Vein Used in Bypass
AP Medical Writer
2:03 PM EST; October 5, 1999; Boston, MA (AP) -- Harvard Medical School researchers have genetically altered the blood vessel used in heart bypass surgery in a quest to keep it from reclogging, and they said Tuesday the first few patients treated have shown a significantly lower incidence of relapse. Failure of heart bypass surgery is a big problem: Up to 30 percent of bypass patients have their heart arteries reclog badly in just a year. Few patients survive 10 years without needing retreatment, and high-risk patients -- such as those who already have undergone repeat surgery -- reclog at even greater rates.
The question is how to make bypasses last longer. To do a bypass, surgeons typically remove a vein from the leg and implant it around the original clogged heart artery. But a vein, which has thinner walls than an artery, is not accustomed to the intense pressure of blood pounding that an artery is. So the vein reacts in shock, causing rapid growth of cells against the vessel wall that result in a flabby, dangerous thickening.
Harvard researcher Dr. Victor Dzau has genetically manipulated this vein to look and act more like a trim, muscular artery. He removes the vein from a patient's leg and bathes it in a solution containing a short piece of DNA. This DNA binds to, or soaks up, a protein that otherwise would switch on the gene responsible for driving the cell growth that reclogs so many bypass patients' vessels. The result: The bypass graft is "more muscular, what I call the Schwarzenegger effect," he told a seminar Tuesday. "It begins to look more like an artery."
In his first experiment at Brigham & Women's Hospital in Boston, 17 high-risk patients had their vein bathed in the DNA solution for about 10 minutes before continuing bypass surgery. Another 16 patients had regular bypass surgery. A year later, more than 60 percent of the high-risk patients who had traditional bypass operations had failed -- they had undergone repeat surgery or were suffering severe reclogging. Just over 20 percent of patients who received the genetically altered bypass had failed, Dzau said Tuesday. Dzau could give no further details of the study, which has not yet been published in a medical journal. Fellow heart experts have not yet seen his results, which he will present next month at an American Heart Association meeting.
But Dzau stressed that while highly promising, the study was too small to be sure of the technique's effectiveness. "It may be a fluke," he cautioned. Still, he has won Food and Drug Administration permission for a 2,000-patient study. The study, to be performed at several hospitals around the country, should begin soon, he said. Dzau said his study did show the experiment was safe. The genetic manipulation all takes place while the vein is outside of the patient's body, providing further reassurance of its safety, he said.