BOSTON (Reuters) - A new device may help doctors decide the best way to use artery-clearing stents, reducing serious risks and unnecessary followup procedures by 28 percent, U.S. researchers said on Wednesday.

The device, made by a unit of medical device maker St. Jude Medical Inc, uses a pressure-sensitive wire to guide the placement of tiny wire mesh tubes, or stents, used to keep blood flowing through diseased heart arteries.

The wire allows doctors to find precise spots where pressure drops along the blood vessels feeding the heart, the researchers reported in the New England Journal of Medicine

Traditionally, doctors try to find them by injecting dye into those vessels and, using X-rays, watching how it flows, a technique known as angiography.

Dr. William Fearon, who worked on the study known as FAME, said the new technique is far more precise. Stents can now be placed at the best location to keep blood feeding the heart muscle, he said.

"Sometimes a narrowing may look innocent on the angiogram, but it's actually causing a severe drop off in blood flow," Fearon, of the Stanford University Medical Center in California, said in a telephone interview.

"If you're just relying on the angiogram, you may not put a stent there. By using the pressure wire, you're better able to identify the high-risk areas. It helps you place them more accurately."

St. Jude-owned Radi Medical Systems paid for the testing among more than 1,000 patients at 20 medical centers in the United States and Europe.

Only 13.2 percent of patients whose surgeons used the device needed repeat surgery, suffered a heart attack or died within the first year after their operation. The rate was 18.3 percent for patients whose stents were placed using just the dye.

The researchers calculated that equipment costs using the pressure-sensitive wire technique, known as fractional flow reserve, were $675 less than the $6,000 price tag associated with traditional stent placement. Both techniques took about 70 minutes.

One reason for the savings: "You avoid unnecessary stents," Fearon said.

In 37 percent of the potential trouble spots identified by traditional angiography, the wire showed that blood flow was at least 80 percent of normal, so no stent was used.

Fearon said although half of U.S. cardiac catheterization labs have the equipment to do pressure readings in the arteries, only about 5 percent to 10 percent of stents are placed using the technique.

It has not been more popular because "people still wanted to see more data. That's where we hope this study will provide that," Fearon said. "We think the data from this will have a big impact."

Heart disease is very common and stents have become very popular.

About 40 percent of Americans over the age of 60 have one or more narrowings in their coronary arteries, and more than 1.2 million angioplasty procedures in which clogged arteries are cleaned out and propped open with a stent are performed each year in the United States, according to the American Heart Association.

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