Improvement in exercise performance and hemodynamics by labetalol in patients with idiopathic dilated cardiomyopathy

Abstract

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 less than 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 less than 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 less than 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.