The present study has found that LAV, Total-EAT density and LA-EAT density of recurrent group was significantly higher than the matched groups. In addition, LAV, Total-EAT density and LA-EAT density were independent predictors of AF recurrence. Furthermore, the density of LA-EAT was significantly higher than that of Total-EAT.
The density of inflamed tissues has a higher CT value than that of non-inflamed tissues[23]. We found that Total-EAT and LA-EAT densities were associated with post-ablation recurrence of AF. Each increase in the average CT value of Total-EAT by 1 unit increases the risk of AF recurrence by 1.09 times, and each increase in the average CT value of LA-EAT by 1 unit increases the risk of AF recurrence by 1.12 times. As a part of the visceral adipose tissue in the human body, EAT is located in the pericardial sac and is closely connected to the outer wall of the myocardium[24]. At present, the specific pathogenesis of EAT affecting AF is still unclear, previous studies thought that the occurrence and development of AF may be a process involving multiple factors, including abnormal electrophysiological conduction, EAT secretion of adipokines, EAT activates autonomic nerves, EAT releases inflammatory mediators, etc.[25, 26]. Local inflammatory processes play a role in the pathophysiology of AF. Inflammation markers, such as CRP, IL-6 and TNF-α are related to the occurrence, severity and recurrence of AF after ablation[27–30]. These markers are secreted by EAT, which may have a local pro-inflammatory effect on the adjacent atrial myocardium, thereby promoting the occurrence and development of arrhythmia. In addition, we also found that the density of LA-EAT was significantly higher than that of Total-EAT. Indeed, some studies have pointed out that LA-EAT may be a better independent risk factor associated with AF severity or prognosis than total EAT[31, 32]. Atrial biopsies from patients with AF have shown the infiltration of inflammatory cells[33]. Therefore, the study of the correlation between EAT and recurrence of AF should pay more attention to the role of LA-EAT in it.
Previous studies showed that the volume of the Total-EAT and LA-EAT are associated with AF recurrence after catheter ablation.[34, 35] In our study, the Total-EAT and LA-EAT volumes of patients with recurrence after AF ablation were higher than those of patients without recurrence, but the difference was not statistically significant. Since we balance the confounding factors with PSM, this may indicate that the density of the EAT may more accurately reflect the relationship between EAT and the prognosis of AF.
We also found that the patients with AF recurrence had a larger LA, suggestive of progressive atrial remodeling. Left atrial volume enlargement is risk predictor after ablation of AF because AF causes remodeling and fibrosis of the LA[36]. Cardiac endothelin-1 expression correlates with enlarged left atrium size and responds to the wall stress caused by enlarged left atrium, thus promoting hypertrophy of myocytes and fibrosis of myocardial interstitium. Atrial fibrosis in patches can cause slow conduction and change dynamic repolarization in some areas, consequently shifting the initiation focus and AF maintenance to the left atrium from the pulmonary veins[37, 38]. In this case, radiofrequency ablation may be insufficient, resulting in an increased rate of recurrence.
This study still has certain limitations. This study is a single-center retrospective study with a small sample size. Further study should consider expanding the sample for further confirmation. In addition, PSM can only control known risk factors, and there may be some unknown factors that bias the results, but we have tried our best to control all the indicators that can be collected. Further, Statistics about the time of recurrence should be as accurate as possible in follow-up studies. Conclusion
Total-EAT density, LA-EAT density and LAV were independent predictors of AF recurrence. In addition, the density of LA-EAT was significantly higher than that of Total-EAT. LA-EAT mediated inflammation plays an important role in the prognosis of AF. Therefore, assessment of LA-EAT density can improve ablation outcomes by refining patient selection.