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Related Concept Videos

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

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers

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 the heart's...
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

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

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

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 indirectly block calcium...
Dysrhythmias II: Classification of Tachyarrhythmias01:28

Dysrhythmias II: Classification of Tachyarrhythmias

Tachyarrhythmias are a type of dysrhythmia where the heart rate exceeds 100 beats per minute. Here are some common types of tachyarrhythmias:Sinus TachycardiaSinus tachycardia originates from increased impulses from the sinus node, leading to an elevated heart rate. It is often triggered by stress, fever, or exercise.Patients may experience palpitations, a sensation of a racing heart, dizziness, and chest discomfort.Causes and Risk Factors: Common causes include physical exertion, emotional...
Heart Failure Drugs: Inotropic Agents01:26

Heart Failure Drugs: Inotropic Agents

Positive inotropic agents are commonly used as the first line of treatment for heart failure. One such agent is digoxin, derived from the genus Digitalis, which has been known for centuries but effectively utilized since 1785. However, these cardiac glycosides can have potentially toxic effects due to their mechanism of action, which involves inhibiting Na+/K+-ATPase and increasing contractility. Digoxin is absorbed orally and distributed in various tissues, including the CNS. It has a long...

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Related Experiment Video

Updated: Jul 18, 2026

Laser-Induced Action Potential-Like Measurements of Cardiomyocytes on Microelectrode Arrays for Increased Predictivity of Safety Pharmacology
10:41

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Published on: September 13, 2022

Dofetilide: a new class III antiarrhythmic agent.

Henri Roukoz1, Walid Saliba

  • 1Department of Cardiovascular Medicine/F15, Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195, USA.

Expert Review of Cardiovascular Therapy
|December 26, 2006
PubMed
Summary

Dofetilide effectively converts and maintains normal heart rhythm for atrial fibrillation and flutter. Careful patient selection and monitoring minimize the risk of torsades de pointes, a potential side effect.

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Area of Science:

  • Cardiology
  • Pharmacology

Background:

  • Dofetilide is a Class III antiarrhythmic agent.
  • It selectively blocks the rapid component of the cardiac ion channel delayed rectifier current.

Purpose of the Study:

  • To evaluate the efficacy and safety of oral dofetilide.
  • To assess its role in converting and maintaining sinus rhythm in patients with atrial fibrillation and flutter.

Main Methods:

  • Dosage adjustment based on creatinine clearance and QT(c) interval.
  • Patient selection to exclude known risk factors for torsades de pointes.
  • Initiation of treatment in a monitored hospital setting for the first 3 days.

Main Results:

  • Oral dofetilide is effective in converting atrial fibrillation and flutter to sinus rhythm.
  • It also maintains sinus rhythm after conversion.
  • Torsades de pointes is a potential risk, but minimized by careful management.

Conclusions:

  • Dofetilide is an important alternative for atrial fibrillation and flutter treatment.
  • It offers a favorable safety profile, particularly in patients with heart failure or recent myocardial infarction.
  • Risk mitigation strategies are crucial for safe dofetilide therapy.