High-resolution noncontact charge-density mapping of endocardial activation
Andrew Grace, … , Günter Scharf, Graydon Beatty
Andrew Grace, … , Günter Scharf, Graydon Beatty
Published March 21, 2019
Citation Information: JCI Insight. 2019;4(6):e126422. https://doi.org/10.1172/jci.insight.126422.
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Clinical Medicine Cardiology

High-resolution noncontact charge-density mapping of endocardial activation

Abstract

BACKGROUND. Spatial resolution in cardiac activation maps based on voltage measurement is limited by far-field interference. Precise characterization of electrical sources would resolve this limitation; however, practical charge-based cardiac mapping has not been achieved. METHODS. A prototype algorithm, developed from first principles of electrostatic field theory, derives charge density (CD) as a spatial representation of the true sources of the cardiac field. The algorithm processes multiple, simultaneous, noncontact voltage measurements within the cardiac chamber to inversely derive the global distribution of CD sources across the endocardial surface. RESULTS. Comparison of CD to an established computer-simulated model of atrial conduction demonstrated feasibility in terms of spatial, temporal, and morphologic metrics. Inverse reconstruction matched simulation with median spatial errors of 1.73 mm and 2.41 mm for CD and voltage, respectively. Median temporal error was less than 0.96 ms and morphologic correlation was greater than 0.90 for both CD and voltage. Activation patterns observed in human atrial flutter reproduced those established through contact maps, with a 4-fold improvement in resolution noted for CD over voltage. Global activation maps (charge density–based) are reported in atrial fibrillation with confirmed reduction of far-field interference. Arrhythmia cycle-length slowing and termination achieved through ablation of critical points demonstrated in the maps indicates both mechanistic and pathophysiological relevance. CONCLUSION. Global maps of cardiac activation based on CD enable classification of conduction patterns and localized nonpulmonary vein therapeutic targets in atrial fibrillation. The measurement capabilities of the approach have roles spanning deep phenotyping to therapeutic application. TRIAL REGISTRATION. ClinicalTrials.gov NCT01875614. FUNDING. The National Institute for Health Research (NIHR) Translational Research Program at Royal Papworth Hospital and Acutus Medical.

Authors

Andrew Grace, Stephan Willems, Christian Meyer, Atul Verma, Patrick Heck, Min Zhu, Xinwei Shi, Derrick Chou, Lam Dang, Christoph Scharf, Günter Scharf, Graydon Beatty

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Figure 1

Spatiotemporal relationships among charge density, voltage, and action potential.

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Spatiotemporal relationships among charge density, voltage, and action p...
(A) The cardiac voltage field arises as a spatially broad summation of local, dipolar charge sources generated by the action of cellular ion channels throughout the myocardium. Charge density (CD; coulombs/cm) represents the magnitude of these sources with reduced contribution from far-field sources. (B) Depiction of a CD waveform overlaid on a corresponding voltage-based EGM that represents the sharper, narrower nature of CD and a 4-fold improvement in temporal resolution over voltage. (C) Area of depolarization shown on a CD map at a specific instant of time, with the red region depicting the associated negative phase of CD. The area-spanning space is correlated with the temporal duration of the negative phase of the CD waveform and with phase 2 of the action potential. (D) Spatial distribution of depolarization area for a CD map displayed beside the corresponding voltage-based map that demonstrates a 4-fold improvement in spatial resolution of CD over voltage. Spatial maps display the magnitude of all points at one fiducial instant of time (t0) corresponding to the yellow time cursor in the waveform in panel E. Propagation is ascertained by animation of the maps from each sample instant through time. PA, posterior-anterior. (E) Temporal CD waveform overlaid on the corresponding voltage-based waveform that demonstrates an average 4-fold improvement in temporal resolution of CD over voltage. Temporal waveforms display the magnitude of one point at all instants of time. The lower-magnitude, fractionated morphology represents localized irregular activation (LIA; see Figure 6A), which is the dominant conduction pattern in AF and for which the resolution of CD is improved the most over voltage. The larger-magnitude, organized morphology represents localized rotational activation (LRA; see Figure 6A), which is a nondominant, regionally organized conduction pattern in AF and for which the resolution of CD is improved over voltage, but less so than noted for LIA. LIPV, LSPV, RIPV, RSPV are left and right inferior and superior pulmonary veins, respectively; MV, mitral valve.