Use of the Multipole Expansion to Extract Significant Features of the Surface Electrocardiogram

Electrical activity associated with excitation and recovery of heart muscle is manifest as a time-varying potential distribution on the surface of the body. The surface electrocardiogram may be represented by a multipole expansion. The multipole terms can be derived from the surface potentials, and in turn are related to the cardiac sources. Studies indicate that a substantial portion of the information is contained in the dipole plus quadrupole terms of the multipole expansion. An investigation of one normal subject has revealed that surface isopotential maps reconstructed from the dipole-quadrupole are similar to maps constructed from recordings at several hundred electrodes. Preliminary results indicate that accurate dipole and quadrupole components may be obtained from a lead system utilizing as few as 17 electrodes. A theory for possible refinement of the lead system to correct for body size is presented.