Functional Substrate Mapping and Rotational Activation Patterns in Catheter Ablation for Ventricular Tachycardia : Implications for Treatment Optimization

Abstract

For patients presenting with sustained ventricular tachycardia（VT）originating from structural heart disease, catheter ablation stands as a contemporary imperative therapeutic approach, particularly in scenarios of VT storm or worsening heart failure. Substrate functional mapping delineates the abnormal conduction properties discerned during sinus rhythm and/or ventricular pacing. Areas of decreased conduction velocity are reflected as isochronal crowding（IC）within the three-dimensional electroanatomical mapping system, indicative of the VT circuit substrate, thereby making them optimal sites for ablation. However, in clinical practice, IC may manifest across multiple locations, sometimes appearing as a long-distance band lesion. We have focused on the presence of an area directly above the IC or at the edge of the IC that exhibits an excitation propagation pattern with an inward curvature of 90° or more, which we defined as a rotational activation pattern（RAP）. In a retrospective analysis of 45 VTs in 37 patients who underwent catheter ablation, RAP was found in 70％ of a total of 33 VTs in which the circuit was identified by direct cessation of radiofrequency energy application or by the pace-mapping technique. Notably, in four cases, RAP was absent during baseline rhythm but emerged upon ventricular pacing from different sites, while in six cases, the VT circuit was located in the midmyocardium or epicardium and the VT became inducible following the ablation to the endocardial surface without RAP. Functional substrate mapping plays a pivotal role in catheter ablation procedures targeting VT in patients with structural heart disease, with areas exhibiting RAP potentially representing optimal treatment targets.