A tiny diamond-cutting tool spinning at 200,000 times per minute successfully tunneled through deposits clogging arteries in 95 percent of 315 patients tested, scientists report.

"It has been an exceedingly useful device to treat blood vessels in a different way," Dr. Maurice Buchbinder, a cardiologist at the University of California, San Diego, said Monday.Side effects were minimal, Buchbinder said in a report at the annual meeting of the American College of Cardiology. About 6 percent of the patients suffered heart attacks after the procedure, but most of those attacks were not the most severe type, he said.

There were no deaths and about two-thirds of the patients' arteries remained open six months after the procedure, he said.

Dr. William Untereker of the Philadelphia Heart Institute, an authority on the use of lasers to open blocked arteries, said it is too soon to know how the diamond-tipped device will compare with lasers or other devices intended to scour the inside of arteries.

"A lot of this is theoretical," he said. "We think with the laser we're getting a clean cut. I would predict it would be a year or two before this is sorted out," he said.

He reported a 96 percent success rate using a laser to open re-clogged blood vessels in patients who had previously undergone bypass surgery.

Buchbinder's device, called a Rotablator, is manufactured by Heart Technology Inc. of Bellevue, Wash. It was developed by David Auth, the company's chairman.

The Rotablator is powered by compressed air that runs a turbine outside the body, turning a flexible shaft threaded through the artery. The egg-shaped tip, covered with thousands of microscopic diamond chips, cuts hard materials such as the tough plaques that clog arteries but does not cut flexible tissue, such as the artery walls, Buchbinder said.