EFFECT ON EXERCISE PERFORMANCE OF ENALAPRIL THERAPY INITIATED EARLY AFTER MYOCARDIAL-INFARCTION

Objectives. The Nordic Enalapril Exercise Trial was a multicenter subt rial of the Cooperative New Scandinavian Enalapril Survival Study (CON SENSUS II) designed to evaluate the effect on maximal exercise perform ance of a 6-month period of enalapril treatment initiated early after myocardial infarction. Background. When begun early after myocardial i nfarction, converting enzyme inhibition therapy has been shown to atte nuate infarct expansion and reduce left ventricular volume. Therapy ha s been associated with improved exercise performance. Methods. Three h undred twenty-seven men (mean age 63.3 +/-10.9 years) with documented acute myocardial infarction were randomized to treatment with enalapri l or placebo on a double-blind basis. Intravenous enalaprilat or place bo therapy was initiated within 24 h after the onset of symptoms. Oral therapy was continued at a target dose of 20 mg/day. Patients exercis ed maximally at 1 month and 6 months after infarction to symptom-limit ed end points on a cycle ergometer with a 20 W/min incremental protoco l. Results. The treatment and control groups were comparable in patien t age, concurrent therapy and type and site of infarction. At 1 month, for all patients, mean total work performed was 34.9 +/- 20.9 kJ in t he enalapril group (n = 169) versus 28.5 +/- 20.6 kJ in the placebo gr oup (n = 158) (difference = 18.4%, p < 0.01). This between-group diffe rence in favor of enalapril was greatest in patients >70 years old (di fference = 41.4%, p < 0.01, n = 105) and those with clinical evidence of heart failure (difference = 33.0%, p < 0.01, n = 122). At 6 months for all patients, mean total work performed was 35.4 +/- 23.8 kj in th e enalapril group versus 34.0 +/- 23.9 kJ in the placebo group (differ ence = 4.1%, NS). Conclusions. This trial found that chronic convertin g enzyme inhibition initiated early after myocardial infarction was as sociated with significantly greater exercise capacity in men tested at 1 month. This difference was independent of type or site of infarctio n, patient age or the presence of clinical heart failure. The differen ce between the treatment and control groups was not significant at 6 m onths because of improvement in the placebo group. Further research is needed to elucidate the potential mechanisms involved, profile those patients most likely to profit from early therapy and establish the op timal timing and duration for intervention.