Accuracy of Currently Available Diagnostic Criteria for” Clinical” Cardiac Sarcoidosis Using FDG PET and CMR as Reference Standard

Introduction: In absence of myocardial tissue diagnosis of cardiac sarcoidosis (CS), the Heart Rhythm Society (HRS) and the Japanese Circulation Society (JCS) are used for diagnosis of “clinical” CS. Cardiac [ 18 F] FDG PET-CT and magnetic resonance imaging (CMR) are used to screen for and monitor activity in CS. We investigated the diagnostic accuracy of HRS and JCS with FDG PET/CT or CMR as the reference standard for clinical CS.

Methods: Consecutive patients with biopsy confirmed extra-cardiac sarcoidosis undergoing cardiac [ 18 F] FDG PET-CT or 1.5 T CMR from Oct 2019 -June 2021. Standard [ 18 F] FDG PET-CT and CMR criteria suggesting CS was used for diagnosis. HRS and JCS criteria were applied to study group.

Results: Among 32 consecutive patients (median age 59 years [IQR 50, 69], 66% male and 62% African American) undergoing cardiac PET-CT and/or CMR, median duration from diagnosis of extracardiac sarcoidosis to PET-CT was 4 years (IQR 1, 10). There were 50% and 47% patients with history of VT and on defibrillator therapy, respectively. Only 2 patients had Mobitz II or above conduction block. Around 60% patients were already on immunosuppressive therapy. Ten patients (31.3%) had evidence of perfusion-metabolism mismatch on PET/CT suggestive of active CS. The most common involved segments were the basal anterolateral and inferolateral segments (both 70%). Among 16 patients undergoing cardiac MRI; 8 had late gadolinium enhancement suggestive of CS. 23 patients (71.9%) met diagnostic criteria for “clinical” CS by the HRS criteria. The sensitivity and specificity of HRS criteria was 100% and 41.9%, and 100% and 25%, with PET-CT and CMR as the reference standard, respectively. Nineteen (59.4%) patients met diagnostic criteria for CS by the JCS criteria. The sensitivity and specificity of JCS criteria was 100% and 59.1%, and 100% and 50%, with PET-CT and MRI as the reference standard, respectively.

Conclusions: We report excellent sensitivity but poor specificity of HRS and JCS diagnostic criteria “clinical” CS when compared to PET-CT or CMR with JCS having higher specificity. Clinicians should be aware of limitations in existing criteria. Pre-existing immunosuppressive therapy may have influenced the results.

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