ANAHEIM, CALIF. -- The loud whirring sound startled the audience to laughter, but it didn't stop the packed room from staring intently at the videotaped X-ray images flashing on the screen: a diamond-tipped burr on the end of a thin flexible tube drilling through an inches-long fatty blockage in an artery of a human leg.

The diamond drill is just one of the latest techniques designed to open blocked arteries and prevent heart attacks that was featured at the 60th scientific conference of the American Heart Association here last week.

From lasers to balloons to tiny drills to wire-mesh tubes, physicians are looking for new ways to solve the plumbing problems of the heart.

Yet each new technique to keep these blood vessel lifelines open has created a new set of problems. Instead of one magic solution to get rid of the fatty deposits or plaque that can build up on artery walls, researchers now envision a range of techniques for use in different types of patients.

When balloon angioplasty first was tried 10 years ago, it seemed like a miracle. A narrowed artery could be cleared without open-heart surgery to bypass the blockage. The cardiologist slides a thin flexible tube called a catheter into the heart's arteries until it reaches the blockage. A second tube, passed through the first, positions an oblong balloon that is then inflated to push back the blockage, opening the narrowing and restoring blood flow.

The technique is such a success that balloon angioplasty has become one of the most common procedures in treating heart disease. From 100,000 cases in 1985, more than twice that many are expected to be done this year. With between 500,000 and 1 million Americans developing the crushing chest pains of angina every year -- an indication that the chances of a heart attack are high -- the potential number of balloon procedures clearly is much higher.

But the technique is not effective on all patients. Studies show that between 30 and 40 percent of the balloon-opened arteries clog up again and the procedure must be repeated. Five percent will need emergency open-heart surgery; 1 to 3 percent will die.

That's because arteries contain dozens of different kinds of cells that respond to the injury caused by the angioplasty balloon. As a result, the artery can have a spasm and close or, within a few weeks, grow shut as nearby cells try to heal the injury.

Some researchers are searching for drugs that will prevent reclosing. Others are taking a more direct, mechanical approach and implanting a flexible metal cylinder -- called a stent -- into the blood vessel to keep it from collapsing.

Stents look like tiny springs. They can pass through a catheter and arrive in an artery just treated with angioplasty. The cylinder acts like a scaffold within the vessel. If they prove successful, stents could keep some patients from needing repeat angioplasty.

So far, 13 patients have received stents in leg arteries at the University of Texas Health Science Center in San Antonio. "That data is encouraging," said Dr. Richard A. Schatz of the University of Texas.

But stents, too, have drawbacks. In general, these bits of metal tend to cause the blood to clot, which plugs the artery and can cause a heart attack. To prevent blood clots, anti-clotting drugs must be taken for a fairly long time, perhaps 18 months or more.

Dr. Ulrich Sigwart of Lausanne, Switzeland, reported that his research group implanted 64 stents in the coronary arteries of patients who were also treated with drugs. Most of the stents have been successful in the Swiss patients up to a year and a half later, Swigart reported. "So far, there is very little occlusion," he said.

Not everyone, however, is enthusiastic about stents. "I would voice a word of caution about coronary stents," said Dr. Martial G. Gourassa of the Montreal Heart Institute in Montreal, Canada. "The complication and reocclusion rate is fairly high."

Despite all these problems, most physicians are enthusiastic about balloon angioplasty. Nearly 60 percent of all those treated with balloons are free of all symptoms, according to one U.S. study. Other studies show success rates as high as 90 percent. And even with those patients who need the procedure repeated, three out of four do well, another study showed.

Another approach involves lasers, which were first used in the early 1980s to clear blocked arteries. In this technique, a fiberoptic thread is used to carry the laser light inside the artery where it instantly heats the material until cells explode as the water within them boils and other materials vaporize. At least, that's the idea."Everyone wants to zap and have the blockage go away," said Dr. John B. Simpson of Palo Alto, Calif.

Instead, there have been problems, including the chance that the laser can accidentally burn through the artery wall, causing a rupture that could be fatal.

Researchers are trying to modify lasers to avoid the risk of burn-through. Some groups only use the laser to heat a metal tip on the end of the catheter and then take the hot tip to burn through the blockage.

In one experiment, Dr. Robert J. Siegel from the University of California at Los Angeles used a radio frequency generator to produce a hot, gold-tipped catheter, which then acts like a laser-heated tip. The UCLA group already has used the new catheter to treat the narrowings in the leg arteries of five patients, successfully opening four.

Dr. Leonard Nordstrom from Methodist Hospital in Minneapolis uses a balloon catheter to center the laser beam in the artery, reducing the odds that the laser will burn through the artery wall. So far, he has used the laser in the legs of 33 patients, reporting success in 94 percent of the cases.

But like balloons, lasers don't guarantee the vessels will stay opened. More than a third of the laser-opened arteries reclosed and had to be treated again.

What's more, sometimes deposits in the artery have been so hardened by calcium that neither balloons nor lasers effectively break them up. As a result, a number of devices that cut, grind or shave have been devised to solve that problem. One approach generating interest uses the diamond drill, developed by a group at Baylor College of Medicine and the Methodist Hospital, both in Houston. A stiff guide wire passed through a catheter directs the bit, whirring at some 120,000 revolutions per second, to the narrowing, where it pulverizes the hard plaque, opening the artery and leaving a smooth artery wall behind.

By grinding up the plaque, no material is left behind to reclose the artery. But grinding causes problems: The material drifting off with the blood flow could get stuck in a smaller artery or capillary downstream and cause a blockage some place else.

Dr. Nadim Zacca at Methodist Hospital said that in some experiments the group captured the debris and found that the particles were small enough to pass through even the tiniest capillaries.

Earlier this year, the group used the diamond drill to clear clogged arteries in the legs of seven patients. All of the vessels remained open six months later.

The rotational atherectomy device, as the diamond drill is called, has some theoretical advantages over balloons and lasers. While balloons are unable to dislodge hardened blockages, lasers tend to heat hardened material too much, which increases the chance of burning through the artery wall.

But the diamond drill, like the laser and the hot-tipped catheters, can generate particles that could cause clots farther downstream. To solve that problem, a device developed by Devices for Vascular Intervention of Redwood City, Calif., can shave plaque off the artery wall with a blade so small it fits inside the catheter. The device has been used in the legs of 113 patients in Sequoia Hospital, since Simpson first described it two years ago. So far, he said, the recurrence rate has been half that of balloon treatment in the legs. Simpson also said that his approach can be used on plaques too tough for the balloon to open.

For the next five years, most physicians believe that balloon angioplasty will dominate physicians' attempts to open narrowed arteries in most patients. But research is moving so fast that other methods are likely to play more of a role as their advantages become clearer.

"There is no magic," Simpson said. "That is the only thing we know of for sure."