According to new research, aerobic exercise turns an enlarged heart into a trimmer, more efficient organ for pumping blood throughout the body. 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. It's aerobic training that provides the greatest benefit," said Mark J. Haykowsky, Ph.D., an associate professor of rehabilitation medicine at the University of Alberta in Edmonton, Alberta, Canada.
An estimated 5.2 million people in the United States have heart failure, a condition that accounts for more than a million hospitalisations each year. The total direct and indirect costs linked to heart failure exceed 33 billion dollars annually. 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 remodelling. 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 remodelling," Dr. Haykowsky said.
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.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 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.
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.
"If this study proves that training not only improves the exercise capability of patients, but also extends their life and reduces hospitalizations, insurance payers are likely to support this as an important addition to an increasingly potent array of treatments for heart failure," Dr. Rubin said. The study is published in the June 19, 2007, issue of the Journal of the American College of Cardiology (JACC).