Cardiac fiber rotation distorts surface measurements of anisotropic propagation

Anisotropy is often determined experimentally from epicardial propagation measurements. We hypothesize that the direction of wave propagation on the epicardial surface is not aligned with the epicardial fiber orientation, due to intramural fiber rotation. In this paper, we modeled the effect of cardiac tissue fiber rotation on wave propagation. We used a three dimensional computer model of varying thickness with a 120 degree fiber rotation through the thickness. The angle difference between the direction of propagation and fiber orientation was most pronounced for thin tissue, and decreased with increasing tissue thickness. This angle also increased with the time elapsed since stimulation. Finally, we demonstrated that the fiber rotation from epicardium to endocardium results in inaccurate measurements of conduction velocities at the epicardium, particularly in thin tissues.