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BookmarkScienceDaily (Feb. 26, 1999) — by Nancy Mays
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A study shows a new surgical technique used for coronary bypasses is safe, effective and, say the study's authors, an improvement on surgical methods currently used for such operations.
The study, which has been accepted for publication in Annals of Thoracic Surgery, was presented at the annual meeting of the Southern Thoracic Surgical Association.
The researchers examined 650 patients who had undergone coronary bypass operations using the new surgical technique. They tracked operative survival, wound infection and incidences of conditions such as stroke.
"The study showed the operation is safe and can be a better alternative to current techniques used for bypasses," says senior author Hendrick B. Barner, M.D., who developed the technique. Barner, a professor of cardiothoracic surgery at Washington University School of Medicine in St. Louis, co-authored the paper with Thoralf M. Sundt III, M.D., assistant professor of cardiothoracic surgery.
In fact, the mortality rate for patients in the study was 0.2 percent, which means that one person out of the 650 died within 30 days of the operation.
"That's an incredibly low rate," says Barner. "For low-risk patients, the rate for the standard procedures probably ranges from about 1 percent to 3 percent."
Known as a T-graft configuration, Barner's technique uses arteries from both the arm and chest to form a T-shaped conduit around the diseased portions of the heart. The study found the technique offers patients hope for longer-lasting bypasses with reduced chances for postoperative infections. The study's authors say the technique, while complicated to master, offers surgeons a longer, wider conduit to work with as they revascularize the heart compared with using both internal thoracic arteries.
Coronary bypass is a common surgery, performed every year on some 400,000 patients whose arteries are blocked or hardened by disease and therefore are unable to adequately deliver blood to the heart. The surgery creates an alternate route of blood supply for the heart by making a connection between the aorta and the blocked coronary artery, bypassing the obstruction.
The first bypasses, conducted in the 1960s, used a vein, usually taken from the leg, as the conduit. The technique, still popular, works well but for a limited time. The vein, says Barner, doesn't like being part of the arterial system; it's like mixing apples and oranges. What's more, veins used in bypass operations harden -- about half close within 10 years -- leaving patients back where they started. Within 15 years of a bypass operation, some 75 percent of all veins have developed atherosclerotic plaque.
"Some people end up needing another bypass 10 years after the first one," says Barner.
Over the last 20 years, surgeons gradually have been substituting veins with chest arteries, known as internal thoracic arteries, because arteries outpace veins, remaining disease-free at least twice as long. Barner pioneered the use of arteries for bypass surgery.
The Washington University study examined the effectiveness of using one artery from the chest, the left internal thoracic artery, and one from the forearm, the radial artery. The primary benefit, says Barner, is that the radial artery is longer than the right internal thoracic artery, offering surgeons more flexibility when fashioning the alternate conduit. Using the radial artery also lowers the risk of chest wound problems, the study found. When surgeons use both internal thoracic mammary arteries, they run the risk of sternal infections because that artery provides blood to the breastbone or sternum. Infection of the sternum was experienced by only four patients or 0.6 percent of the study group.
Uses fewer arteries What's unique about Barner's technique, though, is the configuration, which uses fewer arteries -- without reducing blood flow. The body hosts seven potential arterial conduits, two in the chest, two in the arm, one in the abdomen and two in the lower abdominal wall, though the latter may be quite short and are of limited usefulness. The T-graft technique differs from other techniques in that only two conduits are utilized instead of three, four or five.
"If you use four arterial conduits in one operation, there's only three left," says Barner. "That could be a problem if you needed another operation at a future date."
The surgical technique is controversial, says Barner, because some surgeons have been concerned that the T-graft may not provide enough blood flow to the heart muscle. Not so, says Barner. Only 2 percent, or 14 patients, experienced temporary low output syndrome, meaning that the heart still functioned below expected levels despite the surgery. Compared with 2 to 5 percent incidence of low cardiac output after coronary grafting, Barner says, "that number was gratifyingly low."
The study's patients were between the ages of 30 and 85. One-fourth of them were diabetic.
Coronary arteries narrow when the fat content of the blood, especially cholesterol, increases. The fat is deposited in the wall of coronary arteries, producing plaque that narrows the artery and reduces the volume of blood flowing through it. What's more, plaque build-up creates a rough surface. When blood flowing through the narrowed passage comes into contact with the irregular surface, it can clot and cause a heart attack.
