Case 3:
A 63 year-old woman with apical hypertrophic cardiomyopathy (HCM)
presented with nearly incessant VT at 115 bpm (RBBB superior axis) that
failed to respond to beta blockers, amiodarone and mexiletine. VT was
controlled with lidocaine that was stopped six hours prior to the study
and she arrived in the EP laboratory in sinus rhythm. PES from the RVa
with up to 3 extra stimuli down to refractoriness following a drive
cycle length of 600 ms failed to induce VT. Polymorphic VT was induced
with 400ms drive cycle length and two extra stimuli requiring external
defibrillation. A substrate modification approach was planned and access
to the LV was obtained by transseptal puncture. Burst pacing from the
rim of the LV apical aneurysm at a cycle lengths of 300 ms readily
induced the previously observed VT (Figure 3, panel A). Entrainment
mapping was consistent with an isthmus at the lateral border of the
aneurysm where the VT was successfully terminated (Figure 3, panel B).
VT was no longer inducible following endocardial and epicardial ablation
targeting the isthmus region.