An Analysis of Transfer Coefficients Calculated Directly from Epicardial and Body Surface Potential Measurements in the Intact Dog

This study dealt with the question of how to estimate body surface potentials from epicardial potential distributions in intact dogs; in particular, the study considered the feasibility of obtaining transfer coefficients directly from sequences of epicardial and body surface measurements of ventricular excitation and repolarization potential distributions, rather than from measurements of the geometry of the volume conductor. The transfer coefficients were calculated from the measured potentials via the mathematical method of using a Bayes estimator. The merit of this approach was that it offered the possibility of accurately representing the characteristics of the volume conductor without directly measuring either the volume conductor's geometry or its inhomogeneities. The experimental protocol made use of measurements from two dogs. Data from the first dog were used to obtain two sets of transfer coefficients, one by the Bayes method as applied to measured sequences of epicardial and body surface potentials, and the other by a method based on the geometric position of each epicardial and body surface electrode. These two sets of transfer coefficients were found to be similar in pattern and value size. Additionally, results of forward simulations in the first dog, based on the measured epicardial potentials and each set of transfer coefficients, were compared to the measured body potentials. The results showed that the simulated potentials were closer to the measured potentials when the transfer coefficients obtained from the potentials were used, rather than when the geometric coefficients were used.