Inclusion Criteria:

HFpEF Patients:

• Adults(>21 yrs) will have no history of dangerous arrhythmias, not be pacemaker dependent, have a body mass index ≤ 35kg/m2, currently be non-smokers with <15 pack year history and be able to exercise (i.e. without significant orthopedic limitations or musculoskeletal disorders limiting their ability to exercise). Although HF medications may influence multiple physiologic systems, we feel it is important, practical, and safe to study these patients under conditions of optimal care. Concurrent withdrawal of ACE-inhibitor, beta-blocker, digoxin, and/or diuretic therapies would likely be associated with moderate decompensation in a high proportion of patients. Accordingly, the impact of our studies will be generalizable to HF patients receiving standard optimized pharmacologic therapy, consistent with the general community. All patients will be managed by their primary care physician or cardiologist with additional review by Dr. Borlaug (Co-Investigator) prior to enrollment to ensure inclusion and exclusion criteria have been satisfied and participation in exercise testing is safe.

Control Participants:

• Adults (≥21 years of age) in the absence of a history of HFpEF or HFrEF, pulmonary, neurologic, orthopedic, or other diseases affecting the neuromuscular system.
• Controls will be matched for age and sex.
• Additional inclusion criteria include:
  • BMI ≤35kg/m2
  • Current non-smokers with smoking history <15 pack years
  • Those who are able to engage in exercise (i.e. without significant orthopedic limitations or musculoskeletal disorders limiting their ability to exercise)

Exclusion Criteria:

• History of dangerous arrhythmias
• Body mass index >35 kg/m2
• Current smokers and/or smoking history >15 pack years
• Pregnant women
• Uremia, history of allergy to iodides
• Impaired renal function
• Creatinine value greater than or equal to 1.3 mg/dL (via clinical record within the past 6 months)
•  Diagnosis of liver disease; or
• Individuals who are not able to engage in exercise.

For individuals agreeing to undergo dual energy x-ray absorptiometry (DEXA) scanning for measurement of body composition as part of their study visit, additional exclusion criteria apply: recently administered gastrointestinal contrast or radionuclides; severe degenerative changes or fracture deformity in measurement areas; or inability to attain correct position and/or remain motionless for the measurement period.