Pacemaker-mediated tachycardias: a new modality of treatment.

Three patients with pacemaker interactive drug resistant tachycardia underwent invasive electrophysiological studies. In the first patient, the retrograde conduction of the artificial reciprocating tachycardia was provided by two right-sided accessory pathways and the antegrade conduction by an atrial synchronous pulse generator. In addition, AV-nodal tachycardia occurred alternately. In the second patient with intermittent atrial flutter, the AV node and, coincidentally, an AV sequential pulse generator provided high-rate antegrade conduction to the ventricles. In the third patient with surgical complete heart block, intermittent AV-nodal tachycardia induced retrograde atrial activation while an atrial synchronous pacemaker provided the antegrade conduction. Electrode catheter exploration of the heart allowed localization and closed-chest ablation of the accessory pathways or AV node by delivering two to seven 200-joule direct-current shocks through the appropriate electrode of the exploring catheter. Thereby, pacemaker-mediated arrhythmias could be controlled in these patients in the follow-up of 6 to 8 months.