Revascularisation and outcomes after acute coronary syndromes in patients with prior coronary artery bypass grafting—ANZACS-QI 67
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In those with acute coronary syndromes (ACS) and previous coronary artery bypass grafts (CABG), invasive coronary angiography and percutaneous coronary intervention (PCI) are technically more challenging. There is an increase in procedural time, contrast use and radiation dose.[[1]] The culprit lesions may be in either a bypass graft or native vessels and the identification and treatment of culprit lesions may be more complex in the context of pre-existing multivessel disease.[[1,2]] Although current guidelines recommend an early invasive strategy in patients with acute coronary syndrome (ACS), these patients were excluded from the randomised clinical trials of invasive management.[[3]] They are an important sub-group to better understand – patients with prior CABG account for around one in 10 of those with ACS.[[4,5]] Patients with prior CABG have been reported to have higher morbidity and mortality up to one year.[[1,2,4–6]] There is currently a lack of randomised clinical trial data in outcomes of invasive management of ACS in patients with prior CABG. Previous trials and guidelines of management of ACS often excluded prior CABG patients.
The All NZ ACS Quality Improvement (ANZACS-QI) registry captures virtually all New Zealand patients hospitalised with ACS who undergo coronary angiography.[[7]] Through the registry and by data linkage with national administrative datasets we are able to track longer-term morbidity and mortality outcomes for all patients.[[8]] We utilised this contemporary registry cohort to describe the clinical characteristics, myocardial revascularisation and longer-term outcomes of ACS patients with prior CABG and compare these to those without prior CABG.
Methods
The methodology of the All NZ ACS Quality Improvement (ANZACS-QI) registries programme was previously described in detail.[[7]] Patients undergoing invasive coronary angiography are continuously captured in the CathPCI dataset and are available to the ANZACS-QI investigators. It contains patient demographics, admission ACS risk stratification information, cardiovascular risk factors, indication for invasive coronary angiography and procedural details. These registries are subject to monthly auditing and consistently achieve complete data collection in over 95% of all those with suspected ACS undergoing coronary angiography. Using the National Health Index (NHI), a unique national alphanumeric patient identifier, the CathPCI data can be linked with the ACS Routine Information cohort arm of the ANZACS-QI to identify those with confirmed ACS undergoing invasive coronary angiography. Over 98% of New Zealanders have an NHI that identifies them in various national and regional health system databases.[[7]]
We included patients 20 years old and above with their first ACS presentation undergoing coronary angiography in public hospitals throughout New Zealand between 1 September 2014 and 31 October 2018. Those that did not survive to hospital discharge were excluded. The follow-up period for this analysis was limited to 31 December 2018.
Definitions
Patients with ACS were categorised into ST-segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction (NSTEMI) and unstable angina (UA). For the purposes of this study, myocardial infarction (MI) was defined according to the Third Universal Definition of MI.[[9]]
The demographic data presented includes age, sex, ethnicity and body mass index (BMI). For patients who recorded more than one ethnic group, ethnicity was prioritised according to the New Zealand Ministry of Health protocol, in the following order: Indigenous Māori, Pacific people, Indian, other Asian and NZ European/other. The only exception was that those of Fijian Indian ethnicity were counted as Indian.[[10]] Several patient characteristics were evaluated including time since CABG (where applicable), prior MI, prior heart failure (HF), diabetes, hypertension, dyslipidaemia, current smoking and Global Registry of Acute Coronary Events (GRACE) score. We report the GRACE score as an estimate of in-hospital mortality post-ACS. It is categorised into low (<1%), medium (1 to <3%) or high (3%).[[11]]
Invasive coronary angiographic procedural and result data included vascular access site, coronary anatomic data and myocardial revascularisation modality (PCI or CABG). In this study, coronary artery stenoses ≥50% were considered significant.
Among those that underwent more than one myocardial revascularisation procedure, a distinction was made between those undergoing elective staged procedures and unplanned procedures. All unplanned revascularisation procedures were categorised as: unplanned repeat PCI during the index hospitalisation; unplanned repeat PCI due to suspected/confirmed ACS in the first subsequent hospitalisation; or unplanned revascularisation with CABG due to suspected/confirmed ACS in the first subsequent hospitalisation.
Guideline-directed medical therapy (GDMT) at discharge were assessed. This included the rate of aspirin, P2Y12 agent, statin, beta-blocker, and angiotensin-converting-enzyme (ACE) inhibitors or angiotensin receptor blocker (ARB). Anti-coagulation prescription was incomplete as data input for dabigatran was added to the ANZACS-QI registry from June 2017 and rivaroxaban from September 2018.
Data linkage and outcomes
In-hospital outcomes were defined as those that occurred during the index hospitalisation and were obtained from the ANZACS-QI registry. These data included major bleeding, stroke, and unplanned myocardial revascularisation procedures (CABG and PCI). Major bleeding was defined using the Bleeding Academic Research Consortium definition for bleeding. We included all BARC Type 3 (3a, 3b and 3c) and Type 5 (5a and 5b).[[12]]
Following index hospitalisation discharge, mortality and rehospitalisation for MI, HF, stroke and major non-CABG related bleeding were identified by individual patient linkage to national datasets using their NHI as previously described.[[7,8,13]] An encrypted version of each NHI was used to anonymously link in-hospital ANZACS-QI patient records with the National Minimum Dataset.[[ 7,8]] We report the rates of these outcomes at 30 days, one year and mean follow-up. Hospitalisation for the outcomes of interest were defined as those in which it was listed as the primary or secondary discharge diagnosis using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification (ICD-10-AM). Unplanned repeat PCI is reported from the prospectively captured ANZACS-QI registry.
Statistical analysis
Categorical data were presented as frequency and column percentage. Continuous data were presented as mean ± standard deviation (SD) and median with inter-quartile range (IQR). Comparisons between groups were done using Chi-squared test and continuous data were done using non-parametric Mann–Whitney U test as the data were not normally distributed. All p-values reported were two-tailed and p-value <0.05 was considered significant. Outcomes were visualised using Kaplan–Meier survival curves. Univariate Cox proportional hazards regression was used to estimate the hazard ratio and 95% confidence intervals for patients with CABG compared to those without CABG for each outcome. Unadjusted 30-day and 1-year mortality from discharge curves were calculated using Kaplan–Meier analyses. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).
Results
Between 1 September 2014 and 31 October 2018, 26,869 patients were admitted to a public hospital in New Zealand with an ACS and underwent invasive coronary angiography. Of these, 1,791 (6.7%) had prior CABG and 25,078 (93.3%) had no prior CABG (Table 1). The mean follow-up was 2.1 years for both groups. The mean age was 65.4 (SD 11.8) years and males account for 69.3% of the cohort. Most patients were of NZ European/Other ethnicity (77.0%) and 11.1% were Māori. The most common presentation was NSTEMI (58.1%) followed by STEMI (26.3%) and UA (15.6%).
A detailed comparison of those with and without prior CABG is presented in Table 1. Patients with prior CABG were older (71.3±8.9 years vs 65.0±11.8 years, p<0.001) and more likely to be male (81.3% vs 68.4%, p<0.001) and of NZ European/Other ethnicity (82.9% vs 76.5%, p<0.001). Those with prior CABG had a higher prevalence of several comorbid conditions—prior MI (68.2% vs 17.6%, p<0.001), prior HF (68.2% vs. 17.6%, p<0.001) and diabetes (34.6% vs 22.3%, p<0.001). Conversely, a lower proportion of those with prior CABG were current smokers (12.1% vs 24.0%, p<0.001). Patients with prior CABG were more likely to present with UA (24.1% vs 15.0%, p<0.001) and less likely to present with STEMI (12.3% vs 27.3%, p<0.001).
The details relating to coronary angiography and myocardial revascularisation during the index hospitalisation are provided in Table 2. While radial arterial access was most commonly used in those without prior CABG (90.4%), femoral arterial access was most commonly used in those with prior CABG (50.6%). Overall, 87.3% of patients had significant coronary artery stenoses and 71.5% received myocardial revascularisation. Nearly all patients (99.5%) with prior CABG had angiographically significant lesions. However, only 49.8% had myocardial revascularisation compared to 73.0% of those with no prior CABG. When PCI was undertaken in patients with prior CABG, the target vessel was most commonly a native vessel alone (59.9%). Graft vessel PCI was most frequently undertaken without concomitant native vessel PCI. Saphenous vein graft PCI accounted for almost all (92.4%) graft vessel PCI. The total numbers of lesions treated were similar among those with and without prior CABG (1.29±0.56 vs 1.36±0.66, respectively). Intracoronary imaging was rarely performed in either group—IVUS (1.0% vs 0.5%) and OCT (0.1% vs 0.5%).
At the time of discharge, guideline-directed medical therapy (GDMT) was high and similar for those with and without prior CABG: aspirin (93.9% vs 95.1%, p=0.031), statin (92.0% vs 93.3%, p=0.047), P2Y12 inhibitor (81.8% vs 78.4%, p<0.001). Clopidogrel use was more common in patients with prior CABG (41.9% vs 27.2%, p<0.001). There were incomplete data relating to anticoagulant use as this field was added to the ANZACS-QI registry after the commencement of the study period. Beta-blocker (83.9% vs 81.4%, p=0.011) and angiotensin-converting enzyme (ACE) inhibitor/angiotensin receptor blocker (72.4% vs 71.2%, p=0.262) prescription was high and similar between patients with and without prior CABG.
In-hospital outcomes and mortality and non-fatal outcomes at a mean follow-up of 2.1 years are documented in Table 3. During the index hospitalisation rates of major bleeding, stroke and unplanned PCI were low in both patients with and without prior CABG. The univariate Cox regression hazard ratios and 95% confidence intervals for CABG, using patients without CABG as the comparator, are as follows for each outcome: all-cause mortality (HR 2.03 (1.80–2.29)), recurrent MI (2.70 (2.40–3.04)), CHF hospitalisation (2.36 (2.10–2.66)), stroke hospitalisation (1.82 (1.41–2.34)) and major bleeding hospitalisation (0.87 (0.75–1.03)).
In the whole cohort, the 1-year mortality was 5.4%. At this time point, a higher mortality was observed in those with prior CABG (9.0% vs 5.1%, p<0.001) (Figure 1). Compared with those without prior CABG, patients with prior CABG were more likely to have recurrent myocardial infarction (18.3% vs 7.0%, p<0.001), heart failure (17.5% vs 7.6%, p<0.001), stroke (3.7% vs 2.0%, p<0.001) and unplanned repeat PCI (8.9% vs 4.1%, p<0.001). There were no significant differences in minor bleeding (8.9% vs 10.0%, p=0.138). Age-specific all-cause mortality and non-fatal outcomes are shown in Figures 2 and 3. A significantly higher all-cause mortality was observed in those with prior CABG under 75 years of age, but not among those over 75 years. Across all age groups, hospitalisation for MI and HF was higher in patients with prior CABG. In those below the age of 75 years, hospitalisation for stroke was higher in those with prior CABG. The rate of major bleeding was similar in both groups for those <60 years, but for those aged over 60 years the major bleeding rate was lower in those with prior CABG. Unplanned repeat PCI after the index hospitalisation was twofold higher in patients with prior CABG (8.9% vs 4.1%, p<0.001).
Discussion
This contemporary registry-based study included all patients with ACS who underwent coronary angiography throughout New Zealand over a four-year period and compared the characteristics, management and outcomes based on whether they had prior CABG. In this cohort, 6.7% had a prior CABG. The key findings were that patients with prior CABG were: 1) older, more comorbid and more likely to have femoral arterial access; 2) less likely to receive myocardial revascularisation and more likely to receive PCI than repeat CABG; 3) more likely to have worse outcomes with higher all-cause mortality, recurrent MI, HF hospitalisation and unplanned PCI at a mean follow-up of 2.1 years.
Baseline characteristics and coronary angiography access
As expected, our results found patients with prior CABG were older, more likely to be male, less likely to present with STEMI and more likely to have femoral arterial access. A sub-analysis of the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial showed that prior CABG is associated with older age, more frequent cardiovascular comorbidities and poorer outcomes, with higher major adverse cardiac events (MACE).[[1]] Several studies have also demonstrated similar findings.[[2,4–6,14]] Prior CABG patients are more likely to present with UA and less likely to present with STEMI. A possible explanation is the formation of coronary arterial collaterals resulting in a smaller infarct size.[[4,6]] More than half of the patients with prior CABG in our cohort had transfemoral access. Transradial access in patients with prior CABG can be more challenging than transfemoral.[[15]] While it is reassuring that the major bleeding rate was similar for those with and without CABG, the Randomized Comparison of the Transradial and Transfemoral Approaches for Coronary Artery Bypass Graft Angiography and Intervention (RADIAL-CABG) trial found transradial diagnostic angiography was associated with greater contrast use, longer procedure and fluoroscopy time and greater radiation exposure when compared with transfemoral access.[[16]]
Myocardial revascularisation
In this study, half of patients with prior CABG vs three-quarters of patients without prior CABG had coronary revascularisation. Redo CABG was uncommon for patients with prior CABG. Most revascularisation for patients with prior CABG was therefore by PCI, which was most commonly performed on native vessels. Approximately 40% of these PCI cases were performed on graft vessels alone. Venous grafts have been found to occlude more commonly than arterial grafts and late saphenous venous graft patency following CABG is reported to be 55–60% at 10 years.[[17–20]] Although there is an evidence gap in the management of ACS in patients with prior CABG, PCI rates in this group has been consistently lower compared with patients without prior CABG.[[2,4,14,21–22]] Patients with prior CABG in our study were significantly less likely to be referred for surgical revascularisation, likely due to older age, more complex coronary anatomy and higher risk profile. Previous studies have demonstrated higher mortality risk with repeat CABG when compared with medical management and revascularisation with PCI.[[1,4]]
Short- and long-term outcomes
Our study found that over a mean follow-up of 2.1 years after an ACS, the rates of all-cause mortality, recurrent MI, HF and unplanned repeat PCI were approximately twofold higher in patients with prior CABG when compared with patients without prior CABG. The increased risk of all-cause mortality was most evident in those aged under 75 years. This has also been observed in other studies where a history of previous CABG was not associated with increased major adverse cardiovascular events (MACE) at one-year in patients aged 75 years and older presenting with ACS.[[14]] Another study demonstrated a higher burden of comorbidities in patients with prior CABG, but after multivariable adjustment previous CABG itself was not an independent predictor of increased one-year mortality.[[2]] One older clinical trial reported higher recurrent MI and unplanned revascularisation up to 1 year in those with prior CABG.[[1]] More contemporary registry studies have not reported morbidity beyond 30 days.[[2,14]] Our study found higher rates of recurrent MI and HF in patients with prior CABG across all age groups, reflecting a more comorbid and higher risk group. Lastly, patients with prior CABG with ACS are more likely to have multivessel disease and less likely to present with STEMI.[[2,4,18]] Identifying the culprit lesion in this group can be difficult and may result in repeat hospitalisations with suspected or confirmed ACS. This likely contributes to the higher rates of unplanned repeat PCI in patients with prior CABG found in this study. An intriguing finding is that in those over 60 years, the rate of major bleeding was lower in patients with prior CABG. Our study found the use of clopidogrel was more common in those with prior CABG, consistent with previous studies.[[2]] The use of lower intensity and short duration of anti-platelet therapy due to lower rates of PCI possibly accounts for the lower major bleeding rates in this subgroup.
Clinical implications
In this contemporary cohort of patients with ACS and prior CABG, half of those judged clinically appropriate for an invasive management strategy in routine practice were considered suitable for revascularisation. Patients and clinicians should be aware of the considerably higher rates of mortality, recurrent MI, HF and unplanned revascularisation in these patients. Approach to the treatment of these patients should be assessed on a case-by-case basis, but medication optimisation and cardiac rehab remain integral parts of the management.
Limitations
This study was subject to the known limitations of registry-based studies. For instance, there is likely to be a lack of uniformity in the management of patients by different clinicians, multiple centres, and over the duration of the study period. Symptom status was not available and may have been an important factor in determining patient management. We used ICD coding following hospital discharge to capture events during the follow-up period. As a result, important outcomes treated in the outpatient setting would not be included. The contribution of continued medication prescription and adherence could not be evaluated in this analysis. Lastly, we did not study patients with ACS managed with a conservative or non-invasive approach. While with any statistical analysis there can be a risk of Type II (false negative) errors, the very large sample size (and subsequent power) in this study makes it unlikely that the differences between any of the variables analysed are falsely negative. Similarly, while there is a risk of Type I (false positive) errors in any descriptive study, that risk is clearly minimised in a study of this size.
Conclusion
In patients with ACS, a history of prior CABG was associated with a high burden of comorbidities when compared with patients without prior CABG. All-cause mortality, recurrent MI and HF hospitalisations were higher in patients with prior CABG. Despite accounting for a growing proportion of ACS patients, deciding treatment modalities for this subgroup is still a complex and challenging process. Further trials are needed to study the management strategies to improve prognosis in this high-risk group.
Summary
Abstract
Aim
Coronary angiography in patients with previous coronary artery bypass grafts (CABG) is technically more difficult with increased procedure time, radiation exposure and in-hospital complications. In a contemporary national registry of acute coronary syndrome (ACS) patients undergoing an invasive strategy, we compared the management and outcomes of patients with and without prior CABG.
Method
The All New Zealand ACS Quality Improvement (ANZACS-QI) registry was used to identify patients admitted to New Zealand public hospitals with an ACS who underwent invasive coronary angiography (2014–2018). Outcomes were ascertained by anonymised linkage to national datasets.
Results
Of 26,869 patients, 1,791 (6.7%) had prior CABG and 25,078 (93.3%) had no prior CABG. Prior CABG patients were older (mean age 71 years vs 65 years), more comorbid and less likely to be revascularised than those without CABG (49.8% vs 73.0%). Compared to patients without CABG, at a mean follow-up of 2.1 years, patients with prior CABG had higher all-cause mortality (HR 2.03 (1.80–2.29)), and were more likely to have recurrent myocardial infarction (HR 2.70 (2.40–3.04)), rehospitalisation with congestive cardiac failure (HR 2.36 (2.10–2.66)) and stroke (HR 1.82 (1.41–2.34)).
Conclusion
In contemporary real-world practice, despite half of the patients with ACS and prior CABG receiving PCI, the outcomes remain poor compared with those without prior CABG.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
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2) Ribeiro JM, Teixeira R, Siserman A, Puga L, Lopes J, Sousa JP, et al. Impact of previous coronary artery bypass grafting in patients presenting with an acute coronary syndrome: current trends and clinical implications. Eur Heart J Acute Cardiovasc Care. 2020;9(7):731-40.
3) Collet JP, Thiele H, Barbato E, Barthélémy O, Bauersachs J, Dorobantu M, et al. 2020 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent STsegment elevation: The task force for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation of the European Society of Cardiology (ESC). Eur Heart J. 2021;42:1289-367.
4) Marcuschamer I, Zusman O, Iakobishvili Z, Assali AR, Vaknin-Assa H, Goldenberg I, et al. Outcome of patients with prior coronary bypass surgery admitted with an acute coronary syndrome. Heart. 2021;107(22):1820-5.
5) Shoaib A, Kinnaird T, Curzen N, Kontopantelis E, Ludman P, de Belder M, et al. Outcomes following percutaneous coronary intervention in non-ST-segment-elevation myocardial infarction patients with coronary artery bypass grafts. Circ Cardiovasc Interv. 2018;11(11):1-10.
6) Al-Aqeedi R, Sulaiman K, Al Suwaidi J, Alhabib K, El-Menyar A, Panduranga P, et al. Characteristics, management and outcomes of patients with acute coronary syndrome and prior coronary artery bypass surgery: findings from the second Gulf Registry of Acute Coronary Events. Interact Cardiovasc Thorac Surg. 2011;13(6):611-8.
7) Kerr A, Williams MJ, White H, Doughty R, Nunn C, Devlin G, et al. The All New Zealand Acute Coronary Syndrome Quality Improvement Programme: Implementation, Methodology and Cohorts (ANZACS-QI 9). NZ Med J. 2016;129(1439):23-6.
8) National Health Board. National Minimum Dataset (Hospital Events). Data Dictionary. Wellington, New Zealand: Ministry of Health; 2014.
9) Thygesen K, Alpert JS, Jaffe AS, Simoons ML, Chaitman BR, White HD, et al. Third universal definition of myocardial infarction. Eur Heart J. 2012;33(20):2551-67.
10) Ministry of Health. Ethnicity data protocols for the health and disabilty sector. Wellington, New Zealand: Ministry of Health; 2004.
11) Granger CB, Goldberg RJ, Dabbous O, Pieper KS, Eagle KA, Cannon CP, et al. Predictors of hospital mortality in the global registry of acute coronary events. Arch Intern Med. 2003;163(19):2345-53.
12) Mehran R, Rao SV, Bhatt DL, Gibson CM, Caixeta A, Eikelboom J, et al. Standardized bleeding definitions for cardiovascular clinical trials: a consensus report from the Bleeding Academic Research Consortium. Circulation. 2011;123(23):2736-47.
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15) Rigattieri S, Sciahbasi A, Brilakis ES, Burzotta F, Rathore S, Pugliese FR, et al. Meta-Analysis of radial versus femoral artery approach for coronary procedures in patients with previous coronary artery bypass grafting. Am J Cardiol. 2016;117(8):1248-55.
16) Michael TT, Alomar M, Papayannis A, Mogabgab O, Patel VG, Rangan BV, et al. A randomized comparison of the transradial and transfemoral approaches for coronary artery bypass graft angiography and intervention: the RADIAL-CABG Trial (RADIAL Versus Femoral Access for Coronary Artery Bypass Graft Angiography and Intervention). JACC Cardiovasc Interv. 2013;6(11):1138-44.
17) Al-Aqeedi RF, Al Suwaidi J. Outcomes of patients with prior coronary artery bypass graft who present with acute coronary syndrome. Expert Rev Cardiovasc Ther. 2014;12(6):715-32.
18) Blachutzik F, Achenbach S, Troebs M, Roether J, Nef H, Hamm C, et al. Angiographic findings and revascularization success in patients with acute myocardial infarction and previous coronary bypass grafting. Am J Cardiol. 2016;118(4):473-6.
19) Goldman S, Zadina K, Moritz T, Ovitt T, Sethi G, Copeland JG, et al. Long-term patency of saphenous vein and left internal mammary artery grafts after coronary artery bypass surgery: results from a department of veterans affairs cooperative study. J Am Coll Cardiol. 2004;44(11):2149-56.
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Revascularisation and outcomes after acute coronary syndromes in patients with prior coronary artery bypass grafting—ANZACS-QI 67
View Article PDF
In those with acute coronary syndromes (ACS) and previous coronary artery bypass grafts (CABG), invasive coronary angiography and percutaneous coronary intervention (PCI) are technically more challenging. There is an increase in procedural time, contrast use and radiation dose.[[1]] The culprit lesions may be in either a bypass graft or native vessels and the identification and treatment of culprit lesions may be more complex in the context of pre-existing multivessel disease.[[1,2]] Although current guidelines recommend an early invasive strategy in patients with acute coronary syndrome (ACS), these patients were excluded from the randomised clinical trials of invasive management.[[3]] They are an important sub-group to better understand – patients with prior CABG account for around one in 10 of those with ACS.[[4,5]] Patients with prior CABG have been reported to have higher morbidity and mortality up to one year.[[1,2,4–6]] There is currently a lack of randomised clinical trial data in outcomes of invasive management of ACS in patients with prior CABG. Previous trials and guidelines of management of ACS often excluded prior CABG patients.
The All NZ ACS Quality Improvement (ANZACS-QI) registry captures virtually all New Zealand patients hospitalised with ACS who undergo coronary angiography.[[7]] Through the registry and by data linkage with national administrative datasets we are able to track longer-term morbidity and mortality outcomes for all patients.[[8]] We utilised this contemporary registry cohort to describe the clinical characteristics, myocardial revascularisation and longer-term outcomes of ACS patients with prior CABG and compare these to those without prior CABG.
Methods
The methodology of the All NZ ACS Quality Improvement (ANZACS-QI) registries programme was previously described in detail.[[7]] Patients undergoing invasive coronary angiography are continuously captured in the CathPCI dataset and are available to the ANZACS-QI investigators. It contains patient demographics, admission ACS risk stratification information, cardiovascular risk factors, indication for invasive coronary angiography and procedural details. These registries are subject to monthly auditing and consistently achieve complete data collection in over 95% of all those with suspected ACS undergoing coronary angiography. Using the National Health Index (NHI), a unique national alphanumeric patient identifier, the CathPCI data can be linked with the ACS Routine Information cohort arm of the ANZACS-QI to identify those with confirmed ACS undergoing invasive coronary angiography. Over 98% of New Zealanders have an NHI that identifies them in various national and regional health system databases.[[7]]
We included patients 20 years old and above with their first ACS presentation undergoing coronary angiography in public hospitals throughout New Zealand between 1 September 2014 and 31 October 2018. Those that did not survive to hospital discharge were excluded. The follow-up period for this analysis was limited to 31 December 2018.
Definitions
Patients with ACS were categorised into ST-segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction (NSTEMI) and unstable angina (UA). For the purposes of this study, myocardial infarction (MI) was defined according to the Third Universal Definition of MI.[[9]]
The demographic data presented includes age, sex, ethnicity and body mass index (BMI). For patients who recorded more than one ethnic group, ethnicity was prioritised according to the New Zealand Ministry of Health protocol, in the following order: Indigenous Māori, Pacific people, Indian, other Asian and NZ European/other. The only exception was that those of Fijian Indian ethnicity were counted as Indian.[[10]] Several patient characteristics were evaluated including time since CABG (where applicable), prior MI, prior heart failure (HF), diabetes, hypertension, dyslipidaemia, current smoking and Global Registry of Acute Coronary Events (GRACE) score. We report the GRACE score as an estimate of in-hospital mortality post-ACS. It is categorised into low (<1%), medium (1 to <3%) or high (3%).[[11]]
Invasive coronary angiographic procedural and result data included vascular access site, coronary anatomic data and myocardial revascularisation modality (PCI or CABG). In this study, coronary artery stenoses ≥50% were considered significant.
Among those that underwent more than one myocardial revascularisation procedure, a distinction was made between those undergoing elective staged procedures and unplanned procedures. All unplanned revascularisation procedures were categorised as: unplanned repeat PCI during the index hospitalisation; unplanned repeat PCI due to suspected/confirmed ACS in the first subsequent hospitalisation; or unplanned revascularisation with CABG due to suspected/confirmed ACS in the first subsequent hospitalisation.
Guideline-directed medical therapy (GDMT) at discharge were assessed. This included the rate of aspirin, P2Y12 agent, statin, beta-blocker, and angiotensin-converting-enzyme (ACE) inhibitors or angiotensin receptor blocker (ARB). Anti-coagulation prescription was incomplete as data input for dabigatran was added to the ANZACS-QI registry from June 2017 and rivaroxaban from September 2018.
Data linkage and outcomes
In-hospital outcomes were defined as those that occurred during the index hospitalisation and were obtained from the ANZACS-QI registry. These data included major bleeding, stroke, and unplanned myocardial revascularisation procedures (CABG and PCI). Major bleeding was defined using the Bleeding Academic Research Consortium definition for bleeding. We included all BARC Type 3 (3a, 3b and 3c) and Type 5 (5a and 5b).[[12]]
Following index hospitalisation discharge, mortality and rehospitalisation for MI, HF, stroke and major non-CABG related bleeding were identified by individual patient linkage to national datasets using their NHI as previously described.[[7,8,13]] An encrypted version of each NHI was used to anonymously link in-hospital ANZACS-QI patient records with the National Minimum Dataset.[[ 7,8]] We report the rates of these outcomes at 30 days, one year and mean follow-up. Hospitalisation for the outcomes of interest were defined as those in which it was listed as the primary or secondary discharge diagnosis using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification (ICD-10-AM). Unplanned repeat PCI is reported from the prospectively captured ANZACS-QI registry.
Statistical analysis
Categorical data were presented as frequency and column percentage. Continuous data were presented as mean ± standard deviation (SD) and median with inter-quartile range (IQR). Comparisons between groups were done using Chi-squared test and continuous data were done using non-parametric Mann–Whitney U test as the data were not normally distributed. All p-values reported were two-tailed and p-value <0.05 was considered significant. Outcomes were visualised using Kaplan–Meier survival curves. Univariate Cox proportional hazards regression was used to estimate the hazard ratio and 95% confidence intervals for patients with CABG compared to those without CABG for each outcome. Unadjusted 30-day and 1-year mortality from discharge curves were calculated using Kaplan–Meier analyses. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).
Results
Between 1 September 2014 and 31 October 2018, 26,869 patients were admitted to a public hospital in New Zealand with an ACS and underwent invasive coronary angiography. Of these, 1,791 (6.7%) had prior CABG and 25,078 (93.3%) had no prior CABG (Table 1). The mean follow-up was 2.1 years for both groups. The mean age was 65.4 (SD 11.8) years and males account for 69.3% of the cohort. Most patients were of NZ European/Other ethnicity (77.0%) and 11.1% were Māori. The most common presentation was NSTEMI (58.1%) followed by STEMI (26.3%) and UA (15.6%).
A detailed comparison of those with and without prior CABG is presented in Table 1. Patients with prior CABG were older (71.3±8.9 years vs 65.0±11.8 years, p<0.001) and more likely to be male (81.3% vs 68.4%, p<0.001) and of NZ European/Other ethnicity (82.9% vs 76.5%, p<0.001). Those with prior CABG had a higher prevalence of several comorbid conditions—prior MI (68.2% vs 17.6%, p<0.001), prior HF (68.2% vs. 17.6%, p<0.001) and diabetes (34.6% vs 22.3%, p<0.001). Conversely, a lower proportion of those with prior CABG were current smokers (12.1% vs 24.0%, p<0.001). Patients with prior CABG were more likely to present with UA (24.1% vs 15.0%, p<0.001) and less likely to present with STEMI (12.3% vs 27.3%, p<0.001).
The details relating to coronary angiography and myocardial revascularisation during the index hospitalisation are provided in Table 2. While radial arterial access was most commonly used in those without prior CABG (90.4%), femoral arterial access was most commonly used in those with prior CABG (50.6%). Overall, 87.3% of patients had significant coronary artery stenoses and 71.5% received myocardial revascularisation. Nearly all patients (99.5%) with prior CABG had angiographically significant lesions. However, only 49.8% had myocardial revascularisation compared to 73.0% of those with no prior CABG. When PCI was undertaken in patients with prior CABG, the target vessel was most commonly a native vessel alone (59.9%). Graft vessel PCI was most frequently undertaken without concomitant native vessel PCI. Saphenous vein graft PCI accounted for almost all (92.4%) graft vessel PCI. The total numbers of lesions treated were similar among those with and without prior CABG (1.29±0.56 vs 1.36±0.66, respectively). Intracoronary imaging was rarely performed in either group—IVUS (1.0% vs 0.5%) and OCT (0.1% vs 0.5%).
At the time of discharge, guideline-directed medical therapy (GDMT) was high and similar for those with and without prior CABG: aspirin (93.9% vs 95.1%, p=0.031), statin (92.0% vs 93.3%, p=0.047), P2Y12 inhibitor (81.8% vs 78.4%, p<0.001). Clopidogrel use was more common in patients with prior CABG (41.9% vs 27.2%, p<0.001). There were incomplete data relating to anticoagulant use as this field was added to the ANZACS-QI registry after the commencement of the study period. Beta-blocker (83.9% vs 81.4%, p=0.011) and angiotensin-converting enzyme (ACE) inhibitor/angiotensin receptor blocker (72.4% vs 71.2%, p=0.262) prescription was high and similar between patients with and without prior CABG.
In-hospital outcomes and mortality and non-fatal outcomes at a mean follow-up of 2.1 years are documented in Table 3. During the index hospitalisation rates of major bleeding, stroke and unplanned PCI were low in both patients with and without prior CABG. The univariate Cox regression hazard ratios and 95% confidence intervals for CABG, using patients without CABG as the comparator, are as follows for each outcome: all-cause mortality (HR 2.03 (1.80–2.29)), recurrent MI (2.70 (2.40–3.04)), CHF hospitalisation (2.36 (2.10–2.66)), stroke hospitalisation (1.82 (1.41–2.34)) and major bleeding hospitalisation (0.87 (0.75–1.03)).
In the whole cohort, the 1-year mortality was 5.4%. At this time point, a higher mortality was observed in those with prior CABG (9.0% vs 5.1%, p<0.001) (Figure 1). Compared with those without prior CABG, patients with prior CABG were more likely to have recurrent myocardial infarction (18.3% vs 7.0%, p<0.001), heart failure (17.5% vs 7.6%, p<0.001), stroke (3.7% vs 2.0%, p<0.001) and unplanned repeat PCI (8.9% vs 4.1%, p<0.001). There were no significant differences in minor bleeding (8.9% vs 10.0%, p=0.138). Age-specific all-cause mortality and non-fatal outcomes are shown in Figures 2 and 3. A significantly higher all-cause mortality was observed in those with prior CABG under 75 years of age, but not among those over 75 years. Across all age groups, hospitalisation for MI and HF was higher in patients with prior CABG. In those below the age of 75 years, hospitalisation for stroke was higher in those with prior CABG. The rate of major bleeding was similar in both groups for those <60 years, but for those aged over 60 years the major bleeding rate was lower in those with prior CABG. Unplanned repeat PCI after the index hospitalisation was twofold higher in patients with prior CABG (8.9% vs 4.1%, p<0.001).
Discussion
This contemporary registry-based study included all patients with ACS who underwent coronary angiography throughout New Zealand over a four-year period and compared the characteristics, management and outcomes based on whether they had prior CABG. In this cohort, 6.7% had a prior CABG. The key findings were that patients with prior CABG were: 1) older, more comorbid and more likely to have femoral arterial access; 2) less likely to receive myocardial revascularisation and more likely to receive PCI than repeat CABG; 3) more likely to have worse outcomes with higher all-cause mortality, recurrent MI, HF hospitalisation and unplanned PCI at a mean follow-up of 2.1 years.
Baseline characteristics and coronary angiography access
As expected, our results found patients with prior CABG were older, more likely to be male, less likely to present with STEMI and more likely to have femoral arterial access. A sub-analysis of the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial showed that prior CABG is associated with older age, more frequent cardiovascular comorbidities and poorer outcomes, with higher major adverse cardiac events (MACE).[[1]] Several studies have also demonstrated similar findings.[[2,4–6,14]] Prior CABG patients are more likely to present with UA and less likely to present with STEMI. A possible explanation is the formation of coronary arterial collaterals resulting in a smaller infarct size.[[4,6]] More than half of the patients with prior CABG in our cohort had transfemoral access. Transradial access in patients with prior CABG can be more challenging than transfemoral.[[15]] While it is reassuring that the major bleeding rate was similar for those with and without CABG, the Randomized Comparison of the Transradial and Transfemoral Approaches for Coronary Artery Bypass Graft Angiography and Intervention (RADIAL-CABG) trial found transradial diagnostic angiography was associated with greater contrast use, longer procedure and fluoroscopy time and greater radiation exposure when compared with transfemoral access.[[16]]
Myocardial revascularisation
In this study, half of patients with prior CABG vs three-quarters of patients without prior CABG had coronary revascularisation. Redo CABG was uncommon for patients with prior CABG. Most revascularisation for patients with prior CABG was therefore by PCI, which was most commonly performed on native vessels. Approximately 40% of these PCI cases were performed on graft vessels alone. Venous grafts have been found to occlude more commonly than arterial grafts and late saphenous venous graft patency following CABG is reported to be 55–60% at 10 years.[[17–20]] Although there is an evidence gap in the management of ACS in patients with prior CABG, PCI rates in this group has been consistently lower compared with patients without prior CABG.[[2,4,14,21–22]] Patients with prior CABG in our study were significantly less likely to be referred for surgical revascularisation, likely due to older age, more complex coronary anatomy and higher risk profile. Previous studies have demonstrated higher mortality risk with repeat CABG when compared with medical management and revascularisation with PCI.[[1,4]]
Short- and long-term outcomes
Our study found that over a mean follow-up of 2.1 years after an ACS, the rates of all-cause mortality, recurrent MI, HF and unplanned repeat PCI were approximately twofold higher in patients with prior CABG when compared with patients without prior CABG. The increased risk of all-cause mortality was most evident in those aged under 75 years. This has also been observed in other studies where a history of previous CABG was not associated with increased major adverse cardiovascular events (MACE) at one-year in patients aged 75 years and older presenting with ACS.[[14]] Another study demonstrated a higher burden of comorbidities in patients with prior CABG, but after multivariable adjustment previous CABG itself was not an independent predictor of increased one-year mortality.[[2]] One older clinical trial reported higher recurrent MI and unplanned revascularisation up to 1 year in those with prior CABG.[[1]] More contemporary registry studies have not reported morbidity beyond 30 days.[[2,14]] Our study found higher rates of recurrent MI and HF in patients with prior CABG across all age groups, reflecting a more comorbid and higher risk group. Lastly, patients with prior CABG with ACS are more likely to have multivessel disease and less likely to present with STEMI.[[2,4,18]] Identifying the culprit lesion in this group can be difficult and may result in repeat hospitalisations with suspected or confirmed ACS. This likely contributes to the higher rates of unplanned repeat PCI in patients with prior CABG found in this study. An intriguing finding is that in those over 60 years, the rate of major bleeding was lower in patients with prior CABG. Our study found the use of clopidogrel was more common in those with prior CABG, consistent with previous studies.[[2]] The use of lower intensity and short duration of anti-platelet therapy due to lower rates of PCI possibly accounts for the lower major bleeding rates in this subgroup.
Clinical implications
In this contemporary cohort of patients with ACS and prior CABG, half of those judged clinically appropriate for an invasive management strategy in routine practice were considered suitable for revascularisation. Patients and clinicians should be aware of the considerably higher rates of mortality, recurrent MI, HF and unplanned revascularisation in these patients. Approach to the treatment of these patients should be assessed on a case-by-case basis, but medication optimisation and cardiac rehab remain integral parts of the management.
Limitations
This study was subject to the known limitations of registry-based studies. For instance, there is likely to be a lack of uniformity in the management of patients by different clinicians, multiple centres, and over the duration of the study period. Symptom status was not available and may have been an important factor in determining patient management. We used ICD coding following hospital discharge to capture events during the follow-up period. As a result, important outcomes treated in the outpatient setting would not be included. The contribution of continued medication prescription and adherence could not be evaluated in this analysis. Lastly, we did not study patients with ACS managed with a conservative or non-invasive approach. While with any statistical analysis there can be a risk of Type II (false negative) errors, the very large sample size (and subsequent power) in this study makes it unlikely that the differences between any of the variables analysed are falsely negative. Similarly, while there is a risk of Type I (false positive) errors in any descriptive study, that risk is clearly minimised in a study of this size.
Conclusion
In patients with ACS, a history of prior CABG was associated with a high burden of comorbidities when compared with patients without prior CABG. All-cause mortality, recurrent MI and HF hospitalisations were higher in patients with prior CABG. Despite accounting for a growing proportion of ACS patients, deciding treatment modalities for this subgroup is still a complex and challenging process. Further trials are needed to study the management strategies to improve prognosis in this high-risk group.
Summary
Abstract
Aim
Coronary angiography in patients with previous coronary artery bypass grafts (CABG) is technically more difficult with increased procedure time, radiation exposure and in-hospital complications. In a contemporary national registry of acute coronary syndrome (ACS) patients undergoing an invasive strategy, we compared the management and outcomes of patients with and without prior CABG.
Method
The All New Zealand ACS Quality Improvement (ANZACS-QI) registry was used to identify patients admitted to New Zealand public hospitals with an ACS who underwent invasive coronary angiography (2014–2018). Outcomes were ascertained by anonymised linkage to national datasets.
Results
Of 26,869 patients, 1,791 (6.7%) had prior CABG and 25,078 (93.3%) had no prior CABG. Prior CABG patients were older (mean age 71 years vs 65 years), more comorbid and less likely to be revascularised than those without CABG (49.8% vs 73.0%). Compared to patients without CABG, at a mean follow-up of 2.1 years, patients with prior CABG had higher all-cause mortality (HR 2.03 (1.80–2.29)), and were more likely to have recurrent myocardial infarction (HR 2.70 (2.40–3.04)), rehospitalisation with congestive cardiac failure (HR 2.36 (2.10–2.66)) and stroke (HR 1.82 (1.41–2.34)).
Conclusion
In contemporary real-world practice, despite half of the patients with ACS and prior CABG receiving PCI, the outcomes remain poor compared with those without prior CABG.
Author Information
Acknowledgements
Correspondence
Correspondence Email
Competing Interests
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2) Ribeiro JM, Teixeira R, Siserman A, Puga L, Lopes J, Sousa JP, et al. Impact of previous coronary artery bypass grafting in patients presenting with an acute coronary syndrome: current trends and clinical implications. Eur Heart J Acute Cardiovasc Care. 2020;9(7):731-40.
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6) Al-Aqeedi R, Sulaiman K, Al Suwaidi J, Alhabib K, El-Menyar A, Panduranga P, et al. Characteristics, management and outcomes of patients with acute coronary syndrome and prior coronary artery bypass surgery: findings from the second Gulf Registry of Acute Coronary Events. Interact Cardiovasc Thorac Surg. 2011;13(6):611-8.
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Revascularisation and outcomes after acute coronary syndromes in patients with prior coronary artery bypass grafting—ANZACS-QI 67
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In those with acute coronary syndromes (ACS) and previous coronary artery bypass grafts (CABG), invasive coronary angiography and percutaneous coronary intervention (PCI) are technically more challenging. There is an increase in procedural time, contrast use and radiation dose.[[1]] The culprit lesions may be in either a bypass graft or native vessels and the identification and treatment of culprit lesions may be more complex in the context of pre-existing multivessel disease.[[1,2]] Although current guidelines recommend an early invasive strategy in patients with acute coronary syndrome (ACS), these patients were excluded from the randomised clinical trials of invasive management.[[3]] They are an important sub-group to better understand – patients with prior CABG account for around one in 10 of those with ACS.[[4,5]] Patients with prior CABG have been reported to have higher morbidity and mortality up to one year.[[1,2,4–6]] There is currently a lack of randomised clinical trial data in outcomes of invasive management of ACS in patients with prior CABG. Previous trials and guidelines of management of ACS often excluded prior CABG patients.
The All NZ ACS Quality Improvement (ANZACS-QI) registry captures virtually all New Zealand patients hospitalised with ACS who undergo coronary angiography.[[7]] Through the registry and by data linkage with national administrative datasets we are able to track longer-term morbidity and mortality outcomes for all patients.[[8]] We utilised this contemporary registry cohort to describe the clinical characteristics, myocardial revascularisation and longer-term outcomes of ACS patients with prior CABG and compare these to those without prior CABG.
Methods
The methodology of the All NZ ACS Quality Improvement (ANZACS-QI) registries programme was previously described in detail.[[7]] Patients undergoing invasive coronary angiography are continuously captured in the CathPCI dataset and are available to the ANZACS-QI investigators. It contains patient demographics, admission ACS risk stratification information, cardiovascular risk factors, indication for invasive coronary angiography and procedural details. These registries are subject to monthly auditing and consistently achieve complete data collection in over 95% of all those with suspected ACS undergoing coronary angiography. Using the National Health Index (NHI), a unique national alphanumeric patient identifier, the CathPCI data can be linked with the ACS Routine Information cohort arm of the ANZACS-QI to identify those with confirmed ACS undergoing invasive coronary angiography. Over 98% of New Zealanders have an NHI that identifies them in various national and regional health system databases.[[7]]
We included patients 20 years old and above with their first ACS presentation undergoing coronary angiography in public hospitals throughout New Zealand between 1 September 2014 and 31 October 2018. Those that did not survive to hospital discharge were excluded. The follow-up period for this analysis was limited to 31 December 2018.
Definitions
Patients with ACS were categorised into ST-segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction (NSTEMI) and unstable angina (UA). For the purposes of this study, myocardial infarction (MI) was defined according to the Third Universal Definition of MI.[[9]]
The demographic data presented includes age, sex, ethnicity and body mass index (BMI). For patients who recorded more than one ethnic group, ethnicity was prioritised according to the New Zealand Ministry of Health protocol, in the following order: Indigenous Māori, Pacific people, Indian, other Asian and NZ European/other. The only exception was that those of Fijian Indian ethnicity were counted as Indian.[[10]] Several patient characteristics were evaluated including time since CABG (where applicable), prior MI, prior heart failure (HF), diabetes, hypertension, dyslipidaemia, current smoking and Global Registry of Acute Coronary Events (GRACE) score. We report the GRACE score as an estimate of in-hospital mortality post-ACS. It is categorised into low (<1%), medium (1 to <3%) or high (3%).[[11]]
Invasive coronary angiographic procedural and result data included vascular access site, coronary anatomic data and myocardial revascularisation modality (PCI or CABG). In this study, coronary artery stenoses ≥50% were considered significant.
Among those that underwent more than one myocardial revascularisation procedure, a distinction was made between those undergoing elective staged procedures and unplanned procedures. All unplanned revascularisation procedures were categorised as: unplanned repeat PCI during the index hospitalisation; unplanned repeat PCI due to suspected/confirmed ACS in the first subsequent hospitalisation; or unplanned revascularisation with CABG due to suspected/confirmed ACS in the first subsequent hospitalisation.
Guideline-directed medical therapy (GDMT) at discharge were assessed. This included the rate of aspirin, P2Y12 agent, statin, beta-blocker, and angiotensin-converting-enzyme (ACE) inhibitors or angiotensin receptor blocker (ARB). Anti-coagulation prescription was incomplete as data input for dabigatran was added to the ANZACS-QI registry from June 2017 and rivaroxaban from September 2018.
Data linkage and outcomes
In-hospital outcomes were defined as those that occurred during the index hospitalisation and were obtained from the ANZACS-QI registry. These data included major bleeding, stroke, and unplanned myocardial revascularisation procedures (CABG and PCI). Major bleeding was defined using the Bleeding Academic Research Consortium definition for bleeding. We included all BARC Type 3 (3a, 3b and 3c) and Type 5 (5a and 5b).[[12]]
Following index hospitalisation discharge, mortality and rehospitalisation for MI, HF, stroke and major non-CABG related bleeding were identified by individual patient linkage to national datasets using their NHI as previously described.[[7,8,13]] An encrypted version of each NHI was used to anonymously link in-hospital ANZACS-QI patient records with the National Minimum Dataset.[[ 7,8]] We report the rates of these outcomes at 30 days, one year and mean follow-up. Hospitalisation for the outcomes of interest were defined as those in which it was listed as the primary or secondary discharge diagnosis using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Australian Modification (ICD-10-AM). Unplanned repeat PCI is reported from the prospectively captured ANZACS-QI registry.
Statistical analysis
Categorical data were presented as frequency and column percentage. Continuous data were presented as mean ± standard deviation (SD) and median with inter-quartile range (IQR). Comparisons between groups were done using Chi-squared test and continuous data were done using non-parametric Mann–Whitney U test as the data were not normally distributed. All p-values reported were two-tailed and p-value <0.05 was considered significant. Outcomes were visualised using Kaplan–Meier survival curves. Univariate Cox proportional hazards regression was used to estimate the hazard ratio and 95% confidence intervals for patients with CABG compared to those without CABG for each outcome. Unadjusted 30-day and 1-year mortality from discharge curves were calculated using Kaplan–Meier analyses. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC).
Results
Between 1 September 2014 and 31 October 2018, 26,869 patients were admitted to a public hospital in New Zealand with an ACS and underwent invasive coronary angiography. Of these, 1,791 (6.7%) had prior CABG and 25,078 (93.3%) had no prior CABG (Table 1). The mean follow-up was 2.1 years for both groups. The mean age was 65.4 (SD 11.8) years and males account for 69.3% of the cohort. Most patients were of NZ European/Other ethnicity (77.0%) and 11.1% were Māori. The most common presentation was NSTEMI (58.1%) followed by STEMI (26.3%) and UA (15.6%).
A detailed comparison of those with and without prior CABG is presented in Table 1. Patients with prior CABG were older (71.3±8.9 years vs 65.0±11.8 years, p<0.001) and more likely to be male (81.3% vs 68.4%, p<0.001) and of NZ European/Other ethnicity (82.9% vs 76.5%, p<0.001). Those with prior CABG had a higher prevalence of several comorbid conditions—prior MI (68.2% vs 17.6%, p<0.001), prior HF (68.2% vs. 17.6%, p<0.001) and diabetes (34.6% vs 22.3%, p<0.001). Conversely, a lower proportion of those with prior CABG were current smokers (12.1% vs 24.0%, p<0.001). Patients with prior CABG were more likely to present with UA (24.1% vs 15.0%, p<0.001) and less likely to present with STEMI (12.3% vs 27.3%, p<0.001).
The details relating to coronary angiography and myocardial revascularisation during the index hospitalisation are provided in Table 2. While radial arterial access was most commonly used in those without prior CABG (90.4%), femoral arterial access was most commonly used in those with prior CABG (50.6%). Overall, 87.3% of patients had significant coronary artery stenoses and 71.5% received myocardial revascularisation. Nearly all patients (99.5%) with prior CABG had angiographically significant lesions. However, only 49.8% had myocardial revascularisation compared to 73.0% of those with no prior CABG. When PCI was undertaken in patients with prior CABG, the target vessel was most commonly a native vessel alone (59.9%). Graft vessel PCI was most frequently undertaken without concomitant native vessel PCI. Saphenous vein graft PCI accounted for almost all (92.4%) graft vessel PCI. The total numbers of lesions treated were similar among those with and without prior CABG (1.29±0.56 vs 1.36±0.66, respectively). Intracoronary imaging was rarely performed in either group—IVUS (1.0% vs 0.5%) and OCT (0.1% vs 0.5%).
At the time of discharge, guideline-directed medical therapy (GDMT) was high and similar for those with and without prior CABG: aspirin (93.9% vs 95.1%, p=0.031), statin (92.0% vs 93.3%, p=0.047), P2Y12 inhibitor (81.8% vs 78.4%, p<0.001). Clopidogrel use was more common in patients with prior CABG (41.9% vs 27.2%, p<0.001). There were incomplete data relating to anticoagulant use as this field was added to the ANZACS-QI registry after the commencement of the study period. Beta-blocker (83.9% vs 81.4%, p=0.011) and angiotensin-converting enzyme (ACE) inhibitor/angiotensin receptor blocker (72.4% vs 71.2%, p=0.262) prescription was high and similar between patients with and without prior CABG.
In-hospital outcomes and mortality and non-fatal outcomes at a mean follow-up of 2.1 years are documented in Table 3. During the index hospitalisation rates of major bleeding, stroke and unplanned PCI were low in both patients with and without prior CABG. The univariate Cox regression hazard ratios and 95% confidence intervals for CABG, using patients without CABG as the comparator, are as follows for each outcome: all-cause mortality (HR 2.03 (1.80–2.29)), recurrent MI (2.70 (2.40–3.04)), CHF hospitalisation (2.36 (2.10–2.66)), stroke hospitalisation (1.82 (1.41–2.34)) and major bleeding hospitalisation (0.87 (0.75–1.03)).
In the whole cohort, the 1-year mortality was 5.4%. At this time point, a higher mortality was observed in those with prior CABG (9.0% vs 5.1%, p<0.001) (Figure 1). Compared with those without prior CABG, patients with prior CABG were more likely to have recurrent myocardial infarction (18.3% vs 7.0%, p<0.001), heart failure (17.5% vs 7.6%, p<0.001), stroke (3.7% vs 2.0%, p<0.001) and unplanned repeat PCI (8.9% vs 4.1%, p<0.001). There were no significant differences in minor bleeding (8.9% vs 10.0%, p=0.138). Age-specific all-cause mortality and non-fatal outcomes are shown in Figures 2 and 3. A significantly higher all-cause mortality was observed in those with prior CABG under 75 years of age, but not among those over 75 years. Across all age groups, hospitalisation for MI and HF was higher in patients with prior CABG. In those below the age of 75 years, hospitalisation for stroke was higher in those with prior CABG. The rate of major bleeding was similar in both groups for those <60 years, but for those aged over 60 years the major bleeding rate was lower in those with prior CABG. Unplanned repeat PCI after the index hospitalisation was twofold higher in patients with prior CABG (8.9% vs 4.1%, p<0.001).
Discussion
This contemporary registry-based study included all patients with ACS who underwent coronary angiography throughout New Zealand over a four-year period and compared the characteristics, management and outcomes based on whether they had prior CABG. In this cohort, 6.7% had a prior CABG. The key findings were that patients with prior CABG were: 1) older, more comorbid and more likely to have femoral arterial access; 2) less likely to receive myocardial revascularisation and more likely to receive PCI than repeat CABG; 3) more likely to have worse outcomes with higher all-cause mortality, recurrent MI, HF hospitalisation and unplanned PCI at a mean follow-up of 2.1 years.
Baseline characteristics and coronary angiography access
As expected, our results found patients with prior CABG were older, more likely to be male, less likely to present with STEMI and more likely to have femoral arterial access. A sub-analysis of the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial showed that prior CABG is associated with older age, more frequent cardiovascular comorbidities and poorer outcomes, with higher major adverse cardiac events (MACE).[[1]] Several studies have also demonstrated similar findings.[[2,4–6,14]] Prior CABG patients are more likely to present with UA and less likely to present with STEMI. A possible explanation is the formation of coronary arterial collaterals resulting in a smaller infarct size.[[4,6]] More than half of the patients with prior CABG in our cohort had transfemoral access. Transradial access in patients with prior CABG can be more challenging than transfemoral.[[15]] While it is reassuring that the major bleeding rate was similar for those with and without CABG, the Randomized Comparison of the Transradial and Transfemoral Approaches for Coronary Artery Bypass Graft Angiography and Intervention (RADIAL-CABG) trial found transradial diagnostic angiography was associated with greater contrast use, longer procedure and fluoroscopy time and greater radiation exposure when compared with transfemoral access.[[16]]
Myocardial revascularisation
In this study, half of patients with prior CABG vs three-quarters of patients without prior CABG had coronary revascularisation. Redo CABG was uncommon for patients with prior CABG. Most revascularisation for patients with prior CABG was therefore by PCI, which was most commonly performed on native vessels. Approximately 40% of these PCI cases were performed on graft vessels alone. Venous grafts have been found to occlude more commonly than arterial grafts and late saphenous venous graft patency following CABG is reported to be 55–60% at 10 years.[[17–20]] Although there is an evidence gap in the management of ACS in patients with prior CABG, PCI rates in this group has been consistently lower compared with patients without prior CABG.[[2,4,14,21–22]] Patients with prior CABG in our study were significantly less likely to be referred for surgical revascularisation, likely due to older age, more complex coronary anatomy and higher risk profile. Previous studies have demonstrated higher mortality risk with repeat CABG when compared with medical management and revascularisation with PCI.[[1,4]]
Short- and long-term outcomes
Our study found that over a mean follow-up of 2.1 years after an ACS, the rates of all-cause mortality, recurrent MI, HF and unplanned repeat PCI were approximately twofold higher in patients with prior CABG when compared with patients without prior CABG. The increased risk of all-cause mortality was most evident in those aged under 75 years. This has also been observed in other studies where a history of previous CABG was not associated with increased major adverse cardiovascular events (MACE) at one-year in patients aged 75 years and older presenting with ACS.[[14]] Another study demonstrated a higher burden of comorbidities in patients with prior CABG, but after multivariable adjustment previous CABG itself was not an independent predictor of increased one-year mortality.[[2]] One older clinical trial reported higher recurrent MI and unplanned revascularisation up to 1 year in those with prior CABG.[[1]] More contemporary registry studies have not reported morbidity beyond 30 days.[[2,14]] Our study found higher rates of recurrent MI and HF in patients with prior CABG across all age groups, reflecting a more comorbid and higher risk group. Lastly, patients with prior CABG with ACS are more likely to have multivessel disease and less likely to present with STEMI.[[2,4,18]] Identifying the culprit lesion in this group can be difficult and may result in repeat hospitalisations with suspected or confirmed ACS. This likely contributes to the higher rates of unplanned repeat PCI in patients with prior CABG found in this study. An intriguing finding is that in those over 60 years, the rate of major bleeding was lower in patients with prior CABG. Our study found the use of clopidogrel was more common in those with prior CABG, consistent with previous studies.[[2]] The use of lower intensity and short duration of anti-platelet therapy due to lower rates of PCI possibly accounts for the lower major bleeding rates in this subgroup.
Clinical implications
In this contemporary cohort of patients with ACS and prior CABG, half of those judged clinically appropriate for an invasive management strategy in routine practice were considered suitable for revascularisation. Patients and clinicians should be aware of the considerably higher rates of mortality, recurrent MI, HF and unplanned revascularisation in these patients. Approach to the treatment of these patients should be assessed on a case-by-case basis, but medication optimisation and cardiac rehab remain integral parts of the management.
Limitations
This study was subject to the known limitations of registry-based studies. For instance, there is likely to be a lack of uniformity in the management of patients by different clinicians, multiple centres, and over the duration of the study period. Symptom status was not available and may have been an important factor in determining patient management. We used ICD coding following hospital discharge to capture events during the follow-up period. As a result, important outcomes treated in the outpatient setting would not be included. The contribution of continued medication prescription and adherence could not be evaluated in this analysis. Lastly, we did not study patients with ACS managed with a conservative or non-invasive approach. While with any statistical analysis there can be a risk of Type II (false negative) errors, the very large sample size (and subsequent power) in this study makes it unlikely that the differences between any of the variables analysed are falsely negative. Similarly, while there is a risk of Type I (false positive) errors in any descriptive study, that risk is clearly minimised in a study of this size.
Conclusion
In patients with ACS, a history of prior CABG was associated with a high burden of comorbidities when compared with patients without prior CABG. All-cause mortality, recurrent MI and HF hospitalisations were higher in patients with prior CABG. Despite accounting for a growing proportion of ACS patients, deciding treatment modalities for this subgroup is still a complex and challenging process. Further trials are needed to study the management strategies to improve prognosis in this high-risk group.
Summary
Abstract
Aim
Coronary angiography in patients with previous coronary artery bypass grafts (CABG) is technically more difficult with increased procedure time, radiation exposure and in-hospital complications. In a contemporary national registry of acute coronary syndrome (ACS) patients undergoing an invasive strategy, we compared the management and outcomes of patients with and without prior CABG.
Method
The All New Zealand ACS Quality Improvement (ANZACS-QI) registry was used to identify patients admitted to New Zealand public hospitals with an ACS who underwent invasive coronary angiography (2014–2018). Outcomes were ascertained by anonymised linkage to national datasets.
Results
Of 26,869 patients, 1,791 (6.7%) had prior CABG and 25,078 (93.3%) had no prior CABG. Prior CABG patients were older (mean age 71 years vs 65 years), more comorbid and less likely to be revascularised than those without CABG (49.8% vs 73.0%). Compared to patients without CABG, at a mean follow-up of 2.1 years, patients with prior CABG had higher all-cause mortality (HR 2.03 (1.80–2.29)), and were more likely to have recurrent myocardial infarction (HR 2.70 (2.40–3.04)), rehospitalisation with congestive cardiac failure (HR 2.36 (2.10–2.66)) and stroke (HR 1.82 (1.41–2.34)).
Conclusion
In contemporary real-world practice, despite half of the patients with ACS and prior CABG receiving PCI, the outcomes remain poor compared with those without prior CABG.
Author Information
Acknowledgements
Correspondence
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Competing Interests
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Revascularisation and outcomes after acute coronary syndromes in patients with prior coronary artery bypass grafting—ANZACS-QI 67
In those with acute coronary syndromes (ACS) and previous coronary artery bypass grafts (CABG), invasive coronary angiography and percutaneous coronary intervention (PCI) are technically more challenging.
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