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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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Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

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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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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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Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

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Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which...
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Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

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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.
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Depolarizing Blockers: Mechanism of Action01:28

Depolarizing Blockers: Mechanism of Action

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Depolarizing blockers act on skeletal muscle fibers' membranes and induce their depolarization. Most depolarizing blockers have two quaternary N+ atoms that bind the nicotinic acetylcholine receptors and cause neuromuscular blockade within minutes.
Succinylcholine is the most commonly used depolarizing blocker. Chemically, it constitutes two molecules of acetylcholine joined together by an acetate methyl group. They act on the receptors in the same way as acetylcholine. Because...
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Updated: Jun 28, 2025

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice
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[High-degree atrioventricular (AV) block].

Peter Hammarlund1, Erik Ljungström2, Daniel Bremell3

  • 1Specialistläkare, kardiologsektionen, Helsingborgs lasarett.

Lakartidningen
|April 10, 2024
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Summary
This summary is machine-generated.

High-degree atrioventricular block in younger patients may be caused by Lyme carditis, a reversible condition. Prompt diagnosis and antibiotic treatment can prevent the need for unnecessary pacemaker implantation.

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Area of Science:

  • Cardiology
  • Infectious Diseases
  • Electrophysiology

Context:

  • High-degree atrioventricular (AV) block in the elderly is typically due to irreversible cardiac conduction system degeneration.
  • In younger individuals, reversible causes of AV block are more common and varied.
  • Lyme carditis, a manifestation of Lyme borreliosis, is a rare but treatable cause of AV block.

Purpose:

  • To highlight Lyme carditis as a critical, reversible differential diagnosis for AV block in specific patient populations.
  • To emphasize the importance of considering infectious etiologies before pacemaker implantation.
  • To guide clinicians on diagnostic and therapeutic strategies for suspected Lyme carditis.

Summary:

  • Lyme carditis, caused by Borrelia burgdorferi, can present as high-degree AV block, particularly in young and middle-aged patients.
  • A thorough evaluation for reversible causes, including Lyme carditis, is essential prior to pacemaker implantation.
  • Positive serological tests in patients with intermediate to high pretest probability strongly suggest Lyme carditis, which is treatable with antibiotics.

Impact:

  • Early diagnosis and antibiotic treatment of Lyme carditis can potentially avert the need for permanent pacemaker implantation.
  • Increased awareness of Lyme carditis may lead to earlier diagnosis and improved patient outcomes.
  • This understanding can refine clinical decision-making algorithms for AV block management.