Initial Experience with High-density Mapping of Ischemic Ventricular Tachycardia Using a Narrow 0.1-mV to 0.25-mV Border-zone Window

This study sought to determine (1) whether the use of a narrow border-zone voltage of 0.1 to 0.25 mV predicts the ventricular tachycardia (VT) exit site better than when using the conventional 0.5 to 1.5 mV window and (2) the feasibility of utilizing the Rhythmia mapping system (Boston Scientific, Natick, MA, USA) to map hemodynamically unstable VT without hemodynamic support. The Ablation of ischemic VT is challenging especially in the setting of hemodynamic instability, yet efficient and accurate mapping of VT and VT substrate is critical for procedural success. In this study, a total of 24 patients with ischemic cardiomyopathy and recurrent monomorphic VT underwent mapping and ablation using the Rhythmia system. Contact-force sensing ablation catheters were use in two cases. In patients with mappable VTs, the distance between the exit site and border zone was calculated for border zone-voltage windows of 0.5 to 1.5 mV and 0.1 to 0.25 mV. The percentage of LV scar for each patient was visually estimated into quartiles of scar burden in both windows. Twenty patients were inducible into VT, while 15 patients had mappable VTs for a total of 16 VTs (11 stable VTs and five unstable VTs). There were no adverse complications in patients who underwent mapping in unstable VT. The mean distance from the VT exit site to the border zone was 13.3 mm in the conventional window and 3.4 mm in the narrow window (95% confidence interval: 4.0–15.8; p = 0.003). Separately, 94% (15/16) of the VTs were mapped to the narrow border-zone voltage versus 31% (5/16) using the conventional border zone (p = 0.0006). The use of a narrow 0.1- to 0.25-mV border-zone window highlights relevant scar and constitutes a border zone where VT exit sites are frequently located. We also found that exit sites of hemodynamically unstable VTs can be identified without an increase in procedural complications using the Orion catheter (Boston Scientific, Natick, MA, USA).