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Related Concept Videos

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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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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ECG Interpretation of Rhythms01:24

ECG Interpretation of Rhythms

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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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Correlation between ECG and Cardiac Cycle01:25

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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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Exercise Stress Test01:26

Exercise Stress Test

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Introduction
Exercise stress testing, commonly known as a treadmill test, is a noninvasive procedure used to evaluate cardiovascular function and diagnose heart conditions.
Definition
An exercise stress test measures the heart's response to exertion using a treadmill or stationary bicycle. Chest electrodes record the heart's electrical activity through an ECG, and blood pressure is monitored regularly.
Purposes
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Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

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Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
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Characterization of electrocardiogram changes throughout a marathon.

Vanessa Franco1, Clifton Callaway, David Salcido

  • 1Department of Emergency Medicine, University of Pittsburgh, Iroquois 400A, 3600 Meyran Avenue, Pittsburgh, PA, 15261, US, vfranco@mednet.ucla.edu.

European Journal of Applied Physiology
|May 17, 2014
PubMed
Summary
This summary is machine-generated.

Cardiovascular physiology during marathons shows increased heart rate variability and T-wave alternans (TWA) as the race progresses. These changes appear to be physiological, with no cardiac events observed in runners.

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Area of Science:

  • Cardiovascular physiology
  • Exercise science
  • Sports medicine

Background:

  • Limited data exists on cardiovascular physiological changes during marathon running.
  • Continuous electrocardiographic monitoring provides insights into cardiac function during endurance events.

Purpose of the Study:

  • To continuously characterize electrocardiographic activity throughout a marathon.
  • To investigate changes in heart rate, heart rate variability, and T-wave characteristics during marathon running.

Main Methods:

  • 19 marathon runners (14 men, 5 women; age 39 ± 16 years) were monitored using Holter devices.
  • Continuous evaluation of heart rate (HR), heart rate variability (HRV), T-wave amplitude, T-wave amplitude variability, and T-wave alternans (TWA) throughout the race.
  • Data analyzed for changes occurring during the marathon and immediately post-race.

Main Results:

  • Heart rate variability (HRV), T-wave amplitude variability, and T-wave alternans (TWA) increased progressively throughout the marathon.
  • Complex oscillatory patterns and TWA were observed in 86% of subjects, indicating increased T-wave amplitude variability.
  • Post-marathon, heart rate (HR) was elevated and HRV was suppressed compared to pre-marathon levels.

Conclusions:

  • Both HRV and T-wave amplitude variability, particularly TWA, increase during marathon running.
  • The observed increase in TWA is likely a physiological adaptation to prolonged exertion, as no arrhythmias or cardiac events were detected.
  • Continuous ECG monitoring reveals dynamic cardiovascular adaptations during endurance events.