Abstract

BackgroundThe presence of dynamic substrate changes may facilitate functional block and reentry in ventricular tachycardia (VT).ObjectiveWe aimed to study dynamic ventricular repolarization changes in critical regions of the VT circuit during sensed single extrastimulus pacing known as the Sense Protocol (SP).MethodsTwenty patients (aged 67 ± 9 years, 17 male) underwent VT ablation. A bipolar voltage map was obtained during sinus rhythm (SR) and right ventricular SP pacing at 20 ms above ventricular effective refractory period. Ventricular repolarization maps were constructed. Ventricular repolarization time (RT) was calculated from unipolar electrogram T waves, using the Wyatt method, as the dV/dtmax of the unipolar T wave. Entrainment or pace mapping confirmed critical sites for ablation.ResultsThe median global repolarization range (max-min RT per patient) was 166 ms (interquartile range [IQR] 143–181 ms) during SR mapping vs 208 ms (IQR 182–234) during SP mapping (P = .0003 vs intrinsic rhythm). Regions of late potentials (LP) had a longer RT during SP mapping compared to regions without LP (mean 394 ± 40 ms vs 342 ± 25 ms, P < .001). In paired regions of normal myocardium there was no significant spatial dispersion of repolarization (SDR)/10 mm2 during SP mapping vs SR mapping (SDR 11 ± 6 ms vs 10 ± 6 ms, P = .54). SDR/10 mm2 was greater in critical areas of the VT circuit during SP mapping 63 ± 29 ms vs SR mapping 16 ± 9 ms (P < .001).ConclusionVentricular repolarization is prolonged in regions of LP and increases dynamically, resulting in dynamic SDR in critical areas of the VT circuit. These dynamic substrate changes may be an important factor that facilitates VT circuits.

Highlights

  • Ventricular tachycardia (VT) in the context of ischemic heart disease is commonly due to a reentrant arrhythmia using a fixed anatomical structure

  • Regions of late potentials (LP) had a longer repolarization time (RT) during Sense Protocol (SP) mapping compared to regions without LP

  • Ventricular repolarization is prolonged in regions of LP and increases dynamically, resulting in dynamic spatial dispersion of repolarization (SDR) in critical areas of the ventricular tachycardia (VT) circuit

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Summary

Introduction

Ventricular tachycardia (VT) in the context of ischemic heart disease is commonly due to a reentrant arrhythmia using a fixed anatomical structure. Myocardial scar acts as an anatomical substrate, containing within it channels of slow electrical conduction that facilitate reentry. The components of these channels are often dynamic and functional in nature. The presence of dynamic substrate changes may facilitate functional block and reentry in ventricular tachycardia (VT)

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