Unclogging arteries? Radiation helps.

Radiation therapy is not just for cancer anymore. A new study offers evidence that one-shot artery irradiation dramatically decreases the chance that newly unclogged vessels will become congested again.

Each year, U.S. cardiologists perform more than 500,000 angioplasties, to open dangerously clogged arteries. For roughly half of the patients, however, this balloon-inflation surgical procedure falls to bring lasting relief, eventually requiring surgeons to go back and perform a more invasive and costly arterial bypass operation.

Angioplasty failures generally trace to two problems. Either the vessel "recoils"--collapses and constricts--or injury to the vessel wall causes an overzealous healing response that results in an excessive buildup of smooth muscle cells. In either case, the artery suffers restenosis, or narrowing to the point where healthy blood flow is again impaired. Chest pains and even a heart attack can ensue.

To counter the first problem, cardiologists frequently insert a metal lattice, or stent, to prop open the newly unclogged artery. However, the stent itself call promote an overproliferation of smooth muscle.

Clinicians at the Scripps Clinic and Research Foundation in La Jolla, Calif., now report substantially cutting the risk of such an overproliferation.

They performed an angioplasty on 55 restenosis patients, giving each a stent. They then threaded a ribbon containing metal seeds through the just-treated artery and let it remain there for 30 to 40 minutes. Half of the ribbons contained gamma-ray-emitting iridium-92 seeds; the other half held nonradioactive pellets. The surgeons didn't know which patients were receiving the therapeutic iridium.

Ordinarily, any restenosis takes place within 6 months. Indeed, in the Scripps study, 54 percent of the nonirradiated patients showed restenosis in their treated arteries within that time. In contrast, only 17 percent of the irradiated patients suffered a similar narrowing of their treated arteries. Cardiologist Paul S. Teirstein and his coworkers report their findings in the June 12 New England Journal of Medicine.

This relatively low-cost irradiation "is one of the first things to come along that seems to do anything about restenosis," says Howard I. Amols, a medical physicist at Columbia University whose team pioneered much of the animal work on which the Scripps study was based.

The new findings "certainly look interesting," agrees cardiologist Stephen E. Epstein of the National Heart, Lung, and Blood Institute in Bethesda, Md. The radiation appears "to reduce that proliferative response of smooth muscle cells by making them incapable of responding to [angioplasty or stenting] injury."

However, he and Amols caution, it's still too early to tell whether radiation prevents or merely delays restenosis. The scientists also suggested that other types of radiation, such as beta particles, might provide a greater margin of safety for treated vessels, nearby healthy tissue, and operating-room staff.