Histological evidence of inflammatory reaction associated with fibrosis in the atrial and ventricular walls in a case-control study of patients with history of atrial fibrillation.

Aims: Chronic inflammation in the atrial myocardium was shown to play an important role in the development of atrial fibrosis in patients with atrial fibrillation (AF). However, it is not clear to what extent atrial inflammatory reaction associated with AF extends on the ventricular myocardium. Our aim was to assess the extent of fibrosis and lymphomononuclear infiltration in human ventricular myocardium and explore its association with AF.
Methods and Results: Medical records from consecutive autopsies were checked for presence of AF. Heart specimens from 30 patients died from cardiovascular causes (64 ± 12 years, 17 men) were collected in three equal groups: no AF, paroxysmal AF, and permanent AF. Tissue samples were taken from the Bachmann's bundle, crista terminalis, posterior left atrium, left ventricle and right ventricle free walls and stained with Masson's trichrome for analysis of fibrosis extent. Immunohistochemistry was performed using antibodies against CD3- and CD45-antigens and quantified as number of antigen-positive cells per 1 mm ² . Fibrosis extent, CD3+ and CD45+ cell counts were elevated in AF patients at all sites (P < 0.001 for all). Fibrosis extent demonstrated correlation with both CD3+ and CD45+ cell counts in the right (r = 0.781, P < 0.001 for CD45+ and r = 0.720, P < 0.001 for CD3+) and the left (r = 0.515, P = 0.004 for CD45+ and r = 0.573, P = 0.001 for CD3+) ventricles. Neither fibrosis nor inflammatory cell count showed association with either age or comorbidities.
Conclusion: Histological signs of chronic inflammation affecting ventricular myocardium are strongly associated with AF and demonstrate significant correlation with fibrosis extent that cannot be explained by cardiovascular comorbidities otherwise.
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