Electrophysiologic implications of PET-defined, active cardiac sarcoidosis

Objectives Sarcoidosis is an inflammatory disease where myocardial involvement and its activity are essential for prognosis. It has been suggested that FDG PET is useful for identifying cardiac sarcoidosis, but there are few reports about the pathophysiologic implications of PET-defined active myocardial inflammation in advanced sarcoid disease.

Methods Cardiac and whole-body glucose utilization were studied under rigorous fasting conditions in 18 patients with a long history of sarcoidosis (4.4±3.7 years) All had increased clinical risk of cardiac sarcoidosis according to Japanese Ministry of Health criteria, and all had an implantable cardioverter defibrillator (ICD). LVEF was reduced(38±16%), and ECG abnormalities were reported in all patients. None had history of diabetes mellitus or ischemic heart disease.

Results Abnormal focal FDG uptake was observed in 10 patients even under steroid treatment (Prednisone, 7.5-40mg/d). 5 patients had history of appropriate ICD discharge before or after 1 year of the FDG PET study. The discharge was associated with abnormal cardiac FDG uptake (accuracy 72.2%), while less associated with other parameters such as presence of extracardiac active lesions (accuracy 55.6%), perfusion defect on Rb-82 PET (accuracy 33.3%), or clinical parameters such as LVEF, duration of disease and steroid dose.

Conclusions Abnormal focal FDG uptake in the heart may be present in cardiac sarcoidosis despite steroid treatment. Focal myocardial uptake was associated more strongly with ICD discharge than other clinical and imaging parameters. FDG PET may thus be useful not only in primary detection, but also in risk stratification of patients with known cardiac sarcoid