Biophysical Tissue Characterization of Ventricular Tachycardia Substrate With Local Impedance Mapping to Predict Critical Sites.

ABSTRACT

BACKGROUND: New tools are needed to improve ventricular tachycardia (VT) substrate characterization and optimize outcomes. LI provides biophysical tissue characterization. OBJECTIVES: The purpose of this study was to test local impedance (LI)-based mapping to predict critical ventricular tachycardia components after myocardial infarction (MI). METHODS: One month after a nonreperfused anterior MI, endo-epicardial high-density electroanatomic mapping and endocardial LI mapping were performed in 23 Landrace Large X White pigs. LI thresholds were set using the blood pool value to define a 10 Ω range low (<blood pool -1Ω), intermediate (≥blood pool -1Ω and ≤blood pool +9Ω), and high (normal) tissue resistance (>blood pool +9Ω). RESULTS: Low LI was detected in low-voltage areas in 100% of cases, but intermediate LI was found in both core (87%) and border zone (12.5%) voltage areas. A total of 17 VTs were induced (VT isthmus identified in 9 animals). VT inducibility was associated with the size of intermediate LI area (OR 1.19 [95% CI 1.0-1.4]; P = 0.039) and the presence of specific LI patterns LI corridor (OR 15.0 [95% CI 1.3-169.9]; P = 0.029); LI gradient (OR 30.0 [95% CI 2.1-421.1]; P = 0.012), high LI heterogeneity (OR 21.7 [95% CI 1.8-260.6]; P = 0.015), and presence of ≥2 low LI regions (OR 11.3 [95% CI 1.0-130.2]; P = 0.053). Potential VT isthmuses were in areas of intermediate LI and colocalized to LI patterns associated with VT inducibility in all cases (LI corridors or LI gradient). Low LI regions did not actively participate in the VT circuit (0%). CONCLUSIONS: LI mapping is feasible and may add useful characterization of the VT substrate. Specific LI patterns (ie, corridors, gradients) were associated with VT inducibility and colocalized with the VT isthmus, thus representing a potential new target for ablation in substrate-based procedures.