Effect of L-arginine on human coronary endothelium-dependent and physiologic vasodilation.

OBJECTIVES: We hypothesized that L-arginine would improve abnormal coronary vasodilation in response to physiologic stress in patients with atherosclerosis and its risk factors by reversing coronary endothelial dysfunction.
BACKGROUND: Studies have demonstrated that physiologic coronary vasodilation correlates with endothelial function and that L-arginine, the substrate for nitric oxide synthesis, improves the response to acetylcholine (Ach).
METHODS: Changes in coronary blood flow and epicardial diameter response to Ach, adenosine and cardiac pacing were measured in 32 patients with coronary atherosclerosis or its risk factors and in 7 patients without risk factors and normal coronary angiograms.
RESULTS: Intracoronary L-arginine did not alter baseline coronary vascular tone, but the epicardial and microvascular responses to Ach were enhanced (both p < 0.001). The improvement after L-arginine was greater in epicardial segments that initially constricted with Ach; similarly, L-arginine abolished microvascular constriction produced by higher doses of Ach. Thus, there was a negative correlation between the initial epicardial and vascular resistance responses to Ach and the magnitude of improvement with L-arginine (r = -0.55 and r = -0.50, respectively, p < 0.001). D-Arginine did not affect the responses to Ach, and adenosine responses were unchanged with L-arginine. Cardiac pacing-induced epicardial constriction was abolished by L-arginine, but microvascular dilation remained unaffected.
CONCLUSIONS: Thus, L-arginine improved endothelium-dependent coronary epicardial and microvascular function in patients with endothelial dysfunction. Prevention of epicardial constriction during physiologic stress by L-arginine in patients with endothelial dysfunction may be of therapeutic value in the treatment of myocardial ischemia.