A novel, stent-shaped device that provides external buttressing to saphenous vein grafts placed during coronary artery bypass surgery was safe, but failed to improve 12-month patency of vein grafts, in a prospective study with 224 patients.
Dr. John D. Puskas
Despite the neutral result, “we are cautiously optimistic” about the prospects for the device to reduce the risk for failure of coronary vein grafts caused by intimal hyperplasia of the internal lining of the vein graft that leads to graft occlusion, said John D. Puskas, MD, lead investigator of the study, who reported the results at the American Heart Association scientific sessions.
In the trial, called VEST, each buttressed vein graft was compared with a similar, unbuttressed graft in the same patient. Perhaps the biggest issue faced by the study was the unexpectedly high 42% rate of vein-graft occlusion or diffuse disease seen in the studied grafts 12 months after placement. This rate included both the vein grafts placed within the external buttressing device and control vein grafts that underwent the same postharvest preparation but weren’t placed within an external sheath, which is formed from woven cobalt chromium wire.
Dr. Puskas attributed this high failure rate to the need to remove all adventitia tissue and fat from the harvested saphenous vein segments before grafting, a step required to allow the vein conduit to fit inside the wire sheath. The potential exists to further optimize this step, he said in an interview.
Dr. Joanna Chikwe
“I was very surprised by the low 12-month patency rates” in both treatment arms of the study, commented Joanna Chikwe, MD, chair of cardiac surgery at Cedars-Sinai Medical Center in Los Angeles.
External scaffold to counter blood pressure
The concept behind the external buttressing sheath is that the walls of saphenous vein grafts are not structured to accommodate arterial blood pressure, and over time this pressure produces accelerated atherosclerotic changes and premature occlusion and graft failure. The external support is supposed to impede vein wall dilatation, reduce irregularities of the inner lumen surface, and improve hemodynamics and shear stress.
The VEST trial ran at 14 U.S. and 3 Canadian centers and enrolled 224 patients scheduled for coronary artery bypass grafting with planned use of at least two saphenous vein grafts, along with an internal mammary artery graft for the left anterior descending coronary artery. The patients averaged 66 years of age, 21% were women, and 51% had diabetes.
All patients successfully underwent their surgery, with 203 returning after 12 months for their primary follow-up examination by intravascular ultrasound. However, because of the high rate of vein occlusion or development of diffuse intragraft disease, successful intravascular ultrasound (IVUS) examination of both vein grafts occurred in only 113 patients.
The IVUS examinations showed that the study’s primary endpoint, the intimal hyperplasia area in all 224 patients who received vein grafts, averaged 5.11 mm2 in the grafts placed within the wire sleeve and 5.79 mm2 for control grafts not placed in the wire sheath, a difference that fell short of significance (P = .072). However, in a sensitivity analysis that focused on only the 113 patients who had both vein grafts successfully assayed by IVUS, the average area of intimal hyperplasia was 4.58 mm2 in the grafts within a wire sheath and 5.12 mm2 in the control grafts, a significant difference (P = .043).
The combined rate of major adverse cardiovascular events after 12 months was 7%, including a 2% mortality rate, a 3% stroke rate, and 3% rate of Mis, outcomes that suggested “no safety signals,” said Dr. Puskas, chair of cardiovascular surgery at Mount Sinai St. Luke’s in New York.
Although a large body of evidence has shown the superiority of arterial grafts for long-term graft patency, vein grafts have many advantages that have maintained them as the most widely used conduits worldwide for coronary artery bypass surgery, Dr. Puskas said.
Saphenous vein segments are readily available from patients and easy to harvest; they nicely conform to the coronary arteries that require bypass, rarely leak, are easy to work with, and can successfully hold stitches. Surgeons performing coronary artery bypass are unlikely to abandon vein grafts anytime soon, which makes improving the performance of vein grafts a priority, Dr. Puskas said.
The study was sponsored by Vascular Graft Solutions, the company developing the venous graft external support. Dr. Puskas and Dr. Chikwe had no disclosures related to the study.