Left atrial epicardial adipose tissue: correlation to left atrial fibrosis and arrhythmia recurrence post atrial fibrillation ablation

Abstract Background Left atrial (LA) fibrosis is a significant contributor to the pathophysiology of atrial fibrillation (AF) and a well-known predictor for arrhythmia recurrence post ablation. LA epicardial adipose tissue (EAT) plays a role in cardiac metabolism, can influence local inflammation and is associated with AF. Recent data suggests that beside LA EAT volume, its status of inflammation, as identified by higher values of attenuation, plays a significant role in the development and maintenance of AF as well. However, data on the association of LA EAT and LA fibrosis are scarce. Aims To evaluate the correlation of LA EAT volume and inflammation with LA fibrosis in patients presenting for first time AF ablation of symptomatic AF. Methods Consecutive patients presenting for first time AF ablation were included. All patients underwent computed tomography one day prior to the ablation procedure. LA area was manually traced and surrounding tissue within 1 cm of the LA, with Hounsfield units (HU) ranging from -195 to -45, was identified as EAT. For identification of study subjects with inflammatory LA EAT changes, the study population was divided by the median HU value. All participants underwent high density mapping of the LA in sinus rhythm for evaluation of general bipolar voltage and for identification of areas of low voltage (<0.5mV) prior to AF ablation. Follow-up and outcome data were collected. Results In total, 107 patients (44% female, age 65±11years, 45% persistent AF) were enrolled. The median LA bipolar voltage and low voltage area were 1.87mV (IQR 0.97-2.70) and 32.63 cm² (IQR 3.98-34.97). Elevated absolute volumes of LA EAT showed a correlation to decreased levels of LA bipolar voltage (r=-0.228; p=0.022) and to increased areas of low voltage (r=0.225; p=0.033). After adjustment for LA volume however, this correlation did not remain significant. Attenuation of LA EAT did not correlate with LA bipolar voltage. After stratification for the median HU value (-91.3), patients with a higher attenuation (≥-91.3 HU) (as a marker for inflammatory changes of the LA EAT) were younger (63±12 vs 68±9 years; p=0.039) and more often male (66 vs 46%, p=0.049), when compared to the study population with lower attenuation (<-91.3 HU). After a median follow up of 13 months (IQR 7-36) 44 patients (41%) experienced arrhythmia recurrence. Patients with higher LA EAT attenuation suffered from a higher rate of arrhythmia recurrence (p=0.030) (Figure 1). Conclusion Higher tissue attenuation as a sign for LA EAT inflammatory changes did not correlate with LA fibrotic changes in patients presenting for AF ablation but is associated with higher rates of arrhythmia recurrence post ablation, when compared to patients with lower attenuation.