Myocardial Revascularization by Internal Mammary Artery Implants with open and Ligated Branches:A Micro-angiographical and Histological Study in the Dog

Abstract

Internal mammary artery intramyocardial implantations were performed in 24 dogs. In 11 dogs three main branches of the implant were left open in the myocardial tunnel. In 13 dogs all major branches of the implant were ligated prior to the implantation. Six of the dogs with open branches of the implant and six with ligated branches were sacrificed, after at least 45 days, whereafter contrast medium was injected into the implanted artery. In five living dogs with open implant branches and seven with ligated branches, contrast medium was injected into the implanted artery at least 66 days after the implantation. Micro-angiographical and histological investigations revealed that there was a wider and denser distribution of contrast medium in the myocardium of dogs in which branches had been left open in the myocardial tunnel than in those with all major branches ligated. Thrombosis was seen in one implant with open branches, and was restricted to its distal segment. The results indicate that open implant branches facilitate the development of anastomosing vessels between the implant and the myocardial vasculature, and that the blood flowing through this vascular system can reach the myocardial capillaries. They further indicate that the more extensive exposure of damaged intima in implants with open branches does not enhance thrombus formation. Thus, intramyocardial vessel implants for revascularization purposes should have as many open branches as possible.