Session P7C.1

Effect of Ectopic Focus Frequency on Fibrillatory Conduction in Atrial Remodelling Tissue: A Simulation Study

C Tobón*, J Sáiz, JM Ferrero, G Moltó, JM Alonso

Universidad Politécnica de Valencia
Valencia, Spain

Atrial fibrillation (AF) is the most common atrial tachyarrhythmia. The presence of AF is associated with a considerable increase in morbidity and in mortality. Despite many years of research, the mechanisms of AF are still poorly understood. It has been observed that pulmonary vein ectopy can trigger reentry in the presence of a vulnerable substrate. It can lead to multiple-circuit reentry and to result in fibrillatory conduction. Experimental studies have suggested the role of high sinus frequency and of rapid focal activity to contribute in the generation of fibrillatory conduction. The objective of this work was to examine the effect of ectopic focus frequency, when a recurrent focus is applied between right pulmonary veins (PVs), in a remodelling atrial tissue. In this study, the effects of remodelling on ionic currents were incorporated in a model of human atrial action potential and were integrated in a two-dimensional (2D) anisotropic model of human left atrial (LA) tissue including orifices for right pulmonary veins (PVs). The cycle length (CL) of ectopic focus was changed, range between 130 ms to 390 ms. The basic cycle length (BCL) of sinus rhythm took values between 300 ms to 1000 ms. Unipolar electrograms (EGs) were computed in back and right lateral wall. Spectral analysis of signals was performed with Fast Fourier Transform (FFT). In all simulations, ectopic activity initiated a stable reentry around PVs. With a relatively slow sinus rhythm (BCL > 800 ms), the reentrant mechanism not lead to fibrillatory conduction, at any ectopic focus frequency tested. Pseudo-EGs shown stable and regular atrial activation, FFT analyses show a similar DF peak in both, posterior and right lateral wall, corresponding with 1:1 activation pattern. With a rapid sinus rhythm (BCL < 800 ms), fibrillatory conduction was generated. Nevertheless, this fibrillatory activity was maintained during all simulation period only to high rates of ectopic activity (CL < 390 ms). In these cases, pseudo-EGs shown unstable and irregular atrial activation and signal polymorphism was greater in proximity to collisions and wavebreaks. FFT analyses show broadbands with multiple frequency peaks. The dominant frequency (DF) was different in back and right lateral wall, indicating CL variations, corresponding to fibrillatory conduction. Additionally, DF was increased when the CL of ectopic focus decreased. The DF range obtained (6.5 – 7.7 Hz) is agreement with the frequencies observed during AF in humans. When the CL of ectopic focus was greater to 390 ms, fibrillatory conduction and the reentry around PVs were finished very quickly (< 1 s). Our study suggests that, the interaction of high frequency ectopic activity and rapid sinus rhythm facilitates the progress from a stable reentrant mechanism to fibrillatory conduction in remodelling atrial tissue.

(Abstract Control Number: 140)