CABG patients with IMA graft likely to require revascularization, study says

December 16, 2015 – Renato Lopes, MD, MHS, PhD, said the study could change how clinicians make decisions about patients who undergo the procedure.

Patients who undergo coronary artery bypass grafting (CABG) via the internal mammary artery (IMA) are more likely to require revascularization, according to a new study by DCRI researchers.

The study appears online in the journal Circulation.

The IMA conduit is widely used as a means of bypassing the left anterior descending (LAD) coronary artery during CABG procedures. Earlier research has shown the IMA-to-LAD graft to be more durable than other arterial and vein grafts, and improved patient outcomes may owe something to the procedure’s reliability. Yet until now there have been few high-quality studies of IMA graft failure rates.

renato-lopesIn this study, DCRI researchers sought to identify the factors associated with IMA graft failure and study the association between graft failure and patients outcomes. To do so, they analyzed patient data from the PREVENT IV trial. That trial was a double-blind, multicenter, randomized clinical trial that was designed to assess the effectiveness and safety of edifoligide on angiographic vein graft failure after CABG, as well as the effect of edifoligide on major adverse cardiac events (MACE) following CABG. The trial enrolled 3,014 participants at 107 U.S. sites between 2002 and 2003.

The current analysis included 1,539 patients who underwent IMA-LAD revascularization and had 12-18-month angiographic follow-up. The researchers found that IMA failure occurred in 132 participants (8.6 percent) of the study population. Factors associated with IMA graft failure included LAD stenosis less than 75 percent, additional bypass graft to diagonal branch, and not having diabetes.

LAD stenosis and additional diagonal graft were also associated with IMA failure in an alternative model that included angiographic failure or death before angiography as the outcome.

IMA failure was also associated with a significantly higher incidence of subsequent acute clinical events, a relationship that was  attributed to a higher rate of repeat revascularization, according to Renato D. Lopes, MD, MHS, PhD (pictured), the study’s senior author.

“This study represents the first robust assessment of IMA graft failure and long-term clinical outcomes in a large cohort of patients undergoing coronary artery bypass grafting surgery with systematic angiographic follow-up, regardless of symptom status,” Lopes said. “Our findings raise concerns about the performance of coronary artery bypass grafting with the use of IMA in the treatment of native vessels with only mild or moderate stenosis, as well as the use of an additional bypass graft to the diagonal branch, confirming that the severity of LAD stenosis and competitive flow are of key importance for patency of the IMA-LAD graft. This information might help physicians on decision-making and likely change practice among patients undergoing CABG surgery.”

In addition to Lopes, the study’s DCRI and Duke authors included Ralf E. Harskamp, MD; John H. Alexander, MD, MHS; Brian Englum, MD; Daniel Wojdyla, MS; Phillip J. Schulte, PhD; Eric D. Peterson, MD, MPH; and Peter K. Smith, MD.