An Experimental Study of the Electromotive Forces of the Heart.

P rogress in understanding the relationship between differences in potential measured in a lead and the electromotive forces of the heart has been closely related to the improved understanding of the nature of these forces and the development of the concepts of the lead vector’ and lead field.2 The latter concepts permit us to explain how the electromotive forces of the heart produce voltage in leads in finite and nonhomogeneous media. With regard to the electromotive forces themselves, the studies of Craib and Canfield and Wilson* replaced the crude bipole model proposed by Waller,5 in 1589, with a more sophisticated picture of the heart’s electrical activity as generated by a complex of electromotive surfaces located at the junction between active and resting muscle. At any instant of time this junction constitutes a continuous layer within the confines of the heart, with its positive side toward resting tissue and its negative side toward active tissue. A single element of this surface produces an electrical field equivalent to that produced by a dipole consisting of a point source and point sink of current, of equal size and close to one another. The potential equation for an electromotive surface consisting of two layers placed in a resistive, linear, and isotropic media of infinite size is: