DIFFERENCE IN ACETYLCHOLINE-INDUCED NITRIC-OXIDE RELEASE OF ARTERIAL AND VENOUS GRAFTS IN PATIENTS AFTER CORONARY-BYPASS OPERATIONS

Objectives: In vivo investigation of nitric oxide release in coronary bypass grafts has not been reported. We studied acetylcholine-induced nitric oxide release in vivo of coronary bypass grafts and vasomotor r esponses to acetylcholine of grafted coronary arteries in patients aft er coronary bypass grafting. Methods: We examined 24 internal thoracic artery grafts and 16 saphenous vein grafts in 39 patients. The mean a ges of the patients were 65 years for the arterial grafts and 68 gears for the venous grafts. Nitric oxide was measured as the plasma nitrit e level by the Griess reaction. Before and after intragraft acetylchol ine infusion (5 mu g), blood was sampled from the distal end of the gr aft, and angiograms were taken and analyzed by cine-densitometry. Resu lts: The plasma nitrite concentration after stimulation with acetylcho line compared with the control value was 134% +/- 52% at 4 minutes (p = 0.05) and 184% +/- 107% at 6 minutes (p = 0.01) in the arterial graf ts; in the venous grafts these values were 101% +/- 24% at 4 minutes ( p = 0.96) and 108% +/- 36% at 6 minutes (p = 0.69). Low-dose acetylcho line dilated the coronary arteries supplied by arterial grafts by 6.3% +/- 16.6% whereas coronary arteries supplied by venous grafts were re duced by 9.8% +/- 11.8% in diameter and the vasoactive responses were different (p = 0.01). Conclusions: In vivo internal thoracic artery gr afts had more endothelium-derived nitric oxide release in response to acetylcholine than did saphenous vein grafts after coronary bypass gra fting.