Abstract
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Objectives: FDG-PET and cardiac MR (CMR) are both described in the diagnosis of cardiac sarcoidosis (CS) but identify different aspects of the disease process (1). FDG-PET shows active myocardial inflammation whereas CMR with late gadolinium enhancement (LGE) assesses biventricular function and the presence of scar. We compared FDG-PET and CMR in the follow-up of patients treated for CS.
Methods: 17 patients with proven extra-cardiac sarcoidosis and possible CS were identified from the local sarcoidosis registry. All had FDG-PET and CMR within 2 weeks, the majority the same day. Patients having FDG-PET followed a 24 hour ultra low-carbohydrate diet and overnight fast (2). CMR included SSFP cine assessment of biventricular function and LGE. All patients were steroid naive and were suspected to have CS following combined FDG PET and CMR. 12 patients were treated with oral steroids ± methotrexate for 3 months or longer. In 5 cases, the clinician chose not to treat or the patient refused treatment. Combined FDG PET and CMR were repeated 180-380 days later. Images for all studies were reviewed by 2 readers. SUV max and mean values for blood pool, mediastinal nodes, normal myocardium and FDG-avid myocardium were recorded. Biventricular function and volumes were measured on CMR and extent of edema and LGE assessed qualitatively on a 17 segment model.
Results: 10 of 12 treated patients had significant myocardial FDG uptake on visit 1 (myocardial maxSUV >3.6) which had improved or resolved in all cases on visit 2. There was a significant fall in myocardial max SUV for the cohort (p< 0.01). The fall in myocardial max SUV was matched by a significant fall in abnormal mediastinal node maxSUV (p< 0.05). 5 of the treated patients also had myocardial LGE on CMR but in none of these was there a change in pattern or extent of LGE. There was no significant change in LV/RV function or volumes. 5 patients had no immunosuppression between visits despite all showing abnormal myocardial FDG uptake on visit 1. The untreated group showed no significant fall in myocardial FDG uptake or change in any of the other FDG-PET or CMR parameters. Only 1 of this group showed LGE on CMR.
Conclusion: Myocardial FDG uptake in suspected CS is presumed to represent active inflammation. When treated with oral steroids this improved or resolved on short term follow up. Despite several of the treated cases showing LGE on the initial CMR this was not altered by treatment and there was no change in LV/RV function or volumes. Untreated patients showed no change on follow-up FDG PET or CMR. Although oral steroids modify myocardial disease activity, it remains to be seen whether treatment will alter long term cardiac outcome. (1) Coulden et al. RSNA 2016:archive.rsna.org/2016/16009768.html. (2) Coulden et al. Eur Radiol 2012;22:2221 Research Support: IRB approved cardiac sarcoidosis imaging registry supported by internal department research fund. $$graphic_97EFC066-6342-4FDB-B8E9-03757F7E02FD$$