Additional Heparin Preadministration Improves Cardiac Glucose Metabolism Suppression over Low-Carbohydrate Diet Alone in ¹⁸F-FDG PET Imaging

Adequate suppression of cardiac glucose metabolism increases the interpretability and diagnostic reliability of (18)F-FDG PET studies performed to detect cardiac inflammation and infection. There are no standardized guidelines, though prolonged fasting (>6 h), carbohydrate-restricted diets, fatty meals, and heparin loading all have been proposed. The aim of this study was to compare the 3 preparatory protocols used in our institution.

METHODS: (18)F-FDG PET scans were selected and grouped according to 3 preparatory protocols (50 consecutive scans per group): 6-h fast (group 1), low-carbohydrate diet plus 12-h fast (group 2), and low-carbohydrate diet plus 12-h fast plus intravenous heparin preadministration (50 IU/kg) (group 3). Consecutive scans were retrospectively included from time frames during which the particular protocol was used. Group 1 included oncologic indications, and groups 2 and 3 infection or inflammation detection. Cardiac segments for which inflammation or infection foci had been confirmed on other imaging modalities were excluded from the analysis. (18)F-FDG uptake in normal myocardium was scored according to a scale ranging from 0 (uptake less than that in left ventricle blood pool) to 4 (diffuse uptake greater than that in liver). Adequate suppression was defined as uptake less than that in liver and without any focus (scores 0-2).

RESULTS: Adequate suppression differed significantly between groups: 28% in group 1, 54% in group 2, and 88% in group 3 (P< 0.0001 for all comparisons).

CONCLUSION: Single-dose heparin administration before (18)F-FDG PET in addition to a low-carbohydrate diet significantly outperforms a low-carbohydrate diet alone in adequately suppressing cardiac glucose metabolism.