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Related Concept Videos

Electrocardiogram01:29

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 the T...
Electrocardiogram Fundamentals01:28

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 to...
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...
ECG Interpretation of Rhythms01:24

ECG Interpretation of Rhythms

An electrocardiogram (ECG)graphically represents the heart's electrical activity on ECG paper or a monitor.
Components of the Electrocardiogram
The primary components of a normal ECG waveform in Normal sinus rhythm(NSR) include the P wave, PR interval, QRS complex, ST segment, T wave, and occasionally a U wave.
ECG waveforms are divided by vertical and horizontal lines at standard intervals.
The horizontal axis measures time and rate, and the vertical axis measures amplitude or voltage. When...
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 III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

Dysrhythmias, also known as arrhythmias, are irregular heart rhythms that result from abnormal electrical activity in the heart, affecting its ability to circulate blood efficiently. Tachyarrhythmias, a subset of dysrhythmias, are characterized by abnormally fast heart rates exceeding 100 beats per minute. Here are some types of tachyarrhythmias with their distinct ECG features:Sinus Tachycardia:Sinus tachycardia presents a regular heart rhythm with an increased rate of 101-180 beats per minute.

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In Vivo Surface Electrocardiography for Adult Zebrafish
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Published on: August 1, 2019

T(peak)T(end) interval in long QT syndrome.

Jorgen K Kanters1, Christian Haarmark, Esben Vedel-Larsen

  • 1Danish National Research Foundation Center of Arrhythmias (DARC), Copenhagen, Denmark.

Journal of Electrocardiology
|September 30, 2008
PubMed
Summary

The T(peak)T(end) interval, reflecting heart repolarization, does not reliably predict syncope in Long QT Syndrome (LQTS). HERG gene mutations are associated with longer T(peak)T(end) intervals compared to KvLQT1.

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Genetics

Background:

  • The T(peak)T(end) (T(p)T(e)) interval is a measure of transmural dispersion of repolarization.
  • It is considered a potential risk factor in Long QT Syndrome (LQTS).

Purpose of the Study:

  • To investigate the influence of genetic mutations on the T(p)T(e) interval in LQTS patients.
  • To determine if T(p)T(e) interval length correlates with the occurrence of syncope in LQTS.

Main Methods:

  • Electrocardiograms were analyzed in 95 LQTS patients from the Danish LQTS registry.
  • Patients were genotyped for KvLQT1, HERG, and SCN5A mutations.
  • QT, QT(peak), and RR intervals were manually evaluated.

Main Results:

  • T(p)T(e) interval could not differentiate between symptomatic and asymptomatic LQTS patients.
  • Patients with HERG mutations exhibited significantly longer T(p)T(e) intervals than those with KvLQT1 mutations.
  • Heart rate correction was found to be unnecessary for T(p)T(e) intervals in this LQTS cohort.

Conclusions:

  • T(p)T(e) is not a reliable clinical marker for distinguishing symptomatic from asymptomatic LQTS.
  • Genetic variations, specifically HERG mutations, impact T(p)T(e) duration.
  • T(p)T(e) intervals in LQTS patients do not require heart rate correction for clinical assessment.