Effect of L-arginine administration on myocardial thallium-201 perfusion during exercise in patients with angina pectoris and normal coronary angiograms

Objectives. We tested the hypothesis that an exogenous supplement of L-arginine could alleviate coronary perfusion abnormality during exercise in patients with angina pectoris and normal coronary arteries. Methods and Results. Twelve patients underwent exercise thallium-201 scintigraphy without medication (control) and after intravenous administration of L-arginine. Exercise time was prolonged in the L-arginine study compared with the control (482 s vs 540 s, P < .05), Tl-201 extent score was improved in the L-arginine study (0.33 vs 0.26, P < .05), and the severity score was also improved (23.7 vs 16.9, P < .05), In 7 of the 12 patients whose Tl-201 redistribution disappeared in the L-arginine study, the percent increase in serum L-citrulline concentration during exercise was larger than that of the remaining 5 patients (18% vs 0.9 %, P < .01). The percent reduction in epicardial coronary diameter in response to acetylcholine was also greater in the former group (28.3% vs 11,1%, P < .05). Conclusion. Exogenous L-arginine improved myocardial perfusion during exercise in a subset of patients with angina pectoris and normal coronary arteries, probably by increasing production of nitric oxide.