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Cardiac Action Potential

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

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

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...

Correlation between ECG and Cardiac Cycle

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...

Electrophysiology of Normal Cardiac Rhythm

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...

Dysrhythmias II: Classification of Tachyarrhythmias

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...

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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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Related Experiment Video

Updated: Apr 25, 2026

Confirmation of Myocardial Ischemia and Reperfusion Injury in Mice Using Surface Pad Electrocardiography

Confirmation of Myocardial Ischemia and Reperfusion Injury in Mice Using Surface Pad Electrocardiography

Published on: November 24, 2016

Early repolarisation and J wave syndromes.

Kamal K Sethi¹, Kabir Sethi², Surendra K Chutani²

¹Director of Cardiology, Division of Cardiology and Cardiac Electrophysiology, Delhi Heart & Lung Institute, 3 MM II, Panchkuian Road, New Delhi 110 055, India.

Indian Heart Journal

|September 1, 2014

Summary

J wave syndromes, including Early Repolarization (ER) and Brugada Syndrome (BrS), are linked to sudden cardiac death. Understanding their ionic mechanisms is key to identifying high-risk individuals and guiding treatment for ventricular fibrillation (VF).

Keywords:

Early repolarization syndrome (ER)Fibrillation J wave syndrome Tachycardia

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Isolation and Functional Characterization of Human Ventricular Cardiomyocytes from Fresh Surgical Samples

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Area of Science:

Cardiology
Electrophysiology
Genetics

Background:

J wave syndromes, including Early Repolarization (ER) and Brugada Syndrome (BrS), are significant causes of Idiopathic Ventricular Fibrillation (IVF) and sudden cardiac death.
The outward potassium current (Ito) plays a crucial role in ventricular repolarization, with transmural differences proposed to underlie arrhythmogenesis in these syndromes.
While many ER patterns are benign, identifying individuals at risk for sudden cardiac death remains a clinical challenge.

Purpose of the Study:

To review the historical features, epidemiology, electrocardiographic findings, and ionic mechanisms of ER and BrS.
To discuss the clinical presentation and current therapeutic strategies for J wave syndromes.
To evaluate the role of electrophysiology studies and novel interventions like radiofrequency ablation.

Main Methods:

Literature review of existing data on J wave syndromes.
Analysis of electrocardiographic and electrophysiological findings.
Discussion of proposed ionic mechanisms and genetic factors.

Main Results:

ER and BrS are well-characterized J wave syndromes with distinct electrocardiographic features.
Transmural differences in Ito current are implicated in the genesis of ventricular arrhythmias.
Quinidine's efficacy supports the role of Ito current in preventing arrhythmias.
Association with conditions like coronary artery disease has been reported.

Conclusions:

Accurate diagnosis and risk stratification are essential for managing patients with J wave syndromes.
Therapeutic consensus is lacking for many patients, with implantable cardioverter-defibrillators (ICDs) recommended for those resuscitated from VF.
Further research is needed to define the role of electrophysiology studies and ablation therapies.