Contrary effects of acetylcholine on coronary arteries and aortocoronary venous grafts in man.

The endothelium-dependent vasomotor responses differ in arteries and veins, and the transfer of veins into the arterial circulation by venous grafting may change their endothelial function. The purpose of this study was to examine the responses to acetylcholine in aortocoronary venous grafts of coronary arteries in man which may indicate differences in the endothelial function of these vessels. Five patients with venous grafts (12 to 72 months after implantation) and five patients without any angiographic evidence for coronary artery disease (controls) were examined. The effect of local infusions of acetylcholine (7-70 nmol min-1) on the vessel diameters was assessed by quantitative angiography. In controls, acetylcholine caused no consistent reaction, but in patients with venous grafts the arterial segments distal to the bypass anastomoses were contracted (7 nmol min-1: 82 +/- 2%; P greater than 0.01). We observed that aortocoronary venous grafts reacted differently to acetylcholine compared with the coronary arteries (P less than 0.05): a slight but not significant dilatation of the venous graft occurred (7 nmol min-1: 103 +/- 1%). The contraction of atherosclerotic coronary arteries of patients with aortocoronary venous grafts is in accord with the assumption of a loss of endothelium-dependent vasodilatation in coronary artery disease. The cholinergic influence on the vasomotor control of venous grafts seems to be either of little importance or less affected by atherosclerotic endothelial lesions than in coronary arteries.