PO-05-123 UNUSUAL VENTRICULAR ENTRAINMENT RESPONSE IN ATYPICAL ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA (AVNRT): WHAT’S THE MECHANISM?

Ventricular entrainment (V ENT) pacing is one of the most commonly used maneuvers in differential diagnosis narrow complex tachycardia. We encountered a case with consistently short stimulation to atrial minus ventriculoatrial (SA-VA) and corrected post interval tachycardia cycle length (cPPI-TCL) during V ENT which was initially misdiagnosed as atrioventricular reentrant (AVRT). Further electrophysiological study (EPS) confirmed atypical AVNRT bystander accessory pathway (AP). To propose mechanism for but cPPI-TCL SA-VA intervals maneuver not well mentioned before. N/A A 18-year gentleman history left posterior AP ablation done 5 years ago attended our hospital recurrent palpitation. redo procedure scheduled his symptoms. Baseline ECG normal sinus CL 918ms, atrio-His (AH) 74ms, His-ventricular (HV) 40ms, QRS 89ms. AH jump shown by extra stimulus (AEST) at 700 440ms. showed two retrograde activation sequences (RAAS). One concentric earliest (EA) His VA wenckebach 700ms. The other eccentric EA CS 5,6 500ms. SVT induced both or AEST. TCL 310ms, 5,6, 184ms. performed VAV response. PPI- 128ms. delta 58ms. cPPI -TCL 70ms. SA - 70 ms.Figure 1. Initially, recurrence AVRT diagnosed targeting region performed. However, persistently induced. refractory ventricular premature (VPC) then delivered. PVC advanced immediate beat 23ms without resetting This suggested that actually bystander. final AP. Successful slow right inferior extension region. No could be after ablation. For interval, we proposed RAAS due fusion pathway. Atypical can have maneuver.