Serial FDG-PET scans help to identify steroid resistance in cardiac sarcoidosis

Cardiac sarcoidosis (CS) is increasingly being recognized. Immunosuppression with corticosteroids is the mainstay of therapy. But the optimal dose of steroids and how to assess response to therapy is not known. Prognosis is poor if these patients are untreated or undertreated. Fluorine-18-flurodeoxyglucose positron emission computed tomography (¹⁸FDG-PET CT) is a sensitive tool in diagnosing CS. It correlates closely with the level of granulomatous inflammation and can be used to monitor response to therapy.

We identified 15 patients (6 women; mean age, 42.9±12.5years) based on histopathological diagnosis. All had a baseline and follow-up fasting ¹⁸FDG-PET CT scans before and after steroid therapy. Non-responders were defined as those in whom ventricular arrhythmias, symptoms of HF and left ventricular systolic function and/or ventricular arrhythmias did not improve or worsened despite steroid therapy. FDG uptake of involved myocardium and lymph nodes (LN) was compared in clinical responders and non-responders on follow-up.

Of the 15 patients, 4 were clinical non-responders to steroid therapy. Follow-up ¹⁸FDG-PET CT was performed at 125.8±54.2days after the initiation of steroid therapy. Myocardial maximum standardized uptake of FDG (SUVmax) value decreased significantly in responders (p=0.004) while there was an increase in non-responders (p<0.05) on follow-up. Number of left ventricle (LV) segments with FDG uptake significantly decreased in responders (p=0.007), and on increasing trend in non-responders (p=0.465). Heterogeneous FDG uptake on baseline PET scan, increase in intensity as well as area of myocardial inflammation on follow-up PET scan was associated with poor clinical outcome despite steroid therapy.

Serial ¹⁸FDG-PET CT scans can be used to monitor steroid therapy in active CS. Increase in PET uptake after steroid therapy correlates with poor clinical outcome. Repeat PET scan may help to predict steroid-resistant CS and the need for up-titration of immunosuppressive therapy among poor responders to initial therapy.