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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 the T...

Electrocardiogram Fundamentals

Electrocardiogram Fundamentals

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.
Parts of an ECG
An ECG utilizes electrodes on the skin to...

Dysrhythmias V: Evaluating Dysrhythmias

Dysrhythmias V: Evaluating Dysrhythmias

Dysrhythmias, also known as arrhythmias, are disturbances in the heart's rhythm that range from benign to life-threatening. A thorough evaluation is crucial for appropriate management and involves a comprehensive medical history, physical examination, and various diagnostic tests.Medical HistorySymptoms: Collect detailed information on palpitations, dizziness, syncope, chest pain, and fatigue. Note their onset, frequency, and triggers.Previous Cardiac Issues: Document any history of heart...

Cardiac Action Potential

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials

Correlation between ECG and Cardiac Cycle

Correlation between ECG and Cardiac Cycle

The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
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...

ECG Interpretation of Rhythms

ECG Interpretation of Rhythms

An electrocardiogram (ECG)graphically represents the heart's electrical activity on ECG paper or a monitor.
Components of the Electrocardiogram
The primary components of a normal ECG waveform in Normal sinus rhythm(NSR) include the P wave, PR interval, QRS complex, ST segment, T wave, and occasionally a U wave.
ECG waveforms are divided by vertical and horizontal lines at standard intervals.
The horizontal axis measures time and rate, and the vertical axis measures amplitude or voltage. When...

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Related Experiment Video

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In Silico Clinical Trials for Cardiovascular Disease

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Published on: May 27, 2022

T-wave alternans: lessons learned from a biophysical ECG model.

Roberto Sassi¹, Luca T Mainardi

¹Dipartimento di Informatica, Università degli Studi di Milano, Italy. roberto.sassi@unimi.it

Journal of Electrocardiology

|September 11, 2012

Summary

T-wave alternans (TWA) in the ECG can be explained by cellular alternations. Our model links myocyte alternans to T-wave variability, improving TWA estimation precision and lead analysis.

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Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

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Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

Patient-specific Modeling of the Heart: Estimation of Ventricular Fiber Orientations

Published on: January 8, 2013

Area of Science:

Cardiovascular Physiology
Computational Biology
Biomedical Engineering

Background:

T-wave alternans (TWA) signifies beat-to-beat ECG T-wave variations, potentially linked to myocyte alternations in action potential duration and morphology.
The precise relationship between cellular-level alternations and surface ECG T-wave modifications in vivo remains incompletely understood.

Purpose of the Study:

To develop and analyze a generalized stochastic model of ventricular repolarization that incorporates myocyte alternans.
To derive an analytical formula connecting surface ECG T-wave variations to cellular-level alternations.
To investigate the impact of repolarization heterogeneity and noise on TWA estimation.

Main Methods:

Generalization of a previously proposed stochastic ventricular repolarization model to include myocyte alternans.
Application of van Oosterom's electrophysiological formulation to derive a link between cellular and surface ECG signals.
Theoretical analysis of TWA estimation precision, lead dependency, and TWA-T-wave amplitude relationships.

Main Results:

Random variations in repolarization heterogeneity significantly impact TWA estimation accuracy.
TWA exhibits theoretical differences across ECG leads, suggesting multilead approaches can mitigate noise.
The study analyzed the relationship between TWA and T-wave amplitude.

Conclusions:

The generalized model provides a theoretical framework for understanding TWA in relation to myocyte alternans.
Repolarization heterogeneity and beat-to-beat cellular variability are crucial factors influencing TWA.
Multilead ECG analysis is recommended for robust TWA assessment, considering lead-specific variations and noise reduction.