P&S Journal: Spring 1996, Vol.16, No.2
Artery-Graft Confers Survival Advantage in Bypasses
Individuals whose coronary artery bypasses are performed with internal-thoracic-artery grafts survive longer than those who receive saphenous-vein grafts, according to a study reported in a January issue of New England Journal of Medicine. Furthermore, patients with ITA grafts are more likely to be free of atherosclerosis, even years later, says study director Dr. Airlie Cameron, associate professor of clinical medicine in cardiology at St. Luke's-Roosevelt Hospital Center. Dr. George Green, retired attending surgeon at St. Luke's-Roosevelt and Presbyterian Hospital and professor of clinical surgery, developed the direct bypass with ITA grafts in humans in 1968.
Using data from the Coronary Artery Surgery Study-a multicenter study that has tracked patients in the United States and Canada since 1974-the researchers identified 749 patients who received internal-thoracic-artery grafts in their first bypass and 4,888 patients who received saphenous-vein bypass grafts. Statistical analysis of the two groups revealed that an ITA graft was an independent, significant predictor of survival, reducing the risk of dying by a factor of 0.73. This advantage held true for men and women, individuals over age 65, and patients with impaired ventricular function.
"Most surgeons say that the artery bypass is the one of choice, but then they often have reasons why they won't use it in a patient," says Dr. Cameron. For instance, she says, some surgeons may object to using ITA grafts in women because their vessels are small, or they may justify not using it in the elderly because those patients are not going to live for 20 years and therefore don't require grafts that can last that long. In addition, the internal thoracic arteries are small, fragile, and difficult to work with during surgery. (At St. Luke's-Roosevelt, surgeons use an operating microscope during ITA grafts in order to see better.) But, says Dr. Cameron, this study now shows that the benefits of ITA grafts outweigh these difficulties and objections.
Another advantage to ITA grafts, she says, are their long-term tendency to remain patent. Studies show that seven years after surgery, three-quarters of vein bypass grafts are partially or totally obstructed. ITA grafts, however, show little evidence of atherosclerosis at all age groups. "Only about 2 percent of 90-year-olds will have atherosclerosis in the internal thoracic artery, whereas a high percentage will have it elsewhere. So it matters greatly which [graft] you choose with your first operation."