Muscle Thickness and Curvature Influence Atrial Conduction Velocities

Abstract

Electroanatomical mapping is currently used to provide clinicians with information about the electrophysiological state of the heart and to guide interventions like ablation. These maps can be used to identify ectopic triggers of an arrhythmia such as atrial fibrillation (AF) or changes in the conduction velocity (CV) that have been associated with poor cell to cell coupling or fibrosis. Unfortunately, many factors are known to affect CV, including membrane excitability, pacing rate, wavefront curvature, and bath loading, making interpretation challenging. In this work, we show how endocardial conduction velocities are also affected by the geometrical factors of muscle thickness and wall curvature. Using an idealized three-dimensional strand, we show that transverse conductivities and boundary conditions can slow down or speed up signal propagation, depending on the curvature of the muscle tissue. In fact, a planar wavefront that is parallel to a straight line normal to the mid-surface does not remain normal to the mid-surface in a curved domain. We further demonstrate that the conclusions drawn from the idealized test case can be used to explain spatial changes in conduction velocities in a patient-specific reconstruction of the left atrial posterior wall. The simulations suggest that the widespread assumption of treating atrial muscle as a two-dimensional manifold for electrophysiological simulations will not accurately represent the endocardial conduction velocities in regions of the heart thicker than 0.5 mm with significant wall curvature.

Identification of local atrial conduction heterogeneities using high-density conduction velocity estimation

“…As CV is also affected by muscle thickness and wall curvature, these smaller differences in the LA could result in higher CVs. 20 In addition, as morphology of the LA and RA is completely different (smooth vs. trabeculated wall), regional differences between the LA and RA could be expected.…”

Does left atrial epicardial conduction time reflect atrial fibrosis and the risk of atrial fibrillation recurrence after thoracoscopic ablation? Post hoc analysis of the AFACT trial

“…Tissue properties that may impair conduction can be reduced atrial wall thickness, low voltage zones and heterogeneous patterns of conduction. 25 LAECT may, therefore, reflect electrophysiological as well as structural characteristics of the left atrium. The exact distance travelled by the activation front could not be determined from the current data, which precluded actual calculation of conduction velocity.…”

Reduction of Conduction Velocity in Patients with Atrial Fibrillation

“…We only evaluated regional differences in CV between patients with and without AF and not specific areas within each region. As previously mentioned, CV is determined, among other things, by wavefront geometry and muscle thickness [1,2]. The smooth, apparently uniform walls of the LA are composed of multiple layers of differently aligned myocardial fibers, with marked regional variations in thickness [28,29].…”

“…Intra-atrial conduction velocity (CV) is determined by ion channel properties, cellto-cell coupling, wavefront geometry and muscle thickness [1,2]. Areas of reduced CV are associated with initiation and perpetuation of atrial fibrillation (AF) [3].…”