127Diastolic window of interest mapping for fast identification of the critical isthmus in re-entrant ventricular tachycardia
Authors: Kemme M J B , Mulder M J , Allaart C P 
Published: June 2020

Abstract

Background/Introduction
Identification of the critical isthmus in re-entrant ventricular tachycardia (VT) should be fast and accurate as the tachycardia is often tolerated for a limited period of time. Using the standard window of interest (WOI) setting with the beginning and end of the window set at mid diastole, mapping systems may incorrectly annotate far field systolic signals instead of smaller diastolic local bipolar signals. The resulting activation map may not show activation pathways through the scar area.

Purpose
We aimed to study if adjustment of the WOI to the diastolic part of the VT cycle during automatic annotated mapping could aid critical tachycardia isthmus identification.

Methods
Consecutive patients with ischemic cardiomyopathy undergoing endocardial VT ablation between January 2018 and July 2019 were studied. VT mapping was performed using a multipolar mapping catheter. All signals were automatically annotated using the algorithm provided by the 3D mapping system which uses the maximum negative slope of the unipolar signal (-dV/dT) concomitant with a bipolar signal to calculate local activation times. Location of the critical isthmus was either identified or confirmed by pacing showing concealed entrainment. Acquired maps were analysed retrospectively using three methods: (1) automatically annotated using conventional WOI settings with onset of the window fixed in mid-diastole and a window duration spanning the tachycardia cycle length minus 20 ms, (2) similar conventional WOI settings with manual correction assuring annotation of the near field signal and (3) automatically annotated with an adjusted WOI focused on the diastolic part of the VT, thus excluding its systolic part.

Results
Forty ischemic cardiomyopathy patients underwent endocardial VT ablation, of which 8 procedures were identified that included activation mapping of re-entrant VT’s. Using conventional WOI settings, local activation was automatically annotated on far field instead of the actual local bipolar activation signal in a mean of 92 (14%) points, range 17 to 260 (3 to 21 %). In all cases, the resulting map did not show diastolic pathways through the scar (Figure A). After manual correction of annotated signals, maps depicted pathways through the scar area (Figure B). All automatically annotated maps with a diastolic WOI indicated the location of the critical isthmus (Figure C). Diastolic pathways are shown by isochronals coloured red/yellow (early diastolic entry) going over in green to light blue (mid-diastolic) adjacent to blue (late diastolic) to pink (exit area), instead of blue/pink and red/yellow (‘early meets late’) during standard WOI mapping.

Conclusions
Diastolic WOI mapping improves rapid critical isthmus identification in re-entrant ventricular tachycardia, without the need for manual correction. Resulting activation maps may require familiarisation as colour coding differs from standard WOI maps.
Abstract Figure. Standard versus diastolic WOI map