Effects of oral L-arginine supplementation on exercise-induced QT dispersion and exercise tolerance in stable angina pectoris

We assessed the effects of L-arginine (an endogenous precursor of nitric ox ide) on the magnitude of exercise-induced QT dispersion in patients with co ronary artery disease. The study had a randomized double-blind cross-over d esign. Twenty-five patients with stable coronary artery disease underwent t wo separate exercise tests: after oral administration of L-arginine (6 g/24 h for 3 days) or placebo. Indications for cessation of exercise included: pulse limit, exhaustion, chest pain, ST segment depression >2 mm. We found that arginine significantly increased exercise duration from 604 +/- 146 to 647 +/- 159 s (P < 0.03). However, it had no effect on the sum of exercise -induced ST segment depressions (1.9 <plus/minus> 2.3 and 2.4 +/- 3.3 on an d off arginine, respectively, NS). Exercise shortened QT interval to a simi lar extent in patients treated with placebo or arginine. QT dispersion chan ged during exercise from 55 +/- 21 to 60 +/- 19 ms (NS) and from 60 +/- 21 to 53 +/- 17 ms (NS), respectively. We conclude that, in patients with coro nary artery disease, oral supplementation of L-arginine does not affect exe rcise-induced changes in QT interval duration, QT dispersion or the magnitu de of ST segment depression. However, it significantly increases exercise t olerance, most likely due to improved peripheral vasomotion. These results may be of clinical and therapeutic importance. (C) 2000 Elsevier Science Ir eland Ltd. All rights reserved.