Atrial fibrillation in pure rheumatic mitral valvular disease is expression of an atrial histological change

BACKGROUND: Some of theories try to explain the insurgence of atrial fibrillation (AF) in patients with acute articular rheumatism (AAR). These theories remind the close relation between AF and left atrium, or with valvular vitium degree, or monophasic action potential and histological cardiac structure. In 15 years of work in the academic Department of Heart and Big Vessels in Rome, the Authors studied 243 patients with mitral valvular disease post AAR before and after surgical manoeuvres. MATERIALS AND METHODS: Patients were divided in order to monitor atrium and ventricle morphological and functional modifications of the valve according to cardiac rhythm. Patients classification was based on surgical therapy adopted, kind of mitral disease and cardiac rhythm. An histological examination was performed, only in patients treated with valvular replacement. During the operation an histological examination in an atrial tissue fragment was performed. 243 patients with mitral valvular disease post AAR with indication in valvular adjustment were studied. The whole population was treated with mitral transcutaneous valvuloplasty (Group B--130 patients) or with mitral valve replacement surgery (Group A--113 patients). These two groups were divided: in Gr.A in Gr.A1 and Gr.A2, and Gr.B in Gr.B1 and Gr.B2, according to cardiac rhythm (sinus rhythm iSR, AF). These subgroups were also divided in Gr.A1SR, Gr.A1AF; Gr.A2SR, Gr.A2AF; Gr.A3SR, Gr.A3AF, according to mitralic disease's kind (stenosis, stenosis/regurgitation, regurgitation). A complex screening were exerted to all patients using echocardio-doppler technology. Morphological parameters of atrium and ventricle, and functional parameters of mitral valve, aorta and tricuspid were evaluated. In Gr.A group patients during the operation were execute a bioptic sampling from left atrium and a consecutive histological valuation. RESULTS: In Gr.A1 mitral valve area (MtVA) arises smaller (p<0.01) in the group with AF, than those in SR. On the contrary, in subgroups of population of Gr.B there isn't statistic disagreement (p>0.05). Left atrium volume arises elder in patients in AF than in patients in SR (p<0.01), either in patients of subgroups Gr.A1, Gr.A2 or in patients of the whole Gr.B before and after valvuloplasty. In the whole population Gr.B, either Gr.BRS or Gr.BFA, left and right atrial volumes decrease eloquently (p<0.01) after valvoplasty. There's no linear relationship (Pearson r<0.5) between the different subgroups of Gr.A (Gr.A1, Gr.A2, Gr.A3) and those of Gr.B according to mitral valve area (MtVA), volume and left atrial area. Left atrial biopsy shows in patients of SR a normal atrial tissue in the 48% of cases and lightly altered in remaining 52%. On the contrary in patients of AF there are strong anomalies in the 100% of cases. CONCLUSIONS: According to histological view, atrial volumes variations and valvular area variations before and after surgical treatment, and according also to their comparisons in different groups, authors could assume that insurgence of AF and its chronicization could be an expression of a strong atrial myocardial histological alteration. Furthermore while starting moment of AF genesis is characterized by histological alterations of atrial myocardium (expression of rheumatic chronic disease), its chronicization hands to anatomic-volumetric progressive deterioration of the atrial dysfunction.