Minding the gaps in post-myocardial infarction mortality between Sweden and the UK

This editorial refers to ‘Statistics on mortality following acute myocardial infarction in 842897 Europeans’, by O.A. Alabas et al., pp. 149–157. Nationalized registry data for the monitoring and improvement of care after acute myocardial infarction have become an important force for implementation of guideline-directed medical therapy and policy change.1,2 These will undoubtedly continue to play a decisive role in our treatment and understanding of contemporary outcomes and treatment practices in aging and increasingly multimorbid global population and as treatments become more accessible in low- and middle-income countries. Even in nations with high incomes, nationalized registry data can highlight important areas for improvement in the delivery of post-myocardial infarction (MI) care. While nationalized registries cannot in themselves impute causality or highlight complex underlying social and behavioural trends, they form the basis of our understanding of the lag between the evidence and actual clinical practice.3,4 While global rates of mortality from acute coronary syndromes (ACS) and ischaemic heart disease, in general, have been on the decline for the past 25 years, this has not been the case for all countries.5 For example, by some reports, mortality rates from ACS continue to rise in India.6 The USA and the UK have seen reductions in mortality from ACS despite increasing patient complexity.5,7 In the USA, during the past 20 years, there have been declining rates of MI-related mortality and increasing rates of in-hospital percutaneous coronary intervention (PCI) but also significant increases in adjusted cost per MI-related hospitalization.8 Other countries have begun to see a plateau in mortality rates from ACS. Sweden saw a consistent decline in mortality from acute myocardial infarction from 1995 to 2009, but since that time has not seen as much improvement.9 South Korea has seen a similar plateau beginning in about 2012.10 Alabas et al.11 compare the rates of mortality from ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) in the UK vs. Sweden. The data for this analysis came from the Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART), including 180 368 patients from 73 hospitals in Sweden, and the Myocardial Ischaemia National Audit Project (MINAP), including 662 529 patients from 247 hospitals in the UK, both ranging from 2003 to 2013. Mortality rates were adjusted for disease burden, case mix, and treatment strategy, as well as differences in care delivered. The investigators used landmark analysis to distinguish between short- and long-term survival after myocardial infarction. After adjustment, the authors found an increased standardized net probability of death (NPD) in the UK vs. Sweden among patients both with NSTEMI and STEMI during the first month after myocardial infarction. After 6 months, adjusted mortality rates for NSTEMI remained higher in the UK vs. Sweden, but adjusted mortality rates for STEMI were similar between the two countries. It should be noted that there was higher unadjusted total mortality in Sweden vs. the UK for both STEMI (30.4% vs. 22.1%) and NSTEMI (40.5% vs. 32.2%) but that the Swedish patients were in general older and had more comorbidities. Median time to death was much later in Sweden than in the UK for STEMI (1.5 vs. 0.1 years) and NSTEMI (1.7 vs. 0.5 years); many of these later deaths were likely not related to the presenting myocardial infarction. After further adjustment for differences in reperfusion and revascularization, mortality for NSTEMI and STEMI was higher in the UK vs. Sweden for all landmark periods. In addition, as a part of a sensitivity analysis, non-standardized NPDs were higher for the UK than for Sweden for all time periods for both NSTEMI and STEMI. Though such an analysis is not able to reliably establish causality, the authors found striking differences in coronary revascularization and guideline-based medical therapy between the two countries. Specifically, rates of coronary angiography and revascularization, as well as use of dual-antiplatelet therapy and beta blockers, were lower in the UK vs. Sweden, while there was similar or higher use of statins and angiotensin-converting enzyme inhibitors in the UK (Figure 1). Therapies and standardized net probability of death for NSTEMI and STEMI in Sweden and the UK. Drawn from (A) Supplementary Table S4 and (B) Table 1 of Ref.11 This analysis highlights the fact that even in nations with high average incomes, important gaps in care exist as opportunities to improve post-MI mortality. Coronary revascularization is a Class I recommendation in all patients with myocardial infarction.12 Nevertheless, rates of revascularization have not consistently increased for the past decade, though individual and system reasons for this are surely complex and multifactorial.13 In an aging society, older patients continue to be less likely to undergo coronary angiography or PCI, though rates are gradually improving.14 These sophisticated and thoughtful analyses are novel in both analysing standardized death rates and adjusting for underlying treatment differences between two healthcare systems in high-income countries. While national registry data have important known limitations, such as residual confounding, lack of data capture, incomplete disease-specific mortality, and missing data, such evaluations likely provide the most reliable estimate of mortality after ACS in the real world.15,16 Future studies could further explore the characteristics of patients who do not undergo coronary revascularization at the time of myocardial infarction in these two countries, including access to primary PCI hospitals, multimorbidity, and frailty. Temporal trends in post-MI mortality and guideline-mandated therapies will be important in understanding these healthcare systems today, as the data for this study are primarily from the previous decade. The multimorbidity ‘clusters’ so deftly defined in MINAP could be validated among patients in SWEDEHEART.7 Perhaps most importantly, continued surveillance through these two exceptional data repositories will be important in tracking implementation of guideline-based therapies and mortality from myocardial infarction in these countries. Other countries would do well to learn from these experiences and set up similar national registries.