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

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Abstract
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 is described. The method was used in 3 patients with refractory supraventricular tachycardia. After the procedure 2 patients received an atrioventricular sequential pacemaker. The 1st patient had a cardiomyopathy and intermittent Wolff-Parkinson-White syndrome resulting from a septal accessory atrioventricular pathway associated with a 2 yr history of recurrent reciprocating tachycardia and occasional episodes of atrial flutter/fibrillation. Delivery of a direct current shock resulted in 1st 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/min. 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 2nd patient had coronary artery disease with a history of recurrent episodes of atrial fibrillation for 2 yr. 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/min was present. A permanent pacemaker was implanted. The 3rd patient had a 14 yr history of incessant junctional reciprocating tachycardia. After the shock, sinus rhythm appeared with first degree block and anterograde conduction was evident for the 1st time over a posterior septal pathway which exhibited decremental behavior. The follow-up is 15 mo. in the first 2 patients and 11 mo. in the 3rd. Apparently, the technique used, which does not require open heart surgery, can provide effective treatment in patients with this disabling supraventricular arrhythmia.