Dynamic spatial dispersion of repolarization is present in regions critical for ischemic ventricular tachycardia ablation

Figures

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  Figure 1. A: High-density (HD) grid and schematic of the HD wave solution. The HD grid consists of 16 equally spaced electrodes arranged in a 4 × 4 grid. Bipolar wavefronts are measured both along and across the splines with the HD wave solution selecting the highest-amplitude signal from 2 orthogonal bipoles, thus obviating the problem of bipolar blindness whereby a wavefront traveling along the splines would record a low-amplitude signal. B: Schematic of the Wyatt method used to measure repolarization time (RT) from the unipolar contact electrogram (UEG) from the HD grid. The Wyatt method measures ventricular depolarization time as dV/dtmax along the upslope of the unipolar electrogram T wave regardless of polarity (upright or inverted). Repolarization time (RT) is measured as the dV/dtmax of the unipolar intracardiac electrogram T wave. AP = action potential; APD = action potential duration; ARI = activation recovery interval; AT = activation time.

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  Figure 2. Unmasking of repolarization delay and repolarization heterogeneity via the sensed protocol in a patient with posterior/septal basal ventricular tachycardia (VT). Blue dots represent the sites of best diastolic entrainment and the black line marks the circuit with superior exit of VT. Black triangles highlight regions from which the unipolar electrogram (EGM) on the right of each map was sampled. Repolarization time (RT) color maps are shown. A: During intrinsic rhythm the repolarization time along the diastolic pathway is homogenous (highlighted measured RT 400 ms). B: During “Sense Protocol” mapping there is late ventricular repolarization in the diastolic pathway of the VT with highlighted unipolar signal (yellow triangle), showing an RT of 434 ms in a region bounded by shorter repolarization times (C), which line the diastolic pathway (RT 187 ms in highlighted signal region). D: Bipolar voltage map showing VT circuit using a scar border zone region. RT is shown on the color bar to the left of each map, and yellow markers on EGM show the annotated RT based on the Wyatt method.

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  Figure 3. A,B: The relationship between ventricular repolarization time and bipolar voltage during sinus rhythm (A) and Sense Protocol (SP) mapping (B). C,D: Ventricular repolarization time within and outside regions of late potentials during sinus rhythm (C) and SP mapping (D).

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  Figure 4. Dispersion of repolarization at sites critical for ventricular tachycardia ablation in regions of normal myocardium and dense scar based on voltage criteria, during Sense Protocol mapping (dark gray) and sinus rhythm mapping (light gray).

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  Figure 5. Example of ventricular tachycardia (VT) circuit relating to repolarization. A: VT wavefront is shown, corresponding to the late ventricular repolarization (B) wavefront during Sense Protocol. B: The late repolarization corridor corresponded to an area of concealed entrainment (C) and is bounded by early repolarization on either side. Black line represents VT circuit.

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  Figure 6. Voltage substrate map in a patient with apical and anterior scar. A: Black triangle highlights an area on the scar border zone with late potentials (LP) shown on the signals to the right. These do not delay on Sense Protocol single extrastimuli. Insets: Clinical ventricular tachycardia (VT) and pace map (lower right), which does not match the clinical VT in this nondecremental LP area. B: Triangle shows a region within the scar where there are hidden LP and LP delay on the electrograms of the HD grid to the right. Pace map in this region (inset) shows a good correlation to clinical VT with stimulus to electrogram time of 166 ms. C: Repolarization color map of the same region is shown, with early repolarization in region from panel A, and late repolarization in region from panel B. The black line marks the course of the clinical VT with superior exit along a region of late repolarization bounded by early repolarization either side. Unipolar electrograms with repolarization time markers are displayed in the electrograms in panel C. Despite LP in both regions, the unipolar T waves are of a different polarity in these nearby regions, resulting in spatial dispersion of repolarization.