Incessant atrioventricular tachycardia involving an accessory pathway: preoperative and intraoperative electrophysiologic studies and surgical correction.

In three patients with incessant supraventricular tachycardia, the anatomic substrate was a left-sided atrioventricular (A-V) accessory pathway. In two patients there was no expression of anterograde conduction through this pathway during spontaneous or induced atrial rhythms. The three patients had had increasingly frequent palpitations for more than 10 years despite adequate antiarrhythmic drug therapy.Preoperative intracardiac studies indicated that a left lateral accessory pathway was utilized in the retrograde limb of supraventricular tachycardia in all three patients. The spontaneous initiation of supraventricular tachycardia was due to (1) frequent spontaneous ventricular premature beats in two patients, (2) increase in sinus rate in two patients, and (3) ventriculoatrial reentry without preceding changes in sinus rate or intracardiac conduction intervals in one patient.At operation the accessory pathway was located in two patients with epicardial and endocardial electrographic mapping and cryothermal mapping. In one patient the His bundle was located with electrographic and cryothermal mapping. The accessory pathway (two patients) or the His bundle (one patient) were cryoablated by freezing over the area of the conducting tissue for 120 seconds at a temperature of ?65 ° C. Attempts to reinitiate supraventricular tachycardia after this procedure were unsuccessful. The operation was without significant morbidity. During follow-up for 3 to 10 months, no patient has experienced any further attacks of supraventricular tachycardia or required antiarrhythmic drugs.These observations confirm that an A-V accessory pathway may be the anatomic substrate for incessant or persistently repetitive tachycardias that may be resistant to medical and pacing therapy. Surgical interruption or cryothermal ablation of part of the reentrant circuit may abolish tachycardia, thus providing proof of the underlying mechanism.