Comparison of combined substrate-based mapping techniques to identify critical sites for ventricular tachycardia ablation

Background: Established electroanatomic mapping techniques for substrate mapping for ventricular tachycardia (VT) ablation includes voltage mapping, isochronal late activation mapping (ILAM), and fractionation mapping. Omnipolar mapping (Abbott Medical, Inc.) is a novel optimized bipolar electrogram creation technique with integrated local conduction velocity annotation. The relative utilities of these mapping techniques are unknown. Objective: The purpose of this study was to evaluate the relative utility of various substrate mapping techniques for the identification of critical sites for VT ablation. Methods: Electroanatomic substrate maps were created and retrospectively analyzed in 27 patients in whom 33 VT critical sites were identified. Results: Both abnormal bipolar voltage and omnipolar voltage encompassed all critical sites and were observed over a median of 66 cm² (interquartile range [IQR] 41.3–86 cm²) and 52 cm² (IQR 37.7–65.5 cm²), respectively. ILAM deceleration zones were observed over a median of 9 cm² (IQR 5.0–11.1 cm²) and encompassed 22 critical sites (67%), while abnormal omnipolar conduction velocity (CV <1 mm/ms) was observed over 10 cm² (IQR 5.3–16.6 cm²) and identified 22 critical sites (67%), and fractionation mapping was observed over a median of 4 cm² (IQR 1.5–7.6 cm²) and encompassed 20 critical sites (61%). The mapping yield was the highest for fractionation + CV (2.1 critical sites/cm²) and least for bipolar voltage mapping (0.5 critical sites/cm²). CV identified 100% of critical sites in areas with a local point density of >50 points/cm². Conclusion: ILAM, fractionation, and CV mapping each identified distinct critical sites and provided a smaller area of interest than did voltage mapping alone. The sensitivity of novel mapping modalities improved with greater local point density.