Clinically-driven angiography after coronary artery bypass surgery : Results from the SWEDEHEART registry

Abstract: The success of coronary artery bypass grafting (CABG) arguably depends on the patency rate of the conduits. The saphenous vein grafts (SVGs) most often used are subject to graft disease and their reduced long-term patency compared to left internal mammary artery (IMA) grafts is well established. Postoperative coronary artery disease (CAD) symptoms, such as angina or myocardial infarction can undoubtedly be linked to graft failure or progression of atherosclerosis in the native coronary vessels, but the contribution from each of these processes is not completely understood.The aim of this thesis was to use clinically-driven angiography as the main outcome measure in studying different bypass conduits and surgical techniques. This endpoint has a very low risk of misclassification, and is likely to have a high association with recurrence of CAD symptoms. The SWEDEHEART registry provides extensive data on all patients undergoing cardiac surgery in Sweden as well as records of angiographies and coronary interventions.We studied the incidence of postoperative angiography in 46 663 CABG patients operated with IMA and SVGs. Young age, female sex, presence of diabetes, normal left ventricle function, previous PCI, prior MI, emergency surgery and one or two distal anastomoses were associated with a higher risk. We also studied 6 977 CABG operated individuals with three or more grafted vessels that experienced a postoperative angiography and had available records on individual graft patency. Almost one third of catheterized individuals with CAD symptoms did not demonstrate any failed grafts and in 18% of early and 10% of late angiographies the IMA-graft had failed.We compared 862 patients operated with bilateral IMA grafts and 1036 cases of IMA and radial artery grafts with 46 343 cases of IMA and SVGs. When adjusted for risk factors no improvement in outcome could be seen for patients operated with multiple arterial grafts. We also compared 1371 patients operated with “no-touch” SVGs with a propensity-matched cohort of patients with conventional SVGs. An improvement in the risk for angiography could be seen for the “no-touch” group but not for the need of repeat intervention or survival.Postoperative angiography is a useful endpoint in studying long-term outcome after CABG surgery. It is less sensitive than mortality to variations in the baseline covariates and thereby possibly less susceptible to confounding by indication. The causation behind the return of CAD symptoms after CABG surgery and the relative importance of the individual contributions from vein graft failures, failure of the IMA graft, as well as from progression of atherosclerotic plaques in both grafted and non-grafted coronary arteries, remains to be determined.