PO-05-226 ORTHODROMIC RECIPROCATING TACHYCARDIA RELYING ON ABERRANT CONDUCTION: NEED FOR A LAGER CIRCUIT

Aberrant conduction during orthodromic reciprocating tachycardia (ORT) can prolong the ventriculo-atrial time, which is found essential for reentry in certain situations. To investigate prevalence and different mechanism of aberrancy-dependent ORT. ORT cases relying on aberrancy from 220 our center were searched using following criteria: (1) Multiple episodes with aberrant ECG ; (2) No baseline BBB sinus rhythm; (3) Absence narrow QRS form unless isoproterenol used; (4) Restoration bundle branch giving rise to termination or circuit alteration. ECGs intracardiac tracings study carefully examined. 3 patients (1.4%) showed phenomenon dependence aberrancy. Clinical short time. All accessory pathways (APs) located at anterolateral regions atrioventricular annulus. None them had block. Creating functional block was necessary induce tachycardias. In first patient left (LBBB), a late-delivered premature ventricular contraction (PVC) able advance next A reset tachycardia, diagnostic Meanwhile, restored narrowed complex. Tachycardia then terminated by advanced wavefront reaching insertion site AP refractory. second case, always preceded spontaneous LBBB restoration, V subsequent MA advanced, suggesting anterograde AV node. other case was, induction required both right slow pathway conduction. When given, fast recovered followed made limb again switched pathway. successfully ablated procedure. have been free arrhythmias least 6 months. Extra transseptal time caused be an integral part ORT, explain infrequent late onset unsustainable useful understanding localizing