Randomized Trial Comparing Bilateral with Single Internal-Thoracic-Artery Grafting for CABG Shows No Significant Difference in All-Cause Mortality Bilateral versus Single Internal-Thoracic-Artery Grafts at 10 Years

A recent study published in the New England Journal of Medicine showed that among patients who were scheduled for CABG and had been randomly assigned to undergo bilateral or single internal-thoracic-artery grafting, there was no significant between-group difference in the rate of death from any cause at 10 years in the intention-to-treat analysis. Coronary-artery bypass grafting (CABG) surgery with the use of left internal- thoracic-artery grafts plus vein grafts had been deemed superior to percutaneous coronary intervention in patients with severe coronary artery disease and in those with diabetes. The benefit of using left internal thoracic artery grafts has been attributed to their superior long-term patency as compared with vein grafts. However, it is hypothesized that multiple arterial grafts may result in longer survival than single arterial grafts after coronary-artery bypass grafting (CABG) surgery. In the light of this, the study aimed to evaluate the use of bilateral internal-thoracic-artery grafts for CABG.

In this study, Taggart et al.assigned patients scheduled for CABG to undergo bilateral or single internal-thoracic-artery grafting. Additional arterial or vein grafts were used as indicated. The primary outcome was death from any cause at 10 years. The composite of death from any cause, myocardial infarction, or stroke was a secondary outcome. The bilateral-graft group and single-graft group comprised of 1548 and 1554 patients respectively. The investigators reported that in the bilateral-graft group,13.9% of the patients received only a single internal-thoracic-artery graft, and in the single-graft group, 21.8% of the patients also received a radial-artery graft. The study reported that in the intention-to-treat analysis at 10 years, there were a total of 315 deaths (20.3% of the patients) in the bilateral-graft group and a total of 329 deaths (21.2%) in the single-graft group (hazard ratio, 0.96; 95% confidence interval [CI], 0.82 to 1.12; P = 0.62). While considering the composite outcome of death, myocardial infarction, or stroke, there were 385 patients (24.9%) with an event in the bilateral-graft group and 425 patients (27.3%)with an event in the single-graft group (hazard ratio, 0.90; 95% CI, 0.79 to 1.03). The findings reflected that ART was a randomized trial of bilateral internal-thoracic-artery grafting, as compared with single internal-thoracic-artery grafting, in patients undergoing CABG. In the intention-to-treat analysis, the study found no significant differences between the two groups in the rate of death from any cause or the rate of the composite outcome of death, myocardial infarction, or stroke.

The investigators acknowledged certain limitations such as ART being an unblinded trial in which the treatment-group assignment was known to the patients, investigators, and care providers, and as a result, biases may have been introduced in the treatment of patients, depending on their randomization assignment. Moreover, crucial center-, surgeon-, and patient-driven effects may not have been fully accounted for, and the generalizability of surgical trials may have been more difficult to ensure as compared to the generalizability of trials of medication-based therapies. Lastly, no follow-up angiograms or studies of myocardial viability were carried out, which limited the consideration of graft patency and patterns of ischemia. Taggart and his colleagues believed that further studies were needed to determine whether multiple arterial grafts would provide better outcomes than a single internal-thoracic-artery graft.

Summarizing the findings of his study, the primary investigator Dr. David P. Taggart stated, “ART was a randomized trial that compared bilateral with single internal-thoracic-artery grafting for CABG. At 10 years, in intention-to-treat analyses, there were no significant between-group differences in all-cause mortality; in the rate of the composite outcome of death, myocardial infarction, or stroke; or in the rate of repeat revascularization.” Further, “The results of this trial are not consistent with data from previous, nonrandomized studies. Potential benefits of the use  of the second internal thoracic artery for grafting were suggested by a combination of reported reductions in mortality in observational studies and strong evidence of superior rates of angiographic patency of both left and right internal-thoracic-artery grafts as compared with saphenous vein grafts.”