Which is the better treatment for people with several clogged arteries -- bypass surgery or the nonsurgical technique called angioplasty? Doctors at the National Heart, Lung and Blood Institute hope to find out in a new study.

"We are about to commission a clinical trial to compare angioplasty and bypass surgery in patients with multivessel disease," Dr. Eugene Passamani, associate director for cardiology at the National Heart, Lung and Blood Institute (NHLBI) said Monday.

Angioplasty -- known officially as percutaneous transluminal coronary angioplasty -- is quickly challenging bypass surgery as the treatment of choice for many heart patients with blocked coronary arteries. The National Center for Health Statistics estimates that 100,000 people underwent angioplasty in 1985 -- some 10 times the number predicted when the procedure was first introduced nine years ago.

In angioplasty, a deflated balloon attached to the end of a probe is threaded through arteries to the blocked area. Once there, doctors inflate the balloon and open the artery. In bypass surgery, an artery is grafted from the leg or elsewhere to carry blood around the blockage.

Unlike bypass surgery, angioplasty is performed under local anesthesia, requires only two to three days of hospitalization and costs $5,000 -- about one third the cost of bypass surgery.

The drawback to angioplasty is that it is difficult to perform in "crooked" arteries, in arteries that are inaccessible or in those that are completely blocked by plaque that extends over large areas.