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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 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 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 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...
Pharmacokinetics: Drug–Drug Interactions01:25

Pharmacokinetics: Drug–Drug Interactions

Drug interactions occur when the pharmacological effect of one drug is altered by another substance, either enhancing or diminishing its activity. The drug whose activity is altered is known as the object drug, and the substance causing the alteration is called the agent drug or the precipitant. The net effects of these interactions are mostly undesirable, leading to decreased effectiveness or increased adverse effects. In rare cases, interactions can be beneficial, such as the enhanced...
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...

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Related Experiment Video

Updated: Jun 12, 2026

Electrocardiogram Recordings in Anesthetized Mice using Lead II
04:16

Electrocardiogram Recordings in Anesthetized Mice using Lead II

Published on: June 20, 2020

Drug-induced QT-interval prolongation: considerations for clinicians.

Edward C Li1, John S Esterly, Shaunte Pohl

  • 1National Comprehensive Cancer Network, Fort Washington, Pennsylvania, USA.

Pharmacotherapy
|June 26, 2010
PubMed
Summary
This summary is machine-generated.

Drug-induced proarrhythmia, often caused by blocking the I(Kr) potassium current, increases cardiac risks. Understanding varying QT interval prolongation risks is crucial for clinicians to prevent adverse events.

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Last Updated: Jun 12, 2026

Electrocardiogram Recordings in Anesthetized Mice using Lead II
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Determining the Likelihood of Variant Pathogenicity Using Amino Acid-level Signal-to-Noise Analysis of Genetic Variation
07:15

Determining the Likelihood of Variant Pathogenicity Using Amino Acid-level Signal-to-Noise Analysis of Genetic Variation

Published on: January 16, 2019

Area of Science:

  • Cardiology
  • Pharmacology
  • Clinical Medicine

Background:

  • Drug-induced proarrhythmia is a significant clinical issue, leading to drug withdrawals.
  • Suppression of the rapid delayed rectifier potassium current (I(Kr)) is a primary mechanism for QT interval prolongation.
  • The risk of proarrhythmia varies due to factors reducing cardiac repolarization reserve.

Purpose of the Study:

  • To highlight the clinical significance of drug-induced proarrhythmia.
  • To explain the pharmacodynamic basis of QT interval prolongation.
  • To emphasize the differential mortality risks associated with antiarrhythmic vs. non-cardiovascular QT-prolonging drugs.

Main Methods:

  • Review of existing clinical data and pharmacological mechanisms.
  • Analysis of drug effects on the I(Kr) current and QT interval.
  • Comparison of mortality risks between different drug classes and patient risk profiles.

Main Results:

  • QT interval prolongation is linked to I(Kr) suppression and reduced repolarization reserve.
  • Antiarrhythmic drugs with QT prolongation show increased mortality risk only in high-risk patients.
  • Non-cardiovascular drugs causing QT prolongation are associated with increased mortality in lower-risk patients.

Conclusions:

  • Clinicians must recognize varying proarrhythmia risks associated with different QT-prolonging drugs.
  • Pharmacists play a key role in managing drug-induced proarrhythmia risks.
  • Strategies for preventing or reducing proarrhythmia are essential for patient safety.