L-arginine supplementation improves exercise capacity after a heart transplant.

BACKGROUND Endothelial dysfunction is associated with the decreased exercise capacity observed in heart-transplant (HTx) recipients. L-arginine supplementation (LAS) stimulates the nitric oxide (NO) pathway and restores endothelial function. OBJECTIVE We compared exercise capacity in healthy subjects and HTx patients and investigated whether chronic LAS might improve exercise capacity and NO/endothelin balance after an HTx. DESIGN Clinical, echocardiographic, and exercise characteristics were measured in 11 control subjects and 22 HTx recipients. In a prospective, double-blind study, the 22 HTx recipients performed a 6-min exercise [6-min-walk test (6MWT)] and a maximal bicycle exercise test before and after a 6-wk period of placebo intake or LAS. Endothelial function was measured by analyzing blood NO metabolites, endothelin, and the resulting NO/endothelin balance. RESULTS Exercise capacity decreased after transplantation. Unlike with the placebo intake, 6 wk of LAS improved quality of life in HTx recipients (mean +/- SEM Minnesota Score: from 15.3 +/- 1.3 to 10.6 +/- 1.1; P < 0.001) and their submaximal exercise capacity. The distance walked during the 6MWT increased (from 525 +/- 20 to 580 +/- 20 m; P = 0.002), and the ventilatory threshold during the incremental test was delayed by 1.2 min (P = 0.01). Central factors such as resting stroke volume, systolic pulmonary arterial pressure, cardiac systolodiastolic functions, and heart-rate reserve were not modified, but LAS significantly increased the NO:endothelin ratio (from 2.49 +/- 0.38 to 3.31 +/- 0.39; P = 0.03). CONCLUSION Oral LAS may be a useful adjuvant therapeutic to improve quality of life and exercise tolerance in HTx recipients.