Body surface distribution of QRS deflection areas in experimental ventricular preexcitation

The utility of QRS isoarea maps for recognition of preexcitation sites was evaluated in chronic experiments in dogs. Pacing electrodes were surgically implanted on the atrium and ventricular sites near the AV ring. Electrocardiograms from 192 torso sites were simultaneously recorded during pacing of the atrium together with each of the ventricular sites. Tiem phase of atrial and ventricular stimuli was varied to yield both preexcitation with clear delta waves and more subtle forms of preexcitation with sites activated earlier than normal but after onset of the normal QRS. QRS area maps were determined by integrating QRS amplitudes at 1 msec intervals over the QRS duration. Results showed a systematic relation between the body surface location of the minimum in the QRS area maps and the preexcitation site. In addition there was a linear relation between the magnitude of maxima and minima in the QRS isoarea maps over different degrees of preexcitation, and the slope of curves showing this relation differed for different sites of preexcitation. Findings suggest that a single display of the QRS isoarea map may permit identification and localization of preexcitation including subtle forms occurring after the onset of the QRS.