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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...

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...

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...

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.

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...

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Related Experiment Video

Updated: Apr 17, 2026

Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus

Methods for ECG Evaluation of Indicators of Cardiac Risk, and Susceptibility to Aconitine-induced Arrhythmias in Rats Following Status Epilepticus

Published on: April 5, 2011

Relationship between Neurocardiogenic Syncope and Ventricular Repolarization.

Murat Sucu¹, Orhan Ozer, Vedat Davutoglu

¹Electrophysiology Division, Cardiology Department, Gaziantep University, Gaziantep, Turkey.

Pacing and Clinical Electrophysiology : PACE

|February 4, 2015

Summary

This summary is machine-generated.

Neurocardiogenic syncope (NCS) is associated with prolonged ventricular repolarization parameters. These ECG findings, including T-peak-T-end interval and corrected QT interval (QTc), may indicate increased arrhythmogenesis risk in NCS patients.

Keywords:

electrocardiogram neurocardiogenic syncope repolarization

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Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice

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Area of Science:

Cardiology
Electrophysiology
Medical Diagnostics

Background:

Neurocardiogenic syncope (NCS) is a common cause of syncope.
Ventricular repolarization abnormalities are linked to arrhythmogenesis.
Assessing repolarization may help understand NCS pathophysiology.

Purpose of the Study:

To analyze ventricular repolarization parameters in NCS patients.
To compare ECG repolarization indices between NCS patients and controls.
To investigate the association of repolarization parameters with potential arrhythmogenesis in NCS.

Main Methods:

Study included 33 NCS patients (head-up tilt table test positive) and 33 controls (head-up tilt table test negative).
Measured ECG parameters included T-peak-T-end interval, QT dispersion (QTd), corrected QT interval (QTc), QT index (QTI), and their corrected versions (JTc, JTd).
Statistical analysis compared these parameters between the NCS and control groups.

Main Results:

NCS patients showed significantly prolonged QTd, QTc, QTc index (QTcI), QT index (QTI), JTc, and JTd compared to controls.
T-peak-T-end interval was significantly prolonged in NCS patients.
T-peak-T-end/QT ratio and T-peak-T-end/QTc ratio were significantly higher in the NCS group.

Conclusions:

Electrocardiographic ventricular repolarization parameters are prolonged in patients with NCS.
These prolonged parameters (T-peak-T-end interval, QTc, QTd, JTc, JTd) suggest an increased risk of ventricular arrhythmogenesis in NCS.
ECG repolarization analysis offers insights into the arrhythmogenic potential in NCS.