Complementary Roles of Cardiac MRI and FDG-PET/CT in the Evaluation of Cardiac Sarcoidosis: Insights From a...

To evaluate the correlation between cardiac MRI and FDG-PET/CT findings in the diagnosis of cardiac sarcoidosis (CS) and assess their complementary roles in clinical decision-making.

A retrospective study was conducted on patients referred for both FDG-PET/CT and cardiac MRI for suspected CS at a single tertiary Australian hospital between January 2022 and June 2024. Imaging studies were categorised as 'negative', 'equivocal' or 'probable/positive' for CS. Clinical diagnosis was determined based on imaging, histopathology, and multidisciplinary assessment. Concordance between MRI, FDG-PET/CT and final clinical diagnosis was analysed.

Twenty patients met inclusion criteria (mean age 55.6 ± 13.8 years, 70% male). MRI identified eight positive, seven equivocal, and five negative cases, whereas FDG-PET/CT detected eight positive and 12 negative cases. Clinical diagnosis confirmed CS in eight patients, with nine deemed negative and one equivocal. Direct concordance between MRI and FDG-PET/CT was observed in 9 of 20 cases (45%), with positive agreement in five and negative agreement in four cases. Imaging findings correlated with clinical diagnosis in seven of eight confirmed CS cases. Discordant imaging findings occurred in four cases, including MRI-positive but FDG-PET/CT-negative cases, later diagnosed as myocarditis or non-ischaemic cardiomyopathy.

Cardiac MRI and FDG-PET/CT demonstrate a complementary role in CS evaluation, with MRI excelling in detecting fibrosis and structural abnormalities, while FDG-PET/CT identifies active inflammation. Concordant imaging findings strongly correlated with clinical diagnosis, reinforcing the need for a multimodal approach in CS assessment and management.