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Related Concept Videos

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias

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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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Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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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...
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Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
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Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

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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...
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Cardiac Action Potential01:30

Cardiac Action Potential

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Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
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Cardiac Cycle01:29

Cardiac Cycle

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The cardiac cycle refers to the sequence of events that occur in the heart from the beginning of one heartbeat to the next. It's characterized by alternating periods of contraction (systole) and relaxation (diastole) of the heart muscles.
During the cardiac cycle, blood flow through the heart is regulated entirely by changing pressure gradients. This sequence of events begins with the heart in a state of total relaxation, known as mid-to-late diastole, during which blood passively flows from...
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Related Experiment Video

Updated: Mar 19, 2026

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation
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Practice viewpoints: AICD, who and when?

R J Sung1, N-Y Chan2

  • 1Institute of Life Sciences, National Central University, Jhongli, Taoyuan, Taiwan; Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California, USA.

Heart Asia
|June 22, 2016
PubMed
Summary
This summary is machine-generated.

Automatic implantable cardioverter-defibrillators (AICD) prevent sudden cardiac death (SCD) but require better risk stratification. Identifying and correcting reversible causes of arrhythmias can avoid unnecessary AICD implantation, improving cost-effectiveness.

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Area of Science:

  • Cardiology
  • Medical Devices
  • Genetics

Background:

  • Sudden cardiac death (SCD) prevention is crucial, with automatic implantable cardioverter-defibrillators (AICDs) being an effective but costly option.
  • Atherosclerotic heart disease (ASHD) is a primary cause of SCD in adults, with varying SCD rates across racial/ethnic groups.
  • Current risk stratification for AICD implantation in ASHD patients, particularly post-myocardial infarction, lacks specificity.

Purpose of the Study:

  • To review the current landscape of AICD use for sudden cardiac death prevention.
  • To emphasize the importance of identifying and addressing reversible causes of ventricular arrhythmias before AICD implantation.
  • To highlight the need for improved risk stratification markers, including genetic factors, for AICD candidates.

Main Methods:

  • Literature review and analysis of existing data on SCD causes and AICD efficacy.
  • Discussion of diagnostic work-up protocols for identifying transient or reversible causes of lethal arrhythmias.
  • Exploration of potential genetic markers for risk stratification in ASHD patients.

Main Results:

  • Reversible causes of lethal ventricular tachyarrhythmias can often be corrected, potentially negating the need for AICD implantation.
  • Left ventricular function status alone is insufficient for guiding AICD decisions in ASHD patients post-myocardial infarction.
  • Development of better biological, physiological, or genetic markers is urgently needed for accurate patient selection.

Conclusions:

  • Physicians must thoroughly evaluate patients for reversible causes of arrhythmias before considering AICD implantation.
  • Enhanced risk stratification strategies, potentially incorporating genetic markers, are essential for optimizing AICD use and cost-effectiveness.
  • Further research into genetic markers is warranted for precise SCD risk assessment in ASHD patients.