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

Characterising mid-myocardial substrate during ventricular tachycardia (VT) ablation is challenging.

We evaluated how electrode spacing, multipolar signal annotation, and functional mapping affect the identification of conduction delay over endocardial and mid-myocardial substrate.

18 patients with ischaemic cardiomyopathy underwent VT ablation with co-registered MRI scar models. Substrate was mapped in sinus rhythm (SR) and after a single sensed extra-stimulus (SE) from the right ventricle. Twelve patients (bipolar [BP] group) were mapped with both short-spline (Oct-S) and long-spline (Oct-L) Octaray catheters. Six patients (multipolar [MP] group) were mapped with both Oct-S and the OPTRELL catheter (OPT). Points within 1cm geodesic distance of MRI conduction corridors were analysed for late potentials (LPs), conduction velocity (CV), and anisotropic ratio (AR).

Over endocardial substrate, SE mapping increased LP density versus SR for all catheters (Oct-L 6→14%, Oct-S 1→32%, OPT 21→45%; p<0.001). MP annotation identified more LPs than BP over endocardial (27% vs 9%, p<0.001) and mid-myocardial (41% vs 12%, p<0.001) corridors. With BP annotation, median LAT and CV were similar when stratified by corridor depth (p>0.1). With MP annotation, LAT delayed 12 ms per 10% increase in depth in SR and by 7 ms with SE (p<0.001), and CV slowed over mid-myocardial corridors (18cm/s vs 39cm/s, p<0.001). Substrate-adjacent conduction vector heterogeneity was greatest with functional MP mapping (AR: 0.59) and smallest with SR BP mapping (AR: 0.76, p<0.001).

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