ACC: Radial arteries best saphenous vein grafts for CABG at 5 years
Graft patency is a key determinant of early and long-term outcomes following CABG surgery, according to the study authors. The internal thoracic artery provides better long-term patency than the saphenous vein for CABG, prompting surgeons to consider additional arterial grafts, including the radial artery.
Stephen E. Fremes, MD, head of the division of cardiac and vascular surgery at the Schulich Heart Centre, Sunnybrook Health Sciences Centre in Toronto, and colleagues compared the patency of radial and saphenous veins in the randomized RAPS trial, which involved patients from 12 Canadian centers and one in New Zealand.
The original RAPS study sought to determine if the angiographic patency of the radial artery exceeded that of the saphenous vein graft at one year following surgery. In this study, patients were randomized to receive either a radial artery to the RCA and saphenous vein to the circumflex territory or a radial artery to the RCA territory and a saphenous vein to the circumflex region. “Randomization was performed within each patient rather than between patients,” Fremes explained.
This one-year study showed that complete graft occlusion was significantly reduced in the radial artery compared to the saphenous vein, while partial graft occlusion was similar between the two conduits (N Eng J Med 2004;351:2302-2309).
This five-year RAPS study sought to determine if the angiographic patency of the radial artery exceeded that of the saphenous vein graft more than five years following surgery.
To accomplish this goal, they enrolled 561 patients who underwent CABG surgery for three-vessel disease. Each patient received both a radial artery graft and a saphenous vein graft at two different diseased vessel sites. The primary endpoint of functional graft occlusion was determined through invasive angiography at least five years after surgery. The secondary endpoint was complete graft occlusion determined through invasive angiography or CT angiography.
The researchers conducted late angiography on 440 patients alive at one year and on 269 patients at a mean of 7.6 years post-procedure. In the latter follow-up, they found that significantly fewer radial arteries became partially occluded than saphenous vein grafts, at 12 percent and 18.8 percent, respectively. Significantly fewer radial arteries also became completely occluded, at 8.9 percent, than saphenous veins, at 17.8 percent.
“Our study shows that the radial artery does seem to offer an improvement in graft patency compared with vein grafts,” said Fremes.
“The left internal thoracic artery was shown in the 1980s to be superior to a vein graft, and as a result, there was a wave of enthusiasm to use this artery – as well as other arteries – for either more complete arterial revascularization or total arterial revascularization,” he said. “The radial artery possesses some advantages relative to the internal thoracic artery; it has thicker walls, which makes suturing easier, and a greater length that can reach all targets on the heart.”
In addition to finding lower rates of occlusion in the radial artery grafts, the researchers also found that radial artery grafts worked better when grafted to more thoroughly diseased vessels. Specifically, the researchers separated the target vessels into three groups: those with 70 to 89 percent narrowing, 90 to 99 percent narrowing and 100 percent narrowing. They found a much lower failure rate (approximately 50 percent) for radial artery grafts that were grafted to vessels with 90 percent narrowing or more.
“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 said.
He also noted that because each study patient received both graft types, the researchers were unable to associate clinical outcomes with a specific grafting strategy. The long-term findings from an Australian study and a study conducted by the Veterans Affairs Cooperative Studies program will provide both angiographic and clinical outcomes. Another limitation is that patients recruited into the study were young and generally low risk.
As one of the study’s discussant, Steven F. Bolling, MD, thoracic surgeon at the University of Michigan Medical Center in Ann Arbor, Mich., said that this is “a wonderful study because the elective angiography performed downstream to see what is really going on with what we think are successful revascularizations. That said, we are looking for the Holy Grail of the greatest benefit for the longest term. This study is not quite as good as internal mammary artery patency data, but certainly better than vein graft data.”
The study was funded by the Canadian Institutes of Health Research.