Dispersion of Activation in Single-Beat Global Maps During Programmed Ventricular Stimulation Identifies Infarct-Related Ventricular Tachycardia Isthmus Sites

Background: Electrophysiological characterization of ventricular tachycardia (VT) isthmus sites is complex and time-consuming. We aimed at developing and validating a global mapping strategy during programmed ventricular stimulation (PVS) to reveal the underlying electrophysiological properties of the infarct-related substrate and to enable identification of highly heterogeneous activation sites associated with protected VT isthmus sites.

Methods and results: Experimental study that included 22 pigs with established myocardial infarction undergoing in vivo characterization of the anatomical and functional myocardial substrate associated with potential arrhythmogenicity. High-density sequential activation maps during ventricular pacing and VT were compared with single-beat maps using a 64-pole basket catheter positioned in the left ventricle. Further analyses were performed using a novel local activation time-dispersion score to identify regional activation time heterogeneities on both baseline drive pacing and each of the extrastimuli of the PVS protocol. Basket catheter splines covered a median of 81.2% of the endocardial surface of the left ventricle. Basket-catheter-derived single-beat activation maps (N=16) during pacing showed a linear relationship with high-density sequential activation maps. Induction of ventricular arrhythmias was associated with higher local activation time-dispersion score values on single-beat global maps during PVS (N=6, 46 arrhythmia induction attempts). Single-beat-derived local activation time-dispersion score maps during successive coupled extrastimuli of the PVS showed a progressive increase in the predictive performance to identify monomorphic VT isthmus sites within the scar region (area under the curve = 0.779 in S2, area under the curve = 0.859 in S4; N=7).

Conclusions: Sixty-four-pole-derived single-beat local activation time-dispersion score global maps during PVS identify infarct-related endocardial regions with highly heterogeneous activation times that are associated with protected VT isthmus sites.