Effects of occlusion devices for minimally invasive coronary artery bypasssurgery on coronary endothelial function of atherosclerotic arteries

BACKGROUND: During minimally invasive coronary artery bypass grafting surge ry, technical devices are required to obtain an optimal operative field. Ho wever, these devices can cause lesions to the endothelium. Previous studies of the effect of devices on coronary endothelial function have been perfor med on normal coronary arteries. Balloon denudation is followed by regenera tion of the endothelium, which is dysfunctional and by intimal hyperplasia resembling atherosclerosis. The Anastaflo(TM) (Baxter, Mississauga, Ontario , Canada) shunt is a surgical device used during the performance of coronar y anastomoses that allows a continuous flow inside the artery during the su rgery. METHODS: We compared the effects of three commonly used techniques on endot helial function: 1) using the Anastaflo(TM) shunt, 2) using Retract-o-tape( R) (Genzyme, Cambridge, MA) silicone air cushion snaring, and 3) using a bu lldog clamp on arteries submitted to balloon denudation 30 days prior to th e surgical experiment on an in vivo model of beating heart off-pump coronar y artery bypass (OPCAB). Balloon denudation was performed on the left anter ior descending artery and on the right coronary artery.The devices were app lied for 15 minutes on porcine epicardial coronary arteries, on the beating heart, after median sternotomy. Denuded control rings were taken at the si te of denudation on which no devices were applied while non-denuded control rings were taken from the left circumflex artery. The endothelial function of control and instrumented arterial rings was studied in organ chambers f illed with a modified Krebs-Ringer bicarbonate solution. After contraction to prostaglandin F-2 alpha, endothelium-dependent relaxation to serotonin ( an agonist coupled to Gi-proteins) and bradykinin (a non-Gi-protein coupled agonist) were compared in the shunting group, the snaring group, the clamp ing group, and in controls. RESULTS: There was a significant decrease in the relaxations to serotonin a nd bradykinin in the denuded control group compared with the non-denuded co ntrol group, confirming that balloon denudation caused an endothelial dysfu nction. However, there was no significant difference between the denuded co ntrol group and the hemostatic device groups (shunting, snaring and clampin g) in the relaxation to serotonin. CONCLUSION: These results suggest that hemostatic devices used for OPCAB do not cause any greater injury in atherosclerotic coronary arteries already harbouring an endothelial dysfunction. The effects on platelet aggregation, intimal dissection, and plaque rupture remain to be determined.