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Related Concept Videos

Disturbances in Heart Rhythm01:29

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Arrhythmia or dysrhythmia refers to an abnormal heart rhythm caused by a defect in the heart's conduction system. It can cause the heart to beat irregularly, too quickly, or too slowly, leading to symptoms like chest pain, shortness of breath, and fainting. Factors such as stress, caffeine, alcohol, nicotine, cocaine, certain drugs, congenital defects, diseases, and electrolyte abnormalities can trigger arrhythmias.
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Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

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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...
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Conduction System of the Heart01:19

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Autorhythmicity is a term that refers to the heart's inherent ability to generate electrical signals and instigate muscle contractions. This self-regulating conduction system within the heart consists of two key components: the pacemaker cells and specialized conducting cells.
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Electrophysiology of Normal Cardiac Rhythm01:19

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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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Dysrhythmias III: Characteristics of Dysrhythmias01:29

Dysrhythmias III: Characteristics of Dysrhythmias

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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...
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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.
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Updated: Apr 4, 2026

Real-Time Cardiac Mapping with a Noninvasive Imageless Electrocardiographic Imaging System
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Functional Conduction Block During Extrastimulus Mapping Masks Deceleration Zones and Reveals Additional VT

Ali-Razak Rashid1, Ursula Rohrer1, Robert Arnold2

  • 1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom.

JACC. Clinical Electrophysiology
|April 3, 2026
PubMed
Summary
This summary is machine-generated.

Extrastimulus pacing reveals additional ventricular tachycardia substrate but can mask areas of concern. Analyzing both steady-state and extrastimulus pacing maps provides a comprehensive view for ablation targets.

Keywords:
decremental conductionfunctional substrateisochronal late activation mapping

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Area of Science:

  • Electrophysiology
  • Cardiac Arrhythmia Research
  • Medical Device Technology

Background:

  • Extrastimulus pacing may expose decremental conduction, a proarrhythmic property, during ventricular tachycardia (VT) substrate identification.
  • The role of functional conduction block during extrastimulus pacing as a marker of arrhythmogenicity remains unclear.

Purpose of the Study:

  • To compare ventricular tachycardia substrate identification using steady-state (S1) and single extrastimulus (S2) pacing.
  • To analyze deceleration zones (DZs) and annotation delta (ΔS1S2) to understand substrate behavior changes.

Main Methods:

  • Isochronal late activation mapping with S1 and S2 pacing (ventricular effective refractory period +20 ms) during right ventricular pacing.
  • Identification of DZs and calculation of ΔS1S2 to assess decremental conduction and functional block.
  • Analysis of DZ location and ΔS1S2 changes to characterize altered substrate behavior.

Main Results:

  • DZ locations differed significantly between S1 and S2 maps.
  • Extrastimulus pacing identified 5 new DZs, but functional block masked 4 DZs on S2 maps.
  • Significant ΔS1S2 regions colocalized with primary DZs in most cases.

Conclusions:

  • Extrastimulus pacing alters DZ location and can reveal additional VT substrate.
  • Functional block during S2 pacing may mask critical substrate areas.
  • Combined analysis of S1 and S2 maps enhances substrate characterization and identifies potential ablation targets.