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Cardiac MRI and FDG-PET in the diagnosis of cardiac sarcoidosis
© Coulden et al.; licensee BioMed Central Ltd. 2014
Published: 16 January 2014
Sarcoidosis is a multisystem disorder with cardiac involvement in 25% of cases . Diagnosis of cardiac sarcoidosis is challenging with FDG-PET and cardiac MRI (CMRI) proving most reliable. We compare FDG-PET and CMRI with delayed enhancement (LGE) in patients with biopsy proven extra-cardiac sarcoidosis being investigated for cardiac involvement.
30 patients meeting Japanese Ministry of Health & Welfare guidelines  for clinical cardiac sarcoidosis were investigated with FDG-PET CT (Gemini TF Philips) and CMRI (Aera 1.5T Siemens) on the same day. Patients undergoing FDG-PET followed a 24 hour low-carbohydrate diet and overnight fast . CMRI examination included SSFP assessment of left ventricular (LV) function, short axis T2-weighted STIR and PSIR-LGE 10 minutes post 0.2 mmol/kg GdDTPA. Images were reviewed by experienced readers blinded to the results of the other examination. FDG-PET was considered positive if any segment (AHA 17 segment model) had an SUVmax > 3.6 (3). CMRI was considered positive if any segment showed 'sarcoid-type' LGE. In no case was edema present on STIR imaging without LGE in the same segment on subsequent PSIR.
Previous single modality studies have suggested sensitivity and specificity for FDG-PET of 89% and 78% and CMRI of 75% and 77% respectively. In our study, 43% showed no cardiac sarcoidosis by either modality and half of these had minimal or no FDG-PET evidence of active sarcoidosis elsewhere. Are these false -ve FDG-PET/CMRI studies or are the clinical criteria too sensitive? Our findings suggest FDG-PET and CMRI-LGE show different degrees of cardiac sarcoid involvement: FDG-PET indicating active inflammatory disease, LGE showing severe edema and scar. Those patients with LGE and no myocardial FDG uptake appear to have 'burnt-out' disease.
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