Noninvasive electrocardiographic imaging of chronic myocardial infarct scar

Abstract

Background Myocardial infarction (MI) scar constitutes a substrate for ventricular tachycardia (VT), and an accurate delineation of infarct scar may help to identify reentrant circuits and thus facilitate catheter ablation. One of the recent advancements in characterization of a VT substrate is its volumetric delineation within the ventricular wall by noninvasive electrocardiographic imaging. This paper compares, in four specific cases, epicardial and volumetric inverse solutions, using magnetic resonance imaging (MRI) with late gadolinium enhancement as a gold standard. Methods For patients with chronic MI, who presented at Glasgow Western Infirmary, delayed-enhancement MRI and 120-lead body surface potential mapping (BSPM) data were acquired and 4 selected cases were later made available to a wider community as part of the 2007 PhysioNet/Computers in Cardiology Challenge. These data were used to perform patient-specific inverse solutions for epicardial electrograms and morphology-based criteria were applied to delineate infarct scar on the epicardial surface. Later, the Rochester group analyzed the same data by means of a novel inverse solution for reconstructing intramural transmembrane potentials, to delineate infarct scar in three dimensions. Comparison of the performance of three specific inverse-solution algorithms is presented here, using scores based on the 17-segment ventricular division scheme recommended by the American Heart Association. Results The noninvasive methods delineating infarct scar as three-dimensional (3D) intramural distribution of transmembrane action potentials outperform estimates providing scar delineation on the epicardial surface in all scores used for comparison. In particular, the extent of infarct scar (its percentage mass relative to the total ventricular mass) is rendered more accurately by the 3D estimate. Moreover, the volumetric rendition of scar border provides better clues to potential targets for catheter ablation. Conclusions Electrocardiographic inverse solution providing transmural distribution of ventricular action potentials is a promising tool for noninvasively delineating the extent and location of chronic MI scar. Further validation on a larger data set with detailed gold-standard data is needed to confirm observations reported in this study.

Cardiac stereotactic body radiation therapy for ventricular tachycardia: Current experience and technical gaps

“…[47][48][49][50] Technically, the use of ECGI to delineate myocardial scar has been validated using MRI and voltage mapping. 47,51,52 Clinically, the literature on ECGI is comprised of single-center case reports with robust clinical validation still forthcoming. One technical limitation of ECGI is that it does not have sufficient resolution to differentiate between low-amplitude signal at critical isthmus sites and highamplitude far field signals.…”

Validation and Opportunities of Electrocardiographic Imaging: From Technical Achievements to Clinical Applications

“…For VT mapping, a small number of human studies have investigated the use of ECGI to map the exit sites and activation pattern of reentry circuits, using both epicardial ECGI ( Wang et al, 2011 ; Sapp et al, 2012 ; Zhang et al, 2012 ) and more recently using epicardial-endocardial and 3D ECGI ( Tsyganov et al, 2017 ; Wang et al, 2018 ). For substrate mapping, while the use of ECGI to delineate myocardial scar has been validated using MRI or voltage mapping ( Cuculich et al, 2011 ; Wang et al, 2013 ; Horáček et al, 2015 ), studies are just emerging to examine its ability to reveal local abnormal electrograms, such as fractionated electrograms, that are suggestive of potential central pathways forming the VT circuit ( Wang et al, 2018 ). In all of these studies, a significant challenge arises from the difficulty to establish the clinical ground truth for the exit sites and central pathway for VT; as a result, most existing validation studies are limited to qualitative or semi-quantitative evaluations.…”

Statistical guidance of VT ablation

“…Ideally, ECGI or reduced ECG-based approaches such as that presented by Zhou et al 6 would identify not just potentially critical sites, but ranges of voltages, potential (and not just realized) isthmuses, scar areas, 17 and other functional measures of arrhythmic vulnerability. 18,19 …”

“…Ideally, ECGI or reduced ECG-based approaches such as that presented by Zhou et al 6 would identify not just potentially critical sites, but ranges of voltages, potential (and not just realized) isthmuses, scar areas, 17 and other functional measures of arrhythmic vulnerability. 18,19 However, the optimal set of structural data needed to reconstruct cardiac electrical activation in this way is undefined. A major unresolved issue is to provide direct measures of conductivity and their potential rate dependence (restitution) of different tissues within the thorax, which should improve the inverse solution.…”