Quantitative Analysis of Electro-Anatomical Maps: Application to an Experimental Model of Left Bundle Branch Block/Cardiac Resynchronization Therapy

Abstract

Electro-anatomical maps (EAMs) are commonly acquired in clinical routine for guiding ablation therapies. They provide voltage and activation time information on a 3-D anatomical mesh representation, making them useful for analyzing the electrical activation patterns in specific pathologies. However, the variability between the different acquisitions and anatomies hampers the comparison between different maps. This paper presents two contributions for the analysis of electrical patterns in EAM data from biventricular surfaces of cardiac chambers. The first contribution is an integrated automatic 2-D disk representation (2-D bull's eye plot) of the left ventricle (LV) and right ventricle (RV) obtained with a quasi-conformal mapping from the 3-D EAM meshes, that allows an analysis of cardiac resynchronization therapy (CRT) lead positioning, interpretation of global (total activation time), and local indices (local activation time (LAT), surrogates of conduction velocity, inter-ventricular, and transmural delays) that characterize changes in the electrical activation pattern. The second contribution is a set of indices derived from the electrical activation: speed maps, computed from LAT values, to study the electrical wave propagation, and histograms of isochrones to analyze regional electrical heterogeneities in the ventricles. We have applied the proposed methods to look for the underlying physiological mechanisms of left bundle branch block (LBBB) and CRT, with the goal of optimizing the therapy by improving CRT response. To better illustrate the benefits of the proposed tools, we created a set of synthetically generated and fully controlled activation patterns, where the proposed representation and indices were validated. Then, the proposed analysis tools are used to analyze EAM data from an experimental swine model of induced LBBB with an implanted CRT device. We have analyzed and compared the electrical activation patterns at baseline, LBBB, and CRT stages in four animals: two without any structural disease and two with an induced infarction. By relating the CRT lead location with electrical dyssynchrony, we evaluated current hypotheses about lead placement in CRT and showed that optimal pacing sites should target the RV lead close to the apex and the LV one distant from it.

Keywords: Cardiac resynchronization therapy; electro-anatomical mapping system; lead placement; left bundle branch block; quantitative pattern analysis; subject-specific 2D and 3D data representation.

FIGURE 1.

Different representations for endocardial (ENDO) and epicardial (EPI) electrical activity. a) Classical electro-anatomical maps (EAMs) meshes from the mapping system; b) 2D flattening of the left (LV) and right (RV) ventricles with a quasi-conformal mapping technique (QCM); c) 3D bull’s eye plot (BEP) representation of the flattened disk that allows to relate local activation times (LAT) with conduction velocities (altitude gradient). Colors represent local activation times (the maximum and minimum values were not specified since this figure is only used for illustrative purposes). The two faces represent the EAM orientation as indicated in the electro-anatomical navigation system.

FIGURE 2.

Illustration of the original electro-anatomical map (EAM) surfaces and the corresponding 2D maps. (1) EAM landmark selection for left ventricle (LV) endocardium and LV and right ventricle (RV) epicardium (2) Quasi-conformal mapping (QCM) sequence for endocardial and epicardial EAMs illustrating the correspondence; the selected landmarks are also show: Posterior landmark (PL), anterior landmark (AL), apical landmark (ApL).

FIGURE 3.

First column: Top, local activation time (LAT) of the electro-anatomical map (EAM) mapped to the 2D standardized space; bottom, 3D Bull’s eye plot (BEP) representation, from the earliest activation (red) to the latest one (blue); Second column: Top, speed map; bottom, speed classification using k-means, form the slowest velocities (blue) to the highest ones (red).

FIGURE 6.

Infarcted case (#3). 1) Endocardial and epicardial electro-anatomical maps (EAM)s 2) 2D bull’s eye plot (BEP) of endo (LV) and epicardial (RV/LV) EAMs; BT RV: electrical breakthrough from the right ventricle (RV); it includes a 2D disk with the 17 AHA segments affected by the scar and its transmurality, defined on a pre-operative DE-MRI; 3) Histogram of isochrones (missing RV endocardium) 4) Speed classification from endo and epicardial velocity maps 5) 3D BEP from endo and epicardial representations; Local activation time (LAT) values and speed scales are shown as min/max since they are different between each protocol stage.

FIGURE 4.

Synthetic activation patterns: a) Circular activation pattern (baseline) b) Elliptical activation pattern left bundle branch block (LBBB); 1) 2D BEP applying quasi-conformal mapping (QCM) for endocardium and epicardium from the earliest activation (red) to the latest one (blue); 2) Histogram of isochrones for LV/RV epicardium and LV endocardium (RV endocardium is not available); 3) 3D bull’s eye plot (BEP) for endocardium and epicardium from the earliest activation (red) to the latest one (blue); 4) Speed maps for endocardium and epicardium for slow speeds (blue) and fast speeds (red).

FIGURE 5.

Non-infarcted case (#1). 1) Endocardial and epicardial electro-anatomical maps (EAM)s 2) 2D bull’s eye plot (BEP) of endo (LV) and epicardial (RV/LV) EAMs; BT RV: electrical breakthrough from the right ventricle (RV); 3) Histogram of isochrones (missing RV endocardium) 4) Speed classification from endo and epicardial velocity maps 5) 3D BEP from endo and epicardial representations; Local activation time (LAT) values and speed scales are shown as min/max since they are different between each protocol stage.