Abstract
AIMS: Several clinical factors, such as ageing and atrial dilatation, are associated with post-discharge atrial fibrillation (late-POAF) after cardiac surgery, but it is currently unknown if atrial histological characteristics are linked to late-POAF. Therefore, the aim of this study was to determine the association of atrial histological characteristics with POAF incidence and burden during 2.5 years of continuous rhythm monitoring after cardiac surgery. METHODS AND RESULTS: Consecutive patients with and without AF history were prospectively included. Intraoperatively, biopsies were taken of left (LAA) and right atrial appendages (RAA), and all patients received an implantable loop recorder for 2.5 years. Biopsies were analysed for overall and endomysial fibrosis, cardiomyocyte diameter, capillary density and size, and fibroblast density. POAF incidence was defined as any AF episode during the follow-up, while POAF burden was the percentage of time in AF. A total of 133 patients were included (90 without and 43 with AF history). Late-POAF occurred in 53 patients (40.8%). While several histological traits were associated with POAF incidence in the unadjusted analyses, none of the histological traits were significantly associated with POAF incidence after adjustments for clinical confounders. Increased RAA endomysial fibrosis was the only histological trait significantly associated with increased overall (St. Beta = 0.32, 95% CI: 0.06-0.58, P = 0.017) and late-POAF burden (St. Beta = 0.43, 95% CI: 0.13-0.72, P = 0.006) after adjusting for age, sex, type of surgery, reduced LV function, RA volume, and AF history. CONCLUSION: Increased RAA endomysial fibrosis appears to be associated with increased late-POAF persistence, reflected by increased burden, but not with incidental late-POAF recurrences.