Assessing the Clinical Value of Myocardial Perfusion SPECT in Cardiac Sarcoidosis with Diffuse Myocardial 18F-FDG Uptake.

Background: Myocardial ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake is a sign of active inflammation in patients with cardiac sarcoidosis (CS) under the correct circumstance. However, even under the proper preparation, diffuse myocardial ¹⁸F-FDG uptake is frequently observed in the failing heart and misleads the CS disease activity. The aim of this study was to establish the diagnostic value of resting myocardial perfusion single photon emission computed tomography (SPECT) for assessing CS disease activity in patients with diffuse myocardial ¹⁸F-FDG uptake. Methods: We examined 39 patients with either histologically or clinically proven CS. All patients underwent ¹⁸F-FDG positron emission tomography (PET) and resting ^99mTc-SPECT. The presence of perfusion-metabolic mismatch was evaluated with generating polar maps of ¹⁸F-FDG PET and ^99mTc-SPECT images. Results: Increased myocardial ¹⁸F-FDG uptake was observed in 33 (85%) of 39 patients. Focal ¹⁸F-FDG uptake was detected in 16 patients and diffuse ¹⁸F-FDG uptake was seen in 17 patients. Brain natriuretic peptide (BNP) levels were significantly higher in patients with diffuse ¹⁸F-FDG uptake than those with focal ¹⁸F-FDG uptake (p=0.002). With comparing polar maps of ¹⁸F-FDG PET and ^99mTc-SPECT images, 8 of 16 patients with diffuse ¹⁸F-FDG uptake and myocardial perfusion defects demonstrated perfusion-metabolic mismatch which represented active inflammatory lesions in CS. Conclusions: Simultaneous evaluation of myocardial ¹⁸F-FDG PET and ^99mTc-SPECT by polar map analysis provides more relevant information for assessing disease activity in CS than ¹⁸F-FDG PET images alone. Perfusion-metabolic mismatch might indicate latent active inflammation in CS patients with diffuse myocardial ¹⁸F-FDG uptake, who had advanced heart failure.