Fasting FDG PET compared to MPI SPECT in cardiac sarcoidosis

Abstract

Introduction. Cardiac involvement occurs in a significant minority (5%-30%) of patients with sarcoidosis and can have a benign or life-threatening course. Clinical manifestations include conduction abnormalities, ventricular and supraventricular arrhythmias, valvular dysfunction, and heart failure. 1 The diagnosis of cardiac sarcoidosis is often difficult to make, and is suggested by relatively nonspecific findings such as electrocardiographic abnormalities (particularly heart block) or abnormalities in left ventricular function. Endomyocardial biopsy, while providing improved specificity, is invasive and has poor sensitivity. Initial strategies using nuclear imaging techniques such as gallium or myocardial perfusion imaging (MPI) demonstrated relatively poor sensitivity and specificity for cardiac sarcoidosis. Recently, FDG (F-18 fluorodeoxyglucose) positron emission tomography (PET), performed under fasting conditions, has been shown to have improved sensitivity and specificity for the diagnosis of cardiac sarcoidosis compared to other modalities. A case of a 73-year-old man with known pulmonary sarcoidosis and multiple coronary risk factors who presented with a new cardiomyopathy is presented in this study. Initial evaluation with single photon emission computed tomography (SPECT) technetium 99m (Tc-99m) tetrofosmin MPI strongly suggested an ischemic etiology. Subsequent coronary angiography and FDG PET, however, was consistent with cardiac sarcoidosis, highlighting the potential value of PET imaging in the evaluation of suspected cardiac sarcoidosis. Case report. A 73-year-old man with a history of biopsy-proven stage I pulmonary sarcoidosis presented with acute respiratory failure. His past medical history included sarcoidosis, diabetes mellitus, end-stage renal disease on hemodialysis, and atrial fibrillation. The patient was diagnosed with pulmonary sarcoidosis approximately 30 years ago by routine chest x-ray. He underwent a lung biopsy at that time that was positive for granulomatous inflammation consistent with sarcoidosis. He was asymptomatic until approximately 1 month prior to admission at which time developed worsening dyspnea on exertion. This progressed to shortness of breath at rest which prompted him to seek medical attention.