In silico validation of electrocardiographic imaging to reconstruct the endocardial and epicardial repolarization pattern using the equivalent dipole layer source model

Abstract

The solution of the inverse problem of electrocardiology allows the reconstruction of the spatial distribution of the electrical activity of the heart from the body surface electrocardiogram (electrocardiographic imaging, ECGI). ECGI using the equivalent dipole layer (EDL) model has shown to be accurate for cardiac activation times. However, validation of this method to determine repolarization times is lacking. In the present study, we determined the accuracy of the EDL model in reconstructing cardiac repolarization times, and assessed the robustness of the method under less ideal conditions (addition of noise and errors in tissue conductivity). A monodomain model was used to determine the transmembrane potentials in three different excitation-repolarization patterns (sinus beat and ventricular ectopic beats) as the gold standard. These were used to calculate the body surface ECGs using a finite element model. The resulting body surface electrograms (ECGs) were used as input for the EDL-based inverse reconstruction of repolarization times. The reconstructed repolarization times correlated well (COR > 0.85) with the gold standard, with almost no decrease in correlation after adding errors in tissue conductivity of the model or noise to the body surface ECG. Therefore, ECGI using the EDL model allows adequate reconstruction of cardiac repolarization times.

Ex vivo Validation of Noninvasive Epicardial and Endocardial Repolarization Mapping

“…However, given the more complex nature of repolarization compared to activation (i.e., less voltage differences, the effect of cardiac motion, and more difficulty in reliably obtaining gold standards), this is more complicated. In a previous in silico study, we have shown that this method gives accurate results in reconstructing RTs (van der Waal et al, 2020).…”

“…The inverse computation was performed using the EDL method, as previously described in the study by van der Waal et al (2020). A brief explanation is given in this study.…”

“…In the same way, the His-conducted beats up to five additional foci are added until there is no further significant improvement of the correlation. As an initial estimate for repolarization, a pattern that is inversely dependent on ATs is used for atrially paced beats, while for ventricularly paced beats, the activation estimate is used with a time delay, as explained in the study by van der Waal et al (2020).…”

“…This technique combines the recording of multiple body surface ECGs with a patient-specific heart-torso geometry to mathematically reconstruct cardiac electrical activity through the solution of the inverse problem. Several inverse calculation methods exist; the most commonly used methods are the epicardial potential (EP) model (Barr et al, 1977;Rudy, 1999;Ramanathan et al, 2004;Cluitmans et al, 2017) and the equivalent dipole layer (EDL) model (Oosterhoff et al, 2016;Janssen et al, 2018;van der Waal et al, 2020). In contrast to the EP method, the EDL method allows simultaneous calculation of both the endocardial and epicardial activation and repolarization times (AT and RT), thereby identifying transmural timing differences that are potentially important for arrhythmogenesis (Antzelevitch et al, 1999;Sabir et al, 2007).…”

Atrial location optimization by electrical measures for Electrocardiographic Imaging

“…This regularization methodology was used on this manuscript as their intrinsic parameter (L-curve curvature) allows to refine the heart anatomy as a secondary outcome. However, the use of Tikhonov regularization on the location process do not become a limitation, once the heart is properly located, to the use of novel and more accurate inverse-problem methodologies enabling better ECGI reconstructions and/or including transmural differences [32][33][34].…”