The Effect of Internal Mammary Artery Implantation on Myocardial Blood Flow During Temporary Coronary Occlusion in Dogs

The blood supply to a myocardial section, where the cognate artery had been acutely clamped, was studied with the Kr95 and Xe133 clearance technique in dogs in which an internal mammary artery implantation had been performed, either acutely or 3 to 6 weeks earlier. The blood flow in the acutely ischaemic myocardium was computed both when the implanted artery was clamped and when it was left open. However, the collateral blood supply was significantly increased on opening the implanted artery when the implantation had been performed 3 weeks earlier, but almost doubled when it had been carried out 6 weeks earlier. The present data thus indicate that the blood flow from the implanted mammary artery to the myocardium is truly nutritive and distributed evenly within the underperfused muscle region. Experiments with simultaneous implantation and coronary artery ligation indicate that interarterial connections between the implantation and the coronary vessels develop faster in chronically ischaemic surroundings. It could also be observed that the function of the implanted artery seems to be dependent on the site where the mammary artery is inserted into the myocardial tissue.