An association between raised renin levels and myocardial infarction has been reported. We studied the effects of enalapril, an angiotensin-converting enzyme (ACE) inhibitor, on the development of myocardial infarction and unstable angina in 6797 patients with ejection fractions ≤0·35 enrolled into the two Studies of Left Ventricular Dysfunction (SOLVD) trials.

Patients were randomly assigned to placebo (n=3401) or enalapril (n=3396) at doses of 2·5-20 mg per day in two concurrent double-blind trials with the same protocol. Patients with heart failure entered the treatment trial (n=2569) and those without heart failure entered the prevention trial (n=4228). Follow-up averaged 40 months. In each trial there were significant reductions in the number of patients developing myocardial infarction (treatment trial: 158 placebo vs 127 enalapril, P<0·02; prevention trial: 204 vs 161 p<0·01) or unstable angina (240 vs 187 p<0·001; 355 vs 312, p<0·05). Combined, there were 362 placebo group patients with myocardial infarction compared with 288 in the enalapril group (risk reduction 23%, 95% Cl 11-34%; p<0·001). 595 placebo group patients developed unstable angina compared with 499 in the enalapril group (risk reduction 20%, 95% Cl 9-29%, p<0·001). There was also a reduction in cardiac deaths (711 placebo, 615 enalapril; P<0·003), so that the reduction in the combined endpoint of deaths, myocardial infarction, and unstable angina was highly significant (20% risk reduction, 95% Cl 14-26%; p<0·0001).

Enalapril treatment significantly reduced myocardial infarction, unstable angina, and cardiac mortality in patients with low ejection fractions.