RESUMEN
BACKGROUND: In congestive heart failure (CHF), endothelial dysfunction may contribute to impairment of exercise induced vasodilatation and decreased exercise capacity. We hypothesised that administration of L-arginine, a precursor of nitric oxide (NO) and postulated antioxidant, may improve endothelium-dependent vasodilatation and exercise capacity and also exert antioxidant activity. AIMS: To investigate the effect of oral supplementation with L-arginine on exercise capacity and markers of oxidative stress in patients with mild to moderate CHF. METHODS: The study had a randomised double-blind cross-over design. Twenty one patients with stable NYHA II-III CHF underwent three exercise tests: initially, after oral administration of L-arginine (9 g/day for 7 days) or placebo. Blood was sampled prior to each test for plasma lipid peroxides, reduced sulphydryl groups and leukocyte oxygen free radical production. RESULTS: We found a higher prolongation of exercise duration time after L-arginine than after placebo (99+/-106 vs 70+/-99 s, p<0.05). There were no significant differences in markers of free radical activity. CONCLUSIONS: In patients with chronic stable CHF, oral supplementation with L-arginine prolongs exercise duration which may be due to NO-induced peripheral vasodilatation. The antioxidant properties of L-arginine have not been confirmed in this ex vivo study.