Heart failure is a major health concern and is the leading cause of hospitalization among elderly Americans. Currently 5.7 million Americans are estimated to have heart failure and the estimated direct and indirect costs of treating heart failure are approximately $37.2 billion. Approximately 40% of those diagnosed with heart failure will have heart failure with preserved ejection fraction (HFPEF). These individuals have significant restrictions in their ability to carry out activities of daily living. Exercise training has been established as adjuvant therapy in heart failure. Although exercise training guidelines for treatment of heart failure with reduced ejection fraction (HFREF) are well established, no consensus exercise guidelines exist for management of HFPEF. Aerobic and cardiovascular adaptations are generally greater after high-intensity exercise training; interval-type exercise facilitates this type of training because it allows for rest periods that make it possible for patients with heart failure to perform short (e.g., 1-4 minutes) work periods at intensities that are higher than would be possible during continuous exercise. High-intensity aerobic interval training presents a unique, yet untested, therapeutic modality for the exercise training of patients with heart failure with preserved ejection fraction. Pilot testing is warranted, results of which may have important implications for reducing cardiovascular risk, increasing short- and long-term quality of life and survival, and reducing healthcare costs in this patient population. The investigators primary specific aim is to determine the efficacy of a novel, high-intensity aerobic interval exercise training program for improving VO2peak (peak oxygen uptake), endothelial function, and arterial stiffness in patients with HFPEF. The investigators secondary aim is to determine whether the vascular changes are correlated with the changes in VO2peak.

Heart failure is a major health concern and is the leading cause of hospitalization among elderly Americans. Currently 5.7 million Americans are estimated to have heart failure and the estimated direct and indirect costs of treating heart failure are approximately $37.2 billion. Approximately 40% of those diagnosed with heart failure will have heart failure with preserved ejection fraction (HFPEF).2 These individuals have significant restrictions in their ability to carry out activities of daily living.

Exercise training has been established as adjuvant therapy in heart failure.4 Although exercise training guidelines for treatment of heart failure with reduced ejection fraction (HFREF) are well established, no consensus exercise guidelines exist for management of HFPEF. Exercise training increases VO2peak, thus improving prognosis for patients with heart failure. Indeed, VO2peak has been reported to be the single best predictor of mortality in those with cardiac disease.6 Exercise training also improves endothelial function and reduces arterial stiffness, as well as enhancing quality of life.7,8 Because HFPEF is associated with a both diastolic dysfunction and a loss of compensatory systemic vasodilator reserves, arterial stiffness and endothelial function are especially important in this population.

Aerobic and cardiovascular adaptations are generally greater after high-intensity exercise training; interval-type exercise facilitates this type of training because it allows for rest periods that make it possible for patients with heart failure to perform short (e.g., 1-4 minutes) work periods at intensities that are higher than would be possible during continuous exercise. For example, Wisloff et al. demonstrated the superiority of high-intensity aerobic interval training, as compared to continuous, moderate-intensity exercise training, in patients with stable postinfarction heart failure (with reduced ejection fraction). Not only was VO2peak and FMD improved more, patients tolerated the high-intensity program without reported incident. Furthermore, they found it "motivating to have a varied procedure to follow," whereas patients found the continuous exercise group training sessions to be "quite boring." High-intensity aerobic interval training presents a unique, yet untested, therapeutic modality for the exercise training of patients with heart failure with preserved ejection fraction.

Pilot testing is warranted, results of which may have important implications for reducing cardiovascular risk, increasing short- and long-term quality of life and survival, and reducing healthcare costs in this patient population.Patients undergoing exercise training live on average 2.16 years longer at the extremely low cost-effectiveness ratio of $1494 per life year saved.Since the majority of this patient population belongs to the Medicare age group, this intervention has significant potential to reduce healthcare costs.

Hypotheses and Specific Aims Our primary specific aim is to determine the efficacy of a novel, high-intensity aerobic interval exercise training program for improving VO2peak, endothelial function, and arterial stiffness in patients with HFPEF. Our secondary aim is to determine whether the vascular changes are correlated with the changes in VO2peak.

We hypothesize that improvements in VO2peak, endothelial function, and arterial stiffness will be greater after the high-intensity aerobic interval training program and that vascular adaptations will be correlated with changes in VO2peak.

Inclusion Criteria:

• HFpEF diagnosis with New York Heart Association heart failure Class II-III symptoms

Exclusion Criteria:

• Unstable angina
• Myocardial infarction in the past 4 weeks
• Uncompensated heart failure
• New York Heart Association class IV symptoms
• Complex ventricular arrhythmias (at rest or during the maximal exercise test)
• Medical or orthopedic conditions that precluded treadmill walking
• Symptomatic severe aortic stenosis
• Acute pulmonary embolus
• Acute myocarditis
• Medication non-compliance