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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

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...

Electrocardiogram Fundamentals

Electrocardiogram Fundamentals

Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
Definition
An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
An ECG utilizes electrodes on the skin...

Electrocardiogram

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...

Mechanism of Cardiac Arrhythmias

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 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...

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Related Experiment Video

Updated: Jun 27, 2025

Ablation of Ischemic Ventricular Tachycardia Using a Multipolar Catheter and 3-dimensional Mapping System for High-density Electro-anatomical Reconstruction

Ablation of Ischemic Ventricular Tachycardia Using a Multipolar Catheter and 3-dimensional Mapping System for High-density Electro-anatomical Reconstruction

Published on: January 31, 2019

Distinct Electrogram Features and Ventricular Arrhythmia Induction Modes Between Repolarization and Conduction

Estelle Renard¹, Elodie Surget¹, Richard D Walton¹

¹IHU LIRYC, L'Institut des maladies du RYthme Cardiaque, Fondation Bordeaux Université, Bordeaux, France; University of Bordeaux, Inserm, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France.

JACC. Clinical Electrophysiology

|April 25, 2024

Summary

This summary is machine-generated.

Localized electrical abnormalities are key in ventricular fibrillation and J-wave syndrome. Microstructural changes, especially with sodium channel blockers, significantly impact electrograms and arrhythmia vulnerability.

Keywords:

J wave syndromes electrogram fragmentation idiopathic ventricular fibrillation sudden cardiac death ventricular fibrillation

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Area of Science:

Cardiac Electrophysiology
Arrhythmogenesis Research
Cardiovascular Pharmacology

Background:

Localized electrical abnormalities are increasingly recognized in idiopathic ventricular fibrillation and J-wave syndrome.
Understanding these abnormalities is crucial for predicting arrhythmia risk.

Purpose of the Study:

To characterize electrical signatures of localized repolarization and conduction heterogeneities.
To determine their role in cardiac vulnerability to arrhythmias.

Main Methods:

Optical mapping in porcine ventricles with induced repolarization shortening (pinacidil) or conduction slowing (flecainide).
Local epicardial tissue destruction was used to create structural heterogeneity.
Electrograms were recorded, and spontaneous/induced arrhythmias were quantified.

Main Results:

Conduction slowing and structural heterogeneity caused electrogram fragmentation, particularly with flecainide.
Spontaneous arrhythmias increased with repolarization shortening and conduction slowing.
Arrhythmia vulnerability was highest with conduction slowing and lowest with repolarization shortening.

Conclusions:

Microstructural substrates significantly impact electrograms, especially when combined with sodium channel blockers.
Local action potential duration shortening increases spontaneous arrhythmias but does not cause electrogram fragmentation.