The Role of FDG PET/CT in Assessing Cardiac Sarcoidosis with No High-Risk Cardiac Features and Normal CMR.

Background: Diagnosing cardiac sarcoidosis (CS) is challenging due to the variable presentation and the lack of consensus on optimal screening strategies. Early identification is critical to prevent adverse outcomes. This study evaluates the role of FDG-PET/CT in assessing CS in patients with no high-risk cardiac features and normal cardiac magnetic resonance (CMR).

Methods: This retrospective, single-centre cohort included biopsy-confirmed extracardiac sarcoidosis patients who underwent CMR and FDG-PET/CT. Patients with no high-risk cardiac features and normal CMR were included. The primary outcome was the diagnostic value of FDG-PET/CT in the assessment for CS by a multidisciplinary team (MDT). Secondary outcome included the occurrence of adverse cardiac events.

Results: In total, 305 (94.1%) patients were classified as "unlikely CS", 17 (5.3%) as "possible CS" and 2 (0.6%) as "probable CS". Cardiac FDG uptake was observed in 69 of 324 patients (21.3%). Within the MDT, FDG-PET/CT findings demonstrated limited diagnostic value, as 55.2% with uptake patterns suggestive of CS were ultimately classified as "unlikely CS" based on other clinical and imaging findings. During a median follow-up of 38.1 months, the overall event rate was low: 15 events (3.4%; annualized 1.1%), with all five cardiac deaths occurring in the "unlikely CS" group. Only five of 69 patients (7.2%) with cardiac FDG uptake experienced an adverse cardiac event.

Conclusion: FDG-PET/CT offers limited diagnostic and prognostic value in sarcoidosis patients with no high-risk cardiac features and normal CMR. Our findings confirm that this population has a low risk of adverse cardiac events.