Volumetric quantification of peri-atrial fat inflammation in atrial fibrillation patients

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Centre for Research Excellence Award III (RE/18/5/34216). SEW is supported by the British Heart Foundation (FS/20/26/34952). MCW is supported by the British Heart Foundation (FS/ICRF/20/26002) INTRODUCTION: Peri-atrial fat may have pro-inflammatory and pro-fibrotic effects on atrial myocardium and increase the risk of developing atrial fibrillation. Both peri-atrial fat volume and density have been proposed as markers for atrial fibrillation risk, but prior studies considered only single-plane analysis or peri-atrial fat attenuation limited to the posterior left atrium. PURPOSE: We aimed to assess total peri-atrial fat volume and attenuation and to explore the relationship between both parameters and the occurrence of atrial fibrillation. METHODS: Contrast-enhanced cardiac computed tomography (CT) imaging was performed pre-ablation in atrial fibrillation patients (n=32) and in control patients (n=37) without atrial fibrillation undergoing investigation for chest pain. We developed a volumetric method for peri-atrial fat segmentation and quantification using seg3D2 and CEMRGapp. Peri-atrial fat volume and attenuation (Hounsfield units, HU) were compared between patients with and without atrial fibrillation in univariable and multivariable analyses. A sensitivity analysis was performed to assess the impact of fat proximity to the left atrial wall. RESULTS: Atrial fibrillation participants were older (64±11 years vs 58±7 years, P=0.004) and more likely to have a history of coronary artery disease (50% vs 25%, P=0.03). Participants with atrial fibrillation had greater left atrial volume (88±28 ml vs 69±19 ml, P=0.002) and mass (29±6 g vs 14±0.9 g, P=0.018) compared to controls. Peri-atrial fat volume was greater in those with than without atrial fibrillation (18.5±6.6 ml vs 14.2±7.0 ml, adjusted odds ratio (AOR) per ml 1.21; 95% confidence interval [CI] 1.03-1.48), after adjusting for age, body mass index, comorbidities, left atrial dimensions and mass. However, total peri-atrial fat attenuation was not significantly different between groups (-74.8 vs -73.0 HU; AOR per HU 1.01; 95% CI 0.82-1.22). Sensitivity analysis did not identify an interaction between interrogation distance from the left atrial wall and peri-atrial fat attenuation on prevalent atrial fibrillation (p=0.872). CONCLUSION: Peri-atrial fat volume, but not attenuation, is associated with prevalent atrial fibrillation. Further mechanistic studies are needed to study the role of peri-atrial fat in atrial fibrillation pathogenesis. [Figure: see text]