Objectives: Assessment of fibrotic remodeling of the left atrial appendage in association with atrial fibrillation and postoperative events.

Background: Increased atrial fibrosis has been associated with atrial fibrillation (AF) and higher AF recurrence rates post ablation. However, the impact of fibrosis of the left atrial appendage (LAA) on atrial fibrillation and postoperative events remains unexplored.

Methods: Histologically sectioned LAA tissue from 164 coronary heart disease (CHD) patients was stained with Masson-Goldner trichrome and quantified using QuPath bioimaging software. Out of 164 Patients, LAA fibrosis of 43 propensity score matched subjects with atrial fibrillation and sinus rhythm were compared. Further comparison of subgroups was performed, to consider MR (mitral regurgitation) separately: SR, SR+MR, AF and AF+MR. Additionally, the associations between LAA fibrosis and mortality, postoperative stroke and postoperative atrial fibrillation were assessed.

Results: Subgrouping showed significant fibrotic remodeling when comparing patients with SR and patients with AF (27.24% ± 12.22% and 35.26% ± 13.68%, p=0.049) and when comparing patients with SR and patients with SR+MR (27.24% ± 12.22% and 34.87% ± 9.14%, p=0.027). Follow-up data suggest there is no association between LAA fibrosis and mortality, postoperative stroke or postoperative atrial fibrillation.

Conclusion: AF or MR are associated with increased LAA fibrosis and may act as a structural substrate inducing atrial fibrillation. LAA fibrosis does not contribute towards mortality, postoperative stroke or postoperative atrial fibrillation.