[Selective ablation of slow conduction pathway in a patient with atrioventricular nodal reentrant tachycardia].

In a 42-year female with paroxysmal atrioventricular nodal reentrant tachycardia of the type I (slow/fast) verapamil did not prevent it. Verapamil injections terminated tachycardia but marked hypotonia followed. Electrophysiologic study revealed dual conduction pathway within the atrioventricular node that made the substrate for reentrant tachycardia. An effective refractory period od the slow conduction pathway in antegrade direction was less than 220 msec. An effective refractory period of the fast pathway in antegrade and retrograde directions was 300 msec. Radiofrequency current ablation was performed at the site of slow pathway morphology electrogram recording. A single application of the radiofrequency current that lasted 40 sec. producing the maximum 60C successively ablated the slow pathway. Follow-up electrophysiologic study before and after atropine administration proved the success of this procedure. No other heart structures were damaged. A 4-month follow-up period did not show tachycardia.