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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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Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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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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Correlation between ECG and Cardiac Cycle01:25

Correlation between ECG and Cardiac Cycle

10.4K
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.
The horizontal axis measures time and rate, and the vertical axis measures amplitude or voltage....
8.4K
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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Outcomes of conduction system and right ventricular pacing in bradyarrhythmia indications: A systematic review and meta-analysis of propensity-score matched and randomized studies.

Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing·2026
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UHF-ECG Outperforms QRS Duration and Morphology in Predicting Responders to Biventricular Cardiac Resynchronization Therapy.

JACC. Clinical electrophysiology·2026
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Left bundle branch pacing optimized right ventricular resynchronization in a patient with severe right ventricular dilatation.

HeartRhythm case reports·2026
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Optimal pace timing for left bundle branch area pacing with or without an additional LV lead: results from the CSPOT study.

Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology·2026
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Left Bundle Branch Area Pacing: Does Lead Position Matter?

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Inappropriate Surface ECG Signal Filtering Significantly Reduces Physicians' Ability to Recognize LBBB.

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Related Experiment Video

Updated: Nov 15, 2025

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
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Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing

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Physiology-based electrocardiographic criteria for left bundle branch capture.

Marek Jastrzębski1, Grzegorz Kiełbasa1, Karol Curila2

  • 1First Department of Cardiology, Interventional Electrocardiology and Hypertension, Jagiellonian University, Medical College, Kraków, Poland.

Heart Rhythm
|March 7, 2021
PubMed
Summary

Confirming left bundle branch (LBB) capture during pacing is crucial. New electrocardiogram (ECG) criteria using V6 R-wave peak time (RWPT) accurately diagnose LBB capture, ensuring effective left ventricular (LV) pacing.

Keywords:
Electrocardiographic criteriaLeft bundle branch pacingLeft ventricular activation timePhysiological pacingR-wave peak time

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Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
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Area of Science:

  • Cardiology
  • Electrophysiology
  • Medical Devices

Background:

  • Accurate confirmation of left bundle branch (LBB) capture during LBB area pacing is essential.
  • Distinguishing true LBB capture from adjacent left ventricular (LV) myocardial pacing is critical for effective therapy.

Purpose of the Study:

  • To establish reliable electrocardiogram (ECG) criteria for diagnosing LBB capture.
  • To validate the hypothesis that native QRS morphology serves as a reference for LBB capture diagnosis.

Main Methods:

  • Analysis of 357 ECGs from 124 patients with native rhythm and various types of LBB area pacing.
  • Comparison of QRS characteristics, specifically V6 R-wave peak time (RWPT), between native rhythm and paced rhythms.

Main Results:

  • The study validated hypotheses regarding V6 RWPT during LBB capture, showing equivalency with native rhythm.
  • Developed ECG criteria demonstrated high sensitivity (88.2%-98.0%) and specificity (85.7%-95.4%) for LBB capture diagnosis.
  • A V6 RWPT cutoff of 74 ms was identified as 100% specific for LBB capture in specific patient groups.

Conclusions:

  • ECG during LBB capture shows equivalency in LV activation times compared to native conduction.
  • An increased V6 RWPT during pacing indicates a lack of true LBB capture, guiding procedural adjustments.