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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.
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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.
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Electrocardiogram01:29

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

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

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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...
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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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Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers

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Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of...
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Electrocardiogram Recordings in Anesthetized Mice using Lead II
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Normal Ventricular Repolarization and QT Interval: Ionic Background, Modifiers, and Measurements.

Emanuela T Locati1, Giuseppe Bagliani2, Luigi Padeletti3

  • 1Electrophysiology Unit, Cardiology Division, Cardiovascular Department, ASST GOM Niguarda Hospital, Piazza Ospedale Maggiore, 3, 20162 Milano, Italy.

Cardiac Electrophysiology Clinics
|August 26, 2017
PubMed
Summary
This summary is machine-generated.

The QT interval reflects ventricular electrical activity. Factors like potassium ion transport, heart rate, and genetic mutations can alter this interval, increasing arrhythmia risk.

Keywords:
Electric memoryJ pointQT intervalST segmentT waveT wave alternansU waveVentricular repolarization

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Molecular Biology

Background:

  • The QT interval on an electrocardiogram (ECG) measures ventricular depolarization and repolarization.
  • Ventricular repolarization relies on potassium ion (K+) transport, crucial for restoring cellular electrical balance.
  • This process is influenced by heart rate, autonomic activity, and ion channel function.

Purpose of the Study:

  • To explain the physiological basis of the QT interval and its determinants.
  • To highlight factors affecting ventricular repolarization.
  • To discuss the implications of altered repolarization on cardiac health.

Main Methods:

  • Review of existing literature on cardiac electrophysiology.
  • Analysis of the role of potassium channels in ventricular repolarization.
  • Examination of factors influencing QT interval duration.

Main Results:

  • The QT interval encompasses ventricular depolarization and repolarization.
  • Potassium ion outward transport is key for repolarization and endocellular electronegativity.
  • Heterogeneous outward potassium channels are modulated by heart rate and autonomic activity.

Conclusions:

  • Altered ventricular repolarization, indicated by QT interval changes, can arise from various factors.
  • Drugs, diseases, and genetic mutations (channelopathies) affecting potassium channels can prolong or shorten the QT interval.
  • These alterations increase susceptibility to potentially fatal ventricular arrhythmias.