Aims: Inhibition of nitric oxide synthesis causes a decrease in the basal diameter of normal distal epicardial coronary arteries in normal subjects. The effects of inhibition of nitric oxide in atheromatous coronary arteries is unknown. This study assessed the effects of the inhibition of nitric oxide synthesis in epicardial coronary arteries in patients with coronary artery disease.
Methods and results: The effects of an intracoronary infusion of NG-monomethyl-L-arginine (LNMMA, an inhibitor of nitric oxide synthesis), were studied in 13 patients with chronic stable angina and coronary artery disease. The diameter of angiographically normal proximal and distal segments and coronary stenoses was measured by quantitative angiography. In response to an LNMMA infusion of 16 mumol min-1 for 4 min there was a significant reduction (P < 0.01) in the luminal diameter of the distal segments of diseased arteries (from 1.32 +/- 0.07 to 1.17 +/- 0.06 mm) and at the site of stenosis (from 1.15 +/- 0.22 to 1.06 +/- 0.20 mm), but no change (P = NS) in the luminal diameter of the proximal segments (from 3.16 +/- 0.12 to 3.08 +/- 0.14 mm) of diseased arteries.
Conclusions: The average effect of inhibition of basal nitric oxide synthesis in epicardial coronary arteries in patients with stable angina and coronary artery disease was only distal constriction. Coronary stenoses constricted at the highest LNMMA concentration.