April 5, 2011 (New Orleans, Louisiana) — The radial artery has outperformed the saphenous vein as a conduit for coronary artery bypass grafting (CABG) in a five-year follow-up of patients with multivessel disease undergoing surgery in a randomized, multicenter Canadian study.
These new longer-term findings show that the radial artery does seem to offer an improvement in graft patency, compared with the vein graft, said Dr Stephen Fremes (Sunnybrook Health Sciences Center, Toronto, ON), who presented the findings from the Radial Arterial Patency Study (RAPS) during a late-breaking clinical-trial session today here at the American College of Cardiology 2011 Scientific Sessions. Earlier one-year results from RAPS showed that the radial artery had better overall patency than the saphenous vein, but so-called "perfect" patency was similar between the two, he noted.
"I think that the longitudinal data are the most important and much more informative--you get misled in many cases by early results," Fremes told heartwire . "This is particularly true in coronary surgery, because often you see results in different groups diverge after longer follow-up."
The data on this subject prior to these new RAPS results have been "mixed," Fremes explained, with mostly observational data and only a small number of randomized trials. The moderator of the press conference, Dr Spencer King (Emory University, Atlanta, GA), said that "previous studies have indicated that the radial artery is not much better than a saphenous vein graft, but this [new study] challenges that."
Why Use the Radial Artery? Depends on Who Is Harvesting and How
Fremes explained to heartwire that most patients who undergo CABG have multiple vessel disease and multiple bypasses. "In our study, the number of bypasses was three and a half, and we would recommend a radial artery as a second or third conduit, after a mammary artery."
Previous studies have indicated that the radial artery is not much better than a saphenous vein graft, but this [new study] challenges that.
The reasons that his group and others consider the radial artery as a good second option for grafting after the internal mammary artery are because of its length, diameter, and wall thickness and because of the lack of harvest-site complications, Fremes said. However, he acknowledged that the latter, in particular, depends on who is harvesting the vessel. "If you're in a teaching institution, a junior resident or an intern might be harvesting, and you may be reluctant to assign radial artery harvesting to an early trainee. But in the US, often it is physician assistants, who are very skilled at harvesting, [who] do the radial artery." Also, many patients worldwide now have their veins harvested endoscopically, Fremes said, and it is "more difficult" to harvest a radial artery endoscopically than a vein, he conceded.
Another issue is the increasing use of the radial arterial route for access in PCI. Fremes said that it would not be possible to perform a cath through a radial artery that has already been used for bypass. Nor would surgeons consider using a radial artery for bypass after it had been used for PCI access. "But we've almost exclusively used radial artery from the nondominant hand (which for most people is the left), while interventionalists usually use the right radial artery," he pointed out.
Fewer Complete and Partial Occlusions With Radial Artery at Five Years
RAPS was conducted at 13 sites across Canada and enrolled 561 patients undergoing CABG for three-vessel disease; at the time the study was conducted, there was very little use of PCI in patients with triple-vessel disease, Fremes told heartwire . Each patient in the study received both a radial artery graft and a saphenous vein graft at two vessel sites, so the randomization was within patient, not between patients, he noted.
In all, 269 patients were available for the five-year angiographic follow-up. Significantly fewer radial arteries became partially occluded than saphenous vein grafts (12% vs 18.8%; odds ratio, 0.64; p=0.05); the same applied to complete occlusions (8.9% vs 17.8%; odds ratio, 0.50; p=0.004).
In addition to finding lower rates of occlusion in the radial artery grafts, the team also found that radial artery grafts worked better when grafted to more thoroughly diseased vessels. There was an approximately 50% lower failure rate for radial artery grafts that were grafted to vessels with 90% or greater narrowing.
"The implications from our one-year study were confirmed in the five-year results--radial artery bypass grafts should be used preferentially for the most severely narrowed coronary arteries," Fremes noted. In addition, there were more patients with events attributed to saphenous vein grafts than to radial artery grafts, he explained.
"Poignant" Illustration of the Importance of Long-Term Follow-up
During the panel discussion that followed the presentation of the late-breaking trials, Dr James B McClurken (Temple University, Philadelphia, PA) said: "This is a very poignant illustration of the importance of long-term follow-up. I think the radial artery is a great conduit, and I use it frequently with an internal mammary artery." Dr Steven F Bolling (University of Michigan Cardiovascular Center, Ann Arbor) agreed: "It's a cultural change for us, but data like these reemphasize that we will change in response to good results."
During the press conference, King asked Fremes how these new RAPS results could be reconciled with one-year results from a VA study published recently, which found that radial artery grafts were no better than saphenous vein grafts. Fremes pointed out that the VA study enrolled only men, that the results are short term, and that vein grafts seem to have performed better than expected in that trial. The VA trial "has been refunded for five-year results," which will be interesting to see, he noted.
There is also an ongoing Australian study, which has published a number of "interim" results and which will be reporting both clinical and angiographic outcomes out to 10 years, he said.
Fremes, Bolling, and McClurken report no conflicts of interest. King receives consulting fees from Celonova Biosciences and Northpoint Domain.
Heartwire from Medscape © 2011 Medscape, LLC
Cite this: Radial Artery Favored Over Saphenous Vein Grafts for CABG - Medscape - Apr 05, 2011.