Introduction: Post-myocardial infarction (MI) ventricular tachycardias (VT) are typically related to fixed conduction block in transmural or sub-endocardial scars. However, fast VTs with cycle lengths near the refractory period may be linked to functional re-entry in the scar border zone and difficult to target with current ablation techniques.
Purpose: This study aims to (1) describe electroanatomical voltage map (EAVM) characteristics in post-MI patients with fast VTs and (2) assess the relationship between scar border zone size and ablation outcomes.
Methods: Post-MI patients undergoing VT ablation. Fast VT was defined as a VT cycle length (VTCL) = ventricular refractory period at 500ms + max. 30ms. Scar border zones (0.5mv – 2.1/3.0mV BV, dependent on LV remodelling state) were measured on the EAVM and correlated with clinical outcomes.
Results: 138 patients (86% male, LVEF 35±10%, 86% remodelled LV), were included. The median scar border zone size was 27% of the left ventricular endocardial surface. Median VTCL of presenting fast VTs was 275±52ms. Patients with presenting fast VT had a larger border zone than those with slower VT (32% vs. 25%, p=0.01).
Post-ablation, 79 (57%) patients remained inducible for any VT, with 59/79 (75%) being inducible for fast VT. These patients had larger border zones than those inducible for slower VTs (35% vs. 26%, p<0.001). Over a median follow-up of 26 months, 33% experienced VT recurrence, with higher rates in those with above-median scar border zones (40% vs. 24%, p=0.03).
Conclusion: Spontaneous or post-ablation inducible fast VTs are associated with larger scar border zones, which in turn correlate with higher VT recurrence rates. These results suggests that scar border zones play a critical role in (fast) VT substrate and may be difficult to target with current ablation techniques.