gms | German Medical Science

Question: Underlying mechanisms of atrial antitachycardial pacing (AATP) with respect to AF are not fully known yet. Computer models of AATP can be used to examine the effect of different electrode positions and pacing strategies on the excitation propagation in AF. Excitation pattern of the whole atrium can be visualized and analysed, being a great advantage to understand the effects of AATP in AF.

Method used: In a computer model of the Visible Female heart (National Library of Medicine, Bethseda, Maryland, USA), 3 ectopic foci situated at the left pulmonary veins were simulated, all creating permanent AF or re-entrant circuits. 36 different virtual electrodes were placed interactively on the right atrium. Pacing was initiated with frequencies ranging between 400 - 1200 bpm to terminate AF. The pacing was stopped after 15 s. Success was defined if normal sinus rhythm was established. The excitation propagation was simulated using an adaptive cellular automaton where electrophysiological parameters depending on tissue types can be set. In this work, only the conduction velocity was reduced.

Results: The initiation of AF through ectopic foci creates re-entrant circuits and quasi-chaotic excitation pattern in the computer model. First results show that the excitation pattern of the fibrillatory atria can be broken up. Slower pacing frequencies show less effect in terminating AF. The electrodes were placed in areas of different excitation pattern during AF, which has an influence on the success of breaking up the pattern.

Conclusion: The effect of breaking up AF over a large area and finally of the whole atrium depends on the excitation pattern around the electrode and the pacing frequency. In the near future, adaptive algorithms will be studied. A validation through clinical studies is due to start. Through the ability to carry out an arbitrary number of pacing algorithms, computer models allow to advance the development of sophisticated pacing algorithms for AATP.