Related Experiment Video
Updated: Aug 12, 2026
07:29
Programmed Electrical Stimulation in Mice
Published on: May 27, 2010
Exercise induced atrioventricular block with gap phenomenon in atrioventricular conduction
T Toeda1, S Suetake, K Tsuchida
1Department of Cardiology, Niigata City General Hospital, Japan.
Pacing and Clinical Electrophysiology : PACE
|May 4, 2000
Summary
Exercise-induced atrioventricular (AV) block in a patient was linked to a rate-dependent infranodal AV block and abnormal His-Purkinje system function. Supernormal conduction may explain the observed gap phenomenon during electrophysiological testing.
Area of Science:
- Cardiology
- Electrophysiology
- Human Physiology
Background:
- Atrioventricular (AV) block can manifest during physical exertion, impacting cardiac function.
- Understanding the mechanisms of exercise-induced AV block is crucial for patient management.
- The His-Purkinje system's role in conduction abnormalities requires further investigation.
Observation:
- A 54-year-old male presented with a 4-year history of presyncope during exercise.
- Treadmill testing revealed exercise-induced atrioventricular (AV) block.
- Electrophysiological study was performed to investigate the underlying cardiac conduction disturbance.
Findings:
- Electrophysiological study demonstrated rate-dependent infranodal AV block.
- Abnormal refractory periods within the His-Purkinje system were identified.
- A 'gap phenomenon' in AV conduction occurred during programmed stimulation, suggesting supernormal conduction as a potential mechanism.
Implications:
- This case highlights a specific mechanism of exercise-induced AV block.
- Supernormal conduction may play a role in the 'gap phenomenon' of AV conduction.
- Further research into His-Purkinje system dynamics during exercise is warranted for improved diagnosis and treatment of syncope.
Related Concept Videos
01:19Electrophysiology 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...
01:28Mechanism of Cardiac Arrhythmias
Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
01:19Conduction System of the Heart
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.
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
01:29Disturbances 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...
Arrhythmias are categorized by their speed, rhythm, and origin. A slow heart...
01:20Conduction System of the Heart
The cardiac conduction system produces and transmits electrical impulses that prompt myocardial contraction, ensuring efficient heart function. This intricate system ensures that the heart beats in a coordinated and efficient manner, beginning with the atria and then the ventricles. The conduction system optimizes cardiac output by maintaining this precise sequence, which is crucial for adequate blood circulation.
This system relies on the unique properties of nodal and Purkinje cells:...
This system relies on the unique properties of nodal and Purkinje cells:...
01:18Dysrhythmias 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...