International comparisons of acute myocardial infarction
Authors: Chris P Gale, Keith A A Fox
Journal: The Lancet (2014)

Sheng-Chia Chung and colleagues1Chung S-C Gedeborg R Nicholas O et al.Acute myocardial infarction: a comparison of short-term survival in national outcome registries in Sweden and the UK.Lancet. 2014; (published online Jan 23.)http://dx.doi.org/10.1016/S0140-6736(13)62070-XSummary Full Text Full Text PDF Scopus (212) Google Scholar report in The Lancet that, in their comparison of short-term outcomes in patients with acute myocardial infarction, unadjusted 30-day mortality was more than a third higher in the UK than in Sweden during 2004–10. They suggest that this difference is due largely to the divergent speed of implementation of policy initiatives to improve care. Chung and colleagues compared the UK data with those for Sweden because the two countries have similar health systems for, and spending on, acute myocardial infarction, but diffusion of evidence-based changes to practice and new technologies has been notably quicker in Sweden. Records for 119 786 patients in Sweden and 391 077 in the UK were assessed. This fundamental prognosis research,2Hemingway H Croft P Perel P et al.Prognosis research strategy (PROGRESS) 1: a framework for researching clinical outcomes.BMJ. 2013; 346: e5595Crossref PubMed Scopus (336) Google Scholar which used whole-country data, showed much higher unadjusted mortality in patients with acute myocardial infarction in the UK than in Sweden: 30-day mortality was 10·5% (95% CI 10·4–10·6) in the UK and 7·6% (7·4–7·7) in Sweden. The UK to Sweden standardised mortality ratio was 1·37 (1·30–1·45), which suggests that more than 11 000 deaths due to acute myocardial infarction might have been avoided during the period of the study. Importantly, although the difference in mortality rates decreased over time, mortality was always higher in the UK, even in clinical subgroups such as those defined by troponin concentration or ST-segment elevation. After standardisation for the Swedish casemix by use of a 17-variable model that took into account patients' risk at baseline, UK 30-day mortality decreased by around 3%. This finding suggests that factors from the point of first medical contact to 30 days from hospital admission differentially affect outcomes. Chung and colleagues explored what factors might account for the international differences in mortality. Their findings imply that between-country differences in the use and dissemination of treatments recommended in guidelines was an important factor, as they noted that in the UK the uptake of primary percutaneous coronary intervention (PCI) was lower at the starting point and prescribing rates for β blockers at discharge were lower than in Sweden. Implementation of cardiovascular evidence-based practice in the UK has been reported to lag behind that of other countries. Laut and colleagues3Laut KG Gale CP Pedersen AB Fox KA Lash TL Kristensen SD Persistent geographical disparities in the use of primary percutaneous coronary intervention in 120 European regions: exploring the variation.EuroIntervention. 2013; 9: 469-476Crossref PubMed Scopus (22) Google Scholar, 4Laut KG Gale CP Lash TL Kristensen SD Determinants and patterns of utilization of primary percutaneous coronary intervention across 12 European countries: 2003–2008.Int J Cardiol. 2013; 168: 2745-2753Summary Full Text Full Text PDF PubMed Scopus (17) Google Scholar compared diffusion of primary PCI across countries in the European Union and found that England was a late and low adopter. Yet, in Chung and colleagues' study,1Chung S-C Gedeborg R Nicholas O et al.Acute myocardial infarction: a comparison of short-term survival in national outcome registries in Sweden and the UK.Lancet. 2014; (published online Jan 23.)http://dx.doi.org/10.1016/S0140-6736(13)62070-XSummary Full Text Full Text PDF Scopus (212) Google Scholar prescription of statins and angiotensin-converting-enzyme inhibitors or angiotensin-receptor blockers at discharge was greater in the UK than in Sweden, which suggests that unless primary PCI and β blockers have a stronger association with survival than these treatments, other factors might lead to differences in mortality. Although estimates equally favoured reduced 30-day mortality for primary PCI over that for thrombolysis in Sweden and the UK, in line with other studies,5Keeley EC Boura JA Grines CL Primary angioplasty versus intravenous thrombolytic therapy for acute myocardial infarction: a quantitative review of 23 randomised trials.Lancet. 2003; 361: 13-20Summary Full Text Full Text PDF PubMed Scopus (3558) Google Scholar the associations between statins, angiotensin-converting-enzyme inhibitors, and angiotensin-receptor blockers are not provided by the authors. Moreover, if the UK had adopted Swedish levels of use of primary PCI and β blockers, the standardised mortality ratio would only have reduced to 1·31, with primary PCI leading to around 2000 and β blockers to less than 50 lives saved over the 7 years of study. When the use of in-hospital treatments was considered in addition to casemix, the standardised mortality ratio decreased but did not reach unity. The restricted improvement in standardised mortality ratio after adjustment for imbalanced treatments suggests that factors outside hospital-based cardiac interventions are also important. Indeed, Chung and colleagues' study highlights the similarities between the UK and Sweden for thrombolysis and primary PCI process measures and that, overall, reperfusion rates were higher in the UK than in Sweden (77% vs 71%). The difference in mortality rates, however, was upheld after matching by propensity score. This finding is not surprising because the scores were derived from the same 17-factor model. For these reasons, unmeasured factors, such as imbalanced case ascertainment, unmeasured confounders, non-modelled covariates or missing data, and hospital care systems are probably responsible for the international difference in mortality. Aspects of health care, such as a patient's appropriateness for therapy and drug adherence, might have differed between the UK and Sweden. These data, which are not routinely collected in national electronic health-care records, could have influenced the UK mortality rates. In an attempt to mitigate bias due to absent data in one source but recorded elsewhere, the authors imputed missing data. This approach, however, is unlikely to have alleviated all systematic bias and would not account for data missing by design. The modelling of latent classes could have offered greater insight into the effects of unmeasured factors. Furthermore, the authors undertook an asymmetric analysis intended to assess what would have happened if UK patients had been transferred to Sweden, but the results of a bi-directional simulation might have been more informative. Nonetheless, through highlighting the prospect of a substantial excess of deaths in the UK compared with Sweden, Chung and colleagues have drawn our attention to the need for further comparative effectiveness research for acute myocardial infarction. Efforts to improve cardiovascular outcomes in the UK should, therefore, concentrate on data enhancement through the linkage of electronic health-care records and the early and systematic implementation of evidence-based therapies across the National Health Service. The authors reveal large international inequalities in the management and outcomes for these patients. Despite substantial reductions in early mortality rates after acute myocardial infarction, cardiovascular disease remains one of the biggest killers in developed countries.6Gale CP Cattle BA Woolston A et al.Resolving inequalities in care? Reduced mortality in the elderly after acute coronary syndromes. The Myocardial Ischaemia National Audit Project 2003–2010.Eur Heart J. 2011; 33: 630-639Crossref PubMed Scopus (157) Google Scholar, 7Lozano R Naghavi M Foreman K et al.Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010.Lancet. 2012; 380: 2095-2128Summary Full Text Full Text PDF PubMed Scopus (9753) Google Scholar The prevention of premature cardiovascular death must, therefore, continue to be a priority for research. We declare that we have no conflicts of interest. Acute myocardial infarction: a comparison of short-term survival in national outcome registries in Sweden and the UKWe found clinically important differences between countries in acute myocardial infarction care and outcomes. International comparisons research might help to improve health systems and prevent deaths. Full-Text PDF Open Access