EARLY TREATMENT WITH LOW-DOSE ENALAPRIL AFTER ACUTE MYOCARDIAL-INFARCTION - AN EQUILIBRIUM RADIONUCLIDE ANGIOGRAPHIC STUDY

Background. To further elucidate the mechanisms involved in the treatm ent of acute myocardial infarction (AMI) with angiotensin-converting e nzyme inhibitors, we compared the effects on left ventricular volumes of early (<48 hours) versus late (45 days) administration of a fixed l ow dose of enalapril (10 mg) in patients with AMI. We also analyzed th e changes of left ventricular volumes after withdrawal of the study dr ug, Reduced dilation of the left ventricle is one of the beneficial ef fects of angiotensin-converting enzyme inhibition after AMI. However, the nature of this effect is not completely understood. Methods and Re sults. We included 89 patients within 48 hours after onset of a first AMI and radionuclide left ventricular ejection fraction less than 45%. The study was double-blind and compared enalapril and placebo with a crossover design. All patients were randomly assigned to a sequence A (enalapril, 45 days; placebo, 45 days) or B (placebo, 45 days; enalapr il, 45 days). The end point was the change of left ventricular volume at 45 and 90 days. Thrombolysis was administered to 26 patients (70%) in group A and 25 (75%) in group B, All pretreatment clinical variable s were similar in both groups. Median and 95% confidence intervals (CI s) of left ventricular diastolic volumes were 46.8 ml/m(2) (39 to 61 m l/m(2)) and 46.6 ml/m(2) (39 to 60 ml/m(2)) for groups A and B, respec tively, Baseline end systolic volumes were 28.5 ml/m(2) (20 to 36 ml/m (2)) and 28.9 ml/m(2) (23 to 28 ml/m(2)) in the same groups. Placebo t reatment during the initial 45 days was associated with an increase of left ventricular diastolic volume of 8.75 ml/m(2) (95% CI, 3.25 to 17 .1 ml/m(2); p < 0.01) and end-systolic volume of 4.20 ml/m(2) (95% CI, 0.00 to 10.1 ml/m(2); p < 0.05). No significant changes during other phases of the study were observed, At 45 days left ventricular diastol ic volume was 11.1 ml/m(2) (95% CI, 0.5 to 2.2 ml/m(2)), greater in pl acebo-treated patients compared with patients receiving enalapril. Con clusions. In patients with a first Q wave AMI and left ventricular eje ction fraction less than 45%, treatment with enalapril can prevent lef t ventricular dilation. This protective effect involves at least parti ally a structural modification of the left ventricle. Hence, maximal b enefit can be obtained only with early initiation of treatment.