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Related Concept Videos

Decreased pulse rate01:14

Decreased pulse rate

1.0K
Bradycardia is a medical condition in which the heart rate is slower than normal. It occurs when the heart's natural pacemaker, the sinus node, generates slower electrical impulses than the standard rhythm. In adults, bradycardia is diagnosed when the pulse rate falls below 60 beats per minute, indicating a deviation from the normal heart rate range.
There are specific risk factors that can elevate the likelihood of developing bradycardia. Advanced age is a significant factor, with...
1.0K
Dysrhythmias IV: Characteristics of Bradyarrhythmias01:18

Dysrhythmias IV: Characteristics of Bradyarrhythmias

810
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...
810
Disturbances in Heart Rhythm01:29

Disturbances in Heart Rhythm

3.6K
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...
3.6K
ECG Interpretation of Arrhythmias I: Sinus Arrhythmias01:16

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

1.1K
Arrhythmias are disturbances in the heart's rhythm that lead to abnormal heartbeats. These irregularities can originate from different parts of the heart and are classified based on their origin and nature.
Types of Arrhythmias
Sinus Node Arrhythmias
Sinus Bradycardia: Originating from the sinoatrial (SA) node, sinus bradycardia involves slower impulses, resulting in a heart rate of less than 60 beats per minute (bpm). Causes include sleep, vagal stimulation, beta-blockers, hypothyroidism,...
1.1K
Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

2.6K
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.
2.6K
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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Related Experiment Video

Updated: Mar 30, 2026

Optogenetic Activation of Intrinsic Cardiac Autonomic Neurons in Excised Perfused Mouse Hearts
08:29

Optogenetic Activation of Intrinsic Cardiac Autonomic Neurons in Excised Perfused Mouse Hearts

Published on: March 28, 2025

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Bradycardia from flash stimulation.

Michael Einspenner1, Donald G Brunet1, Lysa Boissé Lomax2

  • 1Department of Medicine, Division of Neurology (Clinical Neurophysiology).

Epileptic Disorders : International Epilepsy Journal with Videotape
|November 18, 2015
PubMed
Summary
This summary is machine-generated.

Photic stimulation during an electroencephalogram (EEG) can trigger a vasovagal reaction, causing significant bradycardia (slow heart rate) and asystole in susceptible individuals. This case highlights a rare but serious reflex response to visual stimuli during neurological assessments.

Area of Science:

  • Neurology
  • Cardiology
  • Clinical Neurophysiology

Background:

  • Photosensitive epilepsy is a known condition where flashing lights can trigger seizures.
Keywords:
bradycardiacase studyflash stimulationsyncope

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  • Electroencephalogram (EEG) recordings are standard for evaluating brain activity, including in patients with epilepsy.
  • Photic stimulation is a common component of EEG to assess for photosensitivity.