICDs were implanted. New ICD implant rates increased from 41.4/million in 2005 to 98.2/million in 2019, an average increase of 5.4%/year (p<0.01). The highest age-standardised implant rates were among Māori, followed by Pacific, European/Other and Asian ethnicities. The largest increase was seen in Pacific people at 8.9%/year (p <0.01), followed by Māori and Asian people at 4.7%/year and 4.3%/year respectively (both p<0.01). In European/Other patients, ICD implant rates increased by 10.3%/year (p<0.01) between 2005 to 2012, then plateaued at -0.4%/year (p=0.71) between 2012 to 2019. By 2019, the age-standardised implant rates in Māori and Pacific people were two-fold higher than European/Others.

Conclusion

There is marked ethnic variation in ICD implant rates in New Zealand. The higher implant rates in Māori and Pacific parallel known ethnic differences in rates of underlying cardiac disease. The more rapid increase in implant rates in these ethnic groups may represent more equitable treatment over time.

Author Information

Fang Shawn Foo: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Department of Cardiology, North Shore Hospital, Auckland, New Zealand. Mildred Lee: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Katrina K Poppe: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; Department of Medicine, University of Auckland, New Zealand. Corina Grey: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Geoffrey C Clare: Department of Cardiology, Christchurch Hospital, Christchurch, New Zealand; University of Otago, Christchurch, New Zealand. Martin K. Stiles: Waikato Clinical School, Faculty of Medical and Health Sciences, University of Auckland; Department of Cardiology, Waikato Hospital, Hamilton, New Zealand. David Heaven: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Department of Cardiology, Auckland City Hospital, Auckland, New Zealand. Matthew Webber: Department of Cardiology, Wellington Hospital, Wellington, New Zealand. Matire Harwood: Department of General Practice & Primary Health Care, School of Population Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. Rod Jackson: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Andrew J Kerr: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; Department of Medicine, University of Auckland, New Zealand.

Acknowledgements

ANZACS-QI programme implementation, coordination and analysis: The ANZACS-QI registry software was developed and supported by Enigma Solutions. Programme implementation is coordinated by the National Institute for Health Innovation (NIHI) at the University of Auckland. The ANZACS-QI programme is funded by the New Zealand Ministry of Health and governance is from the ANZACS-QI Governance group. Access to the New Zealand National Administrative Health datasets is governed by the University of Auckland Health Research funded Vascular risk Informatics using Epidemiology & the Web (VIEW) investigators. We acknowledge all the New Zealand cardiologists, physicians, nursing staff and radiographers who have supported and contributed to ANZACS-QI.

Correspondence

Dr Fang Shawn Foo, Department of Cardiology, Middlemore Hospital, Private Bag 93311, Otahuhu, Auckland, New Zealand, +649 2760061 (phone), +649 2709746 (fax)

Correspondence Email

shawnfoo@icloud.com

Competing Interests

Dr Katrina Poppe receives funding from the Heart Foundation of New Zealand – senior fellowship; and the Health Research Council – programme grant.

1. Hernandez AF, Fonarow GC, Liang L, Al-Khatib SM, Curtis LH, LaBresh KA, et al. Sex and Racial Differences in the Use of Implantable Cardioverter-Defibrillators Among Patients Hospitalized With Heart Failure. JAMA. 2007 Oct 3;298(13):1525-32.

2. Gauri AJ, Davis A, Hong T, Burke MC, Knight BP. Disparities in the Use of Primary Prevention and Defibrillator Therapy Among Blacks and Women. Am J Med. 2006 Feb 1;119(2):167.e17-167.e21.

3. Thomas KL, Al-Khatib SM, Kelsey RC, Bush H, Brosius L, Velazquez EJ, et al. Racial Disparity in the Utilization of Implantable-Cardioverter Defibrillators Among Patients With Prior Myocardial Infarction and an Ejection Fraction of. Am J Cardiol. 2007;100(6):924-9.

4. Mistry A, Vali Z, Sidhu B, Budgeon C, Yuyun MF, Pooranachandran V, et al. Disparity in implantable cardioverter defibrillator therapy among minority South Asians in the United Kingdom. Heart. 2020 May 1;106(9):671-6.

5. Selak V, Poppe K, Grey C, Mehta S, Winter-Smith J, Jackson R, et al. Ethnic differences in cardiovascular risk profiles among 475,241 adults in primary care in Aotearoa, New Zealand. N Z Med J. 2020;133(1521).

6. Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, et al. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014 May;100(10):770-4.

7. 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 Sep;8(3):238-49.

8. Kerr A, Lee M, Grey C, Pegg T, Fisher N, White H, et al. Acute reperfusion for ST-elevation myocardial infarction in New Zealand (2015-2017): patient and system delay (ANZACS-QI 29). N Z Med J. 2019 Jul;132(1498):41-59.

9. Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, et al. 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 Aug;25(8):820-8.

10. Sandiford P, El-Jack SS, Scott AG, Crengle SM, Bramley DM. Different Needs or Treated Differently? Understanding Ethnic Inequalities in Coronary Revascularisation Rates. Heart Lung Circ. 2015;24(10):960-8.

11. Mazengarb J, Grey C, Lee M, Poppe K, Mehta S, Harwood M, et al. Inequity in one-year mortality after first myocardial infarction in Māori and Pacific patients: how much is associated with differences in modifiable clinical risk factors? (ANZACS-QI 49). N Z Med J. 2020 Sep;133(1521):40-54.

12. Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, et al. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018 Jul;131(1478):21-31.

13. Disney G, Teng A, Atkinson J, Wilson N, Blakely T. Changing ethnic inequalities in mortality in New Zealand over 30years: Linked cohort studies with 68.9 million person-years of follow-up. Popul Health Metr. 2017 Dec 26;15(1):15.

14. Teng AM, Atkinson J, Disney G, Wilson N, Sarfati D, McLeod M, et al. Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up. BMC Cancer. 2016 Sep;16(1):755.

15. Tobias M, Blakely T, Matheson D, Rasanathan K, Atkinson J. Changing trends in indigenous inequalities in mortality: lessons from New Zealand. Int J Epidemiol. 2009 Dec;38(6):1711-22.

16. Hobbs M, Ahuriri-Driscoll A, Schluter PJ. Ethnic differences in mortality and hospital admission in a New Zealand population with type 2 diabetes. Lancet Glob Heal. 2021 Feb 1;9(2):e102-3.

17. Yu D, Zhao Z, Osuagwu UL, Pickering K, Baker J, Cutfield R, et al. Ethnic differences in mortality and hospital admission rates between Māori, Pacific, and European New Zealanders with type 2 diabetes between 1994 and 2018: a retrospective, population-based, longitudinal cohort study. Lancet Glob Heal. 2021 Feb;9(2):e209-17.

18. Cunningham R, Shaw C, Blakely T, Atkinson J, Sarfati D. Ethnic and socioeconomic trends in breast cancer incidence in New Zealand. BMC Cancer. 2010;10(1):674.

19. Blakely T, Shaw C, Atkinson J, Tobias M, Bastiampillai N, Sloane K, et al. Cancer Trends: Trends in Cancer Incidence by Ethnic and Socioeconomic Group, New Zealand 1981–2004. Wellingt Univ Otago Minist Heal. 2010.

20. Wilson D, Harding SA, Melton I, Lever NA, Stiles MK, Boddington D, et al. Geographic, Ethnic and Socioeconomic Factors Influencing Access to Implantable Cardioverter Defibrillators (ICDs) in New Zealand. Heart Lung Circ. 2012;21(9):576-81.

21. Statistics New Zealand [Internet]. Projected New Zealand Population. 2019.

22. Raatikainen MJP, Arnar DO, Merkely B, Nielsen JC, Hindricks G, Heidbuchel H, et al. A Decade of Information on the Use of Cardiac Implantable Electronic Devices and Interventional Electrophysiological Procedures in the European Society of Cardiology Countries: 2017 Report from the European Heart Rhythm Association. Europace. 2017;19(2):ii1-90.

23. Al-Khatib SM, Stevenson WG, Ackerman MJ, Bryant WJ, Callans DJ, Curtis AB, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: Executive summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Gui. Heart Rhythm. 2018 Oct 1;15(10):e190-252.

24. Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JGF, Coats AJS, et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J. 2016 Jul 14;37(27):2129-200.

25. Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE, Drazner MH, et al. 2013 ACCF/AHA Guideline for the Management of Heart Failure. J Am Coll Cardiol. 2013;62(16):e147-239.

26. Smith W. New Zealand primary implantable cardioverter defibrillator implantation and biventricular pacing guidelines. N Z Med J. 2010;123(1309):86-96.

27. Foo FS, Stiles MK, Lee M, Looi K-L, Clare GC, Webber M, et al. Ten year trends in cardiac implantable electronic devices in New Zealand: a national data linkage study (ANZACS-QI 51). Intern Med J. 2020 Oct 17.

28. Foo FS, Poppe KK, Lee M, Clare GC, Stiles MK, Looi K-L, et al. Regional variation in cardiac implantable electronic device implants trends in New Zealand over the past decade (ANZACS-QI 54). Intern Med J. 2020 Dec.

29. Ministry of Health [Internet]. National Minimum Dataset (Hospital Inpatient Events). Data Mart - Data Dictionary. Version 7.8.  2016.

30. Foo FS, Lee M, Larsen P, Heaven D, Lever N, Sinclair S, et al. Completeness of ANZACS-QI Cardiac Implanted DEVICE Registry and agreement with national datasets: ANZACS-QI 30. N Z Med J. 2019 Aug 16;132(1500):40-9.

31. Health Information Standards Organisation. HISO 10001:2017. Ethnicity Data Protocols. Minist Heal. 2017.

32. Grey C, Wells S, Riddell T, Pylypchuk R, Marshall R, Drury P, et al. A comparative analysis of cardiovascular disease risk profiles of five Pacific ethnic groups assessed in New Zealand primary care practice: PREDICT CVD-13. N Z Med J. 2010 Nov;123(1325):41-52.

33. Eurostat European Commission [Internet]. Revision of the European Standard Population. Report of Eurostat’s task force. 2013.

34. Kim HJ, Fay MP, Feuer EJ, Midthune DN. Permutation tests for joinpoint regression with applications to cancer rates. Stat Med. 2000 Feb 15;19(3):335-51.

35. Joinpoint Regression Program, Version 4.8.0.1 - April 2020. Statistical Methodology and Applications Branch, Surveillance Research Program, National Cancer Institute.

36. Ministry of Health. 2015. Tatau Kahukura: Māori Health Chart Book 2015 (3rd edition). Wellington: Ministry of Health.

37. Voigt A, Ezzeddine R, Barrington W, Obiaha-Ngwu O, Ganz LI, London B, et al. Utilization of implantable cardioverter-defibrillators in survivors of cardiac arrest in the United States from 1996 to 2001. J Am Coll Cardiol. 2004 Aug;44(4):855-8.

38. Groeneveld PW, Heidenreich PA, Garber AM. Trends in implantable cardioverter-defibrillator racial disparity: the importance of geography. J Am Coll Cardiol. 2005 Jan;45(1):72-8.

39. Patel NJ, Edla S, Deshmukh A, Nalluri N, Patel N, Agnihotri K, et al. Gender, Racial, and Health Insurance Differences in the Trend of Implantable Cardioverter-Defibrillator (ICD) Utilization: A United States Experience Over the Last Decade. Clin Cardiol. 2016 Feb;39(2):63-71.

40. Vaccarino V, Rathore SS, Wenger NK, Frederick PD, Abramson JL, Barron H V, et al. Sex and racial differences in the management of acute myocardial infarction, 1994 through 2002. N Engl J Med. 2005 Aug;353(7):671-82.

41. Hess PL, Hernandez AF, Bhatt DL, Hellkamp AS, Yancy CW, Schwamm LH, et al. Sex and Race/Ethnicity Differences in Implantable Cardioverter-Defibrillator Counseling and Use Among Patients Hospitalized With Heart Failure: Findings from the Get With The Guidelines-Heart Failure Program. Circulation. 2016 Aug 16;134(7):517-26.

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Variation in implantable cardioverter defibrillator (ICD) implant rates by ethnic groups have been identified in the United States and the United Kingdom, with African American and South Asian patients being less likely to receive an ICD compared to White patients.[[1–4]] However, there is limited information on ethnic disparity in ICD implant rates elsewhere. In New Zealand, there is variation in cardiovascular and non-cardiovascular risk factors, investigation, management and outcomes by ethnicity.[[5–19]] ICD implant rates for Māori, Pacific, Asian and New Zealand Europeans have been reported for a single year,[[20]] but whether the reported trend has persisted over a longer time-period is unclear. The main ethnic groups in New Zealand also have differing age structures,[[21]] but the age-specific ICD implant rates by ethnicity are unknown.

The rate of ICD implants has increased globally in recent years.[[22]] In patients with heart failure with reduced ejection fraction ICDs have an important role in the prevention of sudden cardiac death,[[23–26]] in addition to risk factor modification and pharmacological treatment. In New Zealand, ICDs are indicated for primary prevention of sudden cardiac death in patients <75 years old with symptomatic heart failure with reduced ejection fraction, and for the secondary prevention of sudden cardiac death in patients who have survived a cardiac arrest.[[26]] ICD implant rates in New Zealand have increased significantly over the past decade,[[27]] with substantial regional variation.[[28]] This paper aims to provide an analysis of trends in new ICD implants in New Zealand by ethnicity over the past 15 years.

Methodology

All patients who received a new ICD implant, including cardiac resynchronisation therapy defibrillators, between 1 January 2005 to 31 December 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. The Dataset does not include procedures from private hospitals, but ICD implants were rarely performed in the private sector over the study period, as device costs were not covered by health insurance providers in New Zealand. ICD implants were identified using specific codes from the Australian Classification of Health Interventions (ACHI), which were issued as part of the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD10-AM) procedure coding[[29]] (Supplementary Table 1). Specific prioritisation and categorisation rules were applied using a previously validated methodology, which had an excellent ability to capture all permanent pacemaker (PPM) and ICD implants nationally, differentiate between PPM and ICD implants and distinguish between new and replacement procedures.[[30]] Replacement ICD procedures were excluded from this analysis.

Self-identified ethnicity is routinely recorded in all national health databases in New Zealand following a standardised protocol. For patients with multiple ethnic groups recorded, a modified prioritisation of the Ministry of Health’s Ethnicity Data Protocols was used to assign each individual to one ethnic group.[[31]] Prioritisation was performed in the following order: Māori, Pacific (Tokelauan, Fijian, Niuean, Tongan, Cook Island Māori, Samoan, Other Pacific), Asian (Indian, Southeast Asian, Chinese, Other Asian) and European/Other (Middle Eastern, Latin American, African, Other Ethnicity, Other European and New Zealand European). The sole exception were Fijian Indian patients, who were categorised as Indian (in the Asian group) rather than Pacific, as a previous local study demonstrated that these patients have cardiovascular risk profiles that are more similar to Indians than other Pacific groups.[[32]] As Europeans represent >90% of the European/Other group, this group is referred to as “European” in the rest of this paper. Over the study period, the proportion of the population the main ethnic groups were as follows: Māori: 15.7%, Pacific: 6.4%, Asian: 11.8%, European: 66.1%.[[21]]

Statistical analysis

Implant rates per million population by ethnicity were calculated using the number of new ICD implants as the numerator and the estimated population of New Zealand for each year as the denominator.[[21]] The estimated population of New Zealand by ethnicity (the denominator) is prioritised in the same method as described above. These data are available in the 2018 New Zealand Population Projections from Stats NZ.[[21]] Age-specific rates for the age groups <40, 40–69, 70–79 and ≥80 years by ethnicity were calculated. Due to low implant volumes in some age groups, age-specific rates were also combined for the three years at the beginning and the end of the study period (2005–2007 and 2017–2019) to facilitate comparisons. Implant rates per million population were age-standardised using the direct method with the European Standard Population.[[33]] Trend analysis of age-standardised implant rates was performed using a “joinpoint” regression model, to accommodate non-linear trends over time.[[34]] The process fits the simplest model that the data allow and tests whether one or more joinpoints, which indicate a change in slope of the trend, are statistically significant. Annual percentage changes in trend were calculated. Version 4.7.0.0 of the Joinpoint Regression Program was used.[[35]] Other analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).

Ethics

This is a sub-study of ANZACS-QI, which is part of the wider Vascular Informatics using Epidemiology and the Web (VIEW) programme. The VIEW programme was approved by the Northern Region Ethics Committee Y in 2003 (AKY/03/12/314), with subsequent amendments to include the ANZACS-QI registries, and with annual approvals by the National Multi-region Ethics Committee since 2007 (MEC07/19/EXP).

Results

A total of 5,514 new ICDs were implanted between 2005 and 2019. New ICD implant rates increased by 137% over the 15-year period, from 41.4 per million in 2005 to 98.2 per million in 2019, an average increase of 5.4% per year (95% confidence interval (CI): 4.7–6.1%, p<0.01).

Age-specific trends by ethnicity

In all age groups <80 years, Māori and Pacific people had higher implant rates through most of the study period. Asians consistently had the lowest new ICD implant rates across all age groups, with the lowest rate in patients <40 years. Māori and Pacific people in the 40–59 years and 60–69 years age groups had substantially higher age-specific implant rates compared to Europeans and Asians (Figure 1, Supplementary Figure 1). Of note, at the beginning of the study there were no implants in Pacific people over 70 or Māori and Asians over 80. However, new ICD implants in octogenarians across all ethnicities represented only 2.4% of all new ICD implants over the study period (Supplementary Tables 2 and 3).

Figure 1: Age-specific new ICD implant rate per million population by ethnicity and age groups from 2005–2007 to 2017–2019. Age group ≥80 years not included as they accounted for only 2.4% of all new ICD implants.

Trends in age-standardised new ICD implant rates by ethnicity

Between 2005 to 2019, the highest age-standardised new ICD implant rates were among Māori, followed by Pacific, Europeans and Asians. In 2005, age-standardised new ICD implant rates were higher in Māori and Pacific people than Europeans. Since 2005, the largest increase in new ICD implant rates was seen in Pacific patients at 8.9% per year (95% CI: 6.1–11.7%, p<0.01). New ICD implant rates increased by 4.7% per year (95% CI: 2.2–7.2%, p<0.01) in Māori and increased by 4.3% per year (95% CI: 1.3–7.4%, p<0.01) in Asians. In Europeans, new ICD implant rates initially increased by 10.3% per year (95% CI: 17.1–13.6%, p <0.01) between 2005 to 2012, but then plateaued at -0.4% per year (95% CI: -2.6–1.9%, p=0.71) between 2012 to 2019. By 2019, the age-standardised new ICD implant rate in Māori and Pacific people were approximately double that of Europeans and three- to four-fold higher than Asians (Figure 2).

Figure 2: Trends in age-standardised new implantable cardioverter defibrillator implant rates per million population by ethnicity. Solid trend lines indicate statistically significant changes and dotted trend lines indicate non-statistically significant changes. APC, annual percentage change; CI, confidence interval.

Discussion

This is the first nationwide description of ICD implant trends by ethnicity in New Zealand over an extended time-period. In 2005 the age-standardised implant rates for Māori were higher than for Europeans, but implant rates among Pacific people were similar to those for Europeans. By 2019, implant rates in Europeans had plateaued, but implant rates for both Māori and Pacific people continued to increase and diverge from Europeans, resulting in Māori and Pacific people having more than twice the implant rates of Europeans.

Wilson et al have previously shown that Māori patients had a higher crude ICD implant rate compared to Europeans in 2010, but the crude implant rates in Pacific patients lagged behind Europeans despite their known higher incidence of ischaemic heart disease.[[20]] We have shown that, although the age-standardised ICD implant rates plateaued in European patients in recent years, rates have continued to increase for both Māori and Pacific people.

Are ICD implant rates in New Zealand equitable?

In New Zealand, there is evidence of inequitable distribution of risk factors, investigation, management and outcomes for both cardiac and non-cardiac disease.[[5–19]] Although we have reported higher and increasing rates of ICD implantation in Māori and Pacific people relative to Europeans, a key question arising from this work is what the ideal rate of ICD implants should be if clinical guidelines for implantation were strictly adhered to.[[23–26]] Any gap between the ideal rate and observed rates may be attributable to unwarranted variation and therefore evidence of inequitable treatment. In this study we cannot give a definitive answer to this question as a full clinical description of the populations eligible to receive an ICD is not available.

We recently performed an analysis using national administrative datasets, which found that the rates of incident heart failure are two-fold higher in Māori and Pacific patients compared with Europeans (Chan et al, submitted for publication). This confirms other data demonstrating that Māori and Pacific had higher rates of prior heart failure and heart failure hospitalisation compared to Europeans.[[5,11,36]] We also know that, compared with Europeans, the age-standardised burdens of hospitalisation or death due to ischaemic heart disease for Māori and Pacific people were two-fold greater in 2014–2015, and that the case fatality for acute coronary syndromes in 2014–2017 was two- to three-fold higher.[[11,12]] The at least two-fold incidence and mortality of both heart failure and ischaemic heart disease for Māori and Pacific people relative to Europeans is consistent with the higher ICD implant rates observed in this study. However, further work is required to determine whether implant rates are high enough.

In recent years, the age-standardised ICD implant rates in European patients in New Zealand have plateaued. At the same time, there has been a decline in hospitalisations and deaths due to ischaemic heart disease and heart failure [[12]] (Chan et al, submitted for publication). However, this does not take into consideration changes in clinical guidelines for ICD implantation in recent years, level of adherence to clinical guidelines, changes in rates of investigation and risk factor management. Further work is therefore needed to determine whether the appropriate implant rates have been achieved.

Interestingly, our study showed that Asians (including Indians) had substantially lower ICD implant rates compared to other ethnicities, even though Indians have among the highest rates of cardiovascular disease and diabetes in New Zealand.[[5,11]] Due to the small number of ICD implants in Asians, we did not separate Indian and non-Indian Asians in this analysis. Previous research has shown that both Indian and non-Indian Asians had higher overall coronary revascularisation rates in addition to the lowest all-cause mortality after a myocardial infarction compared to other ethnicities.[[9,11,12]] Thus, the favourable cardiovascular outcomes and likely lower incidence of ischaemic cardiomyopathy in Asians may partially explain the lower rates of ICD implants in this ethnic group.

Ethnic variation in ischaemic heart disease and implantable cardioverter defibrillator implants internationally

Ethnic variation in ICD implants has been reported internationally, but data are predominantly limited to the United Kingdom and the United States and only a small number of ethnicities were compared. In the United States, studies from the late 1990s and early 2000s showed that African American patients were less likely to receive ICD implants compared to White patients, irrespective of primary prevention or secondary prevention indications.[[37,38]] However, this disparity may have narrowed in recent years.[[39]] Previous studies have also reported that African American patients were less likely to receive coronary angiography and coronary revascularisation than White patients.[[40]] Mistry et al reported lower ICD implant rates in South Asian patients compared to White patients, despite a higher burden of coronary artery disease.[[4]] In these international studies, poor communication, system-wide failures to address health literacy, a lack of acknowledgement of cultural beliefs and language barriers were hypothesised as reasons for disparity in ICD implant rates.[[2,4]] However, in the United States’ Get With The Guidelines – Heart Failure Program, there was still disparity in the rate of ICD use by ethnicity, even among patients who received counselling for ICD therapy.[[41]]

To ensure equitable treatment and to improve cardiovascular outcomes for Māori and Pacific patients, it is imperative that unwarranted ethnic differences at every stage of the management of cardiovascular disease, particularly for ischaemic heart disease and heart failure, is addressed: from risk-factor modification to treatment with pharmacologic therapy and coronary procedures, and finally with fair and appropriate patient selection for ICD implants. To achieve this, health services must, among other things, recognise the importance of effective communication, continuity of care and integrated models of care that respect and are aligned with the values of diverse communities.

Limitations

This study is a descriptive analysis of ICD implant rates by ethnicity in New Zealand. It has been reported in the context of inequities of underlying disease burden at a population level. However, a detailed patient-level investigation of clinical, geographical or socioeconomic factors that may have impacted on implant rates is beyond the scope of this study.

Self-identified ethnicity may differ between national health databases and the national census. This study uses data from Stats NZ only, but trends in self-identified ethnicity over time is unknown.

Although there have been significant changes in population within each age band as well as age structure by ethnicity over the study period, the calculation of age-specific and age-standardised rates take these changes into account and minimise errors in comparison of implant rates between ethnicities.

Additionally, ICD implants for primary vs secondary prevention indications could not be reliably differentiated in the national level data.

Conclusion

There is marked ethnic variation in ICD implant rates in New Zealand. Implant rates have increased in non-European ethnic groups but have plateaued in European patients in the past seven years. The higher implant rates among Māori and Pacific people parallel known differences between ethnic groups in rates of underlying cardiac disease. The more rapid increase in implant rates in these groups may be due to a greater clinical need or more equitable treatment over time. However, further research at an individual patient level is needed to determine whether implant rates are high enough to represent equity in patient selection for ICD implant.

Supplementary Material

  • Supplementary Table 1: ICD10-AM codes for permanent pacemaker (PPM) and implantable cardioverter defibrillator (ICD) implants. If codes for ICD and PPM were both present in a single episode of care (EoC), this was categorised as an ICD implant. When codes for a new and replacement procedure were both present in a single EoC, it was categorised as a replacement procedure if replacement codes were present on the same day or earlier than the dates of the new procedure codes. Conversely, if replacement codes were one day or more after the date of new procedure codes, the procedure was categorised as a new implant. View Supplementary Table 1.
  • Supplementary Table 2: Number of implantable cardioverter defibrillator implants by ethnicity and age-groups. View Supplementary Table 2.
  • Supplementary Table 3: Age-specific new ICD implant rate per million population by ethnicity and age groups from 2005-2007 to 2017-2019. *European ethnicity includes European/other after ethnic group prioritisation for Māori, Pacific and Asian ethnicities. CI, confidence interval; ICD, implantable cardioverter defibrillator. View Supplementary Table 3.
  • Supplementary Figure 1: Trends in new ICD implant rates by ethnicity and age groups. Excludes replacement procedures. ICD, implantable cardioverter defibrillator. View Supplementary Figure 1.

Summary

There is marked ethnic variation in implantable cardioverter defibrillator (ICD) implant rates in New Zealand. The highest implant rates were among Māori, followed by Pacific, European/Other and Asian ethnicities. Implant rates have increased significantly among Pacific, Māori and Asian ethnic groups but have plateaued in European patients in the past seven years. The more rapid increase in implant rates in these groups may be due to a greater clinical need or more equitable treatment over time. However, further research at an individual patient level is needed to determine whether implant rates are high enough to represent equity in patient selection for ICD implant.

Abstract

Aim

Ethnic variation in implantable cardioverter defibrillator (ICD) implant rates have been reported internationally but have not previously been examined in New Zealand. This study examined trends in new ICD implants by ethnicity over an extended period.

Method

All patients who received a new ICD implant between 2005 and 2019 were identified using the National Minimum Dataset, which collects information on all public hospital admissions in New Zealand. Ethnicity was classified using the following standard prioritisation: Māori, Pacific, Asian and European/Other. New ICD implant rates were analysed by ethnicity and age groups.

Results

A total of 5,514 new ICDs were implanted. New ICD implant rates increased from 41.4/million in 2005 to 98.2/million in 2019, an average increase of 5.4%/year (p<0.01). The highest age-standardised implant rates were among Māori, followed by Pacific, European/Other and Asian ethnicities. The largest increase was seen in Pacific people at 8.9%/year (p <0.01), followed by Māori and Asian people at 4.7%/year and 4.3%/year respectively (both p<0.01). In European/Other patients, ICD implant rates increased by 10.3%/year (p<0.01) between 2005 to 2012, then plateaued at -0.4%/year (p=0.71) between 2012 to 2019. By 2019, the age-standardised implant rates in Māori and Pacific people were two-fold higher than European/Others.

Conclusion

There is marked ethnic variation in ICD implant rates in New Zealand. The higher implant rates in Māori and Pacific parallel known ethnic differences in rates of underlying cardiac disease. The more rapid increase in implant rates in these ethnic groups may represent more equitable treatment over time.

Author Information

Fang Shawn Foo: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Department of Cardiology, North Shore Hospital, Auckland, New Zealand. Mildred Lee: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Katrina K Poppe: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; Department of Medicine, University of Auckland, New Zealand. Corina Grey: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Geoffrey C Clare: Department of Cardiology, Christchurch Hospital, Christchurch, New Zealand; University of Otago, Christchurch, New Zealand. Martin K. Stiles: Waikato Clinical School, Faculty of Medical and Health Sciences, University of Auckland; Department of Cardiology, Waikato Hospital, Hamilton, New Zealand. David Heaven: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Department of Cardiology, Auckland City Hospital, Auckland, New Zealand. Matthew Webber: Department of Cardiology, Wellington Hospital, Wellington, New Zealand. Matire Harwood: Department of General Practice & Primary Health Care, School of Population Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand. Rod Jackson: Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand. Andrew J Kerr: Department of Cardiology, Middlemore Hospital, Otahuhu, Auckland, New Zealand; Section of Epidemiology and Biostatistics, School of Population Health, University of Auckland, Auckland, New Zealand; Department of Medicine, University of Auckland, New Zealand.

Acknowledgements

ANZACS-QI programme implementation, coordination and analysis: The ANZACS-QI registry software was developed and supported by Enigma Solutions. Programme implementation is coordinated by the National Institute for Health Innovation (NIHI) at the University of Auckland. The ANZACS-QI programme is funded by the New Zealand Ministry of Health and governance is from the ANZACS-QI Governance group. Access to the New Zealand National Administrative Health datasets is governed by the University of Auckland Health Research funded Vascular risk Informatics using Epidemiology & the Web (VIEW) investigators. We acknowledge all the New Zealand cardiologists, physicians, nursing staff and radiographers who have supported and contributed to ANZACS-QI.

Correspondence

Dr Fang Shawn Foo, Department of Cardiology, Middlemore Hospital, Private Bag 93311, Otahuhu, Auckland, New Zealand, +649 2760061 (phone), +649 2709746 (fax)

Correspondence Email

shawnfoo@icloud.com

Competing Interests

Dr Katrina Poppe receives funding from the Heart Foundation of New Zealand – senior fellowship; and the Health Research Council – programme grant.

1. Hernandez AF, Fonarow GC, Liang L, Al-Khatib SM, Curtis LH, LaBresh KA, et al. Sex and Racial Differences in the Use of Implantable Cardioverter-Defibrillators Among Patients Hospitalized With Heart Failure. JAMA. 2007 Oct 3;298(13):1525-32.

2. Gauri AJ, Davis A, Hong T, Burke MC, Knight BP. Disparities in the Use of Primary Prevention and Defibrillator Therapy Among Blacks and Women. Am J Med. 2006 Feb 1;119(2):167.e17-167.e21.

3. Thomas KL, Al-Khatib SM, Kelsey RC, Bush H, Brosius L, Velazquez EJ, et al. Racial Disparity in the Utilization of Implantable-Cardioverter Defibrillators Among Patients With Prior Myocardial Infarction and an Ejection Fraction of. Am J Cardiol. 2007;100(6):924-9.

4. Mistry A, Vali Z, Sidhu B, Budgeon C, Yuyun MF, Pooranachandran V, et al. Disparity in implantable cardioverter defibrillator therapy among minority South Asians in the United Kingdom. Heart. 2020 May 1;106(9):671-6.

5. Selak V, Poppe K, Grey C, Mehta S, Winter-Smith J, Jackson R, et al. Ethnic differences in cardiovascular risk profiles among 475,241 adults in primary care in Aotearoa, New Zealand. N Z Med J. 2020;133(1521).

6. Grey C, Jackson R, Wells S, Thornley S, Marshall R, Crengle S, et al. Maintenance of statin use over 3 years following acute coronary syndromes: a national data linkage study (ANZACS-QI-2). Heart. 2014 May;100(10):770-4.

7. 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 Sep;8(3):238-49.

8. Kerr A, Lee M, Grey C, Pegg T, Fisher N, White H, et al. Acute reperfusion for ST-elevation myocardial infarction in New Zealand (2015-2017): patient and system delay (ANZACS-QI 29). N Z Med J. 2019 Jul;132(1498):41-59.

9. Grey C, Jackson R, Wells S, Randall D, Harwood M, Mehta S, et al. 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 Aug;25(8):820-8.

10. Sandiford P, El-Jack SS, Scott AG, Crengle SM, Bramley DM. Different Needs or Treated Differently? Understanding Ethnic Inequalities in Coronary Revascularisation Rates. Heart Lung Circ. 2015;24(10):960-8.

11. Mazengarb J, Grey C, Lee M, Poppe K, Mehta S, Harwood M, et al. Inequity in one-year mortality after first myocardial infarction in Māori and Pacific patients: how much is associated with differences in modifiable clinical risk factors? (ANZACS-QI 49). N Z Med J. 2020 Sep;133(1521):40-54.

12. Grey C, Jackson R, Wells S, Wu B, Poppe K, Harwood M, et al. Trends in ischaemic heart disease: patterns of hospitalisation and mortality rates differ by ethnicity (ANZACS-QI 21). N Z Med J. 2018 Jul;131(1478):21-31.

13. Disney G, Teng A, Atkinson J, Wilson N, Blakely T. Changing ethnic inequalities in mortality in New Zealand over 30years: Linked cohort studies with 68.9 million person-years of follow-up. Popul Health Metr. 2017 Dec 26;15(1):15.

14. Teng AM, Atkinson J, Disney G, Wilson N, Sarfati D, McLeod M, et al. Ethnic inequalities in cancer incidence and mortality: census-linked cohort studies with 87 million years of person-time follow-up. BMC Cancer. 2016 Sep;16(1):755.

15. Tobias M, Blakely T, Matheson D, Rasanathan K, Atkinson J. Changing trends in indigenous inequalities in mortality: lessons from New Zealand. Int J Epidemiol. 2009 Dec;38(6):1711-22.

16. Hobbs M, Ahuriri-Driscoll A, Schluter PJ. Ethnic differences in mortality and hospital admission in a New Zealand population with type 2 diabetes. Lancet Glob Heal. 2021 Feb 1;9(2):e102-3.

17. Yu D, Zhao Z, Osuagwu UL, Pickering K, Baker J, Cutfield R, et al. Ethnic differences in mortality and hospital admission rates between Māori, Pacific, and European New Zealanders with type 2 diabetes between 1994 and 2018: a retrospective, population-based, longitudinal cohort study. Lancet Glob Heal. 2021 Feb;9(2):e209-17.

18. Cunningham R, Shaw C, Blakely T, Atkinson J, Sarfati D. Ethnic and socioeconomic trends in breast cancer incidence in New Zealand. BMC Cancer. 2010;10(1):674.

19. Blakely T, Shaw C, Atkinson J, Tobias M, Bastiampillai N, Sloane K, et al. Cancer Trends: Trends in Cancer Incidence by Ethnic and Socioeconomic Group, New Zealand 1981–2004. Wellingt Univ Otago Minist Heal. 2010.

20. Wilson D, Harding SA, Melton I, Lever NA, Stiles MK, Boddington D, et al. Geographic, Ethnic and Socioeconomic Factors Influencing Access to Implantable Cardioverter Defibrillators (ICDs) in New Zealand. Heart Lung Circ. 2012;21(9):576-81.

21. Statistics New Zealand [Internet]. Projected New Zealand Population. 2019.

22. Raatikainen MJP, Arnar DO, Merkely B, Nielsen JC, Hindricks G, Heidbuchel H, et al. A Decade of Information on the Use of Cardiac Implantable Electronic Devices and Interventional Electrophysiological Procedures in the European Society of Cardiology Countries: 2017 Report from the European Heart Rhythm Association. Europace. 2017;19(2):ii1-90.

23. Al-Khatib SM, Stevenson WG, Ackerman MJ, Bryant WJ, Callans DJ, Curtis AB, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: Executive summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Gui. Heart Rhythm. 2018 Oct 1;15(10):e190-252.

24. Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JGF, Coats AJS, et al. 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J. 2016 Jul 14;37(27):2129-200.

25. Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE, Drazner MH, et al. 2013 ACCF/AHA Guideline for the Management of Heart Failure. J Am Coll Cardiol. 2013;62(16):e147-239.

26. Smith W. New Zealand primary implantable cardioverter defibrillator implantation and biventricular pacing guidelines. N Z Med J. 2010;123(1309):86-96.

27. Foo FS, Stiles MK, Lee M, Looi K-L, Clare GC, Webber M, et al. Ten year trends in cardiac implantable electronic devices in New Zealand: a national data linkage study (ANZACS-QI 51). Intern Med J. 2020 Oct 17.

28. Foo FS, Poppe KK, Lee M, Clare GC, Stiles MK, Looi K-L, et al. Regional variation in cardiac implantable electronic device implants trends in New Zealand over the past decade (ANZACS-QI 54). Intern Med J. 2020 Dec.

29. Ministry of Health [Internet]. National Minimum Dataset (Hospital Inpatient Events). Data Mart - Data Dictionary. Version 7.8.  2016.

30. Foo FS, Lee M, Larsen P, Heaven D, Lever N, Sinclair S, et al. Completeness of ANZACS-QI Cardiac Implanted DEVICE Registry and agreement with national datasets: ANZACS-QI 30. N Z Med J. 2019 Aug 16;132(1500):40-9.

31. Health Information Standards Organisation. HISO 10001:2017. Ethnicity Data Protocols. Minist Heal. 2017.

32. Grey C, Wells S, Riddell T, Pylypchuk R, Marshall R, Drury P, et al. A comparative analysis of cardiovascular disease risk profiles of five Pacific ethnic groups assessed in New Zealand primary care practice: PREDICT CVD-13. N Z Med J. 2010 Nov;123(1325):41-52.

33. Eurostat European Commission [Internet]. Revision of the European Standard Population. Report of Eurostat’s task force. 2013.

34. Kim HJ, Fay MP, Feuer EJ, Midthune DN. Permutation tests for joinpoint regression with applications to cancer rates. Stat Med. 2000 Feb 15;19(3):335-51.

35. Joinpoint Regression Program, Version 4.8.0.1 - April 2020. Statistical Methodology and Applications Branch, Surveillance Research Program, National Cancer Institute.

36. Ministry of Health. 2015. Tatau Kahukura: Māori Health Chart Book 2015 (3rd edition). Wellington: Ministry of Health.

37. Voigt A, Ezzeddine R, Barrington W, Obiaha-Ngwu O, Ganz LI, London B, et al. Utilization of implantable cardioverter-defibrillators in survivors of cardiac arrest in the United States from 1996 to 2001. J Am Coll Cardiol. 2004 Aug;44(4):855-8.

38. Groeneveld PW, Heidenreich PA, Garber AM. Trends in implantable cardioverter-defibrillator racial disparity: the importance of geography. J Am Coll Cardiol. 2005 Jan;45(1):72-8.

39. Patel NJ, Edla S, Deshmukh A, Nalluri N, Patel N, Agnihotri K, et al. Gender, Racial, and Health Insurance Differences in the Trend of Implantable Cardioverter-Defibrillator (ICD) Utilization: A United States Experience Over the Last Decade. Clin Cardiol. 2016 Feb;39(2):63-71.

40. Vaccarino V, Rathore SS, Wenger NK, Frederick PD, Abramson JL, Barron H V, et al. Sex and racial differences in the management of acute myocardial infarction, 1994 through 2002. N Engl J Med. 2005 Aug;353(7):671-82.

41. Hess PL, Hernandez AF, Bhatt DL, Hellkamp AS, Yancy CW, Schwamm LH, et al. Sex and Race/Ethnicity Differences in Implantable Cardioverter-Defibrillator Counseling and Use Among Patients Hospitalized With Heart Failure: Findings from the Get With The Guidelines-Heart Failure Program. Circulation. 2016 Aug 16;134(7):517-26.

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