Effects of injury to the right ventricular conducting tissue of canine hearts on epicardial activation sequence and electrocardiograms.

The distal right ventricular conducting tissues of 45 canine hearts were experimentally interrupted in various degrees by a transmural incision of the right ventricular free wall, a trans-section of the lateral branches of the right bundle or by injury to the endocardial Purkinje network. Right ventriculotomy caused a slight activation delay (less than 10 msec) of the right ventricle which was restricted to the distal area from the incision, but the delay was not long enough to cause a significant prolongation of the QRS duration in the limb lead ECG. In one experiment, a vertical incision in the middle region induced an exceptional, marked alteration of the right ventricular activation sequence and an apparent prolongation of the QRS duration (16 msec) indicating an incomplete RBBB. However, anatomical analysis revealed that the lateral branches were nearly completely interrupted by the incision. An extensive injury to the Purkinje network extending toward the right ventricular outflow tract by a blunt scalpel caused a local activation delay in the outflow tract, without producing any serious delay resulting in an ECG pattern of RBBB. These results may suggest that right ventriculotomy would induce the RBBB pattern of ECG if lateral branches are extensively injured by the surgical procedure, and that the injury to the Purkinje network extending toward the outflow tract does not play a primary role of genesis of RBBB pattern in ECG.