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 responses to acetylcholine of grafted coronary arteries in patients after coronary bypass grafting.

METHODS

We examined 24 internal thoracic artery grafts and 16 saphenous vein grafts in 39 patients. The mean ages of the patients were 65 years for the arterial grafts and 68 years for the venous grafts. Nitric oxide was measured as the plasma nitrite level by the Griess reaction. Before and after intragraft acetylcholine infusion (5 microg), blood was sampled from the distal end of the graft, and angiograms were taken and analyzed by cine-densitometry.

RESULTS

The plasma nitrite concentration after stimulation with acetylcholine 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 grafts; 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 acetylcholine dilated the coronary arteries supplied by arterial grafts by 6.3%+/-16.6% whereas coronary arteries supplied by venous grafts were reduced by 9.8%+/-11.8% in diameter and the vasoactive responses were different (p=0.01).

CONCLUSIONS

In vivo internal thoracic artery grafts had more endothelium-derived nitric oxide release in response to acetylcholine than did saphenous vein grafts after coronary bypass grafting.