Aims: The prognosis after an acute myocardial infarction is worse for patients with diabetes mellitus than for those without. We investigated whether differences in the use of evidence-based treatment may contribute to the differences in 1-year survival in a large cohort of consecutive acute myocardial infarction patients with and without diabetes mellitus.
Methods: We included patients below the age of 80 years from the Register of Information and Knowledge about Swedish Heart Intensive care Admissions (RIKS-HIA), which included all patients admitted to coronary care units at 58 hospitals during 1995-1998. In all 5193 patients had the combination of acute myocardial infarction and diabetes mellitus while 20440 had myocardial infarction but no diabetes diagnosed. Multivariate logistical regression analyses were performed to evaluate the influence of diabetes mellitus on the use of evidence-based treatment and its association with survival during the first year after the index hospitalisation.
Results: The prevalence of diabetes mellitus was 20.3% (males 18.5%; females 24.4%). The 1-year mortality was substantially higher among diabetic patients compared with those without diabetes mellitus (13.0 vs. 22.3% for males and 14.4 vs. 26.1% for female patients, respectively) with an odds ratio (OR) (95% confidence interval (CI)) in three different age groups: <65 years 2.65 (2.23-3.16); 65-74 years 1.81 (1.61-2.04) and >75 years 1.71 (1.50-1.93). During hospital stay patients with diabetes mellitus received significantly less treatment with heparins (37 vs. 43%; p<0.001), intravenous beta blockade (29 vs. 33%; p<0.001), thrombolysis (31 vs. 41%; p<0.001) and acute revascularisation (4 vs. 5%; p<0.003). A similar pattern was apparent at hospital discharge. After multiple adjustments for dissimilarities in baseline characteristics between the two groups, patients with diabetes were significantly less likely to be treated with reperfusion therapy (OR 0.83), heparins (OR 0.88), statins (OR 0.88) or to be revascularised within 14 days from hospital discharge procedures (OR 0.86) while the use of ACE-inhibitors was more prevalent among diabetic patients compared to non-diabetic patients (OR 1.45). The mortality reducing effects of evidence-based treatment like reperfusion, heparins, aspirin, beta-blockers, lipid-lowering treatment and revascularisation were, in multivariate analyses, of equal benefit in diabetic and non-diabetic patients.
Interpretation: Diabetes mellitus continues to be a major independent predictor of 1-year mortality following an acute myocardial infarction, especially in younger age groups. This may partly be explained by less use of evidence-based treatment although treatment benefits are similar in both patients with and without diabetes mellitus. Thus a more extensive use of established treatment has a potential to improve the poor prognosis among patients with acute myocardial infarction and diabetes mellitus.