WASHINGTON (AP) _ Hot tubbing is OK for many people with narrowed coronary arteries, despite doctors' fears that it could set some up for a heart attack, experts say.

A study of 15 men with stable coronary artery disease found no problems in a typical 15-minute soak in 104-degree water.

While this doesn't make hot tubbing always safe for all patients, immersion does seem safer than it had appeared, the experts say.

''Risk is possibly exaggerated in both the public and the professional mind,'' said the report in the Mayo Clinic Proceedings. Earlier reports that suggested danger based on relatively few deaths were poorly done, and their findings were overblown, the study said.

In this study, the men sloshed in water up to their nipples, and rode exercise bikes for 15 minutes so the researchers in Rochester, Minn., could check their responses to hot tubbing and compare them to exercise.

Heart rates generally increased from a normal resting rate of about 60 beats per minute to around 85 as a result of hot tubbing, the study said. In contrast, biking at a moderate intensity that's often prescribed for heart patients raised heart rates to around 112 beats per minute, it said.

One patient reported some chest pain while hot tubbing, while three did during exercise, the study said. And, while no one reported shortness of breath while hot tubbing, nine had mild problems while exercising.

The researchers found that blood pressure in the hot tub changed only mildly, well below the increase created by exercise.

However, they said, getting out of the hot tub can make blood pressure drop, partly because gravity makes blood flow to the legs. Although only one person complained of lightheadedness, the researchers say others who may have greater problems with low blood pressure might feel faint.

The scientists also examined internal and skin temperatures, because heat can make the heart beat faster. They found that both rose in hot tubbing, but by less than 1.5 degrees.

In sum, 15 minutes of biking had a stronger effect than 15 minutes of hot tubbing, said the study's lead author, Thomas G. Allison, a consultant in the Mayo's Division of Cardiovascular Diseases and Internal Medicine.

He feels comfortable in letting people with stable coronary artery disease relax in the hot water, provided they don't overdo it, and he thinks their bodies can tell them what's enough.

''After about 10 or 15 minutes, you start to feel a little overheated, and if you get out, fine,'' Allison said.

The study looks good to Dr. Gerald M. Pohost, who chairs the American Heart Association's Council on Cardiology.

''I'm convinced. It sort of destroys the myth that a lot of us had before.'' said Pohost, the director of the cardiovascular disease division of the University of Alabama at Birmingham. ''I think it is meaningful to patients with stable coronary artery disease.''

Just the same, he said, heart patients should check with their doctors before their first dip and get a stress test, so they can learn the point at which they might develop symptoms, he said.

Allison advises heart-patient hot tubbers to be cautious, especially about alcohol - a warning that can apply to all users, because drinking can cause drowsiness, leading to unconsciousness and possibly drowning.

Other data on deaths in hot tubs show those who drown almost always had been ''laced to the gills,'' he said.

The hot tub and spa industry does not set standards for use by heart patients, but it does stand by the typical warnings posted at public facilities, said Carvin Di Giovanni, technical director for the National Spa and Pool Institute, a trade group in Alexandria, Va.

The spa-side notices direct people with a medical history of heart disease, as well as circulatory or blood pressure problems, to get a doctor's approval before getting in the tub.

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