Should Coronary Artery Bypass Grafting Be Performed in Patients With Moderate Stenosis of the Left Anterior Descending Coronary Artery?

Abstract

In this issue of Circulation , Harskamp and colleagues1 use 12- to 18-month angiographic follow-up data from the Project of Ex-vivo Vein Graft Engineering via Transfection IV (PREVENT IV) trial to determine the frequency of internal thoracic artery (ITA) graft failure, its risk factors, and its association with postoperative clinical events. They identified left anterior descending coronary artery (LAD) stenosis <75%, additional bypass graft to a diagonal, and absence of diabetes mellitus as risk factors for ITA graft failure, and reported that graft failure was associated with a high risk of postoperative repeat revascularization. Because of the association of ITA failure with moderate LAD stenosis and risk of early postoperative revascularization, the authors question the benefit of coronary artery bypass grafting (CABG) in patients with moderate, or non–ischemia-producing, lesions of the LAD. Article see p 131 This article adds to the extensive literature on the association of native coronary artery competitive flow and ITA patency.2–7 Its considerable strength is systematic angiographic follow-up. What is new is their thesis that these findings raise concern that CABG may not be beneficial in patients with moderate stenosis of the LAD. To evaluate whether these concerns are justified, it is necessary to review what is known about the effect of competitive flow on ITA patency, whether saphenous veins are more effective grafts than ITAs to coronary arteries with only moderate stenosis, and whether grafting a coronary artery with moderate stenosis is beneficial or harmful. Competitive flow is the most important factor influencing ITA graft patency (and the patency of all arterial bypass grafts, as well).2 Competitive flow is defined as native coronary artery blood flow in a coronary artery to which a bypass graft has been anastomosed—flow that progressively lessens as proximal coronary artery stenosis increases. Studies evaluating the …