Determination of cardiac equivalent generator properties using a numerical expansion method

The ability of the Karhounen-Loeve (K-L) numerical expansion technique to quantitate cardiac dipolarity was assessed using data recorded from fifteen isolated perfused rabbit hearts. Potentials during the QRS complex, registered from thirty-two surface electrodes, were processed to yield percent dipolarity by a potential equation fit as well as by the K-L expansion. A total of 1174 data points was evaluated. The difference in values computed by the two methods equalled 1.02 +/- 6.99% (mean +/- 1 standard deviation); this difference, although small, was statistically significant (P less than 0.01). The correlation coefficient between the two sets of results equalled 0.53 (P less than 0.001). Thus, experimental support is given to the use of the K-L method to assess field dipolarity. Because ranges of differences were high and predictive accuracy of the regression was limited, the K-L expansion may be used with caution to detect directional shifts in equivalent cardiac generator properties.