Abstract 11825: Reduction in Muscle Mass in the Left Atrial Wall is Associated With Atrial Fibrillation

Abstract

Introduction The left atrium (LA) plays a central role in the occurrence of atrial fibrillation (AF). Although many studies have demonstrated that the dilatation or alteration of the wall thickness of the LA, so called LA remodeling, was strongly associated with AF, the detailed mechanism is still unclear. Materials and Methods We retrospectively analyzed all samples of LA wall obtained during cardiac surgery in Juntendo University Hospital from 2014 to 2020. The samples were processed with Masson’s trichrome staining, then layer analysis was performed. The histological data was compared with the clinical background. Results A total of 60 patients’ samples were analyzed. The thickness of the LA wall was 1257 to 6905 μm. Layer analysis of the LA wall demonstrated that the wall thickness was not associated with the volume (R 2 = 0.0287, p = 0.098). Multiple regression analysis determined that the only factor associated with thinning of the LA was the existence of AF (p <0.05). Moreover, LA wall thickness was well correlated with muscle layer thickness (R 2 = 0.744, p <0.001). In addition, the patients who had AF for one year or more showed significant reduction in muscle mass compared to those with AF for less than one year (18.6% vs. 24.3%, p <0.05). Among 36 patients who underwent concomitant Maze procedure during surgery, 9 had recurrent AF at 1 year after surgery. Age (p <0.05), duration of AF (p <0.01), and muscle area (p <0.01) were detected as risk factors for recurrence. Conclusion AF was detected as the only factor associated with a reduction in the cardiac muscle mass in the LA wall. Chronic AF of more than one year’s duration enhanced the risk of reduction in the LA muscle mass. Furthermore, the reduction of the muscle mass was a comorbid factor for the recurrence of AF after the Maze procedure, along with age and duration of AF. Our results indicate that the muscle mass may be a novel predictor indicating the need for the Maze procedure.