Localization of the Slow Conduction Zone During Reentrant Ventricular Tachycardia

Abstract

Background-Reentrant ventricular tachycardia is sometimes difficult to treat effectively because localizing the slow conduction zone (SCZ) for catheter ablation may be problematic. It was hypothesized that a linear relationship exists between activating wave-front acceleration and deceleration in the SCZ and, respectively, contractions and expansions of the far-field extracellular signal, which could be used for SCZ localization. Methods and Results-To test the hypothesis, a model was developed to approximate SCZ location on the basis of the time interval between activation at the recording site and shifts in electrogram far-field deflections. Electrograms were recorded during reentry from 196 to 312 epicardial sites (canine model, 8 episodes). Activation maps of reentry were constructed to determine wave-front velocity, and piecewise linear adaptive template matching (PLATM) measured time shifts in far-field electrogram deflections. Linear trends of cycle length change often occurred during tachycardia (mean trend, ϩ15 ms/96.8 cardiac cycles; r 2 ϭ0.92). Alteration in the time interval for activation through the SCZ approximated the change in tachycardia cycle length (mean correspondence, 75.7%). The beginning and end times of far-field extracellular waveform time shifts measured by PLATM predicted the time from recording site activation to activation at the SCZ proximal and distal edges, respectively (mean absolute error with respect to activation mapping, 20.3 ms). Conclusions-During reentry, PLATM estimates the time interval from activation at any recording site near the circuit to SCZ activation. PLATM time intervals are convertible to arc lengths along the circuit for potentially more rapid and accurate update of a hand-held probe toward the SCZ for catheter ablation.

Comprehensive Analyses of Arrhythmogenic Substrates and Vulnerability to Ventricular Tachycardia in Left Ventricular Hypertrophy in Salt-Sensitive Hypertensive Rats

“…19 In terms of determining conduction velocity, the limitation of this study is that we defined conduction velocity as the time from the pacing spike to the MAP onset between the center of LV anterior wall and apex, although recent mapping analysis can determine it accurately. 20,21 In this study, we found that conduction velocity diminished at 13W and 16W, though it was not reduced at 10W. Previous studies have shown that conduction velocity is somewhat enhanced early in the hypertrophic process, 6 and that this is related to decreased intercellular junctional impedance and enhanced connexin expression.…”

Characteristics of Wavefront Propagation in Reentrant Circuits Causing Human Ventricular Tachycardia

“…1,2,8,19 Mapping studies performed on intraoperative patients 20 and explanted hearts 21,22 and during catheter mapping [3][4][5][6][7] indicate that although tissue excitability and the cellular action potential may be normal in the infarcted human heart, 23 regions of myocardium forming the diastolic pathway have abnormal conduction properties, but these studies lack the resolution to show which regions of the circuit are responsible for the greatest slowing of conduction. Although anisoptropy, 19 wavefront turning, 10,13 and other factors have been shown to affect conduction in animal studies, which of these factors predominate in causing slowing of conduction in human VT remains uncertain.…”

“…1,2 Mapping studies of the infarcted human left ventricle (LV) have confirmed that ventricular tachycardia (VT) is dependent on slowing of conduction through a discrete, largely endocardial diastolic pathway bordered by lines of conduction block [3][4][5][6][7] ; the precise location and mechanism of conduction slowing within the diastolic pathway are unknown. Slow conduction is necessary to maintain reentry 8 but also occurs in regions prone to conduction block. 9 Understanding the mechanisms of slow conduction in human VT will assist in recognition and localization of regions of circuits most prone to conduction block and termination of tachycardia.…”

Development of Gradient Descent Adaptive Algorithms to Remove Common Mode Artifact for Improvement of Cardiovascular Signal Quality

“…5,7,8,[12][13][14] At convergence to the optimal weighting, the final weighting is a quantitative measure of the degree of similarity between the two signals. APM has been shown to be useful in cardiovascular research for prediction of the location of reentrant ventricular tachycardia 7,8,[12][13][14] and for region-finding in biomedical magnetic resonance images. 5 In fact, ANC can be considered to be a special case of APM in which the pattern (reference signal) is matched to the input (desired signal) discrete point by discrete point for an indefinite interval.…”