MRI-guided multipolar functional substrate mapping identifies intramural conduction corridors: The TRAMPOLINE VT...

Characterizing mid-myocardial substrate during ventricular tachycardia ablation is challenging.

We evaluated how electrode spacing, multipolar (MP) signal annotation, and functional mapping affect the identification of conduction delays over endocardial and mid-myocardial substrates.

18 patients with ischemic cardiomyopathy underwent ventricular tachycardia ablation with coregistered magnetic resonance imaging scar models. The substrate was mapped in sinus rhythm (SR) and after a single sensed extrastimulus (SE) from the right ventricle. 12 patients (bipolar [BP] group) were mapped with both short-spline (Oct-S) and long-spline OCTARAY catheters. 6 patients (MP group) were mapped with both the Oct-S and OPTRELL catheters. Points within a 1-cm geodesic distance of magnetic resonance imaging conduction corridors were analyzed for late potentials (LPs), conduction velocity (CV), and anisotropic ratio (AR).

Over endocardial substrate, SE mapping increased LP density vs SR for all catheters (long-spline OCTARAY: from 6% to 14%; Oct-S: from 1% to 32%; OPTRELL: from 21% to 45%; P < .001). MP annotation identified more LPs than did BP annotation over endocardial (27% vs 9%; P < .001) and mid-myocardial (41% vs 12%; P < .001) corridors. With BP annotation, median local activation time and CV were similar when stratified by corridor depth (P > .1). With MP annotation, local activation time was delayed by 12 ms per 10% increase in depth in SR and by 7 ms after SE (P < .001), and CV slowed over mid-myocardial corridors (18 cm/s vs 39 cm/s; P < .001). Substrate-adjacent conduction vector heterogeneity was greatest with functional MP mapping (AR, 0.59) and smallest with SR BP mapping (AR, 0.76) (P < .001).

Functional mapping improved the identification of delayed conduction for all catheters, and MP annotation enhanced the delineation of intramural conduction corridors via the endocardial surface.

NCT05152784.