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Related Concept Videos

Electrocardiogram01:29

Electrocardiogram

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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...
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ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias01:25

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

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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...
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Interval Level of Measurement00:55

Interval Level of Measurement

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For effective statistical analysis, data are classified into four levels of measurement—nominal, ordinal, interval, and ratio.
Data measured using the interval scale are similar to ordinal level data because they have a definite arrangement. However, in the interval level of measurement, the differences between data values are meaningful even though the data does not have a starting point.
Temperature is measured using the interval scale. It is measurable data, and the difference between...
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ECG Interpretation of Rhythms01:24

ECG Interpretation of Rhythms

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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....
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Electrocardiogram Fundamentals01:28

Electrocardiogram Fundamentals

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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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ECG Interpretation of Arrhythmias I: Sinus Arrhythmias01:16

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

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Arrhythmias are disturbances in the heart's rhythm that lead to abnormal heartbeats. These irregularities can originate from different parts of the heart and are classified based on their origin and nature.
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...
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Related Experiment Video

Updated: Feb 22, 2026

A Functional Assay for Gap Junctional Examination; Electroporation of Adherent Cells on Indium-Tin Oxide
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A Functional Assay for Gap Junctional Examination; Electroporation of Adherent Cells on Indium-Tin Oxide

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JT interval: What does this interval mean?

Wojciech Zareba1, Scott McNitt1, Slava Polonsky1

  • 1The Heart Research Follow-up Program, Cardiology Division, University of Rochester Medical Center, Rochester, NY, United States.

Journal of Electrocardiology
|September 26, 2017
PubMed
Summary
This summary is machine-generated.

The JTp interval (JTpc) shows variable diagnostic and prognostic performance for long QT syndrome (LQTS) types. While similar to QTc in LQT1 and LQT3, JTpc is inferior in LQT2 and not linked to events in LQT3.

Keywords:
JT intervalLQTSLong QT syndromeQT intervalRepolarization duration

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Area of Science:

  • Cardiology
  • Electrophysiology
  • Genetics

Background:

  • The JTp interval is a cardiac repolarization marker of interest for assessing drug effects on ion channels.
  • Accurate measurement of the JTp interval is challenging due to variability in identifying the J point and T wave end.

Purpose of the Study:

  • To evaluate the diagnostic and prognostic utility of the JTp interval, specifically the JTp corrected for heart rate (JTpc), in patients with different types of congenital long QT syndrome (LQTS).

Main Methods:

  • Analysis of electrocardiograms (ECGs) from a large cohort of gene carriers and non-carriers across LQT1, LQT2, and LQT3 families within the International LQTS Registry.
  • Comparison of the diagnostic performance of JTpc against the corrected QT interval (QTc) and assessment of prognostic significance for cardiac events.

Main Results:

  • JTpc demonstrated diagnostic performance comparable to QTc in LQT1 and LQT3 patients, but was inferior in LQT2 patients.
  • Overall repolarization duration showed limited diagnostic value in LQT3.
  • Prognostic significance for predicting cardiac events was similar for JTpc and QTc in LQT1 and LQT2 patients.
  • In LQT3 patients, JTpc was not associated with an increased risk of arrhythmic events.

Conclusions:

  • The diagnostic and prognostic value of JTpc varies across different genetic subtypes of LQTS.
  • JTpc is a potentially useful marker in LQT1 and LQT2 but has limitations in LQT2 diagnosis and LQT3 prognosis.