Muscle Blood Flow Regulation in HFpEF

Inclusion Criteria: * Age 18 years or older and able to give written informed consent * New York Heart Association (NYHA) functional class II or III * Left Ventricular Ejection Fraction (LVEF) \> 50% * Plasma Brain Natriuretic Peptide (BNP) \>200 pg/mL or NT-proBNP 400 pg/mL at enrollment Exclusion Criteria: * Prior EF of \<50%. * NYHA Class IV or HF that cannot be stabilized on optimized pharmacotherapy * Acute coronary syndrome, infiltrative cardiomyopathy, or myocarditis * Patients with HFpEF secondary to significant uncorrected primary valvular disease (except mitral regurgitation secondary to left ventricular dysfunction) * Orthopedic limitations that would prohibit knee-extensor exercise * Women currently taking hormone replacement therapy (HRT) will be excluded from the proposed studies due to the direct vascular effects of HRT * Women who are pregnant or may become pregnant, but the typical age of female patients with HFpEF will be postmenopausal * Current smokers