Preconditioning and proximal ligation did not influence the outcome of direct internal mammary artery bypass grafting in a canine model

The aim of this study was to assess the need for preconditioning and/or exc lusion of competitive flow in minimally invasive coronary bypass grafting p rocedures (MICAB), to prevent early graft occlusion. Eight mongrel dogs ( /- 25 kg) were operated on under intravenous anaesthesia (sodium thiopentha l 15 mg/kg) and maintained with Halothan 1-2% and Pancurorium. A direct ana stomosis between the left internal mammary artery and the left anterior des cending coronary artery was performed, via anterior distal sternotomy, on t he beating heart. Four dogs were preoperatively randomly conditioned by int ravenous bolus injection of Diltiazem (0.0025 g/kg) prior to the procedure and after (meanwhile the left internal mammary artery takedown, the proxima l coronary artery was snared during 15 min). In the absence of ECG changes or rhythm disturbances, a direct anastomosis of the left internal mammary a rtery and the left anterior descending coronary artery was performed, in fo ur control dogs, direct MICAB procedure was done without preconditioning, T he proximal left anterior descending coronary artery was occluded upstream of the arteriotomy in two dogs from both groups to exclude competitive flow from the native coronary artery, All the procedures were successful, excep t for one conditioned dog that sustained preoperative transmural anterior m yocardial infarction, Cardiac enzymes (CK and CKMB) rose in all groups imme diately after the procedure; this was not statistically significant between groups, All survivors were angiographically controlled after 6 to 8 weeks. They showed good patency of all grafts (mean thrombolysis in myocardial in farction-flow equals 2.86). There was perfect matching between the left int ernal mammary artery and left anterior descending coronary artery in the co nditioned and proximal occluded group, which was contrary to the competitiv e flow in the control groups between the open left anterior descending coro nary artery and the left internal mammary artery graft. Permeability of the left internal mammary artery grafts are not influenced by preconditioning nor exclusion of competitive flow in the MICAB technique for the canine mod el. Graft diameter and flow are merely the result of outflow conditions, In one case, preconditioning was followed by fatal myocardial infarction. (C) 1999 The International Society for Cardiovascular Surgery. Published by El sevier Science Ltd. All rights reserved.