A critique of implantation of a systemic artery for myocardial revascularization

Abstract

The extensive experimental data available indicate that about 90 per cent of arterial implants remain patent. The development of collateral circulation is an event which should be analyzed separately from continued patency, for collateral circulation is principally influenced by the degree of regional myocardial ischemia. With extensive collateral circulation, flow rates in the internal mammary artery may increase from 3 to 5 ml./min. following implantation to 30 to 40 ml./min. six months later. Reported clinical studies of over 1,000 operations from different groups indicate an operative mortality between 2 and 5 per cent, with a subsequent late mortality of 5 to 10 per cent in the first two years after operation. Eighty-five to 90 per cent of implanted vessels are subsequently found patent on angiography. Improvement of varying degree in angina pectoris can be anticipated in 60 to 75 per cent of patients. Postoperative angiography of the implanted vessel is the best method available for evaluating the efficacy of an implantation procedure, determining patency, degree of collateral circulation, and establishment of anastomoses with the regional coronary circulation. An arterial implant selectively perfuses only the regional coronary arteries near the implant. Hence, with diffuse coronary artery disease, multiple implants are necessary. A variety of techniques are being evaluated to revascularize the posterior portion of the left ventricle, including an autogenous vein graft, the gastroepiploic artery, a double internal mammary implant, and the splenic artery. 2,4,9,10,23,27–33,35–38 Most experience has been with the double internal mammary implant, which on postoperative study has been found to have patency rates near 90 per cent. Hopefully, in the future, methods for determining the rate of blood flow through the implant will become available, providing a numerical index of efficacy of revascularization. With such a guide, the influence of revascularization upon the risk of subsequent myocardial infarction and longevity can be evaluated. The data thus far available indicate that an implanted internal mammary artery does subsequently behave like a coronary artery and truly revascularize the heart. If such an achievement can be routinely accomplished at operation, a significant beneficial influence on the course of coronary occlusive disease can be anticipated. With the widespread prevalence of coronary artery disease, the consequences are far-reaching, for arterial implantations could soon become more widely needed than all other cardiovascular operations now currently performed.