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Electrocardiogram Fundamentals

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Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
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A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...

Cardiac Action Potential

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Ionic Basis of Cardiac Action Potentials

Electrocardiogram

Electrocardiogram

An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and...

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QRS complex waveform indicators of ventricular activation slowing: Simulation studies.

Ljuba Bacharova¹, Vavrinec Szathmary², Jana Svehlikova³

¹International Laser Center, Bratislava, Slovakia; Institute of Pathological Physiology, Medical Faculty, Comenius University, Bratislava, Slovakia.

Journal of Electrocardiology

|August 25, 2016

Summary

Slowed heart muscle activation can mimic electrocardiogram (ECG) signs of left ventricular hypertrophy (LVH). Computer modeling shows this electrical change alters QRS waveform, impacting LVH criteria interpretation.

Keywords:

Left ventricular hypertrophy Left ventricular mass QRS complex waveform Simulation studies Ventricular activation slowing

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Area of Science:

Cardiology
Computational Biology
Biophysics

Background:

Ventricular activation slowing, due to pathologies like hypertrophy, ischemia, or fibrosis, alters the heart's electrical sequence.
These alterations in activation sequence deform the activation front, leading to changes in the QRS complex on an electrocardiogram (ECG).

Purpose of the Study:

To simulate the effect of slowed ventricular activation on QRS waveform using a computer model.
To investigate ECG changes that mimic established criteria for left ventricular hypertrophy (ECG-LVH).

Main Methods:

Computer modeling of slowed ventricular activation across different regions and depths (transmural, midwall).
Analysis of simulated QRS complex morphology, duration, electrical axis, and amplitude.
Evaluation of simulated ECG criteria for left ventricular hypertrophy, including Sokolow-Lyon index, Cornell voltage, and Gubner criterion.

Main Results:

Diffuse slowing in the left ventricle prolonged QRS duration, shifted the electrical axis leftward, and increased QRS amplitude, impacting key ECG-LVH criteria.
Regional anteroseptal slowing also caused leftward axis shift and increased ECG-LVH criteria, particularly when considering limb and precordial leads.
Transmural slowing produced more pronounced QRS changes than midwall slowing.

Conclusions:

Slowed ventricular activation is a significant factor influencing QRS complex morphology.
Simulated slowed activation can replicate ECG patterns typically interpreted as left ventricular hypertrophy, highlighting the importance of electrical properties beyond anatomical mass.