Assessment of Cardiac Sarcoidosis with PET/CT.

F-FDG PET with CT is an important advanced imaging modality used to assess patients with suspected or known cardiac sarcoidosis (CS). F-FDG PET is indicated for CS work-up in patients with extra-CS and abnormal screening results for cardiac involvement, patients under 60 y old presenting with unexplained high-grade atrioventricular heart block, and patients with suspected CS and idiopathic ventricular arrhythmias. In patients with established CS, serial F-FDG PET can be used to assess response to immunosuppressive therapy and long-term surveillance for reactivation of myocardial inflammation in patients with low-grade or quiescent disease. Patient preparation before F-FDG PET scanning is key in ensuring adequate suppression of physiologic myocardial F-FDG uptake, to maximize the power of the test to detect pathology. Inadequate dietary preparation can cause diffuse or focal-on-diffuse F-FDG uptake in the absence of active inflammation. It is important to assess resting myocardial perfusion, typically with Rb cardiac PET. Several different patterns of abnormalities have been reported in patients with CS, including normal myocardial perfusion with focal or patchy F-FDG uptake suggesting myocardial inflammation without scarring; the presence of a myocardial perfusion defect with abnormal F-FDG uptake suggesting myocardial scarring with inflammation; and the presence of a myocardial perfusion defect without F-FDG uptake indicating myocardial scarring without inflammation. Prognostically, the presence of myocardial perfusion defects and abnormal F-FDG uptake has been shown to be an independent predictor of death or ventricular arrythmias. A high myocardial SUV in the left and right ventricles has been shown to be an independent predictor of adverse clinical outcomes. Although the diagnostic performance of F-FDG PET has been studied, the reference standard for CS tended to rely on clinical criteria, which may be less sensitive than F-FDG PET at detecting CS. Therefore, the diagnosis of CS should rely on a multidisciplinary team approach involving multimodality advanced imaging, including echocardiography, cardiovascular MR, and F-FDG PET.