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Related Concept Videos

Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

Bradyarrhythmias are cardiac rhythm disorders characterized by a slower-than-normal heart rate, typically defined as fewer than 60 beats per minute. Some of which are discussed here:Sinus BradycardiaSinus bradycardia presents a heart rate lower than 60 beats per minute, with a regular rhythm originating from the SA node. The ECG typically shows normal P waves preceding each QRS complex, a normal PR interval (0.12 to 0.20 seconds), and a normal QRS duration (0.06 to 0.10 seconds).First-Degree AV...
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.
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...
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...
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...
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...

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Related Experiment Video

Updated: Jun 19, 2026

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

Short QT syndrome.

Mark J McPate1, Harry J Witchel, Jules C Hancox

  • 1Department of Physiology and Cardiovascular Research Laboratories, School of Medical Sciences, University Walk, Bristol BS81TD, UK. Mark.McPate@bristol.ac.uk

Future Cardiology
|October 7, 2009
PubMed
Summary
This summary is machine-generated.

Idiopathic short QT syndrome (SQTS) is a genetic disorder causing very short QT intervals, increasing arrhythmia and sudden death risk. Research identifies three genetic forms linked to cardiac potassium channel mutations, guiding treatment strategies.

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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

Electrocardiogram Recordings in Anesthetized Mice using Lead II
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Electrocardiogram Recordings in Anesthetized Mice using Lead II

Published on: June 20, 2020

Area of Science:

  • Cardiology
  • Genetics
  • Molecular Biology

Background:

  • Idiopathic short QT syndrome (SQTS) is a rare genetic disorder.
  • Characterized by abbreviated QT intervals (≤300 ms).
  • Associated with increased risk of atrial/ventricular arrhythmias and sudden cardiac death.

Purpose of the Study:

  • Review recent advances in understanding SQTS.
  • Discuss the genetic basis and arrhythmogenic mechanisms.
  • Outline current treatment approaches and future research directions.

Main Methods:

  • Genetic analysis of affected families.
  • Identification of gain-of-function mutations in cardiac potassium channel genes (KCNH2, KCNQ1, KCNJ2).
  • Review of existing literature on SQTS pathophysiology and treatment.

Main Results:

  • Three distinct genetic forms of SQTS identified: SQT1 (KCNH2), SQT2 (KCNQ1), and SQT3 (KCNJ2).
  • Gain-of-function mutations in these potassium channel genes underlie SQTS.
  • Specific mechanisms for arrhythmogenic risk in SQT1 are being elucidated.

Conclusions:

  • SQTS is a genetically determined channelopathy.
  • Understanding the specific genetic defects is crucial for risk stratification and management.
  • Further research is needed to optimize treatment and prevention strategies for SQTS.