Utility of Updated Japanese Circulation Society Guidelines to Diagnose Isolated Cardiac Sarcoidosis

Background In the population with cardiac sarcoidosis (CS), approximately one third lacks extracardiac involvement and is considered to have isolated CS. Recently, the Japanese Circulation Society updated the diagnostic criteria for CS, providing a methodology for diagnosing isolated CS. We aimed to assess the characteristics of isolated CS diagnosed using a multimodal imaging approach according to the updated Japanese Circulation Society guidelines. Methods and Results We retrospectively identified 161 consecutive patients who underwent 18F-fluorodeoxyglucose positron emission tomography for suspected CS between 2012 and 2019. According to the guidelines, patients were classified as having CS with extracardiac involvement, isolated CS, or no CS. We compared the characteristics of multimodality imaging and the prevalence of major adverse cardiovascular events. The Japanese Circulation Society criteria classified 28 patients (17%) as having CS with 4 (2%) with histological confirmation, 21 (13%) as isolated CS, and 112 (70%) as no CS. Compared with CS, isolated CS showed higher left ventricular volume and reduced left ventricular ejection fraction (P<0.01 for all). During the median follow-up period of 522 days, 24 patients had major adverse cardiovascular events. Isolated CS (hazard ratio, 3.35; [95% CI, 1.08-10.39], P=0.036) was independently associated with major adverse cardiovascular events after adjusting for reduced left ventricular ejection fraction and steroid. In the subgroup of 41 patients with serial 18F-fluorodeoxyglucose positron emission tomography evaluation, only updated CS criteria were associated with improvement in myocardial inflammation on 18F-fluorodeoxyglucose positron emission tomography. Conclusions Isolated CS detected using the updated Japanese Circulation Society guidelines was associated with poor event-free survival and should be managed with caution.