Pediatric/Adult Congenital Heart Disease -> Adult Congenital Heart Disease D-PO02 - Poster Session II (ID 47) Poster

D-PO02-075 - On The Mechanism Of Tetralogy Of Fallot Ventricular Tachycardia: Predicting VT Isthmus In Sinus Rhythm (ID 195)


Background: Empirical ablation in sinus rhythm of Tetralogy of Fallot VTs (TOF VTs) is not usually considered when VT is non-inducible or unstable for mapping. The reason for this is the uncertainty about the anatomic location of critical isthmus (isthmus I- Zeppenfeld et al 2007 Circulation, isthmus III-Kapel et al 2017 EHJ) in TOF VTs and lack of heuristic substrate-based strategies that predict isthmus in sinus rhythm.
Objective: To define the commonest anatomic diastolic isthmus and to determine the utility of decremental evoked potentials (DeEP) to predict VT isthmus in sinus rhythm for TOF VTs.
Methods: A customised RV balloon with 112 electrodes was used to record endocardial activation with patients under cardiopulmonary bypass, fig 1(a). VT Isthmus was defined as I- TA to RVOT patch, II- RVOT patch to PV, III- VSD patch to PV, IV- TA to VSD patch. VT was induced with upto five extra-systoles during a drive train of 400-600ms. The local decrement of EGM during the first extra-systole approaching refractoriness was measured from all electrodes.
Results: In 28 consecutive patients 38 VTs were studied. The mean TCL and diastolic interval were 283 ± 47ms and 88 ± 70ms respectively. The VT axis was predominantly superior 22/38(58%). The commonest diastolic isthmus was at the isthmus between PV and VSD patch (isthmus III) in 60%, fig1(b). Maximum local EGM decrement during extra systole accurately predicted the isthmus location in 17/24 VTs (70%).
Conclusion: The commonest isthmus was between PV and VSD patch. During catheter ablation of TOF VT in sinus rhythm, signal based mapping strategy with DeEP mapping could aid identify the isthmus region.