Closed chest modification of atrioventricular conduction system in man for treatment of refractory supraventricular tachycardia.

We describe a technique for interruption/modification of atrioventricular conduction using a direct current shock delivered from a defibrillator to the atrioventricular junctional tissue by means of a conventional electrode wire. The method was used in three patients with refractory supraventricular tachycardia. After the procedure two patients received an atrioventricular sequential pacemaker. The first patient had a cardiomyopathy and intermittent Wolff-Parkinson-White syndrome resulting from a septal accessory atrioventricular pathway associated with a two year history of recurrent reciprocating tachycardia and occasional episodes of atrial flutter/fibrillation. Delivery of a direct current shock resulted in first degree atrioventricular block resulting from conduction delay proximal to the recorded His bundle deflection. Atrial pacing at a cycle length of 580 ms resulted in 2: 1 block and ventricular pacing showed no retrograde conduction. The patient has done well without pacemaker implantation and remains free from reciprocating tachycardia. During atrial flutter/ fibrillation, the ventricular rate ranged from 62 to 75 beats/minute. These results are consistent with modification of the atrioventricular node-His bundle, and complete ablation of conduction over the septal accessory pathway in both the anterograde and retrograde direction. The second patient had coronary artery disease with a history of recurrent episodes of atrial fibrillation for two years. Delivery of a direct current shock resulted in persistent complete atrioventricular block and neither anterograde nor retrograde conduction was present during atrial and ventricular pacing, respectively. During a sustained episode of atrial flutter, complete atrioventricular block with a ventricular rate between 40 and 48 beats/minute was present. A permanent pacemaker was implanted. The third patient had a 14 year history of incessant junctional reciprocating tachycardia. After the shock, sinus rhythm appeared with first degree block and anterograde conduction was evident for the first time over a posterior septal pathway which exhibited decremental behaviour. The follow-up is 15 months in the first two patients and 11 months in the third. We conclude that the technique used, which does not require open heart surgery, can provide effective treatment in patients with this disabling supraventricular arrhythmia.