Enhanced Nitric Oxide–Mediated Vascular Relaxation in Radial Artery Compared With Internal Mammary Artery or Saphenous Vein

Background—The superior long-term patency of internal mammary artery coronary bypass grafts compared with venous grafts has been attributed in part to increased endothelium-derived nitric oxide (zNO) production. Interest in the radial artery as an alternative bypass conduit has recently been revived; however, its biological characteristics remain incompletely defined. The purpose of this study was to compare the zNO-mediated vasomotor properties of the radial artery to those of the internal mammary artery and saphenous vein. Methods and Results—Matched segments of radial artery, internal mammary artery, and saphenous vein (n524 patients) were examined by use of organ-chamber methodology. Endothelium-dependent and-independent vasomotor responses were assessed by dose-response curves to acetylcholine, NG-nitro-L-arginine methyl ester (L-NAME), 8-bromo-cyclic 39,59-guanosine monophosphate (8-bromo-cGMP), and nitroglycerin. Maximum zNO-mediated radial artery relaxation in response to acetylcholine (86610%) was significantly greater than internal mammary artery (5669%) or saphenous vein (1165%, both P,0.0001). Similarly, acetylcholine-stimulated cGMP accumulation in radial artery (9.161.7 pmol/mg protein) was also greater than internal mammary artery (6.260.3 pmol/mg protein) or saphenous vein (1.460.2 pmol/mg protein, both P,0.05). Estimated basal endothelial zNO production, assayed as the percent maximum contraction in response to L-NAME, was greater in radial artery (3965%) than internal mammary artery (2366%) or saphenous vein (562%, both P,0.05). Maximum relaxation of all vessels to nitroglycerin was similar, although th