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Related Concept Videos

Electrocardiogram01:29

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 Fundamentals01:28

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...
ECG Interpretation of Rhythms01:24

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...
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

Arrhythmia is a condition characterized by an irregular heart rhythm, with ECG changes that differ based on its origin and nature. The types of arrhythmias discussed below include atrial, junctional, and ventricular arrhythmias.Atrial ArrhythmiasPremature Atrial Complexes (PACs): PACs are early atrial beats caused by stress, caffeine, alcohol, electrolyte imbalances, hypoxia, hyperthyroidism, or certain medications (e.g., bronchodilators and decongestants). The ECG shows early P waves with an...
Reconstruction of Signal using Interpolation01:10

Reconstruction of Signal using Interpolation

Signal processing techniques are essential for accurately converting continuous signals to digital formats and vice versa. When a continuous signal is sampled with a period T, the resulting sampled signal exhibits replicas of the original spectrum in the frequency domain, spaced at intervals equal to the sampling frequency. To handle this sampled signal, a zero-order hold method can be applied, which creates a piecewise constant signal by retaining each sample's value until the next sampling...
Correlation between ECG and Cardiac Cycle01:25

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...

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2D and 3D Echocardiography in the Axolotl (Ambystoma Mexicanum)
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QRS subtraction for atrial electrograms: flat, linear and spline interpolations.

A Ahmad1, J L Salinet, P Brown

  • 1Department of Engineering, University of Leicester, Leicester LE17RH, UK. aa384@le.ac.uk

Medical & Biological Engineering & Computing
|October 1, 2011
PubMed
Summary

This study compares QRS subtraction methods for atrial electrograms using surface ECG. QRS subtraction significantly reduces signal power above 10 Hz without altering dominant frequencies.

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Area of Science:

  • Biomedical Engineering
  • Cardiac Electrophysiology
  • Signal Processing

Background:

  • Intra-cardiac atrial electrograms are crucial for understanding cardiac arrhythmias.
  • Surface electrocardiograms (ECG) provide a non-invasive reference for cardiac activity.
  • QRS complex interference can obscure important atrial signal information.

Purpose of the Study:

  • To implement and compare different QRS subtraction techniques for intra-cardiac atrial electrograms.
  • To evaluate the effectiveness of QRS subtraction using surface ECG as a reference.
  • To assess the impact of QRS subtraction on signal power and dominant frequencies.

Main Methods:

  • QRS detection involved band-pass filtering (8-20 Hz), rectification, and low-pass filtering (6 Hz).
  • Three QRS subtraction methods were implemented: flat, linear, and spline interpolations.
  • Surface ECG data was used as a reference for QRS complex identification.

Main Results:

  • QRS subtraction was found to affect the overall signal power of atrial electrograms.
  • The dominant frequency of the atrial electrograms remained largely unaffected by QRS subtraction.
  • A significant reduction in average signal power was observed for frequencies above 10 Hz post-subtraction.

Conclusions:

  • QRS subtraction techniques effectively reduce interference in intra-cardiac atrial electrograms.
  • The chosen subtraction methods preserve essential frequency information while diminishing unwanted power.
  • This approach enhances the analysis of atrial activity by improving signal clarity.