The prognostic value of positron emission tomography in the evaluation of suspected cardiac sarcoidosis

Objectives To assess the prognostic value of positron emission tomography (PET) imaging in patients undergoing evaluation for known or suspected cardiac sarcoidosis (CS) while not on active immunotherapy. Background Previous studies have attempted to identify the value of PET imaging to aid in risk stratification of patients with CS, however, most cohorts have included patients currently on immunosuppression, which may confound scan results by suppressing positive findings. Methods We retrospectively analyzed 197 patients not on immunosuppression who underwent 18 F-fluorodeoxyglucose (FDG) PET scans for evaluation of known or suspected CS. The primary endpoint of the study was time to ventricular arrhythmia (VT/VF), or death. Candidate predictors were identified by univariable Cox proportional hazards regression. Independent predictors were identified by performing multivariable Cox regression with stepwise forward selection. Results Median follow-up time was 531 [IQR 309, 748] days. 41 patients met the primary endpoint. After stepwise forward selection, left ventricular ejection fraction (LVEF) (HR 0.98, 95% CI 0.96-0.99, P = 0.02), history of VT/VF (HR 4.19, 95% CI 2.15-8.17, P < 0.001), and summed rest score (SRS) (HR 1.06, 95% CI 1.02-1.12, P = 0.01) were predictive of the primary endpoint. Quantitative and qualitative measures of FDG uptake on PET were not predictive of clinical events. Conclusions Among untreated patients who underwent PET scans to evaluate known or suspected CS, LVEF, history of VT/VF, and SRS were associated with adverse clinical outcomes.