July 24, 1998

Cardiologists test radiation in fight against heart disease

Cardiologists test radiation in fight against heart disease

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Dr. Brigitta Brott is testing the use of radiation to prevent the re-narrowing of arteries following angioplasty. (Photo by Donna Jones Bailey)

Radiation has long been important in the anti-cancer arsenal, but researchers at Vanderbilt University Medical Center are testing radiation as a potential weapon against heart disease.

Cardiologists at VUMC are testing a new device that uses a short dose of radiation to try to prevent the re-narrowing of arteries after they have been opened with balloon angioplasty. Researchers hope the new technique can address the biggest drawback to angioplasty ‹ the too-frequent need for repeat procedures.

"At least a third of people who undergo angioplasty have a recurrence of significant chest pain within six months and have to return for additional angioplasty or by-pass surgery," said Dr. Brigitta C. Brott, assistant professor of Medicine and lead investigator of the trial.

"Preliminary studies using this device suggest that radiation can significantly reduce the rate of re-narrowing. This could be a new breakthrough by reducing the rate of tissue growth inside the artery."

In the United States, doctors perform more than a half million angioplasties each year. The procedure uses a special balloon that is guided on the tip of a catheter to the site of the blockage and then inflated to stretch the artery open.

While the non-surgical technique is effective at opening clogged arteries, the balloon can injure the artery wall, prompting a healing response that leads to the accumulation of scar tissue inside the vessel. This re-narrowing is called restenosis.

Tiny scaffold-like wire supports called stents are frequently used along with angioplasty to prop open the artery. Stents have reduced but not eliminated restenosis.

"With stents, restenosis occurs about 15 percent of the time, so it's still a significant problem," Brott said.

VUMC is the first center in Tennessee to test the new catheter, which delivers a short dose of beta radiation to the coronary artery immediately after angioplasty. The radiation, earlier studies suggest, prevents new cell growth inside the artery.

Beta radiation penetrates much more shallowly than the gamma radiation used in cancer treatment.

"With this device, the radiation penetrates only a short distance, and the patient receives a dose that is less than 1 percent of what they would receive with a dental X-ray," Brott said.

Hydraulic force is used to deliver a closed cylinder containing radioactive beads to the angioplasty site. The beads never come in direct contact with the patient's tissue or blood, and they remain at the angioplasty site only three minutes before being withdrawn. The health professionals conducting the procedure need no additional radiation protection.

The procedure adds less than 10 minutes to the total angioplasty time.

The Phase II study is being conducted at more than 25 centers across the country, and a total of 1,100 patients will be enrolled. Half of the participants will receive radiation while the other half will receive a placebo. Results in the two groups will be compared to see if those receiving radiation fare better than those who did not.

Patients will be followed for two years, with some of them undergoing catheterization at eight months to determine whether re-narrowing has occurred.