IMPROVEMENT IN EXERCISE PERFORMANCE AND HEMODYNAMICS BY LABETALOL IN PATIENTS WITH IDIOPATHIC DILATED CARDIOMYOPATHY

Labetalol, a combined alpha-and beta-blocking agent, was administered to 12 patients (mean age 55 years) with idiopathic dilated cardiomyopathy to examine its effects on symptomatology and exercise performance. Studies were performed before treatment, after 8 weeks of placebo, and after 8 weeks of labetalol therapy in a randomized, crossover, double-blind design. The mean (±SEM)dose of labetalol for the group was 275±29 mg. Compared to treatment with placebo, the maximum duration of symptom-limited exercise was significantly prolonged with labetalol (580±72 seconds to 683±71 seconds; p<0.005). Both the resting and peak exercise heart rate and systolic blood pressure were significantly reduced. Ascending aortic blood flow velocity was also measured by continuous-wave Doppler technique during exercise. Compared to placebo, treatment with labetalol conferred no significant change in cardiac output at rest but significantly improved cardiac output at maximum exercise (14±3%; p<0.001). Doppler-derived peak aortic flow velocity, acceleration, and flow velocity integral were also significantly improved at maximum exercise. Systemic vascular resistance, as derived from mean blood pressure/cardiac output, was reduced by 12±3% and 16±3% at rest and at maximum exercise, respectively. New York Heart Association functional class was improved (3.2±0.2 to 2.2±0.3; p<0.005). No major side effects from labetalol were encountered. Thus labetalol improves symptomatology, exercise capacity, and exercise hemodynamics and reduces systemic vascular resistance in patients with idiopathic dilated cardiomyopathy. © 1990 Mosby-Year Book, Inc.