Myocyte changes and their left atrial distribution in patients with chronic atrial fibrillation related to mitral valve disease.

Summary It has been found that the pulmonary veins and adjacent left atrial posterior wall (LAPW) are deeply involved in both the initiation and maintenance of atrial fibrillation (AF), and the identification of these high-risk sites has aroused great interest in investigating their histopathologic substrate. We used light and conventional electron microscopy to evaluate the differential myocyte and interstitial changes in LAPW and left atrial appendage (LAA) samples from 28 patients with chronic AF undergoing mitral valve surgery and from 12 autoptic controls. There were always more myocytes with loss of sarcomeres in the LAPW than in the LAA (19.9% ± 7.7% versus 8.2% ± 5.0%; P μ m; not significant) but larger than in the controls (11.9 ± 0.8 and 12.1 ± 1.3 μ m, respectively; P P In conclusion, the LAPW in patients with chronic AF related to mitral valve disease seems to be a particular anatomical site in which major myocyte and interstitial changes are concentrated, whereas the LAA is more protected. This remodeling may increase the heterogeneity of LAPW electrical conduction, thus confirming this location as an elective target for the ablation treatment of AF.