PARALLEL-VT: A pilot study of simultaneous multi-wavefront left ventricular mapping for identification of critical...

Functional substrate mapping can identify ventricular tachycardia (VT) ablation targets. Multi-wavefront functional mapping can be laborious. In this study, we explored the feasibility, safety and utility of the new "parallel mapping" algorithm designed to streamline multi-wavefront activation mapping for VT.

This is a single center, prospective pilot study of adults undergoing scar-related VT ablation. Patients underwent endocardial and/or epicardial substrate parallel mapping using 2 distinct activation wavefronts (e.g. right ventricular [RV] and left ventricular [LV] pacing, 8 beats each). Slow-conducting regions were targeted for radiofrequency ablation. Short- and long-term outcomes were analyzed.

Of the 41 ablation subjects, 19 (46.3%) underwent per-protocol parallel mapping. Protocol deviations mostly stemmed from incessant VT necessitating early ablation (n = 9, 40.9%). Most per-protocol treated subjects were male (n = 18, 94.7%) with a mean age of 66 ± 10 years and had a higher prevalence of ischemic heart disease compared to protocol deviations (94.7% vs. 54.6%, respectively, p = 0.005). Primary wavefront mapping was done during RV apical pacing. Secondary wavefront mapping chiefly relied on LV pacing (52.6%). The median procedure duration was 252 min (IQR 190-289). Adverse events occurred in 4 patients (21.1%; at most 1 event directly related to study protocol). In the first year of follow-up, seven (36.8%) individuals received appropriate ICD shocks and three (15.8%) patients died. In exploratory analyses, parallel mapping data appeared most informative in subjects with lateral wall scar.

Parallel substrate mapping using multiple activation wavefronts is a novel, feasible and safe algorithm designed to identify ablation targets in patients with scar-related VT.