A Study of 68Ga-Fibroblast Activation Protein Inhibitor (FAPI) Positron Emission Tomography in Heart Failure

HFpEF Group Inclusion: * Patients aged ≥ 30 years old with exertional dyspnea (NYHA II and III) and LVEF ≥50% * BMI ≥ 30 * New diagnosis of HFpEF based on RHC at baseline (elevated PCWP at rest and/or during exercise) HFpEF Group Exclusion: * Primary cardiomyopathy or pericardial disease or ≥ moderate valvular disease * Dyspnea due to lung disease or CAD * Severe anemia, liver, or renal disease * Active cancer * Systemic active inflammatory or autoimmune disease (e.g. rheumatoid arthritis, SLE, etc.) * Recent hospitalization (\< 30 days) or coronary revascularization (\< 90 days) * Patients already taking SGLT2i and/or GLP-1A * Pregnant or breastfeeding * Inability to tolerate supine position for the PET/CT or CMR scans. * Contraindications for safe CMR scanning (e.g., uncontrolled claustrophobia, cochlear implant, implanted neural stimulator) * Known gadolinium allergy * Presence of implantable cardiac pacemaker or defibrillator or mechanical valve. Cardiac Sarcoid Group Inclusion: * Ambulatory patients aged ≥ 18 years old * New referrals to the Sarcoid Clinic with a confirmed but untreated diagnosis of definite or probable CS based on 2014 HRS consensus (see Table 2) * With a positive cardiac 18F-FDG PET scan within 30 days. Cardiac Sarcoid Group Exclusion: * Already on immunosuppressive therapy * Pregnant or breastfeeding * Severe liver or renal disease (estimated GFR \< 30 or dialysis-dependent) * Recent coronary revascularization (\< 90 days) * Active cancer * Known gadolinium allergy * Inability to tolerate supine position for the PET/CT or CMR scans. * Contraindications for safe CMR scanning (e.g., uncontrolled claustrophobia, cochlear implant, implanted neural stimulator) * Presence of implantable cardiac pacemaker or defibrillator or mechanical valve. Healthy Controls Group Inclusion: * Adults ≥ 30 years old * No major chronic disease (cardiopulmonary, inflammatory, autoimmune, cancer, renal or liver impairment, etc.) * No intake of relevant medication, defined as regular intake of at least one of the following: anticoagulants, antiplatelets, antihypertensive / diuretics, antidiabetics, antiarrhythmic, immunosuppressants, chemotherapy, antibiotics/antivirals/antifungals Healthy Controls Group Exclusion: * BMI ≥ 30 * Pregnant or breastfeeding * Known gadolinium allergy * Inability to tolerate supine position for the PET/CT or CMR scans. * Contraindications for safe CMR scanning (e.g., uncontrolled claustrophobia, cochlear implant, implanted neural stimulator)