Abstract 4370523: Atrial FDG Avidity is Associated with Atrial Volume Expansion

Background: Atrial myopathy includes structural remodeling processes that result in adverse cardiovascular conditions. Metabolic inflexibility, defined by altered substrate availability, plays an important role in atrial fibrillation (AF) initiation and progression. Atrial dilation is a result of AF’s structural remodeling processes, while atrial uptake of 18F-fluorodeoxyglucose (FDG) in positron emission tomography (PET) imaging reflects underlying metabolic shifts. Aim: We aim to investigate the relationship between atrial FDG uptake and atrial dilation. Hypothesis: Atrial FDG uptake reflects an active remodeling process within the atrial myocardium and is associated with increased volumes. Methods: Patients undergoing FDG-PET for the evaluation of cardiac sarcoidosis (CS) were assessed for atrial avidity. Atrial FDG uptake, a semi-quantitative measure, was quantified using standardized uptake value SUV-mean, SUV-max, and normalized to the blood pool as the target-to-background ratio (TBR). Atrial volume assessment was obtained from cardiac magnetic resonance imaging (CMR) scans done prior to PET. Right atrial volume index (RAVi) was obtained from monoplanar 4 chamber view while left atrial volume index (LAVi) was obtained from biplanar method. Results: One hundred and fifty-eight patients (age 61 ± 15 years, 37% female, BMI 29.6 ± 6.5 kg/m2) were included in the study. CS was noted in 43 (27.2%) patients and AF in 49 (31%) patients. Regression analysis showed an association between LAVi and atrial TBRmax (β=0.005, p =0.007) but no association between RAVi and atrial TBRmax (β=0.002, CI -0.002-0.006 p =0.08) after adjustment for AF and cardiac sarcoidosis. Location specific analysis showed that RAVi was associated with right (OR 1.03, p =0.01) and biatrial uptake (OR 1.05 p =0.02). However, LAVi was only associated with biatrial uptake (OR 1.04, p =0.04). Patients with atrial avidity had a significantly higher LAVi and RAVi (46.8±21.7 vs 38.1±13.9 mL/m 2 , p=0.02, 44.4±18.4 vs 36.5±13.1 mL/m 2 , p=0.02). In AF patients specifically, this relationship remained significant with RAVi (51.5±20.6 vs 39.1±14.4 mL/m 2 , p=0.02) while no difference was found with respect to LAVi (54.2±23.5 vs 42.8±14.4 p=0.06). Conclusion: Atrial-specific FDG uptake is associated with dilation of the corresponding chamber. This suggests that altered substrate utilization may contribute to localized atrial remodeling. Further research is needed to explore the temporal nature of this association.