Reduction in ¹⁸F-fluorodeoxyglucose uptake on serial cardiac positron emission tomography is associated with improved left ventricular ejection fraction in patients with cardiac sarcoidosis

Background: Cardiac positron emission tomography (PET) using ¹⁸F-fluorodeoxyglucose (FDG) has been used to diagnose and monitor cardiac sarcoidosis (CS). It is not known whether a reduction in myocardial inflammation, as measured by FDG uptake, is associated with improvement in LV ejection fraction (EF). Methods: For 23 patients with CS followed by a total of 90 serial PET exams (median 4 per patient), two physicians blinded to EF quantified the maximum of standardized uptake value (SUV) and volume of inflamed tissue above two distinct thresholds to assess the intensity and extent of FDG uptake on each study. Using gated ⁸²Rubidium rest myocardial perfusion images, EF was measured blinded to all clinical and FDG data. To account for clustering and differences in scan frequency, a longitudinal mixed effects model was used to evaluate the relationship between FDG uptake and changes in EF on interval scans. Results: Among 23 patients with serial PET exams (mean age 49, 74% male, mean baseline EF 43% ± 13%), the median time between the first and last scan was 2.0 years. Overall, 91% were treated with corticosteroids, 78% with ACE/ARB, 83% with beta-blockers, and 83% had ICDs. Longitudinal regression demonstrated a significant inverse linear relationship between maximum SUV and EF with an expected increase in EF of 7.9% per SUV reduction of 10 g·mL^-1 (P =.008). Likewise, in an analysis based on volume, there was an increase in EF of 2.1% per 100 cm ³ decrease in volume of inflamed tissue using a threshold of 2.7 g·mL^-1 (P =.028) and an increase in EF of 3.8% per 100 cm ³ decrease (P =.022) using a SUV threshold of 4.1 g·mL ^-1. Conclusions: In a longitudinal cohort of CS patients, a reduction in the intensity and extent of myocardial inflammation on FDG PET is associated with improvement in EF. These data suggest serial PET scanning may help guide titration of immunosuppressive therapy to improve or prevent heart failure in CS.