Histopathologic analysis of atrial tissue in patients with atrial fibrillation: comparison between patients with atrial septal defect and patients with mitral valvular heart disease

BackgroundAtrial fibrillation (AF) in adult patients with atrial septal defect (ASD) accompanies an enlarged right atrium (RA) with a less enlarged left atrium (LA), which is the opposite situation in patients with AF and mitral valvular disease. This study was to compare the histopathological change in the atrium of patients with AF of two different etiologies: ASD and mitral disease.MethodsTwenty-four patients were enrolled. Group 1 included patients with ASD (8), Group 2 included patients with ASD with AF (6), and Group 3 included patients with mitral disease with AF (10). Preoperative atrial volumes were measured. Atrial tissues were obtained during surgical procedures and stained with periodic acid-Schiff, smooth muscle actin, Sirius red, and Masson's trichrome to detect histopathologic changes compatible with AF. The severity of histopathological changes was represented with “positivity” and “strong positivity” after analyzing digitalized images of the staining. We investigated the relationship between the degree of atrial dilatation and severity of histopathological changes according to the groups and tissues.ResultsGroup 2 and Group 3 patients showed a tendency toward an enlarged RA volume and enlarged LA volume, respectively, compared with each others. However, in the histopathologic analysis, “positivity” and “strong positivity” showed no significant positive correlations with the degree of atrial volume in special staining.ConclusionsA similar degree of histopathologic changes was observed in both atria in patients with AF (Group 2 and 3) regardless of the degree of dilatation of atrial volume and disease entities.