PHARMACOLOGICAL RELAXATION OF THE SAPHENOUS-VEIN DURING HARVESTING FOR CORONARY-ARTERY BYPASS-GRAFTING

Spasm of the saphenous vein frequently occurs during harvesting from t he leg and high-pressure distention is required to restore an adequate diameter for grafting. Forceful distention has been shown to damage t he intima and media and may predispose to subsequent occlusion of the vein graft. Various pharmacologic vasodilators are capable of relaxing veins; in this study, we carried out a systematic investigation to de termine the appropriate agents and concentrations for use during vein graft operations. In organ baths, human saphenous vein segments were c ontracted with potassium or a thromboxane mimetic, and vasodilator age nts were then applied. Glyceryl trinitrate, 7.2 mug/mL, or papaverine hydrochloride, 11.9 mug/mL, caused 80% to 100% relaxation of contracti on induced by potassium or thromboxane. Verapamil, 15.5 mug/mL, relaxe d the potassium contraction by 100% and the thromboxane contraction by 75%. Comparison of the time course of action showed that glyceryl tri nitrate had a rapid onset and a short duration of maximal action, wher eas verapamil (like papaverine) had delayed onset and a long duration. A mixture of glyceryl trinitrate and verapamil combined rapid onset w ith long duration of action. We now use a mixture of glyceryl trinitra te and verapamil (pH 7.4) topically and intraluminally during harvesti ng of the saphenous vein to provide a relaxed conduit for coronary art ery bypass grafting.