Aims: In the updated guidelines for cardiac sarcoidosis (CS) proposed by the Japanese Circulation Society (JCS), the definition of isolated CS (iCS) was established for the first time. This prompted us to examine the characteristics of patients with CS including iCS according to them by reviewing patients undergoing 18F-fluoro-2-deoxyglucose positron-emission tomography/computerized tomography (FDG-PET/CT), compared with those with CS determined by the conventional international criteria. Methods and results: From 2013 to 2019, 94 patients (61 ± 15 years, 50 female patients) with suspected CS underwent whole-body and cardiac FDG-PET/CT scanning. In contrast to 22 patients with CS based on the international criteria, 34 [27 with systemic sarcoidosis including cardiac involvement (sCS) and 7 with definitive iCS] were diagnosed with CS according to the new JCS guidelines (P = 0.012), and 60 were not (4 suspected iCS, 13 systematic sarcoidosis without cardiac involvement, and 43 no sarcoidosis). In addition to 26 of 34 patients with CS, corticosteroids were also started in 6 of 60 without CS according to clinical need. Conclusions: Diagnostic yield with the new JCS guidelines was higher, with approximately 1.5-fold of the patients diagnosed with CS compared with the previous international criteria and definitive iCS accounting for approximately 20% of the whole CS cohort. In addition to 75% of the patients with sCS or definitive iCS in the updated guidelines, 10% in whom CS was not documented were also started on corticosteroids for clinical indications such as reduced cardiac function or arrhythmia.
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