Effects of enoximone on exercise tolerance in patients with mild to moderate heart failure

To evaluate the efficacy of enoximone on exercise tolerance in patients with mild to moderate heart failure, 33 patients underwent cardiopulmonary exercise tests before and 3 hours after placebo or after receiving 25 or 100 mg of enoximone administered randomly in a double-blind manner. The electrocardiogram was monitored and blood pressure measured every minute throughout cycle ergometer exercise testing with a ramp protocol in which the work rate increased 1 W every 6 seconds after a 4-minute 20-W warm-up. Minute ventilation, oxygen uptake (VO2), and carbon dioxide output were measured every 10 seconds in order to determine anaerobic threshold (AT) and peak VO2. Five patients were excluded from evaluation before breaking the double-blind key because of insufficient data. Heart rate increased and systolic blood pressure decreased throughout the testing only in the group taking 100 mg (n = 10). Significant increases in AT (14.4 to 16.2 ml/min/kg) and peak VO2 (20.8 to 22.9 ml/min/kg) were observed in the group taking 100 mg. The increases in AT showed a dose response, namely +0.7% in the placebo (n = 9), +6.9% in the 25-mg (n = 9) and 12.5% in the 100-mg group. The work rates at the AT point increased in the 25- and 100-mg groups. These results indicate that a single oral administration of enoximone improves exercise tolerance in patients with mild to moderate heart failure.