Latest Weapon in Treating Heart Disease Being Tested by UR Researchers
September 11, 1998
Researchers at the University of Rochester Medical Center have begun testing a new device that may dramatically improve the long-term effectiveness of balloon angioplasty in treating coronary artery disease.
The device, developed by scientists at Emory University in Atlanta using basic research pioneered by researchers here at the University of Rochester, helps to prevent restenosis - a re-narrowing of the inside of the coronary arteries - which occurs in 30 - 50 percent patients within six months after they receive balloon angioplasty. Designed for use in conjunction with balloon angioplasty, the device delivers a small dose of radiation directly to the site of the blocked coronary artery, inhibiting growth of cells that cause restenosis. In an early study, the number of patients who experienced restenosis fell from 30-50 percent to only 10 percent.
The University of Rochester is one of 21 medical centers in the United States - and the only institution in New York State outside of New York City - selected to test the new device, known as Beta-Cath. So far, four patients at the UR Medical Center have been enrolled in the study.
How It Works
The narrowing of coronary arteries occurs when fibrous and fatty tissue deposits, called plaque, accumulate inside the artery and limit blood flow to the heart muscle. During balloon angioplasty, a tiny balloon is fitted into the narrowed section of coronary artery and inflated, widening the section and restoring proper blood flow.
Unfortunately, 30 to 50 percent of patients experience a re-narrowing of their arteries within six months after they receive angioplasty. This re-narrowing occurs because the inflation of the angioplasty balloon stretches the wall of the coronary artery, causing microscopic damage to the cells that form the arterial wall. The body responds by growing scar tissue to strengthen the damaged section of the coronary artery - but the new scar tissue often narrows the coronary artery, making it difficult for blood to pass through. To re-open the narrowed section of coronary artery, some patients must undergo angioplasty a second time. If the problem cannot be corrected by angioplasty, bypass surgery may be necessary.
To reduce the incidence of restenosis, researchers use the Beta-Cath device to send a tiny cylinder along the same guide-wire used to insert the angioplasty balloon. The cylinder settles into the newly widened area and emits low-level beta radiation, which slows the growth of the cells that become scar tissue. The amount of radiation is minimal - about one-one hundredth of the radiation a patient receives during a typical angioplasty procedure - and does not pass through the coronary artery to the surrounding tissue.
"This device has the potential to save angioplasty patients from having to undergo the procedure a second or even third time," says Richard Pomerantz, M.D., the principle Rochester coordinator for the trials. "Balloon angioplasty works very well - we've got it down to a 95-98 percent initial success rate. It's the problem of restenosis that we need to overcome. This device looks like it may be the most effective method yet developed to do that."
Until now the only treatment available to help reduce restenosis was to permanently implant a small metal device called a "stent" into the coronary artery to act as a scaffold to hold the artery open. Stents, however - like balloon angioplasty - also can stretch the artery and cause scar tissue to form. According to Pomerantz, 23 percent of patients who receive a stent experience restenosis, versus 10 percent of patients who have been treated with the Beta-Cath device.
"The Beta-Cath is particularly exciting because beta radiation it uses only penetrates a few tenths of an inch," says Paul Okunieff, M.D., chair of the Department of Radiation Oncology. "This means the radiation is delivered exclusively to the target blood vessel - not to the rest of the body. There haven't been any radiation-related side effects so we're expecting this device to be a great benefit in combating restenosis."
The trials have already begun with the enrollment of four patients. Half of all enrolled patients will receive the beta radiation therapy and the other half will receive a placebo, ensuring the validity of the trials. Researchers will inspect each patient's arterial diameter eight months after the procedure to compare the results of the control group to those of the treated group.
Note to Television Editors: We are supplying you with a 3:30 minute beta videotape containing operating room footage of a cardiologist using the Beta-Cath device and a 3-D computer animation of the Beta-Cath device treating a coronary artery. The tape will arrive shortly by courier.
Dr. Pomerantz is available today, 9/11/98, for interviews.