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Related Concept Videos

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias01:16

ECG Interpretation of Arrhythmias I: Sinus Arrhythmias

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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,...
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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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Dysrhythmias I: Introduction01:15

Dysrhythmias I: Introduction

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Dysrhythmias refers to abnormalities in the heart's rhythm. They result from disruptions in the heart's electrical conduction system, which includes the sinoatrial(SA)node, atrioventricular(AV) node, the bundle of His, bundle branches, and Purkinje fibers.Definition and PathophysiologyDysrhythmias result from disorders of impulse formation, impulse conduction, or both. The heart contains specialized cells in the sinoatrial node, atrioventricular node, and the bundle of His and Purkinje fibers...
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Conduction System of the Heart01:20

Conduction System of the Heart

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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:...
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Conduction System of the Heart01:19

Conduction System of the Heart

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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.
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...
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Decreased pulse rate01:14

Decreased pulse rate

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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...
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Related Experiment Video

Updated: Oct 24, 2025

Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice
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Sinus Node Dysfunction.

Matthew Kendall Hawks1, Madison L B Paul2, Omojo Odihi Malu3

  • 1Uniformed Services University of the Health Sciences, Bethesda, MD, USA.

American Family Physician
|August 12, 2021
PubMed
Summary
This summary is machine-generated.

Sinus node dysfunction, or sick sinus syndrome, affects heart rate regulation due to sinoatrial node issues. Pacemaker implantation is the primary treatment for this condition.

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Related Experiment Videos

Last Updated: Oct 24, 2025

Microelectrode Array Recording of Sinoatrial Node Firing Rate to Identify Intrinsic Cardiac Pacemaking Defects in Mice
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Generation of Murine Cardiac Pacemaker Cell Aggregates Based on ES-Cell-Programming in Combination with Myh6-Promoter-Selection
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Area of Science:

  • Cardiology
  • Electrophysiology

Background:

  • Sinus node dysfunction (SND), formerly sick sinus syndrome, involves abnormal electrical impulse conduction in the sinoatrial node.
  • It can impair the heart's ability to meet physiological demands, particularly during stress or exercise.
  • While occurring at any age, SND is more prevalent in older individuals.

Purpose of the Study:

  • To summarize the causes, diagnostic methods, and treatment of sinus node dysfunction.
  • To highlight the clinical manifestations and diagnostic criteria for SND.

Main Methods:

  • Review of electrocardiography (ECG) findings associated with SND, including bradycardia, pauses, and sinoatrial exit block.
  • Correlation of clinical symptoms, such as syncope and fatigue, with bradyarrhythmias.
  • Assessment of chronotropic incompetence through exercise stress testing.

Main Results:

  • SND can stem from intrinsic factors (fibrosis, remodeling) or extrinsic factors (medications, metabolic issues), with many extrinsic causes being reversible.
  • Common ECG findings include sinus bradycardia, pauses, sinoatrial exit block, and chronotropic incompetence (affecting 50% of patients).
  • Cerebral hypoperfusion symptoms like syncope occur in about 50% of patients.

Conclusions:

  • Diagnosis requires correlating symptoms with bradyarrhythmia and ruling out reversible causes.
  • Permanent pacemaker placement, prioritizing atrial pacing, is the recommended first-line treatment for confirmed SND.