Walking and bicycle riding improve size of heart and ejection fraction, but weight lifting seems to block this improvement in patients with heart failure.

American College of Cardiology – According to new research, aerobic exercise remodels heart size and improves pumping ability (ejection fraction) in patients with stable heart failure, literally turning an enlarged heart into a trimmer, more efficient organ for pumping blood throughout the body.

The research, published in the June 19, 2007 issue of the Journal of the American College of Cardiology (JACC), comes with a caution, however: It may be best to focus on aerobics and leave the weight lifting to someone else.

The study showed that when patients with heart failure did aerobic exercise several times a week, the oversized heart became significantly smaller and better able to pump blood. Researchers were surprised to find that those who added weight lifting to the exercise routine to enhance muscle strength did not enjoy a similar improvement in the heart’s size or function.

“If I were to choose a type of exercise training for a patient with heart failure, I’d choose aerobic exercise,” said Mark J. Haykowsky, Ph.D., an associate professor of rehabilitation medicine at the University of Alberta in Edmonton, Alberta, Canada. “It’s aerobic training that provides the greatest benefit.”

An estimated 5.2 million people in the United States have heart failure. In most cases, heart failure is the result of years of high blood pressure or damage from a heart attack. Over time, the heart becomes enlarged, misshapen, and too weak to effectively pump blood, a process known as remodeling. As a result, patients typically become short of breath even with very little activity.

For many years, doctors recommended that people with heart failure avoid exercise. In some cases, patients were even put on bed rest in an attempt to relieve the heart of any extra stress. Over the last decade, however, it has become increasingly clear that exercise is good for patients with heart failure, not only reducing symptoms and allowing patients to live more active lives, but also reversing some of the harmful hormonal changes that take place as the body attempts to compensate for a weakened heart.

Previous studies have reported conflicting results on the effect of exercise on the heart’s size and function, however. “We knew that exercise could improve fitness and exercise capacity by about 15 percent, and that exercise could make muscles stronger and larger. But we didn’t know the effects of exercise training on ventricular remodeling,” Dr. Haykowsky said.

For the study Dr. Haykowsky and his colleagues analyzed data from 14 separate randomized trials involving a total of 812 patients with heart failure. The trials each quantified the effects of exercise by measuring changes in ejection fraction, the percent of blood pumped from the left ventricle to the blood vessels with each beat of the heart. About half of the studies also measured the heart’s size, both at the end of diastole, the part of the cardiac cycle when the heart is relaxed and filling with blood, and at the end of systole, when the heart is squeezing and forcing blood out into the circulation.

In nine studies, patients did aerobic exercise – walking or bicycling, for example – for 20 to 60 minutes approximately 3 times a week, at an intensity equal to 60 percent to 80 percent of their peak ability. In four studies, patients supplemented aerobic exercise with strength training, and in one study, patients did only strength training. Study participants were clinically stable but had markedly abnormal heart function, with an average ejection fraction of just 23 percent. (A normal ejection fraction is 50 percent or greater.)

The analysis showed that ejection fraction improved significantly in patients who did aerobic training (2.59 percent, on average). Similarly, the patients’ enlarged hearts became significantly smaller, with a reduction in both end-diastolic volume (11.49 mL, on average) and end-systolic volume (12.87 mL). By comparison, patients who combined aerobic exercise with strength training showed no significant improvements in ejection fraction or the size of the heart. The single study that evaluated strength training alone showed a drop in ejection fraction, but it was not statistically significant; the study did not measure changes in the size of the heart.

Dr. Haykowsky speculated that weight lifting and other forms of strength training may not have shown the benefits of aerobic training in reshaping the heart because strength training results in a heightened pressure load, which may actually increase the stress on the heart.

The importance of the new study is that it provides guidance in designing an exercise program for patients with heart failure, according to Stanley A. Rubin, M.D., F.A.C.C., chief of inpatient cardiology and a professor of medicine at the Veterans Affairs-UCLA Medical Program in Los Angeles.

“This study clarifies for heart failure patients and for their doctors the best form of exercise training,” said Dr. Rubin, who wrote an accompanying editorial in the June 19, 2007 issue of JACC. “But it’s not a bed of roses. The patient needs to be motivated, have realistic expectations of the small but real benefit of exercise and, in particular, understand that this form of treatment must be accompanied by extensive dietary, lifestyle and, especially, medication and device treatments tailored to meet their needs. It’s not a substitute.”

Dr. Rubin added that patients with heart failure should not initiate exercise training on their own. To be safe, they should first be evaluated by a cardiologist and monitored during exercise, at least initially. Finding a way to pay for supervised exercise training is a challenge, however, as Medicare and most private insurance carriers approve payment for cardiac rehabilitation only if the patient has recently experienced a heart attack (Courtesy of EurekAlert!, a service of AAAS).