Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

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...
Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

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.
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
Depolarizing Blockers: Mechanism of Action01:28

Depolarizing Blockers: Mechanism of Action

Depolarizing blockers act on skeletal muscle fibers' membranes and induce their depolarization. Most depolarizing blockers have two quaternary N+ atoms that bind the nicotinic acetylcholine receptors and cause neuromuscular blockade within minutes.
Succinylcholine is the most commonly used depolarizing blocker. Chemically, it constitutes two molecules of acetylcholine joined together by an acetate methyl group. They act on the receptors in the same way as acetylcholine. Because succinylcholine...
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
Heart Failure Drugs: β-Blockers01:22

Heart Failure Drugs: β-Blockers

β-adrenergic antagonists, commonly known as β-blockers, block the effects of sympathetic neurotransmitters such as noradrenaline (NA) and adrenaline (ADR). They have several beneficial effects in heart failure treatment. They reduce heart rate, the force of contraction, and cardiac muscle relaxation. They also slow the atrial-ventricular conduction rate and raise the threshold for arrhythmias. The concentration of β-blockers determines their effects on bronchodilation, vasodilation, and...
Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

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 of...

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

Histopathological Evidence of Neurodegenerative Pathology in Epilepsy: A Systematic Review.

Annals of clinical and translational neurology·2026
Same author

Trends in thyroid Bethesda category III in the era of molecular testing: a single-center study.

Journal of the American Society of Cytopathology·2026
Same author

Wild-Type Transthyretin Cardiac Amyloidosis Presenting As Progressive Heart Failure and Conduction Disease Despite Guideline-Directed Medical Therapy.

Cureus·2026
Same author

Persistent Left Superior Vena Cava in an Adult Presenting With Atrial Fibrillation.

Cureus·2026
Same author

Silent Circuit: Incidental Finding of Wolff-Parkinson-White Pattern in Late Pregnancy Complicated by Severe Preeclampsia.

Cureus·2026
Same author

Photo Quiz: An unexpected colon companion.

Journal of clinical microbiology·2026

Related Experiment Video

Updated: Jul 14, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
12:45

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

Published on: December 11, 2017

Exercise-Induced Complete Heart Block and Sinoatrial Exit Block in Baseline Bifascicular Block.

Asher Gorantla1, Peter Cwalina2, Aleksander Łuniewski3

  • 1Division of Cardiovascular Medicine, SUNY Health Sciences University, Brooklyn, NY, USA.

The American Journal of Case Reports
|July 13, 2026
PubMed
Summary

Exercise stress testing is valuable for diagnosing syncope in patients with bifascicular block. It revealed transient complete atrioventricular block and sinoatrial exit block, guiding pacemaker implantation and symptom resolution.

More Related Videos

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation
09:17

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice
08:05

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice

Published on: June 29, 2022

Related Experiment Videos

Last Updated: Jul 14, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
12:45

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

Published on: December 11, 2017

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation
09:17

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Published on: July 29, 2011

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice
08:05

Optimization of Transesophageal Atrial Pacing to Assess Atrial Fibrillation Susceptibility in Mice

Published on: June 29, 2022

Area of Science:

  • Cardiology
  • Electrophysiology
  • Diagnostic Medicine

Background:

  • Bifascicular block often presents asymptomatically but can progress to severe conduction issues.
  • Exercise stress testing can identify transient conduction abnormalities in patients with unexplained syncope.
  • While not standard for known atrioventricular block, stress testing aids in diagnosing the cause of syncope when resting block is absent.

Purpose of the Study:

  • To highlight the diagnostic utility of exercise stress testing in patients experiencing syncope with underlying conduction abnormalities.
  • To report a rare case of concurrent atrioventricular block and sinoatrial exit block during stress testing.
  • To demonstrate how provoked conduction abnormalities can guide management decisions.

Main Methods:

  • A 72-year-old male with right bundle branch block and left anterior fascicular block underwent exercise stress testing due to recurrent exertional syncope.
  • The patient developed transient complete atrioventricular block and sinoatrial exit block during the Bruce protocol.
  • Computed tomography coronary angiography was performed to rule out coronary artery disease.

Main Results:

  • Exercise stress testing provoked transient complete atrioventricular block and sinoatrial exit block, correlating with near-syncope.
  • The patient later developed Mobitz II atrioventricular block and sinoatrial Wenckebach block during recovery.
  • No obstructive coronary lesions were found; a dual-chamber pacemaker was implanted, leading to symptom resolution.

Conclusions:

  • Exercise stress testing is crucial for evaluating syncope in patients with bifascicular block, revealing transient high-grade block.
  • The concurrent development of atrioventricular and sinoatrial block during stress testing is uncommon but diagnostically significant.
  • Provoked block during stress testing can predict progressive conduction system disease and supports timely pacemaker implantation.