On the Initial Estimate of Repolarization Times for Inverse Reconstruction Using the Equivalent Dipole Layer Source Model

The equivalent dipole layer (EDL) source model for noninvasive reconstruction of cardiac electrical activity applies a nonlinear parameter estimation procedure starting from an initial estimate of activation and repolarization times. In this paper, we compare two methods to determine the initial estimate for repolarization from that of activation: reversely (method 1) and directly (method 2). In a pig experiment, we found lower errors with higher correlation coefficients between measured and reconstructed repolarization times using method 2 as initial estimate for repolarization for both atrially and ventricularly paced beats. This corresponds with the linear positive relation between measured activation and repolarization time and the discordance of QRS complex and T-wave polarity on the body surface potentials in both atrially and ventricularly paced beats, indicating a similar sequence of activation and repolarization. In human data, there is a big difference in reconstructed repolarization pattern when using method 1 or 2 for initial estimate of repolarization. Here, there is a concordance in the majority of leads for a sinus beat and a discordance in the majority of leads for PVCs. We recommend using the relation of the QRS complex and T-wave to determine which method for initial estimate for the EDL method of the inverse solution is most suitable for each individual beat.