Impact of diabetes on clinical outcome among elderly patients with acute coronary syndrome treated with percutaneous coronary intervention: insights from the ELDERLY ACS 2 trial

BACKGROUND: Despite recent improvements in percutaneous coronary revascularization and antithrombotic therapies for the treatment of acute coronary syndromes, the outcome is still unsatisfactory in high-risk patients, such as the elderly and patients with diabetes. The aim of the current study was to investigate the prognostic impact of diabetes on clinical outcome among patients included in the Elderly-ACS 2 trial, a randomized, open-label, blinded endpoint study carried out at 32 centers in Italy. METHODS: Our population is represented by 1443 patients included in the Elderly-ACS 2 trial. Diabetes was defined as known history of diabetes at admission. The primary endpoint of this analysis was cardiovascular mortality, while secondary endpoints were all-cause death, recurrent myocardial infarction, Bleeding Academic Research Consortium type 2 or 3 bleeding, and rehospitalization for cardiovascular event or stent thrombosis within 12 months after index admission. RESULTS: Diabetes was present in 419 (29%) out of 1443 patients. Diabetic status was significantly associated with major cardiovascular risk factors and history of previous coronary disease, presentation with non-ST segment elevation myocardial infarction (P = 0.01) more extensive coronary disease (P = 0.02), more advanced Killip class at presentation (P = 0.003), use at admission of statins (P = 0.004) and diuretics at discharge (P < 0.001). Median follow-up was 367 days (interquartile range: 337-378 days). Diabetic status was associated with an absolute increase in the rate of cardiovascular mortality as compared with patients without diabetes [5.5 vs. 3.3%, hazard ratio (HR) 1.7 (0.99-2.8), P = 0.054], particularly among those treated with clopidogrel [HR (95% confidence interval (CI)) = 1.89 (0.93-3.87), P = 0.08]. However, this difference disappeared after correction for baseline differences [Adjusted HR (95% CI) 1.1(0.4-2.9), P = 0.86]. Similar findings were observed for other secondary endpoints, except for bleeding complications, significantly more frequent in diabetic patients [HR (95% CI) 2.02 (1.14-3.6), P = 0.02; adjusted HR (95% CI) = 2.1 (1.01-4.3), P = 0.05]. No significant interaction was observed between type of dual antiplatelet therapy, diabetic status and outcome. CONCLUSION: Among elderly patients with acute coronary syndromes, diabetic status was associated with higher rates of comorbidities, more severe cardiovascular risk profile and major bleeding complications fully accounting for the absolute increase in mortality. In fact, diabetes mellitus did not emerge as an independent predictor of survival in advanced age.