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Clenbuterol, a beta(2)-agonist with potent anabolic properties, has been shown to improve skeletal muscle function in healthy subjects, and in high doses, promotes cardiac recovery in patients with left ventricular assist devices. In a small, randomized controlled study, we investigated the effect of clenbuterol on skeletal muscle function, cardiac function, and exercise capacity in patients with chronic heart failure. Clenbuterol was well tolerated and led to a significant increase in both lean mass and the lean/fat ratio. Maximal strength increased significantly with both clenbuterol (27%) and placebo (14%); however, endurance and exercise duration decreased after clenbuterol. Prior data support combining exercise training with clenbuterol to maximize performance, and on-going studies will evaluate this approach.

BACKGROUND:High-dose clenbuterol (a selective beta2-adrenergic agonist) has been proposed to promote myocardial recovery during left ventricular assist device (LVAD) support, but its effects on cardiac and skeletal muscle are largely unknown. METHODS:Seven subjects with heart failure (5 ischemic, 2 non-ischemic) were started on oral clenbuterol 5 to 46 weeks post-LVAD implantation and up-titrated to daily doses of 720 microg. The following procedures were performed at baseline and after 3 months of therapy: echocardiography at reduced support (4 liters/min); cardiopulmonary exercise testing; body composition analysis; and quadriceps maximal voluntary contraction (MVC). Myocardial histologic analysis was measured at device implantation and explantation. RESULTS:There were no serious adverse events or arrhythmias. Creatine phosphokinase (CPK) was elevated in 4 subjects, with no clinical sequelae. No change in ejection fraction was seen. End-diastolic dimension increased significantly (4.73 +/- 0.67 vs 5.24 +/- 0.66; p < 0.01), despite a trend toward increased LV mass. Body weight and lean mass increased significantly (75.5 +/- 17.9 vs 79.2 +/- 25.1 kg, 21.1 +/- 8.9 vs 23.6 +/- 9.7 kg, respectively; both p < 0.05). Exercise capacity did not change, but MVC improved significantly from 37.0 +/- 15.7 to 45.8 +/- 20.6 kg (p < 0.05). No significant change in myocyte size or collagen deposition was seen. CONCLUSIONS:Cardiac function did not improve in this cohort of LVAD patients treated with high-dose clenbuterol. However, clenbuterol therapy increased skeletal muscle mass and strength and prevented the expected decrease in myocyte size during LVAD support. Further study will clarify its potential for cardiac and skeletal muscle recovery.