A Patchwork Inverse Method in Combination with the Activation Time Gradient to Detect Regions of Slow Conduction in Sinus Rhythm

Abstract

Noninvasive electrocardiographic imaging (ECGI) methods are known to produce artificial lines of block in healthy tissue. However, it remains unclear if ECGI can detect regions of slow conduction in damaged hearts. The aim of this study was to develop and test a method to detect the presence of slow conduction zones using ECGI.Activation times were estimated from simulated electrocardiograms using two classical ECGI methods and a new method called the Patchwork Method (PM), which locally selects the optimal ECGI method. Five different methods (maximum, minimum, mean, nearest neighbor and random) to compute activation time gradients were then tested to pinpoint the slow conduction zones.Overall, the local maximum and mean gradients both accurately located the zones of tissue damage. While the classical ECGI methods did not identify any of these regions, the Patchwork Method succeeded in identifying 5 of the 6 slow conduction zones. This novel approach thus overcomes some of the limitations of classic ECGI methods to detect regions of slow conduction.

Evaluation of the ECGI Patchwork Method Using Experimental Data in Sinus Rhythm

“…That is, classical methods reconstruct electrograms with a "W" shape during the QRS so that small changes in the voltage can cause the activation marker to jump quickly between the two downslopes and produce this artificial line. Previous studies have also seen this phenomenon [4,6] and suspect that the appearance of W-shaped electrograms results from the reconstructed potentials representing a distant field of both the epicardial and endocardial electrical activity and not a purely local epicardial activation. These W-shaped electrograms are less apparent in the PM reconstructions, and hence the activation wavefront travels more smoothly across the epicardial surface, similar to the recorded case.…”

“…The PM, as has previously been described in [4], locally selects the optimal solution among several classical ECGI methods. According to classical ECGI methods, the linear relationship between cardiac sources and the resulting torso surface potentials can be written in matrix form:…”

“…In a recent study, we described a novel method: the Patchwork Method (PM) and evaluated it using simulated data. This method combines the solutions obtained with FEM and MFS, using the BEM formulation to compare their residuals in order to select the most accurate method [4]. We therefore hypothesize that this PM is more accurate than classical ECGI methods in the reconstruction of activation maps and localisation of breakthrough site, and in particular can reduce the frequency of artificial lines of block in reconstructed activation maps.…”

A Patchwork Method to Improve the Performance of Current Methods for Solving the Inverse Problem of Electrocardiography

“…That is, the detection of focal activity, and epicardial breakthrough sites can be missing or misplaced. The problem is seen not only with clinical data [5] but also in torso tank experiments [1], [4] and in simulated data [7], [8] where forward models are well defined, suggesting that the issue lies with the inverse methods themselves.New inverse methods are therefore needed to improve the performance and the accuracy of ECGI in the reconstruction of focal activity, and epicardial breakthrough sites.…”