Background: Vasospasm of arterial conduits used for coronary surgical procedures is an important cause of postoperative graft failure. Mounting experimental evidence suggests that estrogen reverses acetylcholine-induced vasospasm of the coronary arteries in animals and humans. Estrogen also affects endothelium-derived constrictor factors. We therefore investigated the in vivo vasomotor responses to transdermal 17beta-estradiol of the left internal mammary artery (LIMA) grafted on the anterior descending coronary artery.
Methods: We studied 20 women, mean age of 62 +/- 7.2 years (range, 48 to 73 years), who had undergone cardiopulmonary bypass for coronary artery bypass grafting. They received transdermal 17beta-estradiol on the fifth day after operation. The diameter, cross-sectional area, and blood flow of the LIMA graft were measured by transthoracic color Doppler echography before (basal values) and after the transdermal administration of 50 microg of 17beta-estradiol (control).
Results: LIMA graft vasodilation after the administration of 17beta-estradiol was observed. A significant increase in diameter (2.06 +/- 0.4 mm versus 2.37 +/- 0.28 mm; p = 0.035) and cross-sectional area (3.45 +/- 1. 2 mm2 versus 4.24 +/- 1 mm2; p = 0.039) was registered. The LIMA graft mean flow increased by 49% (44.76 +/- 27.19 mL/min versus 56.62 +/- 27.69 mL/min), but this increase was not statistically significant (p = 0.06).
Conclusions: The acute postoperative transdermal administration of 17beta-estradiol induced a significant increase of LIMA graft diameter and cross-sectional area in postmenopausal women who underwent coronary artery bypass grafting. The LIMA graft vasodilation was also associated with an improvement in LIMA blood flow.