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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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Dysrhythmias V: Evaluating Dysrhythmias01:30

Dysrhythmias V: Evaluating Dysrhythmias

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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...
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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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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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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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Electrocardiography in euthyroid individuals: a Danish general population study.

Jonas L Isaksen1, Morten W Skov2, Claus Graff3

  • 1Department of Biomedical Sciences, Laboratory of Experimental Cardiology, University of Copenhagen, Copenhagen, Denmark.

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Even within normal ranges, thyroid hormones impact heart rate and ECG. This study found associations between thyroid hormone levels and electrocardiographic changes in individuals without thyroid disease.

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Area of Science:

  • Endocrinology
  • Cardiology
  • Clinical Electrophysiology

Background:

  • Thyroid hormones (T3, T4) are crucial for metabolism.
  • Euthyroid thyroid hormone levels are linked to heart rate but not fully understood regarding ECG.
  • Previous research has not comprehensively assessed ECG markers in relation to euthyroid thyroid hormone levels.

Purpose of the Study:

  • To investigate the association between euthyroid thyroid hormone concentrations and various electrocardiographic (ECG) markers.
  • To explore these relationships in individuals without diagnosed thyroid disease.

Main Methods:

  • Utilized electrocardiograms (ECG) and blood samples from 20,852 general population subjects (GESUS study).
  • Measured free T4, total T3, and thyrotropin (TSH) levels.
  • Assessed associations between thyroid hormones and heart rate, QTc, QRS duration, PR interval, P-wave duration, and T-wave morphology using multivariate adjusted linear models stratified by sex.

Main Results:

  • Increased heart rate correlated with higher T3 and T4 concentrations in both sexes.
  • PR interval and QRS duration decreased with higher T3 levels.
  • QTc interval increased with higher T4 in men, and T-wave morphology alterations (flattening, asymmetry, notching) were associated with higher T4.

Conclusions:

  • Euthyroid thyroid hormone levels are associated with significant changes in electrocardiographic parameters.
  • These findings highlight the subclinical impact of thyroid hormones on cardiac electrical activity in the general population.