Rearrangement of Atrial Bundle Architecture and Consequent Changes in Anisotropy of Conduction Constitute the 3-Dimensional Substrate for Atrial Fibrillation

Background Anisotropy of conduction facilitates re-entry and is, therefore, a key determinant of the stability of atrial fibrillation (AF). Little is known about the effect of AF on atrial bundle architecture and consequent changes in anisotropy of conduction and maintenance of AF. Methods and Results Direct contact mapping was performed in left atria of goats with acute AF (n=6) or persistent AF (n=5). The degree and direction of anisotropic conduction were analyzed. Mapped tissue regions were imaged by high-resolution MRI for identification of endocardial and epicardial bundle directions. Correlation between endocardial and epicardial bundle directions and between bundle directions and anisotropic conduction was quantified. In persistent AF, epicardial bundles were oriented more perpendicularly to endocardial bundles than in acute AF (% angle