Clinical Pearls & Morning Reports
Published January 30, 2019
The Arterial Revascularization Trial (ART) randomly assigned patients to receive either bilateral internal-thoracic-artery grafts or a standard single left internal-thoracic-artery graft during coronary-artery bypass grafting (CABG). A prespecified interim analysis at 5 years showed no significant differences between the two strategies with regard to all-cause mortality or the rate of the composite outcome of death from any cause, myocardial infarction, or stroke. A current report presents the primary analysis at 10 years of follow-up. Read the NEJM Original Article here.
Q: What is the rationale for using bilateral internal-thoracic-artery grafts for CABG?
A: Pooled observational studies have shown lower long-term mortality when both left and right internal-thoracic-artery grafts are used for CABG than when a single internal-thoracic-artery graft is used. This finding has been attributed to the excellent long-term angiographic patency of the right internal-thoracic-artery graft, which appears to be similar to that of the left. It is hypothesized that routine use of the right internal thoracic artery for grafting in addition to the left would provide better clinical outcomes because of improved long-term graft patency.
Q: Is use of bilateral internal-thoracic-artery grafts for CABG associated with lower mortality at 10 years as compared to use of a single internal-thoracic-artery graft?
A: The primary outcome of the ART trial was death from any cause at 10 years of follow- up. A total of 644 patients (20.8% of the overall trial population) had died by 10 years, with 315 deaths (20.3%) occurring in the bilateral-graft group and 329 (21.2%) in the single-graft group (hazard ratio, 0.96; 95% confidence interval [CI], 0.82 to 1.12; P=0.62). Results were similar after adjustment for age, sex, diabetes status, and ejection fraction (hazard ratio, 0.97; 95% CI, 0.83 to 1.14). Intention-to-treat analyses of the primary outcome according to subgroups did not show any evidence of significant interactions.
A: Regarding the composite outcome of death from any cause, myocardial infarction, or stroke, there were 385 patients (24.9%) with an event in the bilateral-graft group and 425 (27.3%) with an event in the single-graft group (hazard ratio, 0.90; 95% CI, 0.79 to 1.03). There was no significant between-group difference in the rate of repeat revascularization (10.3% in the bilateral-graft group and 10.0% in the single-graft group). There were no significant differences in the rate of early major bleeding events. Sternal wound complications during the first 6 months of follow-up occurred in 54 patients (3.5%) in the bilateral-graft group and in 30 (1.9%) in the single-graft group (relative risk, 1.81; 95% CI, 1.16 to 2.81).
A: Twenty-two percent of those who had been randomly assigned to the single-graft group also received a second arterial graft in the form of a radial-artery graft. When ART was designed in 2001, it was not known that radial-artery grafts would provide additional clinical benefits as compared with saphenous-vein grafts. Since then, there has been growing evidence of the superior angiographic patency of radial-artery grafts as compared with saphenous-vein grafts, which has resulted in better clinical outcomes. Consequently, the use of radial-artery grafts in ART may be a key confounder, because it is likely to preferentially benefit the single-graft group by the addition of an arterial graft to the second most important coronary artery.