Vasomotor effects of L- and D-arginine in stenotic atheromatous coronary plaque

Objective-To examine the effects of exogenous L- and D-arginine on coronary stenosis vasomotion in relation to stenosis morphology. Design-Intracoronary infusions of normal saline, L- and D-arginine (50 and 150 pmol/min), and glyceryl trinitrate (250 mug bolus) were given in 24 pat ients with coronary artery disease and stable angina. Coronary stenoses wer e classified as smooth or complex (irregular borders). The diameter of the coronary stenoses and their adjacent reference segments was measured by com puted quantitative angiography. Results-During L-arginine infusion a larger proportion of complex stenoses than smooth stenoses dilated by greater than or equal to 10% (p < 0.01), an d the magnitude of dilatation was greater at the site of complex stenoses ( p < 0.05). Irrespective of the type of morphology there was a positive corr elation (p < 0.01) between the severity of stenoses and the magnitude of va sodilatation to L-arginine. The response to glyceryl trinitrate was similar in the two groups. No significant change was found in either group in resp onse to D-arginine. Conclusions-In patients with coronary artery disease, coronary stenoses-par ticularly those of complex morphology-dilate in response to the administrat ion of L-arginine but not D-arginine. This finding is consistent with parti al deficiency of the substrate for nitric oxide synthesis, L-arginine, at t he site of complex stenoses.