Comparison of electric- and magnetic- cardiograms produced by myocardial ischemia in models of the human ventricle and torso

Erick A Perez Alday,Michael A Colman,Chen Zhang,Henggui Zhang,Haibo Ni,Zizhao Gan

doi:10.1109/cic.2015.7410961

Abstract

Myocardial ventricular ischemia arises from the lack of blood supply to the heart, which may cause abnormal excitation wave conduction and repolarization patterns in the tissue, leading to cardiac arrhythmias and even sudden death. Current diagnosis of cardiac ischemia by the 12-lead electrocardiogram (ECG) has limitations as they are insensitive in many cases and may showunnoticeable differences compared to normal patterns. As the magnetic field provides extra information of cardiac excitation and is more sensitive to tangential currents to the surface of the chest, whereas the electric field is more sensitive to radial currents, it has been hypothesized that the magnetocardiogram (MCG) may provide a complementary methodto the ECG in ischemic diagnosis. However, it is unclear yet about the differences in the sensitivity of the ECG and MCG signals to ischemic conditions. The aim of this study was to investigate such differences by using multi-scale biophysically detailed computational models of the human ventricles and torso model, to simulate normal and ischemic conditions.

Highlights

Ischemic heart disease is one of the leading causes of death in developed countries and worldwide [1,2,3]
The magnetic field produced by the electrical activity of the heart may provide a greater level of detail of cardiac excitation compared to the body surface potential (BSP), because magnetocardiograms (MCG) are more sensitive to currents tangential to the surface of the chest than ECGs
It was shown that ischemia caused some changes to the profiles of the action potential, including an elevated resting potential, reduced amplitude of AP and shortened action potential durations (APDs)

Summary

Introduction

Ischemic heart disease is one of the leading causes of death in developed countries and worldwide [1,2,3]. The standard 12-lead ECG has been shown to be insensitive to cardiac ischemia; the ECG waveforms of patients with ischemia may only differ by 15–30% compared to none-ischemic patients [3,4,6,8] This suggests that the 12-lead ECG provides insufficient information for satisfactory diagnosis of ischemia. Other non-invasive techniques, including radionuclide methods [9], magnetic resonance imaging [10] and positron computed tomography [11], are far more sensitive to the detection of ischemia They are highly expensive and time consuming, and not practical for day-to-day, bedside monitoring and detection of silent ischemia (i.e. asymptomatic ischemia which does not present as an arrhythmia) [12,13,14]

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Conclusion