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## Background

The Global Electrical Heterogeneity (GEH) concept is based on the theory of Wilson’s electrical gradient vector, which characterizes the degree of heterogeneity of the total recovery time across the ventricles.

The larger the degree of heterogeneity of total recovery time across the ventricles, the larger the spatial ventricular gradient (SVG) magnitude. The SVG vector points towards the area where the total recovery time is shortest. SVG vector points the direction along which non-uniformities in excitation and repolarization are the greatest (i.e., it is perpendicular to the line of conduction block). Experimental and theoretical investigations demonstrated that the SVG is related to global heterogeneity of both action potential duration and morphology.

The concept underlying the SVG was extended to the spatial QRS-T angle, the three-dimensional angle between the QRS- and T-vectors and the sum absolute QRST integral (SAI QRST), a scalar analog of the SVG calculated as the absolute value of the area under the QRS complex and T-wave on the X, Y, and Z leads. The scalar value of SVG can also be calculated as a QT integral on Vector Magnitude signal (iVMQT), as an area under the Vector Magnitude signal curve from the QRS-onset to T-offset. Five GEH metrics (SVG magnitude, elevation, and azimuth, spatial QRS-T angle, and SAI QRST (or QT integral on Vector Magnitude signal, iVMQT) are complementary to each other; all together they characterize global electrophysiological properties of the heart. GEH is independently associated with sudden cardiac death. GEH can be measured on routinely used clinical 12-lead ECG, after its transformation into orthogonal (Frank) XYZ ECG. We recommend using Kors transformation.

## Software Description and Usage

This page contains V.1 of the software. The working repository for this is hosted in the following github page: https://github.com/Tereshchenkolab/Global-Electrical-Heterogeneity.

One test file `90757.mat`

is provided for GEH calculation testing, with a sampling rate 500 Hz and amplitude resolution 1 µV. A raw 12-lead ECG file `12LECG.mat`

is provided to illustrate the Kors transformation from 12-lead to XYZ (Frank) ECG.

For a demonstration, load `12LECG.mat`

and run `Kors_git.m`

, then load `90757.mat`

and run `GEH_analysis_git.m`

## Authors

Erick Andres Perez Alday, PhD, perezald@ohsu.edu Annabel Li-Pershing, BS, lipershi@ohsu.edu Muammar Kabir, PhD, muammar.kabir@gmail.com Larisa Tereshchenko, MD, PhD, tereshch@ohsu.edu