Impact of left atrial appendage fibrosis on atrial fibrillation in patients following coronary bypass surgery

Objectives We aimed to assess the relationship of left atrial appendage (LAA) fibrosis with atrial fibrillation (AF) and postoperative events in patients receiving coronary artery bypass graft surgery (CABG). Background Increased atrial fibrosis has been associated with AF and worse outcome following catheter ablation. Only limited data exists focusing on the impact of LAA fibrosis on AF after CABG. Methods LAA tissue from 164 CABG-patients was stained with Masson-Goldner trichrome. The histological landscape was scanned and segmented into superpixels for software analysis (QuPath). A classification algorithm was extensively trained to detect fibrotic superpixels for quantification. In 43 propensity score matched pairs with AF or sinus rhythm (SR), LAA fibrosis was compared. Moreover, subgroups of mitral valve regurgitation (MR) were analyzed as follows: SR, SR + MR, AF and AF + MR. The predictive value of LAA fibrosis postoperative stroke, postoperative AF and mortality was assessed. Results Fibrotic remodeling (%) showed no significant difference for the total cohort between the SR and AF group (SR: 30.8 +/- 11.4% and AF: 33.8 +/- 16.0%, respectively, p = .32). However, significant fibrotic remodeling was observed for SR and AF subgroups (SR: 27.2 +/- 12.2% vs. AF: 35.3 +/- 13.7%; respectively, p = .049) and between SR and SR + MR subgroups (SR: 27.2 +/- 12.2% vs. SR + MR: 34.9 +/- 9.1%, respectively, p = .027). LAA fibrosis was not significantly associated with postoperative stroke, postoperative AF or overall mortality (all p > .05). Conclusion LAA fibrosis may contribute to an individual arrhythmia substrate for AF in patients with AF but also in those with SR and coincidence of MR. LAA fibrosis was not found to be predictive for clinical events in patients after CABG.