DEDIFFERENTIATION OF ATRIAL CARDIOMYOCYTES AS A RESULT OF CHRONIC ATRIAL-FIBRILLATION

Chronic atrial fibrillation was induced in goats by electrical pacing. After 9 to 23 weeks of sustained atrial fibrillation, the morphology of the atrial structures was examined. The majority of the cardiomyocy tes exhibited marked changes in their cellular substructures, with the replacement of sarcomeres by glycogen as the main characteristic. Usi ng immunohistochemical staining procedures, we assessed the expression and organization of contractile and cytoskeletal proteins in these ca ses and compared them with the expression and organization of these pr oteins in normal atria. Part of the atrial cardiomyocytes acquired a d edifferentiated phenotype, as deduced from the re-expression of cy-smo oth muscle actin, the disappearance of cardiotin, and the staining pat terns of titin, which resembled those of embryonic cardiomyocytes. Fro m these results we conclude that chronic atrial fibrillation induces m yocardial dedifferentiation. This model of chronic atrial fibrillation in goats offers the possibility to study the time course of changes i n cardiac structure during sustained atrial fibrillation and after car dioversion.