Effects of myocardial infarction on cardiac electrical field properties using a numerical expansion technique.

This study was undertaken to quantify basic cardiac electrical field properties using the Karhounen-Loeve (K-L) numerical expansion technique after experimental myocardial infarction. Transmural anterior myocardial infarction was produced in seven dogs by injection of liquid latex into the anterior descending artery; posterior myocardial infarction was produced in five dogs by injection of the circumflex artery. Body surface potentials from 84 electrodes were recorded during sinus rhythm prior to and 1 week after infarction. Electrical field properties during the QRS, ST, and QRST intervals were computed by the K-L method based upon areas calculated for each lead. The ratio of the sum of magnitude of the first three eigenvectors to the sum of all computed eigenvectors expressed as a percentage was used as a measure analogous to field dipolarity. Values before infarction were high during the QRS (97.1% +/- 2.0%, mean +/- 1SD), ST (96.0% +/- 5.1%), and QRST (97.7% +/- 2.7%) intervals, with no significant difference between the three periods. After infarction, the ratio during QRS decreased significantly, with lower values after posterior (61.9% +/- 11.7%) than after anterior (91.1% +/- 6.0%) infarction (p less than 0.001). Values during ST and QRST intervals were not significantly changed by infarction. Spatial patterns of the first eigenvector indicated that the derived QRS area electric field is directed away from the myocardial lesion for both anterior and posterior infarcts. Thus, experimental myocardial infarction produces significant changes in cardiac electrical field properties as measured by the K-L technique.