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Related Concept Videos

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.
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...
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...
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...
Dysrhythmias VI: Management of Dysrhythmias01:25

Dysrhythmias VI: Management of Dysrhythmias

Dysrhythmia management involves a multifaceted approach, incorporating pharmacological treatments, medical procedures, surgical interventions, lifestyle modifications, and patient education.Pharmacological ManagementAntiarrhythmic Drugs:Class I (Sodium Channel Blockers): This class includes quinidine and procainamide, which reduce the speed of impulse conduction in the heart, stabilize the cardiac membrane, and control arrhythmias. Quinidine and procainamide are Class IA agents that prolong the...

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Related Experiment Video

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Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus
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Drug-induced proarrhythmia: Discussion and considerations for clinical practice.

Ralph J Klotzbaugh1, Alejandra Martin, J Rick Turner

  • 1Ralph J. Klotzbaugh is an assistant professor in the University of New Mexico College of Nursing in Albuquerque, N.M. Alejandra Martin is a physician assistant and clinical educator at Goodwin Community Health Center in Somersworth, N.H. J. Rick Turner is an adjunct professor in the Department of Pharmacy Practice at Campbell University College of Pharmacy and Health Sciences in Buies Creek, N.C. The authors have disclosed no potential conflicts of interest, financial or otherwise.

JAAPA : Official Journal of the American Academy of Physician Assistants
|January 29, 2020
PubMed
Summary

This article explains drug-induced proarrhythmia, focusing on torsades de pointes. It details how QT interval prolongation on an ECG is used to assess drug safety and manage risks during clinical development and post-marketing.

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Area of Science:

  • Cardiology
  • Clinical Pharmacology
  • Drug Safety

Background:

  • Drug-induced proarrhythmia is a significant concern in clinical practice.
  • Torsades de pointes is a dangerous polymorphic ventricular tachycardia that can lead to sudden cardiac death.
  • Assessing drug-induced torsades de pointes is crucial for patient safety.

Purpose of the Study:

  • To discuss drug-induced proarrhythmia, specifically torsades de pointes.
  • To explain the role of QT interval prolongation as a biomarker for torsades de pointes risk.
  • To elucidate the rationale behind drug approval and warnings related to proarrhythmic potential.

Main Methods:

  • Review of clinical pharmacology studies assessing drug-induced torsades de pointes.
  • Utilizing electrocardiogram (ECG) QT interval prolongation as a biomarker.
  • Analysis of drug benefit-risk balance in the context of proarrhythmic potential.

Main Results:

  • QT interval prolongation identified during drug development indicates a proarrhythmic propensity.
  • Marketing approval may be granted if the overall benefit-risk is favorable, despite QT prolongation.
  • Prescribing information includes warnings for drugs with identified proarrhythmic risks.

Conclusions:

  • Understanding drug-induced proarrhythmia and torsades de pointes is vital for healthcare professionals.
  • Biomarkers like QT interval prolongation aid in drug safety assessment.
  • Careful benefit-risk evaluation guides regulatory decisions and informs clinical use of medications.