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

This study is using a special type of PET scan involving a tracer called 68Ga-FAPI to look at fibroblast activity (a marker of tissue scarring and inflammation) in the hearts of people with two specific cardiac conditions — heart failure with preserved pumping function (HFpEF) and cardiac sarcoidosis (an inflammatory disease affecting the heart). Healthy volunteers are also included for comparison. **You may be eligible if...** - HFpEF group: You are 30 or older with a BMI of 30 or above, shortness of breath on exertion, normal heart pumping function (LVEF ≥50%), and a new diagnosis confirmed by specialized heart pressure measurements - Cardiac sarcoidosis group: You are 18 or older with a new, untreated diagnosis of cardiac sarcoidosis and a recent positive 18F-FDG PET scan - Healthy controls: You are 30 or older with no major chronic diseases or regular medications and a BMI below 30 **You may NOT be eligible if...** - You have active cancer, active autoimmune or inflammatory disease, severe anemia, kidney or liver disease, or are pregnant - You have a pacemaker, defibrillator, cochlear implant, or mechanical heart valve - You have a known allergy to the MRI contrast agent gadolinium - You are unable to lie flat for the scan or have claustrophobia that cannot be managed Talk to your doctor to see if this trial is right for you.