Computer simulation and experimental analysis of unipolar epicardial potentials in relation to the direction of propagation of the excitation.

A theoretical model for computer simulation has been introduced to predict the unipolar epicardial potentials corresponding to the different angles of propagation of the excitation wavefront. The simulated waveforms were compared with those observed in the animal experiments. In these experiments three unipolar epicardial potentials and one intramural potential were recorded using a thumbtack electrode with and without bipolar epicardial pacing. The direction of the propagation of the excitation was determined from the arrival time of the recorded waveforms. There was a close correspondence between the observed and the simulated waveforms. Furthermore, it was attempted to establish a quantitative relationship between the unipolar potential waveshape and the angle of propagation theta of the excitation. The difference between the positive and the negative peak normalized by the peak-to-peak height was used to define the change in the waveshape. A distinct relation was found to exist between the normalized difference R and the angle theta for the simulated potentials. There was a good correlation (r = 0.96 for n = 85) between angle theta 1 calculated from the arrival times and theta 2 determined from R, which suggest that the angle theta can be estimated from the unipolar epicardial potentials alone, without using any intramural electrode.