Effects of infusion of L-arginine on exercise-induced myocardial ischemic ST-segment changes and capacity to exercise of patients with stable angina pectoris

Abstract

Results of recent studies show that intracoronary administration of L-arginine, the precursor of nitric oxide, restores endothelial function in subjects with coronary risk factors and minimal coronary artery lesions. However, few investigators have examined the clinical feasibility of using L-arginine for treatment of myocardial ischemia due to coronary artery disease. To examine the effect of supplementary L-arginine on exercise-induced myocardial ischemia and capacity to exercise of patients with stable effort angina pectoris. Twelve patients confirmed to have a single epicardial coronary artery stenosis underwent two treadmill exercise tests after infusion of 10% L-arginine solution or placebo (5% dextrose) according to a randomized single-blind crossover design on two days separated by an interval of less than 1 week. Respiratory gas exchange kinetics were measured and myocardial ischemia was estimated by electrocardiography before and during exercise. Infusion of L-arginine did not alter exercise-induced changes in heart rate and blood pressure, and objective parameters of capacity to exercise. Exercise-induced maximum ST-segment depression (by 2.1 +/- 0.9 mm; with L-arginine; by 1.9 +/- 0.9 mm with placebo, NS) and onset of 1 mm ST-segment depression after exercise (after 261 +/- 131 s with L-arginine; after 247 +/- 136 s with placebo, NS) also remained unchanged. However, ST-segment depression was restored to baseline after exercise significantly more quickly after infusion of L-arginine than it did with placebo (after 331 +/- 167 s with L-arginine; after 400 +/- 165 s with placebo: P < 0.01). Intravenous administration of L-arginine did not alter capacity to exercise or the threshold for exercise-induced myocardial ischemia. However, it did reduce the time taken for recovery after ST-segment depression, suggesting that an earlier resolution of exercise-induced myocardial ischemia occurred.