[Pathology of atrial fibrillation].

Atrial fibrillation is one of the most common arrhythmias which is associated with various organic heart diseases or systemic disorders. Although a pathological basis for atrial fibrillation has not been clarified, an anatomical substrate corresponding to long-term atrial fibrillation has been recently demonstrated. Age-related changes of the atrial myocardium were frequently observed in healthy people. Quantitative histological study of the sinoatrial node revealed no difference in the reduction of the nodal cells between 12 patients with atrial fibrillation and 21 age-matched controls. The pathological findings of the myocardium including atrial preferential pathways in patients with long-term atrial fibrillation showed depletion of the muscular bundles, fibrosis and fatty metamorphosis of the atrial myocytes. These findings suggest that atrial fibrillation might be related to reentry in the residual muscular bundles including circumferential muscular bundles in the right atrium.