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Related Concept Videos

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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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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Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

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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...
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Cardiac Action Potential01:30

Cardiac Action Potential

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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
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Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

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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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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.
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Related Experiment Video

Updated: Dec 18, 2025

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

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Right Ventricular Electrogram Characteristics in a T1 Mapping-Validated Normal Population: Implications for Unipolar

Adam C Lee1, Wendy Strugnell2, Eric Vittinghoff3

  • 1Department of Cardiology, The Prince Charles Hospital, Brisbane, Australia; Faculty of Medicine, University of Queensland, Brisbane, Australia; University of California-San Francisco, San Francisco, California, USA.

JACC. Clinical Electrophysiology
|June 20, 2020
PubMed
Summary

This study defines normal ventricular electrographic characteristics in healthy hearts using advanced mapping. New reference values for unipolar voltage in the right ventricular free wall are established, aiding scar detection.

Keywords:
cardiac MRIelectrogramssubstrate mappingunipolar mapping

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Electrophysiological Assessment of Murine Atria with High-Resolution Optical Mapping
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Area of Science:

  • Electrophysiology
  • Cardiac Imaging
  • Cardiology

Background:

  • Reference values for human endocardial ventricular electrographic characteristics are not well-defined with contemporary mapping equipment.
  • Previous studies lack data from patients without heart disease or ventricular arrhythmias.

Purpose of the Study:

  • To define normal ventricular electrographic characteristics in T1 mapping-validated normal patients.
  • To establish reference values using contemporary contact force catheter technology.

Main Methods:

  • Mapping of the right ventricle and cardiac magnetic resonance imaging with T1 mapping in 14 patients undergoing SVT ablation.
  • Analysis of electrograms (EGMs) from sites with >10 g contact force in the right ventricular free wall (RVFW) and right ventricular septum (RVS).
  • Definition of abnormal values as <5th or >95th percentile.

Main Results:

  • Ninety-five percent of bipolar EGMs had <6 (RVFW) or <7 (RVS) deflections and duration <37 ms.
  • Ninety-five percent of unipolar EGMs showed maximum dV/dt >0.23 mV/ms (RVFW) or >0.24 mV/ms (RVS).
  • Ninety-five percent of unipolar EGMs had peak-to-peak voltage >3.8 mV (RVFW) or >4.5 mV (RVS).

Conclusions:

  • The threshold for abnormal endocardial unipolar voltage in the RVFW (3.8 mV) is lower than the current standard (5.5 mV).
  • Unipolar voltage characteristics differ between the RVS, RVFW, and left ventricle.
  • Findings have implications for detecting intramural, epicardial, and midseptal scar.