Relationships between quantitative FDG PET parameters, treatment and disease activity in cardiac sarcoidosis

Objectives Although FDG PET is increasingly used for the diagnosis of cardiac sarcoidosis, there is limited data on the relationships between clinical status, treatment and findings on serial scans. We aimed to evaluate whether changes in quantitative findings on FDG PET reflect changes in clinical status and treatment.

Methods We evaluated all patients referred for diagnosis or monitoring of known or suspected cardiac sarcoidosis with FDG PET from February 2012 through October 2013 who had more than one scan (16 patients, 39 studies). All patients were prepared with a high-fat, low-carbohydrate diet and intravenous heparin. We quantified peak left ventricular (LV) SUV (SUVmax) and percent of LV myocardium with SUV>2.5 (SUV2.5%) using FDG PET images and LV ejection fraction using paired perfusion images with Corridor4DM (INVIA, Ann Arbor, MI). An independent expert categorized clinical status for each patient at each examination as worsening or as stable/improving based on symptoms of heart failure or arrhythmia and EKG and echocardiography findings. Similarly, immunosuppressive treatment was categorized as stable/intensified or as tapered. We evaluated the relationships between PET findings and clinical and treatment status using linear mixed models with per patient random effects.

Results Clinical status was improving/stable for 24 PET exams and worsening for 15 exams. Treatment was stable/intensified for 23 PET exams and tapered for 16 exams. We found that improving/stable compared to worsening status was associated with lower SUVmax (3.6 [95%CI 2.4-4.8] vs. 7.3 [5.7-8.8]; P=0.002) and SUV2.5% (27% [95%CI 16-39%] vs. 62% [46-77%]; P=0.003). Tapered treatment was associated with higher SUVmax (6.8 [95%CI 5.2-8.4] vs. 3.5 [2.1-4.9]; P=0.009) but not SUV2.5% (48% [95%CI 30-66%] vs. 34% [19-50%]; P=0.27). LVEF was related to SUVmax (P=0.025; β=0.99 [95%CI 0.13-1.84) but not SUV2.5% (P=0.39).

Conclusions Quantitative FDG PET parameters of myocardial inflammation are related to disease activity and treatment intensity in patients with cardiac sarcoidosis.