PET in Cardiac Sarcoidosis.

18F-fluorodeoxyglucose (18F-FDG) PET is used to diagnose cardiac sarcoidosis (CS) in patients with extracardiac sarcoidosis and suspected cardiac involvement or suspected isolated CS. Rigorous patient preparation suppresses physiological myocardial uptake. 18F-FDG PET is interpreted with myocardial perfusion imaging: abnormal uptake with normal perfusion indicates inflammation without fibrosis, uptake with a perfusion defect indicates inflammation with fibrosis, and a perfusion defect without uptake indicates fibrosis alone. Abnormal uptake, particularly with perfusion defects, predicts major adverse cardiac events, including death and ventricular arrhythmias. Serial 18F-FDG PET monitors response to immunosuppressive therapy and detects reactivation of myocardial inflammation.