Clinically evident cardiac involvement has been documented in 5% of sarcoidosis patients, primarily manifesting as heart block, ventricular arrhythmias, and heart failure. Heart Rhythm Society consensus guidelines recommend advanced cardiac imaging with fluorodeoxyglucose-positron emission tomography (FDG-PET) scan for diagnosis of cardiac sarcoidosis, given endomyocardial biopsy's low sensitivity.

We describe four patients with cardiac sarcoidosis diagnosed with FDG-PET scan performed using a standardized imaging protocol for cardiac sarcoidosis. Serial FDG-PET scans were performed to monitor disease progression and response to therapy. Patients 1 and 2 presented with heart block, Patient 3 with heart failure and ventricular tachycardia (VT), and Patient 4 with VT. Patient 1 showed an initial decrease in standard uptake value (SUV) on immunosuppression, followed by an increase in SUV, necessitating steroid therapy. Patient 2's SUV decreased on immunosuppression. Patient 3 required 3.5 years of immunosuppression for the SUV to decrease to inactive disease levels, with SUV increasing and decreasing at different times during treatment, and subsequently developed VT. For Patient 4, areas of inflammation on the initial scan matched low voltage areas on the patient's EP study, confirming the arrhythmia's pathophysiological basis.

Cardiac sarcoidosis progression and response to therapy are heterogeneous. Serial FDG-PET scans are useful to diagnose disease, tailor therapy, and monitor the clinical course of disease, allowing treatment decisions to be based on the quantitative level of inflammation seen on FDG-PET.