Abstract 10622: Association of Sustained Ventricular Arrhythmias and Increased Cardiac Metabolic Activity Mimicking Cardiac Sarcoidosis

Introduction: Cardiac sarcoidosis (CS) is increasingly diagnosed using 18F-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT). Patients with sustained ventricular tachycardia/fibrillation (VT/VF) and a positive FDG-PET/CT suggestive of CS often receive immunosuppressive therapy even in the absence of histologic documentation of non-caseating granulomas. Hypothesis: FDG-PET/CT performed early after sustained VT/VF can lead to increased myocardial FDG uptake mimicking CS. Methods: Consecutive patients with non-ischemic cardiomyopathy presenting with sustained VT/VF that underwent FDG-PET/CT immediately following the arrhythmic event were prospectively recruited. Patients with increased metabolic activity consistent with myocardial inflammation were followed. All patients received guideline-directed medical therapy, but without immunosuppressive therapy. Repeat FDG-PET/CT was performed ≥30 days after the last sustained VT/VF episode. Results: Six patients were enrolled with a mean age of 57.1 years (± 5.6), and a left ventricular ejection fraction of 47.5% (±14.8). Coronary artery disease and acute perimyocarditis were excluded. Initial presentation was electrical storm in 2 (33%), appropriate ICD or external shock in 3 (50%) and ATP in 1 (17%) case, respectively. Baseline FDG-PET/CT was performed a median 5.5 days (range 3-17) after sustained VT/VF termination. Distribution of metabolic activity was focal-multifocal in 4 (66%), focal-diffuse in 1 (17%) and focal in 1 (17%) case, respectively. Median SUVmax was 6.8 (range 4.9-18). No extracardiac metabolic foci were observed and histologic diagnosis of non-caseating granuloma could not be established in any patient. Repeat FDG-PET/CT (median after 139, range 38-448 days) showed complete FDG uptake regression in all patients. Final diagnosis of arrhythmogenic cardiomyopathy was made in all patients, and genetic testing was performed. Conclusion: Prolonged VT/VF episodes may result in increased myocardial FDG uptake, potentially leading to an overdiagnosis of CS. FDG-PET/CT to screen for CS should be performed at a VT/VF-free interval prior to immunosuppressive therapy.