NEW ORLEANS – Patients undergoing coronary artery bypass graft (CABG) surgery do not see any 5-year survival advantage when their surgeon uses both internal mammary (thoracic) arteries for grafting rather than just one of them along with a vein, finds an interim analysis from the randomized Arterial Revascularization Trial (ART).
Overall, about 8.5% of the 3,102 patients randomized had died 5 years after surgery, with no significant difference between the bilateral graft and single graft groups, according to data reported at the American Heart Association scientific sessions and simultaneously published (N Engl J Med. 2016 Nov 14. doi: 10.1056/NEJMoa1610021). The former had roughly triple the rate of sternal reconstruction, mainly driven by complications in insulin-dependent diabetes patients having high body mass index.
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There is strong angiographic evidence that vein grafts have a high rate of failure over time because of atherosclerosis, but internal mammary artery grafts retain excellent patency, he elaborated. “People have speculated that this superior patency of internal mammary arteries will translate into a clinical survival benefit,” and observational data indeed suggest that the bilateral artery strategy reduces mortality by about one-fifth relative to the single artery strategy.
Yet uptake of the bilateral procedure has been low. It is used in fewer than 5% of patients undergoing CABG in the United States and fewer than 10% of those in Europe, reflecting concerns about its greater technical complexity, potentially increased mortality and morbidity, and – until now – lack of evidence from randomized trials.
“What I think we can conclude today is that there are excellent 5-year outcomes of CABG in both groups. This study confirms that it’s at least safe to use bilateral grafts over the medium term,” Dr. Taggart commented. He discussed the results in a video interview conducted at the meeting.
These interim ART data probably won’t sway practice one way or the other, he said. “People who believe in arterial grafts will continue to do them, and those who are not enthusiastic about the prospect of a slightly technically more difficult operation [can now] remain comfortable as to why they are not using both internal mammary arteries.”
Pointed questions
Dr. Frank W. Sellke
The lack of difference was possibly due to a very high level of guideline-based medical therapy in the trial (which may have especially protected the vein grafts) or to the fact that the annual failure rate of vein grafts is modest and steady up to 5 years but accelerates thereafter, Dr. Taggart proposed. The trial’s primary outcome of 10-year survival, expected in 2018, will likely differ, speculated Dr. Sellke, who is also program chair for the AHA scientific sessions.
“Do you think multiple arterial grafting is superior to single internal mammary artery grafting considering the lack of improvement in survival and other outcomes in the study, with the increase in sternal wound infections?” he asked.
“I personally, if I needed the operation, would insist on having bilateral internal mammary artery grafts done by an experienced operator because it is totally counterintuitive to believe that having more patent grafts in your heart at 10 to 20 years of follow-up is of no benefit,” Dr. Taggart maintained.
When data meet clinical practice
Dr. Timothy J. Gardner
It may require time for the benefit of the bilateral artery graft to emerge, he agreed. “I’m undeterred from my belief that ... in patients who are getting CABG done in their 40s or 50s or early 60s, betting on a graft that’s going to outperform vein grafts is the better strategy.”
Until the trial’s 10-year results become available, physicians may wish to put these interim results in the context when counseling patients, according to Dr. Gardner.
“We have indisputable evidence that arterial grafts have better long-term patency than vein grafts,” he elaborated. “If we had a very sophisticated patient, we might tell them that we were a little surprised that this head-to-head trial of single versus double didn’t show any survival benefit at 5 years, but we still are persuaded by the data that shows the better patency, and we think in the situation that the patient’s in, that we would still recommend a double mammary, assuming that the patient doesn’t have comorbidities that would make that more dangerous.”