Using measured intracavitary potentials to spatially map left-ventricular endocardial activation sequences

The objective of this study is to (1) calculate endocardial potentials from measured intracavitary potentials during the QRS complex via an inverse solution and (2) derive endocardial activation maps from the calculated endocardial waveforms. A cylindrical [51×11 mm] intracavitary probe with 57 evenly spaced unipolar electrodes on its surface and 49-58 subendocardial plunge electrodes were used to simultaneously record potentials within the left ventricular (LV) cavity and the LV endocardium, respectively. The data necessary to compute the inverse solution has been assembled for two canines. A volume conductor model is constructed based on the geometry of the probe surface, endocardial surface, and boundary integral equations. The inverse solution was implemented using the Tikhonov zero-order regularization technique. For activation sequences arising from LV apical, LV anterior base, LV posterior base and right ventricular outflow tract pacing, the inverse solution yielded on average relative errors ranging from 0.12 to 0.35. The major endocardial electrical events of excitation were seen in all the inverse maps. Specifically, the earliest site of activation spreads from the location on the endocardium nearest the location of the pacing stimulus. The results from this study indicate that it is plausible to obtain the site of origin of ventricular arrhythmias from simultaneous intracavitary recordings. This is significant because utilization of multi-channel intracavity probe recordings would reduce the time of potentially hazardous left ventricular exploration that is presently required to spatiaIly map ventricular arrhythmias