Clinical Outcomes and Cardiovascular Responses to Different Exercise Training Intensities in Heart Failure Patients: A Systematic Review and Meta-Analysis

Study Questions:

Does aerobic exercise training intensity produce different effect sizes for fitness, adherence, event, mortality, and hospitalization rates in heart failure?

Methods:

The authors conducted a MEDLINE search (1985-2012), for exercise-based rehabilitation trials in heart failure, using search terms “exercise training, left ventricular dysfunction, peak VO2, cardiomyopathy, and systolic heart dysfunction.” Seventy-three studies were included, producing 76 intervention groups; nine (11.8%) were high-, 38 (50%) vigorous-, 24 (31.6%) moderate-, and five (6.6%) low-intensity groups, providing a total of 3,265 exercising subjects and 2,612 control subjects.

Results:

Peak VO2 increased by a mean difference of 3.33 ml/kg-1/min-1 (95% confidence interval [CI], 0.53-6.13; p = 0.02) with high-intensity training in exercise groups versus control, equating to a 23% improvement from baseline. The corresponding data for vigorous-intensity was 2.27 ml/kg-1/min-1 (95% CI, 1.70-2.84; p < 0.00001) with an 8% weighted mean; moderate-intensity 2.17 ml/kg-1/min-1 (95% CI, 1.34-2.99; p < 0.00001) with a weighted mean of 13%; and low-intensity 1.04 ml/kg-1/min-1 (95% CI, -2.50 to 4.57; p = 0.57) with a weighted mean of 7%. In 123,479 patient-hours of training, not one death was directly attributable to exercise.

Conclusions:

As exercise training intensity rises, so may magnitude of improvement in cardiorespiratory fitness and lower study withdrawal in exercising patients. Total exercise time may be a confounder.

Perspective:

HF-ACTION, the largest randomized trial of exercise in heart failure, utilized moderate to vigorous continuous exercise and yet it failed to impact survival. Among the explanations was poor adherence in those allocated to exercise, which may have explained the low (4%) difference in peak VO2, which is much lower than expected. There is increasing evidence that the combination of moderate- and high-intensity interval exercise (HIIE) training may provide more benefit to blood pressure, peak VO2, and possibly survival in heart failure. This meta-analysis challenges the opinion that HIIE is too risky in heart failure.

Clinical Topics: Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Prevention, Sports and Exercise Cardiology, Acute Heart Failure, Exercise

Keywords: Ventricular Dysfunction, Oxygen Consumption, Cardiomyopathies, Exercise, Physical Fitness, Exercise Therapy, Heart Failure, Blood Pressure, Confidence Intervals, Systole, MEDLINE


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