OBJECTIVES: This study evaluated the efficacy of long-term treatment with the angiotensin-converting enzyme (ACE) inhibitor trandolapril in diabetic patients with left ventricular dysfunction after acute myocardial infarction (AMI). BACKGROUND: Patients with diabetes mellitus have a high mortality following AMI, probably due to a high risk of congestive heart failure and reinfarction. Because ACE inhibition effectively reduces progression of heart failure, it could be particularly beneficial in diabetic patients after AMI. METHODS: The study is a retrospective analysis using data from the Trandolapril Cardiac Evaluation (TRACE) study, which was a randomized, double-blind, placebo-controlled trial of trandolapril in 1,749 patients with AMI and ejection fraction < or =35%. The mean follow-up time was 26 months. RESULTS: A history of diabetes was found in 237 (14%) of the 1,749 patients. Treatment with trandolapril resulted in a relative risk (RR) of death from any cause for the diabetic group of 0.64 (95% confidence interval 0.45 to 0.91) versus 0.82 (0.69 to 0.97) for the nondiabetic group. In the diabetic group, trandolapril reduced the risk of progression to severe heart failure markedly (RR, 0.38 [0.21 to 0.67]), and no significant reduction of this end point was found in the nondiabetic group. CONCLUSIONS: The ACE inhibition after myocardial infarction complicated by left ventricular dysfunction appears to be of considerable importance in patients with diabetes mellitus by saving lives and substantially reducing the risk of progression to severe heart failure.