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Related Concept Videos

Dysrhythmias III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute.
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

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

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...
Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

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 of...
Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

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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Related Experiment Video

Updated: Jul 14, 2026

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation
09:17

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

Ventricular fibrillation: dynamics and ion channel determinants.

Sami F Noujaim1, David S Auerbach, José Jalife

  • 1Department of Pharmacology and Institute for Cardiovascular Research, SUNY Upstate Medical University, Syracuse, NY 13210, USA.

Circulation Journal : Official Journal of the Japanese Circulation Society
|December 6, 2007
PubMed
Summary

Ventricular fibrillation (VF), a primary cause of sudden cardiac death, involves complex rotor dynamics. Understanding ion channel roles in excitation-recovery is key to unraveling VF mechanisms.

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A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts
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Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry

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Related Experiment Videos

Last Updated: Jul 14, 2026

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation
09:17

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts
07:56

A Model of Long-Term Ventricular Fibrillation in Isolated Rat Hearts

Published on: February 17, 2023

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry
11:32

Determination of the Relative Cell Surface and Total Expression of Recombinant Ion Channels Using Flow Cytometry

Published on: September 28, 2016

Area of Science:

  • Cardiology
  • Electrophysiology
  • Cardiac Arrhythmias

Background:

  • Ventricular fibrillation (VF) is the primary cause of sudden cardiac death.
  • VF is characterized by dynamic rotors responsible for functional reentry.
  • Current understanding of ionic mechanisms underlying VF remains fragmented.

Purpose of the Study:

  • To review the dynamics of rotors in VF.
  • To summarize knowledge on how transmembrane currents and cardiac structure initiate and maintain VF.
  • To highlight the role of ion channels in VF mechanisms.

Main Methods:

  • Review of existing literature on VF.
  • Analysis of the interplay between ionic currents and cardiac structure.
  • Examination of the role of sarcolemmal ion channels in the excitation-recovery process.

Main Results:

  • The interplay between rapid-inward sodium current and inward-rectifier potassium current influences rotor formation, stability, and frequency.
  • L-type calcium current is involved in controlling rotor frequency and VF-to-ventricular tachycardia conversion.
  • The effect of time-dependent outward currents through voltage-gated potassium channels on VF is less clear.

Conclusions:

  • Insights into ion channel function offer hope for understanding VF.
  • Further research using advanced techniques is needed to fully elucidate VF mechanisms.
  • A comprehensive "Theory of VF" is still distant but progress is being made.