Localization of dual accessory pathways using two equivalent dipoles

Vojko Jazbinsek1, Rok Hren1, Gerhard Stroink2,3,4, B. Milan Horácek3,4 and Zvonko Trontelj1

1Institute of Mathematics, Physics, and Mechanics, University of Ljubljana, Ljubljana, Slovenia; 2Department of Physics, 3Department of Physiology & Biophysics, 4School of Biomedical Engineering, Dalhousie University, Halifax, Canada

One of the most often used approaches to solving the inverse problem in electrocardiography and magnetocardiography involves calculating the position and moment of an equivalent single dipole source in the model of the human torso. The equivalent single dipole approximation is adequate only when cardiac activity is confined to a single relatively small volume, e.g., arising due to ectopic foci and accessory pathways between the atria and ventricles. In the presence of multiple ventricular events more complex equivalent generators would achieve better accuracy, and, therefore, a better understanding of the underlying cardiac process. This is particularly important in localizing those accessory atrio-ventricular connections presented in Wolff-Parkinson-White syndrome that consist of dual parallel fibers.

In this study, we investigated whether an equivalent generator consisting of two dipoles could be used to detect dual sites of ventricular activity. A computer model of the human ventricular myocardium was used to simulate activation sequences initiated at 8 different pairs of sites positioned on the epicardial surface of the atrio-ventricular ring. From these sequences, 117-lead body surface potentials (covering the anterior and posterior torso) and 64-lead magnetic field maps (above the anterior chest) were simulated and were then used to localize dual accessory pathways employing pairs of equivalent dipoles. Average localization errors were, respectively, 10 mm and 9 mm when using body surface potentials and magnetic field. Results of our study suggest that the inverse solution for two dipoles could provide additional information on dual accessory pathways prior to electrophysiological study.

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