Imaging cardiac sarcoidosis by cardiac positron emission tomography (PET): a local experience using a high-fat, low-to-no carbohydrate protocol.

Dear Editor, A 40-year-old female presented acutely with syncope and recurrent ventricular tachycardia (VT) requiring repeated cardioversion. Transthoracic echocardiogram (TTE) revealed mildly depressed systolic function of 40% to 45% with normal right ventricular size and function. Coronary angiogram revealed insignifi cant coronary artery disease (CAD). Biopsy of enlarged mediastinal lymph nodes revealed evidence of non-necrotising granulomatous infl ammation, with no evidence of tuberculosis or fungi. To ascertain a diagnosis of cardiac sarcoidosis, an 18F-fl uorodeoxyglucose positron emission tomography/ computed tomography (18F-FDG PET/CT) study was performed under strict, non-fasting, high-fat, lowcarbohydrate dietary modifications. The patient was instructed to consume 2 consecutive meals containing high fat and low-to-no-carbohydrate diet the evening prior to FDG PET/CT imaging, and on the morning of the scan. She was advised to have fatty unsweetened foods such as fried chicken, fried eggs or fried bacon, without bread or rice because these are sources of carbohydrates. She was also advised not to have beverages that contain milk or sugar. On the day of the scan, the patient was injected with 10-millicuries of 18F-FDG intravenously, followed by cardiac 18F-PET/CT imaging 60 minutes later. 18F-FDG PET/CT images were compared to myocardial perfusion imaging (MPI) study by single-photon emission computed tomography (SPECT). The cardiac 18F-FDG PET/CT study revealed markedly increased myocardial FDG uptake involving the mid to basal anterior and distal to basal anteroseptal walls that corresponded to segmental perfusion defects on MPI SPECT study, as well as focal FDG uptake in the right ventricle and distal to basal inferoseptum (Figs. 1a-c). The intense areas of diffuse uptake corresponded to near-transmural enhancement in the septum and anterior myocardium on cardiac magnetic resonance imaging (MRI) (Fig. 1d). The patient was treated with steroids and given an implantable cardio-defi brillator (ICD). Repeat 18F-FDG PET/CT study performed 6 months later demonstrated reductions in FDG uptake in the anterior, anteroseptal, right ventricle and inferoseptal walls, suggesting reduction in active disease activity in the myocardium (Fig. 1e). On the other hand, a 54-year-old woman with biopsyproven pulmonary sarcoidosis was evaluated for sarcoid involvement of the heart by the same 18F-FDG PET/CT imaging protocol and dietary instructions. While the whole body 18F-FDG PET/CT revealed multiple hypermetabolic mediastinal and bilateral hilar lymph nodes consistent with systemic sarcoidosis, there was absent myocardial FDG uptake on the 18F-FDG PET/CT scan, suggestive of the absence of cardiac sarcoid involvement (Fig. 2). Cardiac Sarcoidosis by Cardiac PET—Angela SM Koh et al Letter to the Editor