Beat-to-beat measurement of epicardial conduction and repolarization anisotropy in vivo in the dog

To examine the dependence of ventricular repolarization on tissue anisotropy in vivo from the epicardial surface, an automated technique was developed to measure activation as well as repolarization from an array of electrodes on a beat-by-beat basis. The preliminary results of this study demonstrate that anisotropic repolarization, as reflected by recovery isochronal maps, appears to spread more rapidly than the previous activation sequence, to be dependent on stimulation rate, and to undergo modulation independent of the underlying activation sequence