Nov. 11 (Bloomberg) -- Heart failure patients, once told to take it easy to avoid stressing weakened hearts, can safely exercise, according to the largest study on the topic.

The research found exercising for 30 minutes three times a week didn't raise the risk of heart attack, erratic rhythms, chest pain or fractures. Those who worked out were less likely to be hospitalized for heart failure or die from cardiac causes, though the overall death and hospitalization rates for other reasons didn't decline, the study found.

The findings, reported today at the American Heart Association's annual meeting in New Orleans, may change the way doctors and insurers think about physical activity for heart- failure patients. Previous research and medical practice questioned whether high-risk patients could exercise without supervision or worsening their condition.

``The key finding is whether or not exercise is safe. It's absolutely safe,'' said Gordon Tomaselli, chief of cardiology at Johns Hopkins Medicine in Baltimore. ``Doctors should set up a program that's structured. Don't tell me that exercise is good; tell me what I should be doing. That varies for each patient.''

Most health insurers won't cover exercise training programs for such patients because studies haven't conclusively proven they are effective and worth the cost, she said.

The study, funded by the U.S. government, involved 2,331 patients. Half the patients in the study participated in a 36- week guided exercise program, with a goal of 40 minutes of activity five times a week, and were given a treadmill or exercise bike for home use. The other half received information about the recommendations for performing 30 minutes of physical activity most days of the week.

Heart-Attack Programs

The sessions were similar to those given to patients recovering from a heart attack, programs typically covered by health insurance plans.

After three months, just over half of the intervention group was working out regularly, the study found. That number declined with time, and 25 percent of patients were completing five workout sessions a week after a year.

``This was a compelling study. It wasn't just did it keep you out of the hospital, but it saved lives,'' said Muriel Jessup, director of heart failure and transplants at University of Pennsylvania School of Medicine and Health System. ``You can say to somebody: You can do this without taking another pill that may cost money and give you side effects. Exercise is safe and has been shown to reduce mortality.''

Almost 5 million Americans suffer from heart failure, a weakening of the organ, which can cause fatigue, physical limitations and ultimately death, according to the St. Paul, Minnesota-based Heart Failure Society of America.

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.netTom Randall in New York at trandall6@bloomberg.net

Last Updated: November 11, 2008 12:43 EST