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Related Concept Videos

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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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...
988
Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

918
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.
918
Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

1.4K
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,...
1.4K
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

832
Class IV antiarrhythmic drugs, such as verapamil and diltiazem, block calcium channels. They primarily affect the heart, slowing the conduction in calcium-dependent tissues like the SA and AV nodes. These drugs manage reentrant supraventricular tachycardia (SVT) and reduce ventricular rate in atrial flutter/fibrillation.
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
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Related Experiment Video

Updated: Jun 28, 2025

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

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Understanding the Electrical Substrates Contributing to "Ablation-Resistant" Atrial Fibrillation?

John P Bourke1

  • 1Department of Cardiology, Freeman Hospital, Newcastle upon Tyne NHS Hospitals Foundation Trust, United Kingdom.

The American Journal of Cardiology
|April 21, 2024
PubMed
Summary

Catheter ablation for atrial fibrillation (AF) shows promise, but not all patients benefit. New research identifies specific electrophysiologic footprints in the left atrium that may improve success rates for repeat ablation procedures.

Keywords:
atrial remodelingcatheter ablationelectrical signalsprognosis

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Catheter Ablation in Combination With Left Atrial Appendage Closure for Atrial Fibrillation
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High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation
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Catheter Ablation in Combination With Left Atrial Appendage Closure for Atrial Fibrillation
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Area of Science:

  • Cardiovascular Electrophysiology
  • Cardiac Arrhythmias

Background:

  • Catheter ablation for atrial fibrillation (AF) has evolved significantly since its introduction in 1998.
  • Initial optimism regarding ablation efficacy has tempered with the recognition that not all patients achieve sustained benefit.
  • The complex pathophysiology of AF challenges the notion of a single, universally responsive ablation target.

Discussion:

  • Masuda et al. investigated electrophysiologic "footprints" in the left atrium of patients undergoing repeat ablation after pulmonary vein isolation.
  • This study explores non-pulmonary vein triggers and substrate modifications contributing to AF recurrence.
  • Understanding these specific electrical patterns may refine patient selection and procedural strategy for AF ablation.

Key Insights:

  • Novel electrophysiologic findings in the left atrium provide insights into AF mechanisms beyond pulmonary vein reconnection.
  • Identification of specific "footprints" may differentiate responders from non-responders to repeat ablation procedures.
  • These insights could guide more personalized and effective ablation strategies for difficult-to-treat AF.

Outlook:

  • The findings necessitate prospective validation to confirm their clinical utility.
  • This research may pave the way for improved antiarrhythmic success in patients with unpredictable responses to current ablation techniques.
  • Further investigation into left atrial electrophysiology could optimize outcomes for complex atrial fibrillation cases.