Closed chest permanent atrioventricular block in dogs

Ten mongrel dogs underwent transcutaneous His bundle ablation by means of pulsed synchronized electrical shocks delivered between an electrode catheter adjacent to the His bundle and a metal plate behind the dog's back. Detailed histologic studies were performed 3 months after induction of stable complete atrioventricular (AV) block in nine dogs. The ventricular response ranged from 35 to 51 beats/min (bpm). Graded increases in overdrive ventricular pacing resulted in graded increases in pacemaker suppression up to a paced cycle length of 450 msec. All dogs showed extensive damage to the approaches to the AV node, the AV node, and the penetrating portion of the common bundle. This technique resulted in complete AV block with typical features of an infranodal pacemaker and correlated with the histologic findings of severe damage to the AV junction. The minimal myocardial damage suggests that this technique may be applicable for control of drug refractory supraventricular arrhythmias in humans.