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Related Concept Videos

Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase of...
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.
Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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...
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...
Cardiac Action Potential01:30

Cardiac Action Potential

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
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...

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A Research Method For Detecting Transient Myocardial Ischemia In Patients With Suspected Acute Coronary Syndrome Using Continuous ST-segment Analysis
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Sudden cardiac arrest associated with early repolarization.

Michel Haïssaguerre1, Nicolas Derval, Frederic Sacher

  • 1Université Bordeaux, Hôpital Haut-Lévêque, Bordeaux-Pessac, France. michel.haissaguerre@chu-bordeaux.fr

The New England Journal of Medicine
|May 9, 2008
PubMed
Summary

Early repolarization, an electrocardiographic finding, is more common in patients with idiopathic ventricular fibrillation. This suggests a potential link between early repolarization and cardiac arrest risk.

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Public Health

Background:

  • Early repolarization (ECG) is typically benign.
  • Its role in cardiac arrhythmias and sudden cardiac arrest (SCA) is unclear.

Purpose of the Study:

  • To investigate the association between ECG early repolarization and idiopathic ventricular fibrillation (IVF).

Main Methods:

  • Retrospective review of 206 IVF case subjects and 412 controls.
  • ECG early repolarization defined as QRS-ST junction elevation ≥0.1 mV.
  • Follow-up included implantable defibrillator monitoring.

Main Results:

  • Early repolarization was significantly more prevalent in IVF cases (31%) versus controls (5%).
  • IVF cases with early repolarization had higher rates of recurrent ventricular fibrillation (HR 2.1).
  • Early repolarization was associated with male sex and syncope in IVF patients.

Conclusions:

  • ECG early repolarization is more prevalent in patients with IVF.
  • This finding suggests a potential clinical association with cardiac arrest risk.