Inclusion Criteria:

• Healthy volunteers are eligible to participate in this study if they have are free of symptoms of exertional breathlessness or fatigue and any diagnosis of heart failure.  
• Patients will also be required to have left ventricular EF ≥ 50%.  
• Patients discovered to reduced EF or abnormal resting hemodynamics or other pathologic findings previously undiscovered will be considered screen failures and can be replaced by others to reach the goal enrollment.
• Informed consent were obtained.
• Age ≥ 18 years at the time of signing informed consent.
• No history of heart failure.
• Willing and able to undergo invasive hemodynamic exercise testing, MRI, and other study assessments.

Exclusion Criteria:

• Clinically significant symptoms of exertional dyspnea or fatigue in daily life in the opinion of the investigators.
• Any diagnosis of heart failure.
• Symptomatic coronary artery disease (e.g., patients with chronic angina).
• Symptomatic valvular heart disease.
• Pulmonary hypertension.
• Cardiomyopathies.
• High output heart failure.
• Pericardial disease.
• Clinically significant chronic lung disease in the opinion of the investigators.
• Anemia (hemoglobin < 12 gm/dL in women and < 13 gm/dL in men).
• Estimated glomerular filtration rate < 60.
• Pregnant women.
• Any other disorders or problems that would interfere with the ability to participate safely in the study (e.g. psychiatric disorder or substance abuse).

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 7/24/23. Questions regarding updates should be directed to the study team contact.