Major cardiac events were fewer at 5 years in patients receiving a radial artery graft as the second conduit in coronary bypass surgery (CABG) vs a saphenous-vein graft (SVG) in a patient-level meta-analysis of randomized trials.
Radial arteries were also far more likely than SVGs to remain open at 5 years, but they were not associated with significantly better survival.
Patients in all the trials had undergone isolated CABG using the left internal thoracic artery as the primary conduit, with either a harvested radial artery or SVG as the secondary conduit.
Benefits from use of the radial artery were more pronounced in several subgroups, which observers say could one day potentially guide selection of one vessel or the other as the secondary conduit in individual patients.
The Driver: Repeat Revascularization
Of note, the radial artery group’s 33% reduction in the primary endpoint, a composite of death, myocardial infarction (MI), or repeat revascularization, was driven by reductions in risk for MI and especially repeat revascularization, the latter of which fell by half.
That’s consistent with several large observational studies, but the current meta-analysis “is the first to show there is a benefit from randomized data,” David P. Taggart, MD, University of Oxford, United Kingdom, told theheart.org | Medscape Cardiology.
“The 64-million-dollar question here is, if we followed these patients out to 10 years, would we then also see an actual survival benefit? That’s a real possibility here because we know vein graft failure continues to accelerate between 5 and 10 years, whereas radial artery failure does not,” he said.
Taggart is senior author on the study, published April 30 in the New England Journal of Medicine with lead author Mario Gaudino, MD, Weill Cornell Medicine, New York City.
The meta-analysis, from the Radial Artery Database International Alliance (RADIAL) research group, was presented at the 98th American Association for Thoracic Surgery (AATS) Annual Meeting in San Diego, California, at about the time of its publication.
The study is well designed, but with all the limitations of a meta-analysis, according to Frank W. Sellke, MD, from Brown University and Rhode Island Hospital, Providence, who was not connected with the study.
“Also, the findings aren’t surprising,” he said in an interview. “It adds more data to what most surgeons already believe.”
At his center, the radial artery is used instead of the SVG in about 14% of cases, whereas “nationally it is between 4% and 5%,” he said, citing numbers from the Society of Thoracic Surgery.
Use of the radial artery hasn’t caught on more because surgeons “are not convinced that it really adds that much to the surgery.” The current study might encourage greater use, he said. But because it didn’t show a survival benefit, at least at 5 years, “I don’t think it’s going to move the needle that much.”
Taggart is sure that if a future study shows a survival benefit for the radial artery compared with the SVG in a 10-year follow-up, “it will very dramatically change practice.”
Age Interaction
Sellke brightened when pointing out “the most interesting aspect of the study.” Most studies in the field have been too small to look at treatment effects in specific patient groups, he said. But by combining trials, “I think they were able to do a valid subgroup analysis.”
It found the primary-endpoint reduction with radial artery grafting to be significant in patients younger than 75 years but not older than 75 (P = .008 for interaction), in patients without but not with renal insufficiency (P = .02), and — surprisingly — in women but not in men (P = .01).
The age interaction makes sense because older patients are less likely to survive long enough to reap the benefits of continued late patency with radial artery grafts compared with the SVG. But, Sellke said, “Why women have such a better outcome with the radial artery compared to men, I have no idea!”
“When we talk about the advantage of radial artery grafts over saphenous vein grafts, we tend to lump everybody together. And this, I think for the first time, has perhaps discerned who should get a radial artery, and who should get a saphenous vein graft,” he said.
“I think in these subgroups of patients, we may actually see more radial artery grafts utilized.”
60-Month Outcomes
The six randomized trials combined for the analysis included 534 patients with radial artery grafts and 502 patients who received the SVG.
The risk for perioperative stroke was not significantly different between the two groups; the odds ratio was 0.71 (95% CI, 0.23 – 2.11; P = .53) for radial artery vs SVG patients.
Radial artery patients showed significant reductions in the composite endpoint, death, and MI over a mean follow-up of 60 months.
Table. Hazard Ratios for 5-Year Outcomes With Radial Artery vs SVG as Second Graft in CABG
| Endpoints | Hazard Ratio (95% CI) | P Value |
|---|---|---|
| Death, MI, or repeat revascularization | 0.67 (0.49 – 0.90) | .01 |
| Death | 0.90 (0.59 – 1.41) | .68 |
| MI | 0.72 (0.53 – 0.99) | .04 |
| Repeat revascularization | 0.50 (0.40 – 0.63) | <.001 |
| Graft occlusiona | 0.44 (0.28 – 0.70) | <.001 |
| aAt protocol-specified angiography at a mean of 50 months in 345 radial artery patients and 307 SVG patients. | ||
Neither type of vessel was harvested endoscopically in the trials, Taggart observed, although that is the current standard of care for the saphenous vein. “We do it routinely, and it will become the standard of care for the radial artery as it has for the SVG.”
The study was supported by the Department of Cardiothoracic Surgery of Weill Cornell Medicine, the National Institute for Health Research Bristol Biomedical Research Centre, and the Bernard S. Goldman Chair in Cardiovascular Surgery. Taggart and Gaudino had nothing to disclose; disclosures for the other authors are available at NEJM.org. Sellke discloses consulting for Stryker and being on a trial data safety monitoring board for Octapharma.
N Engl J Med. Published online April 30, 2018. Full text
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