Angiographic assessment of human coronary artery endothelial function by measurement of endothelium-dependent vasodilation.

In isolated atherosclerotic human coronary arteries endothelium-dependent vascular relaxation is abolished with acetylcholine whereas another EDRF-dependent vasodilator, substance P, still produces significant relaxation. To study further these in vitro findings, graded doses of acetylcholine and substance P, which produced no systemic effects, were infused into the left anterior descending artery of patients with angiographically moderate coronary artery disease. The effects of acetylcholine and substance P on LAD diameter were analysed by quantitative angiography. Generally, acetylcholine caused no relaxation but concentration-dependent contraction from 1.67 +/- 0.06 mm to 1.45 +/- 0.09 mm (P less than 0.01), whereas substance P dilated the arteries to 1.89 +/- 0.10 mm (P less than 0.01). In contrast, both drugs caused a marked increase in great cardiac vein oxygen saturation, indicating an increase of coronary flow. The results suggest that the failure of the atherosclerotic epicardial human coronary artery to vasodilate in response to acetylcholine represents a muscarinic endothelial defect. The preserved vasodilation with substance P in the presence of a refractoriness to acetylcholine suggests that atherosclerotic human coronary endothelial cells exposed to appropriate non-muscarinic stimuli are still capable to release EDRF and that atherosclerotic smooth muscle retains a responsive receptor mechanism for EDRF.