The American Heart Association is warning patients who took the drugs fenfluramine or Redux to be tested for heart valve disease.

From Medical Correspondent Elizabeth Cohen

DALLAS (CNN) -- In an official statement at the annual meeting of the American Heart Association, cardiologists urged those who took the diet pill combination fen-phen or the drug Redux to see their doctors to check for possible heart valve disease.

Some 23 million prescriptions were written for the diet pills, which were voluntarily pulled from the market last year because of a link to heart valve problems.

Originally, doctors feared that many diet pill users would need surgery to correct the valve defects. But studies have shown that most of the problems appear to be mild.

Doctors suspect that those who took the drugs for a long time or at higher doses are at greatest risk.

The American Heart Association statement said former users who have no symptoms of heart valve problems need only get a stethoscope examination and a follow-up exam 6 to 8 months later.

Symptoms of heart valve disease include shortness of breath, excessive tiredness, chest pain, fainting and swelling of the legs.

In exams, doctors should listen for heart murmurs, which can indicate a serious valve defect or a tiny hole in the heart. Murmurs can also be harmless.

Those with symptoms or murmurs need to have an ultrasound of the heart, called an echocardiograph, according to the guidelines.

The ultrasound will show whether there is actual valve disease -- for example, whether blood leaks backwards through the valve because it does not close properly.

Some valve problems are treated with surgery. Other times, patients do not need surgery, but have to take antibiotics before dental procedures to prevent bacteria in the mouth from entering the bloodstream and infecting the heart valves.

Since it can be difficult to detect murmurs in people who are very overweight, very large people who took fen-phen or Redux should have an ultrasound exam prior to having dental procedures to determine if they should take precautions.

Fen-phen was a two-pill treatment in which people took both fenfluramine and phentermine. Phentermine remains on the market since it does not appear to cause medical problems. Fenfluramine and dexfenfluramine, sold as Redux, were voluntarily pulled off the market in September 1997.