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Related Concept Videos

Electrocardiogram Fundamentals01:28

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.
Parts of an ECG
An ECG utilizes electrodes on the skin...
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Electrocardiogram01:29

Electrocardiogram

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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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Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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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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Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...
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ECG Interpretation of Rhythms01:24

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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....
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Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

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The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase...
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Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System
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Spatial distribution of physiologic 12-lead QRS complex.

Katerina Hnatkova1, Irena Andršová2, Ondřej Toman2

  • 1National Heart and Lung Institute, Imperial College, ICTEM, Hammersmith Campus, 72 Du Cane Road, Shepherd's Bush, London, W12 0NN, England.

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This study reveals that sex differences in QRS duration are linked to distinct patterns in the electrical activity of the heart. Smoother electrical wave propagation in females likely explains their shorter QRS duration.

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Area of Science:

  • Cardiology
  • Biomedical Engineering
  • Signal Processing

Background:

  • The normal QRS complex duration on an electrocardiogram (ECG) ranges from 80 to 125 ms.
  • Known sex differences in QRS duration exist, but are not fully explained by anatomical variations.
  • Investigating these differences can provide insights into normal cardiac electrical activity and potential abnormalities.

Purpose of the Study:

  • To explore the underlying reasons for sex differences in QRS duration.
  • To investigate the wide range of normal QRS durations.
  • To introduce and validate a novel technology for analyzing QRS complex components.

Main Methods:

  • A novel technology utilizing singular value decomposition (SVD) was employed to separate orthogonal components of the QRS complex.
  • This method allowed classification of components representing the 3D electrocardiographic signal and intricate depolarization sequences.
  • The technology was applied to a large dataset of 382,019 ECG samples from 639 healthy subjects (311 females, 328 males).

Main Results:

  • QRS duration was primarily influenced by the proportions of the first two orthogonal components.
  • Females showed a significantly larger proportion of the first component (64.2% vs. 59.7%, p < 0.00001).
  • Males exhibited a larger proportion of the second component (33.1% vs. 29.6%, p < 0.001) and components related to localized depolarization abnormalities (2.85% vs. 2.42%, p < 0.00001).

Conclusions:

  • The detailed convolution of the depolarization waveform is highly individual.
  • Smoother and less intricate depolarization propagation is likely responsible for the shorter QRS duration observed in females.
  • The developed technology effectively differentiates components contributing to QRS duration and sex-based variations.