4089Prognostic value of cardiac metabolic activity assessed by 18F-FDG PET in patients with cardiac sarcoidosis
Authors: Kobayashi Y , Omote K , Nagai T , Koyanagawa K , Aikawa T , Manabe O , Kamiya K , Kato Y , Komoriyama H , Ohira H , Tsujino I , Tamaki N , Anzai T 
Published: October 2019

Abstract

Background
Sarcoidosis is a systemic granulomatous disease that affects multiple organs. Among these,the presenceof cardiac involvementis recognized as a determinant of worse clinical outcomes. 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a valuable modality for detecting active inflammatory lesions associated with cardiac sarcoidosis (CS). Generally,the maximum standardized uptake value (SUV) is suitable for evaluating disease activity in CS, but this quantitative method had limitations because it does not integrate both volume and intensity of FDG uptake simultaneously. Cardiac metabolic activity (CMA), which is quantitative measures of FDG volume-intensity, could be a diagnostic tool in the evaluation of CS. However, its prognostic implication in patients with CS is unclear.

Purpose
We sought to investigate whether CMA assessed by FDG-PET was associated with long-term worse clinical outcomes in patients with CS.

Methods
A total of 76 consecutive patients suspected CS who underwent FDG-PET between January 2010 and April 2018 in our university hospital were registered. We excluded patients whodid not meet the Japanese Ministry of Health and Welfare 2007 criteria (n=9) and those who received oral corticosteroids at the time of FDG-PET (n=5). Ultimately, 62 CS patients with definitively diagnosed were included in this study.We used a dedicated software to analyze SUV. Cardiac metabolic volume (CMV) was defined as the volume within the boundary determined by the threshold (SUV mean of blood pool × 1.5). CMA was calculated by multiplying CMV by SUV mean. The primary outcome of interest was the composite of advanced atrioventricular block, ventricular tachycardia, ventricular fibrillation, heart failure hospitalization, and all-cause death.

Results
During a median follow-up period of 1287 (IQR 806–1809) days after the first FDG-PET, the adverse events occurred in 12 patients (19%). Events group had significantly higher CMA compared to no events group (83 [IQR 11–330] vs. 354 [IQR 70–577]) (Figure A). Based on ROC analysis, the optimal cut-off value of CMA for the discrimination of the adverse events was 244 ml, and c-index was 0.71 (95% CI, 0.55–0.87). Patients with high CMA (≥244 ml, n=23) had lower LVEF, and higher prevalence of New York Heart Association functional class III or IV, and higher plasma BNP level compared to those with low CMA (<244 ml, n=39). Kaplan-Meier analysis revealed that composite adverse events more frequently occurred in patients with high CMA compared to those with low CMA (Figure B).Univariable Cox regression analysis showed that higher CMA was associated with increased subsequent risk of adverse events (HR 1.47, 95% CI 1.06–2.24).

Conclusions
Higher CMA assessed by FDG-PET was associated with worse clinical long-term outcomes in patients with CS, suggesting that measurement of the volume-intensity of abnormal FDG uptake may be useful for risk stratification in patients with CS.