Relating epicardial to body surface potential distributions by means of transfer coefficients based on geometry measurements
Advances in experimental capabilities have made possible the nearly simultaneous measurement of both cardiac epicardial and corresponding body surface potential distributions from in vivo animal preparations using chronically implanted electrodes to keep the volume conductor intact. A method for finding transfer coefficients that relate these potential distributions to each other is based on knowing the geometric location of each electrode, and on having enough electrodes to establish the geometric shape and the potential distribution of closed epicardial and body surfaces, is described. However, it does not require that either the heart or body surfaces have any special shape, or that any electrical quantities, such as voltage gradients, be known in addition to the potentials. The use of potential distributions to represent heart electrical activity is advantageous since such distortions can be directly measured experimentally, without transformation to any other form. This report includes a statement of the underlying integral equations, the procedure for finding the equations' coefficients from geometry measurements, some considerations for computer algorithms, and an example. The mathematical method also can be used for considering the potential distributions around small cardiac structures
