Denervation of gastroepiploic artery graft can reduce vasospasm.

BACKGROUND: The right gastroepiploic artery is useful as an in situ arterial graft for coronary artery bypass grafting. However, the gastroepiploic artery is more likely to cause vasospasms compared with the internal thoracic artery. We hypothesized that the cause of the spasms is the stimulation of the periarterial sympathetic nerve, because the gastroepiploic artery is classified as a muscular artery. In this study, we examined whether the spasm is reduced by removing the periarterial sympathetic nerve. METHODS: Unused parts of the gastroepiploic artery were obtained from patients who underwent coronary artery bypass grafting. The vessel was cut into 2 segments, and they were assigned to control (N+) and denervation (N-) groups. The periarterial nerve was microscopically removed from the vessels of the N- group. The vessels in both groups were investigated by hematoxylin-eosin or immunohistochemical staining, and they were stimulated by electrical field stimulation with serial frequency for isometric tension measurement. RESULTS: Histologic analyses revealed that periarterial connective tissues including neuropeptide Y were removed to expose the external elastic membrane in the N- vessel, whereas they were preserved in N+. The mean contraction by electrical field stimulation with serial frequency was consistently lower in N- than in N+ (P < .05 at 20 and 50 Hz; n = 8 each). Endothelium-dependent relaxation and contractile function of the smooth muscle were similar in both groups. CONCLUSIONS: The removal of the periarterial sympathetic nerve from the human gastroepiploic artery reduced vascular contraction, elicited by peripheral nerve stimulation, without disturbing endothelial and smooth muscle contractile functions. This reduction may contribute to the prevention of vasospasms.

Influence of nitric oxide on neurogenic contraction and relaxation of the human gastroepiploic artery.

BACKGROUND: The objective of this study was to characterize the neurogenic contraction and relaxation of the human gastroepiploic artery and to determine whether the responses are mediated by nitric oxide (NO) from neural or endothelial origin. METHODS: Rings of human gastroepiploic artery were obtained from 18 patients (12 men, 6 women) undergoing gastrectomy. The rings were suspended in organ baths for isometric recording of tension. We studied the contractile and relaxant responses to electrical field stimulation. RESULTS: In arteries under resting conditions, electrical field stimulation (2 to 8 Hz) caused frequency-dependent contractions that were of greater magnitude in arteries denuded of endothelium and blocked by tetrodotoxin (10(-6) mol/L). The inhibitor of NO synthesis N(G)-monomethyl-L-arginine (L-NMMA, 10(-4) mol/L) increased contractile responses only in arteries with endothelium. In preparations contracted with norepinephrine in the presence of guanethidine (10(-6) mol/L) and atropine (10(-6) mol/L), electrical stimulation induced frequency-dependent relaxations. This neurogenic relaxation was prevented by L-NMMA (10(-4) mol/L) and tetrodotoxin (10(-6) mol/L), but was unaffected by removal of the endothelium. CONCLUSIONS: The results provide functional evidence that NO is released by autonomic nerves of the human gastroepiploic artery. We hypothesize that the release of NO from both endothelial and neurogenic origin may modulate resistance of the human gastroepiploic artery. Dysfunction in any of these sources of NO should be considered in some form of vasospasm.