Catheter Ablation -> SVT/AVNRT/WPW/AT: -> Ablation Techniques D-PO05 - Poster Session V (ID 39) Poster

D-PO05-148 - Pseudo-atypical AVNRT Following Failed Left Free Wall Accessory Pathway Ablation: A Case Series (ID 568)

 U.M. Pandurangi: Nothing relevant to disclose.


Background: Inadvertent mitral isthmus block during RFA for left free wall accessory pathway (LFAP) may result in long HA tachycardia which could be misdiagnosed as atypical AVNRT.
Objective: To demonstrate a regular long HA tachycardia could be the result of previously failed ablation for LFAP.
Results: A regular long HA (>100ms) narrow QRS tachycardia was induced (Fig A) in five patients who had previously failed ablation for LAFP mediated AVRT. Ventricular overdrive pacing from RV resulted in VAV response without change in the atrial activation. Corrected PPI-TCL was long (>150ms) and earliest A was in His catheter. Atrial activation along the length of the coronary sinus was near simultaneous and 20-60ms later than the activation at the His catheter (Fig B). A His refractory PVC from RV apex and base did not alter atrial activation suggesting atypical AVNRT (Fig C). However a His refractory PVC delivered from LV advanced atrial activation and reset the tachycardia establishing the true diagnosis of orthodromic tachycardia using LFAP (Fig D). By transseptal approach mitral annulus was mapped for earliest atrial activation during tachycardia. In all cases either anterior or anterolateral mitral annular region showed atrial activation earlier than His catheter (>50ms) (Fig E). RFA at the site resulted in non-inducibility of the tachycardia. Delayed and counterclockwise conduction towards distal pole of CS catheter was demonstrated by pacing near the left inferior pulmonary vein (mitral isthmus block) in all the cases (Fig G and H).
Conclusion: A long HA tachycardia may mimic as atypical AVNRT because of mitral isthmus block caused by previous RFA.