Session P91.3

Re-Entrant Mechanisms Triggered by Ectopic Activity in a 3D Realistic Atrial Remodeling Model: A Computer Simulation Study

C Tobón*, C Ruiz, J Sáiz, EA Heidenreich, F Hornero

Universitat Politècnica de València
Valencia, Spain

Atrial fibrillation (AF) is the most common cardiac arrhythmia. However the exact mechanisms of AF initiation and maintenance are not completely understood. The pulmonary veins (PVs) have been found to present the predominant source of ectopic activity involved in the initiation of AF. Extrastimulus around the PVs can result in unidirectional conduction block and reentry. Anatomical structures, spatial heterogeneity and nonuniform anisotropy are the keys to reentrant activity initiation. Atrial remodelling, due to rapid and irregular activation of the atrium during atrial arrhythmias, causes a decrease in refractoriness by significant action potential duration (APD) shortening, leaving the atrium vulnerable to reentrant circuits. In this work the initiation and maintenance of re-entrant mechanisms triggered by ectopic activity are investigated in a realistic 3-dimensional anatomical model of human atrium. The effects of remodelling on ionic currents were incorporated in a 3D anisotropic model of human atrium. A single ectopic focus situated near to right pulmonary veins was simulated. It was applied to high frequency (cycle length of 150 ms) during the repolarization phase of sinus beat. Pseudo unipolar electrograms (EGMs) were computed in ten simulated-electrodes located in backwall of left atrial. The ectopic focus induces a figure-of-eight reentry in backwall of left atrial, with a vulnerable window of 4 ms. In our simulations, one of figure-of-eight reentry vortexes was stabilized and converted in a rotor in left atrial. After, collisions and wave breaks were observed. EGMs polymorphism (variability in size and shape) display complexes of low amplitude with double and fragmented potentials, corresponding to chaotic activity. EGM spectral analysis shows broadbands with multiple frequency peaks, as a consequence of the unstable and irregular electrical activity. Dominant frequencies were similar in all measuring points (7, 9 Hz). In conclusion, in this simulation work, mechanisms of initiation of reentrant patterns of activation in remodelling atrium have been analyzed and the study of EGMs provides relevant information.

(Abstract Control Number: 129)