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ISCE 2010 Preconference Tutorial

Computational ECG Models for Dummies: How Can We Use Them?

Session Chair
Wataru Shimizu

Session Co-Chair
Vladimir Shusterman

Presenter & Topic

Colleen Clancy, University of California, Davis, Davis, CA, USA
Novel molecular/cellular models: how can they help in the analysis of surface ECG?

Joel Xue, GE Healthcare, Wauwatosa, WI, USA

Combined cell-to-heart models: what’s the advantage?

Adriaan Van Oosterom, The Netherlands

The utility of forward heart-torso ECG models

Raja Ghanem, Medtronic Inc., Minneapolis, MN, USA

The utility of inverse models/approaches

Natalia Trayanova, Johns Hopkins University, Baltimore, MD, USA

Electromechanical models of the heart

Session Summary

I

Novel molecular/cellular models: how can they help in the analysis of surface ECG?

Colleen E. Clancy

In this session, we will discuss the relationship between cellular and subcellular level processes that underlie cardiac electrophysiology and how alterations in these processes manifest on the body surface ECG. The objective of the tutorial is to relate events such as activation of fast voltage-dependent Na channels, EC-coupling and activation of repolarizing potassium currents to temporal phases on the body surface electrocardiogram (ECG).
We will explore how molecular and cellular models can help to predict how inherited and acquired disease alter subcellular processes, cellular electrical waveforms and consequently, the ECG.

II

Combined cell-to-heart models: what's the advantage?

Joel Xue

Combining cell models with a heart forward model can let us study many interesting topics in more details. For cardiologists who read ECG everyday, this can include studying how certain ion channel’s properties affect ECG morphology? How different types of dispersion across myocardium tissue may play role in ECG components? How sensitive is the lead position on the torso to ECG amplitude and durations, etc?

In this tutorial, we will first introduce the model briefly, and we will then walk through some cases to understand how the model can be used for cardiology studies including action potential prolongation, ischemia and infarction, lead set and lead placement, etc.

We hope researchers can find this model useful, and at the meantime, we hope to get feedback to help us improve the model further.

III

The utility of forward heart-torso ECG models

Adrian van Oosterom
The ECG waveforms present a highly diffuse image of the full complexity of the heart's electric activity. Over more than a century, insight into this complexity has been gathered from the interpretation of clinical and electrophysiological observations.

During this part of the educational session, an interactive simulation program, ECGSIM, is presented. It is used to demonstrate some of current notions of the genesis the ECG, based on a model that takes into account the dominant aspects of the electrophysiology of the heart and includes the most prominent aspects of the biophysics of the electric volume conduction effects of the passive body tissues surrounding the electric sources active in the myocardium.

Against the background of a source specification for healthy myocardium, local as well as global changes in the timing and magnitude of the sources can be introduced interactively. The results of such changes on the ECG, VCG or body surface potential maps are visualized instantaneously. The examples to be given include:

the genesis of the normal T wave;

the effect of local changes in the timing of depolarizarion and repolarization (e.g., bundle branch blocks, WPW, the ECG morphology in Brugada patients, bi-ventricular pacing);

the STT changes observed during acute ischemia, including the effect of the AC coupling of the recording system.

IV

The utility of inverse models/approaches

Raja Ghanem
The focus of this session is to review the methods employed to determine the heart's electrical activity from measurements made away from the heart. Specifically, we will discuss several different approaches for reconstructing the cardiac electrical function from body surface ECG measurements.
Following a brief overview of the theory of the inverse problem of electrocardiography, we will review the pros and cons of each inverse approach paying particular attention to clinical applications.

Electromechanical Models of the Heart

Natalia Trayanova

Over the last decade integrative multiscale models of organ behavior that incorporate detailed biophysical models of the myocyte cellular and subcellular processes have been developed that have made major contributions to obtaining insight into electrical excitation and the mechanisms of arrhythmogenesis and defibrillation in the normal and the diseased heart.

Similarly, finite element continuum models incorporating cardiac anatomy, structure and passive mechanics have been developed and recently, attempts have been made to couple them to biophysical models of cellular active tension. The development of models of these two major physical processes in the heart has occurred largely independently. However, in the last few years coupled models of cardiac electromechanics, in which contraction is triggered by the electrical event, have also emerged.

This tutorial examines the evolution and the current state-of-the-art in cardiac electromechanical model development and discusses the areas of clinical significance where these models are poised to make an important contribution.

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