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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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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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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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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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Disturbances in Heart Rhythm01:28

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...
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Cardiac Action Potential01:30

Cardiac Action Potential

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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
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Updated: Jun 14, 2025

Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus
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QTc Interval Changes in Preeclampsia vs. Normal Pregnancy: A Systematic Review and Meta-Analysis.

Omar A Aboshady1,2, Jess Z Raffa1, Sara K Quinney1,3,4

  • 1Department of Pharmacy Practice, College of Pharmacy, Purdue University, West Lafayette, Indiana, USA.

Clinical Pharmacology and Therapeutics
|February 27, 2025
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Summary

Pregnancy prolongs the heart rate-corrected QT (QTc) interval, with preeclampsia causing even greater QTc lengthening. This highlights potential risks for pregnant individuals, especially when using QT-prolonging medications.

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Author Spotlight: Modeling an Aspect of Preeclampsia in Female Mice Using Hypoxic Human Placenta-Derived Small Extracellular Vesicles

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Area of Science:

  • Cardiology
  • Maternal-Fetal Medicine
  • Pharmacology

Background:

  • Pregnancy significantly alters the cardio-autonomic nervous system.
  • Preeclampsia imposes additional cardiac stress, potentially affecting ventricular repolarization.
  • The impact of normal pregnancy and preeclampsia on the heart rate-corrected QT (QTc) interval is not well understood, despite the use of QT-prolonging drugs.

Purpose of the Study:

  • To quantify changes in the QTc interval during normal pregnancy across trimesters.
  • To assess QTc interval changes in third-trimester preeclampsia compared to normal pregnancy.

Main Methods:

  • Systematic review and meta-analysis of eight databases (up to January 13, 2025).
  • Inclusion of studies reporting QT/QTc intervals and heart rate/RR intervals across pregnancy trimesters or with nonpregnant controls.
  • Random-effect models used to calculate pooled mean differences in QTc intervals.

Main Results:

  • Meta-analyses included 33 studies with 5,153 participants.
  • QTc intervals significantly increased in the first (10.0 msec), second (20.2 msec), and third (23.0 msec) trimesters compared to nonpregnant individuals.
  • Third-trimester preeclampsia showed a further QTc interval increase of 21.7 msec compared to normal pregnancy.

Conclusions:

  • A significant QTc interval prolongation occurs throughout normal pregnancy.
  • Preeclampsia exacerbates QTc interval lengthening in the third trimester.
  • The heightened risk of arrhythmogenicity in preeclampsia, particularly with QT-prolonging drugs, requires further investigation.