Abstract 2347: Atrial Fibrillation Due to Mitral Valve Disease, but Not Lone Atrial Fibrillation is Associated With Increased Left Atrial Fibrosis
Introduction: Surgical procedures for AF are less effective in patients with mitral valve disease (MVD) than in patients with lone AF. Left atrial structural changes due to MVD are likely to be responsible. Because atrial fibrosis constitutes a substrate for AF, we hypothesized that left atrial fibrosis is more pronounced in patients with AF and mitral valve disease (AF+MVD) compared to patients without AF or with lone AF.
Methods: Left and right atrial appendages (LAA and RAA) amputated during Maze III surgery for lone AF or AF+MVD (5 patients in each group) were embedded in paraffin. Atria from 10 post-mortem patients without a cardiac history served as a control. A total of 160 random images (4 μm sections, Picro Sirius Red staining, 10-fold magnification) were obtained and digitalised. The percentage of fibrous tissue was calculated by quantitative morphometry. Perivascular and subepicardial fibrous tissue were excluded from analysis.
Results: The control group showed that the amount of fibrous tissue in the LAA en RAA is representative for the free wall of the left and right atrium. The fibrous content of the LAA and RAA combined was higher in patients with AF+MVD than in patients with lone AF and in the control group (13.6±1.2 % vs. 8.4±1.0 % and 7.1±0.7%, p<0.01, mean±SEM). This difference was mainly caused by an increase in the LAA (12.0±1.8% vs. 6.4±1.0% and 5.9±0.7, respectively, p<0.01). Fibrous content in the RAA of the AF+MVD group was increased compared to the control group (15.2±2.0% vs. 8.2±1.2%, p<0.01). However, the amount of fibrous tissue in the LAA and/or RAA was not different between the lone AF and control group. Overall (three groups combined), more fibrous tissue was present in the RAA than in the corresponding LAA (10.5±1.0% vs. 7.6±0.7%, p<0.01).
Conclusions: This study shows that patients with AF and MVD have more atrial fibrous tissue than patients with lone AF and controls, especially in the LAA. The amount of fibrous tissue does not differ between patients with lone AF and controls. In addition, the study suggests that
AF secondary to MVD is more dependent of structural remodeling than lone AF and
that decreased anti-arrhythmic surgical efficacy for AF with MVD is likely explained by extensive atrial structural changes.