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Related Concept Videos

Electrocardiogram01:29

Electrocardiogram

An electrocardiogram (ECG or EKG) is a critical diagnostic tool that records the electrical signals produced by the heart during each heartbeat. This recording is achieved through electrodes placed strategically on the arms, legs, and chest. The electrocardiograph amplifies these signals and produces 12 distinct tracings, offering a comprehensive understanding of the heart's electrical activity.
Three major waveforms are present in a typical ECG recording: the P wave, the QRS complex, and the T...
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...
Pharmacokinetic–Pharmacodynamic Relationship: Duration of Dose-Effect Relationship01:14

Pharmacokinetic–Pharmacodynamic Relationship: Duration of Dose-Effect Relationship

For drugs producing a quantal response, onset occurs when plasma concentration reaches a minimum effective level (Cmin). The drug's action duration depends on how long the plasma concentration remains above Cmin.Two primary factors influence this duration: dose size and the rate of drug removal from the action site. Both depend on the drug's redistribution to poorly perfused tissues and elimination processes. A larger dose promotes rapid onset and prolongs the effect's duration.Consider a...
Pharmacokinetic–Pharmacodynamic Relationship: Influence of Elimination Half-Life on Effect Duration01:23

Pharmacokinetic–Pharmacodynamic Relationship: Influence of Elimination Half-Life on Effect Duration

Drug elimination from the body primarily occurs through metabolic and excretion pathways. Hepatic metabolism transforms lipophilic drugs into hydrophilic forms for excretion, typically via enzymatic processes classified as phase I (modification) and phase II (conjugation). Renal excretion eliminates drugs and metabolites through filtration and secretion in the kidneys. Impairment in liver or kidney function can hinder these processes, delaying drug clearance and extending the drug’s half-life.
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...
Dysrhythmias III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute.

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In Vivo Surface Electrocardiography for Adult Zebrafish
09:13

In Vivo Surface Electrocardiography for Adult Zebrafish

Published on: August 1, 2019

QTc: how long is too long?

J N Johnson1, M J Ackerman

  • 1Department of Pediatrics/Division of Pediatric Cardiology, Mayo Clinic, Rochester, Minnesota 55905, USA.

British Journal of Sports Medicine
|September 8, 2009
PubMed
Summary
This summary is machine-generated.

Congenital long QT syndrome (LQTS) diagnosis can be challenging, especially with borderline QTc intervals. Accurate ECG measurement and genetic testing are crucial for identifying this potentially lethal genetic heart condition.

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Area of Science:

  • Cardiology
  • Genetics
  • Clinical Diagnostics

Background:

  • Congenital long QT syndrome (LQTS) affects 1 in 2500 people, causing syncope, seizures, or sudden death.
  • Diagnosing LQTS is challenging in asymptomatic individuals with borderline QTc intervals (≥440 ms).
  • A normal QT interval does not rule out a potentially lethal LQTS-causing genetic mutation.

Purpose of the Study:

  • To discuss accurate QTc measurement and diagnosis of LQTS.
  • To re-examine factors affecting QT interval measurement.
  • To clarify recommendations for diagnosing borderline QT prolongation and LQTS in athletes.

Main Methods:

  • Review of current literature on LQTS diagnosis and management.
  • Analysis of factors influencing QT interval measurement accuracy.
  • Summary of guideline recommendations for LQTS diagnosis and athlete evaluation.

Main Results:

  • Accurate QTc measurement is vital for diagnosing LQTS, particularly in borderline cases.
  • The 12-lead ECG, while universal, is prone to errors in calculation, interpretation, and handling.
  • Genetic testing offers significant diagnostic, prognostic, and therapeutic insights.

Conclusions:

  • Accurate ECG interpretation and consideration of genetic testing are essential for definitive LQTS diagnosis.
  • Clear diagnostic criteria are needed for borderline QTc intervals to prevent misdiagnosis.
  • Updated guidelines are necessary for managing LQTS, especially in athletic populations.