Moderate aerobic exercise several times a week such as walking and bicycling can improve heart size and left ventricular function in patients with stable heart failure, according to an article in the June 19 issue of the Journal of the American College of Cardiology.

“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, PhD, an associate professor of rehabilitation medicine at the University of Alberta in Edmonton, Alberta, Canada. “It’s aerobic training that provides the greatest benefit.”

Previous studies have reported conflicting results on the effect of exercise on the heart’s size and function. “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,” Haykowsky said.

In the current study, researchers 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. About half of the studies also measured the heart’s size, both at the end of diastole and during systole.

In nine studies, patients did aerobic exercise-walking or bicycling, for example?for 20 to 60 minutes approximately three times a week, at an intensity equal to 60 to 80 percent of 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 an average ejection fraction of just 23 percent.

The analysis showed that ejection fraction improved significantly in patients who did aerobic training (2.59 percent, on average). Similarly, 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 heart size. 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 heart size.

Haykowsky speculated that 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 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 Rubin, who wrote an accompanying editorial in the June 19 issue. “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.”

There may soon be new evidence on the benefits of exercise in patients with heart failure. A National Heart, Lung, and Blood Institute study, HF-ACTION-short for Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training-is recruiting patients at medical centers in the USA.