Use of 18F-fluorodeoxyglucose positron emission tomography in the differential diagnosis of arrhythmogenic right ventricular cardiomyopathy and cardiac sarcoidosis

Abstract

Abstract Introduction Arrhythmogenic Cardiomyopathy (ACM) is defined as an arrhythmogenic heart muscle disorder not explained by ischemic, hypertensive, or valvular heart disease, which ranges from a systemic immunologic disorder such as cardiac sarcoidosis (CS), to a genetically determined one (arrhythmogenic right ventricular cardiomyopathy=ARVC). The aim of this study was to assess the utility of 18F-fluordeoxyglucose positron emission tomography /computer tomography (18F-FDG-PET/CT) in the differential diagnosis of ACM. Methods This study included 45 patients with a definite diagnosis of ARVC, in whom 18F-FDG-PET/CT was performed to screen for CS. Following a positive PET, diagnosis of CS was pursued according to the 2014 HRS consensus document. The patients were divided into two cohorts: the ARVC Cohort (ARVC-C) and the Cardiac Sarcoidosis Cohort (CS-C). Results All 45 patients received an 18F-FDG-PET/CT, of these 5 had a positive PET showing myocardial hypermetabolism. All 5 patients with a positive PET had a final diagnosis of histologically confirmed CS, as such the 18F-FDG-PET/CT had a negative predictive value (NPV) of 100%. All 45 patients also received genetic testing (cardiomyopathy panel). In the ARVC-C, 23 (58%) patients harbored a pathogenic (P)/likely pathogenic (LP) variant (40% in PKP2). In the CS-C, 1 (20%) patient with histologically confirmed CS harbored a LP DSG2 variant. Nine (23%) subjects in the ARVC-C presented with atrioventricular block (AVB) (grade I) and 7 (18%) with QRS fragmentation, whereas 5 (100%) patients in the CS-C presented with AVB (grade I and higher) and 4 (80%) with QRS fragmentation. On TTE, left ventricular (LV) involvement was less frequent in the ARVC-C (LVEF 52.2 +/- 8.7%; wall motion abnormalities in 19 patients (48%)), while LV-involvement in the CS-C was more frequent (LVEF 44.0 +/- 16.2%; wall motion abnormalities in 3 (60%). On cardiac magnetic resonance imaging (cMRI), late gadolinium enhancement was present in the ARVC-C in 14 (35%) in the RV and 15 (38%) in the LV, while it was present in 3 (60%) patients in the RV and 3 (60%) in the LV in the CS-C. Conclusions CS is an underdiagnosed clinical entity, which can be challenging to differentiate from ARVC. 18F-FDG-PET/CT has a high NPV to exclude CS in patients fulfilling definite ARVC criteria. Hence, we recommend to offer 18F-FDG-PET/CT to patients fulfilling definite ARVC criteria who present with AVB, QRS fragmentation, or biventricular involvement to screen for CS, especially to those who do not have an LP/P variant in the PKP2 gene.