Comparison of isopotential surface mapping and dipole ranging methods for assessing equivalent cardiac generator properties.

The ability of two methods of processing surface electrical potentials to detect nondipolar cardiac activity were compared. These were: 1) visual inspection of surface isopotential contours; and 2) quantitative determination of the cardiac equivalent generator properties of the sensed field using a single moving dipole construct. Data were derived from 26 isolated rabbit heart preparations contained within a spherical test chamber. Results demonstrated that: 1) overtly dipolar isopotential surface patterns were frequently associated with poor quantitative fit of surface potentials by the SMD, with up to 33.3% of recorded summed square (SSQ) potential remaining as nondipolar residual; 2) nondipolar surface patterns existed with as little as 6% of SSQ potential being unattributable to the SMD; and 3) the relationship between isopotential patterns and quantitated dipolarity varied significantly from animal to animal. Thus, these data suggest significant discrepancies between the methods that must be carefully considered when they are utilised to describe electrical field characteristcis.