Vein graft recalls, new tissue engineered artery grafts predicted

The day may be approaching when patients who have undergone coronary artery bypass surgery are notified that their saphenous vein grafts have been recalled as predicted at a conference sponsored by the American College of Cardiology.

The idea would be to bring patients in preemptively and line their vein grafts with a more durable material before the grafts degenerate so badly that they embolize, as so many do, it was explained by the director of cardiac invasive services and the Device development laboratory at Massachusetts General Hospital, Boston. Saphenous vein graft disease remains a major limitation of coronary artery bypass graft (CABG) surgery. The 350,000 CABG operations done per year in the United States include an average of 2.2 vein grafts per case. Everyone gets a mammary artery graft these days, but the bulk of the conduits in most centers include a couple of veins.

Approximately 10 percent – 15 percent of these veins grafts will occlude and fail within the first year. At 10 years, 60 percent of vein grafts remain patent – and half of these have angiographic evidence of significant disease. And 30 percent of CABG patients eventually require repeat CABG due to vein graft failure. The repeat surgery carries twice the mortality risk of the initial surgery, three times the perioperative Ml rate, and reduced angina relief. Catheter-based interventions targeting diseased vein grafts are plaqued by high complication rates and poor durability. The notion of harvesting a saphenous vein from the leg, removing it from its blood supply and supporting structures, turning it upside down, and slapping it on the heart is really not the greatest idea. It was clearly expedient at a certain time, but I propose that we ought not to be doing it. One doctor has been involved in developing new covered-stent technology. Later this year, a clinical trial will get underway using a long, GoreTex-covered, small-diameter stent inside vein grafts, the end point will be durability. Other approaches under active investigation for revising or replacing saphenous vein grafts are tissue-engineered arterial grafts, xenografts, and the use of gene therapy or antisense technology to manipulate vein grafts or the operating table in an effort to render them more durable.

The most appealing of these are tissue-engineered arterial grafts made from cells harvested from the graft recipient. These would be made of living tissue capable of growth and remodeling. It has been working with Boston-area tissue engineers who have convinced him that such grafts are feasible. This is not far-fetched. Getting there is just a matter of time and money.