Optimizing Local Capture of Atrial Fibrillation by Rapid Pacing: Study of the Influence of Tissue Dynamics

Abstract

While successful termination by pacing of organized atrial tachycardias has been observed in patients, rapid pacing of AF can induce a local capture of the atrial tissue but in general no termination. The purpose of this study was to perform a systematic evaluation of the ability to capture AF by rapid pacing in a biophysical model of the atria with different dynamics in terms of conduction velocity (CV) and action potential duration (APD). Rapid pacing was applied during 30 s at five locations on the atria, for pacing cycle lengths in the range 60-110% of the mean AF cycle length (AFCL(mean)). Local AF capture could be achieved using rapid pacing at pacing sites located distal to major anatomical obstacles. Optimal pacing cycle lengths were found in the range 74-80% AFCL(mean) (capture window width: 14.6 ± 3% AFCL(mean)). An increase/decrease in CV or APD led to a significant shrinking/stretching of the capture window. Capture did not depend on AFCL, but did depend on the atrial substrate as characterized by an estimate of its wavelength, a better capture being achieved at shorter wavelengths. This model-based study suggests that a proper selection of the pacing site and cycle length can influence local capture results and that atrial tissue properties (CV and APD) are determinants of the response to rapid pacing.

Estimating the time scale and anatomical location of atrial fibrillation spontaneous termination in a biophysical model

“…In order to permit the simulation of long episodes ([1 min) of atrial arrhythmias and therapeutic interventions [17,18,23], computational requirements were reduced by simplifying these models. In this study, two biophysical models of AF with an identical anatomical structure but with different cellular kinetics were used to simulate AF dynamics with distinct levels of complexity: (a) a model of meandering AF of type I-II according to the classification of Konings et al [11], where only a few reentries circulate on the atria, and (b) a model of multiple wavelet AF [14] that could be classified as type-III AF due to the high number of simultaneous reentries.…”

“…A fine analysis of the dynamical mechanisms can be conducted on different temporal and spatial scales, since all variables of interest are accessible over time and space, including the number of fibrillatory wavelets as well as their trajectories and mutual interactions. We previously developed a biophysical model of human atria and studied different dynamical aspects of AF related to its initiation and perpetuation [8], as well as the feasibility of therapeutic strategies for AF [18,23]. In the present model-based study, we analyzed episodes of spontaneous AF termination to assess the temporal and spatial scales of the mechanisms involved.…”

Modeling of Atrial Fibrillation

“…Simplification of the geometry and membrane model was necessary to enable the simulation of long episodes of atrial arrhythmias [8,9]. Today's computational power allows to run virtual experiments in complex biophysical models, including the simulation of different types of arrhythmias and AF therapies such as ablation [10][11][12], antiarrhythmic drugs [13] and rapid pacing of AF [14]. In this chapter, research in this field is illustrated by a biophysical model developed by the Lausanne Heart Group (http://www.lausanneheart.ch).…”

“…The white arrows represent the direction of propagation of the electrical activity. [10,11,14], thus providing a tool to investigate the mechanisms underlying the success or failure of the therapy and estimate effectiveness in statistical methods.…”

“…Computer modeling permitted a systematic study of ATP algorithms currently used in pacemakers such as burst pacing and a test of the optimal pacing sites and pacing cycle length leading to local capture of AF [14]. As a result a higher ability to sustain capture was found in the right atrial free wall, the left atrial appendage, and the pulmonary veins where the wavefronts induced by pacing encompassed the major part of the paced atrium.…”