FLOW-MEDIATED VASODILATION DURING PACING OF THE FREE EPIGASTRIC ARTERY BYPASS GRAFT EARLY AND LATE POSTOPERATIVELY

Objectives. The free epigastric artery bypass graft is proposed as an alternative conduit to the saphenous vein graft, known for its high ra te of attrition. The aim of our study was to assess its endothelial fu nction in vivo. Background. The endothelium of arterial bypass grafts plays a role in both the performance and the patency of such grafts. M ethods. We studied 73 epigastric grafts early (mean +/- SD 10 +/- 3 da ys) and 36 late (12 +/- 5 months) after coronary bypass surgery with q uantitative angiography at rest, after 2 min of atrial pacing (130 bea ts/min) and after injection of isosorbide dinitrate (1 to 2 mg) into t he graft. Results. At rest, mean epigastric graft diameter was lower i n the late than in the early postoperative period (2.26 +/- 0.39 vs. 2 .61 +/- 0.49 mm, p < 0.001). Early after operation, epigastric grafts with a small or an intermediate runoff, but not those with a large run off, were capable of vasodilation with nitrates (+0.09 +/- 0.10 mm). L ate after operation, vasodilation after administration of isosorbide d initrate was similar in epigastric grafts with a large runoff and in t hose with a small or intermediate runoff (+0.23 +/- 0.09 vs. +0.23 +/- 0.18 mm). Significant vasodilation during pacing was observed late (4 +/- 9%, p < 0.01) but not early postoperatively, except in a subset of patients,vith grafts capable of vasodilation after nitrates. A corr elation between the response to nitrates and the response during pacin g was observed early (r = 0.579, p < 0.001) and late postoperatively ( r = 0.530, p = 0.02). Conclusions. Flow-mediated vasodilation during p acing was observed in most epigastric grafts late, but not early, afte r operation. This endothelium-dependent dilation was correlated with t he importance of the vasodilation observed with nitrates (endothelium- independent), which was related to the importance of the runoff only i n the early postoperative period. The ability of epigastric grafts lat e postoperatively to dynamically adapt their dimensions to an acute in crease in demand could contribute to the good functional results of th is new alternative arterial graft.