Satisfactory Myocardial Suppression of FDG Uptake in the Evaluation of Infected Devices by PET/CT

Objectives: Appropriate suppression of physiologic myocardial 18F-fluorodeoxyglucose (FDG) uptake is absolutely crucial for FDG PET/CT imaging for cardiac implantable electronic device (CIED) and other cardiac device infections. We previously reported a 91% success rate of myocardial suppression for cardiac sarcoidosis (CS) FDG PET/CT studies. Despite similarities, CS and CIED patient preparation protocols have differences at our institution. The goal of the current study was to evaluate the rate of successful myocardial suppression in patients referred for FDG PET/CT for CIED and other cardiac device infection.

Methods: A total of 87 consecutive FDG PET/CT were performed on 73 patients from October 2018 to October 2019 for the indication of “cardiac infection.” Prior to the test, patients are provided detailed written instructions for preparation as recommended by the SNMMI/ASNC of at least 2 high-fat (>35 gm), low-carbohydrate (HFPLC) meals followed by a prolonged fast the day before the FDG PET/CT. However, unlike patient preparation for CS FDG PET/CT, nurses do not call patients to emphasize the importance of following the instructions and to answer questions. All 87 exams were performed according to the clinical protocol and an experienced observer graded myocardial suppression of FDG PET/CT images as either poor or satisfactory myocardial suppression using criteria described in the prior paper of CS FDG PET/CT.

Results: Of the 87 FDG PET/CT images, satisfactory myocardial suppression was observed in 70 (80.5%). All patients who underwent image acquisition reported following preparation instructions. The mean fasting time was 13.3 hours (range 4 to 22 hours) and average blood glucose was 93.7 mg/dl (range 62-135 mg/dl) immediately before FDG injection.

Conclusions: In this single-center study, the rate of satisfactory myocardial suppression of FDG uptake was lower than in a previously reported study for CS FDG PET/CT by 10%. Although a systematic evaluation of differences instructions and an intervention were not performed, we identified the lack of contact by nurses to emphasize the importance of following preparation instructions and to answer questions as one of the important missing steps that should be added to CIED infection FDG PET/CT protocols to increase the success rate of myocardial suppression.