Bradycardia classification
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Overview
Bradycardia is a decrease in the heart rate due to abnormalities in the atria, AV node or ventricles.
Classification
Classification of Bradycardia According to The Origin of Impulse
| Bradyarrhythmia | |||||||||||||||||||||||||||
| The origin of the impulse: Atria | The origin of the impulse: AV junction | The origin of the impulse: Ventricles | |||||||||||||||||||||||||
| Respiratory sinus arrhythmia Sinus bradycardia Low atrial focus bradycardia First degree AV block Second degree AV block Complete or third-degree AV block Sick sinus syndrome | Junctional escape rhythm | Isorhythmic A-V dissociation Slow VT (idioventricular rhythm) Ventricular escape rhythm | |||||||||||||||||||||||||
Classification of Bradycardia According to The Location of the Abnormality
Atria
Respiratory Sinus Arrhythmia
Respiratory sinus arrhythmia, is usually found in young and healthy adults. Heart rate increases during inhalation and decreases during exhalation. This is thought to be caused by changes in the vagal tone during respiration.[1] If the decrease during exhalation drops the heart rate below 60 bpm on each breath, this type of bradycardia is usually deemed benign and a sign of good autonomic tone.
Sinus Bradycardia
Sinus bradycardia is a sinus rhythm of less than 60 bpm. It is a common condition found in both healthy individuals and those who are considered well-conditioned athletes. Studies have found 50-85% of conditioned athletes have benign sinus bradycardia, as compared to 23% of the general population studied.[2] The heart muscle of athletes has become conditioned to have a higher stroke volume, so requires fewer contractions to circulate the same volume of blood.[1]
Sick Sinus Syndrome
Sick sinus syndrome covers conditions that include severe sinus bradycardia, sinoatrial block, sinus arrest, and bradycardia-tachycardia syndrome (atrial fibillation, flutter, and paroxysmal supraventricular tachycardia).[1]
AV Junction
An atrioventricular nodal bradycardia or AV junction rhythm is usually caused by the absence of the electrical impulse from the sinus node. This usually appears on an EKG with a normal QRS complex accompanied with an inverted P wave either before, during, or after the QRS complex.[1] An AV junctional escape is a delayed heartbeat originating from an ectopic focus somewhere in the AV junction. It occurs when the rate of depolarization of the SA node falls below the rate of the AV node.[1] This dysrhythmia also may occur when the electrical impulses from the SA node fail to reach the AV node because of SA or AV block.[3] This is a protective mechanism for the heart, to compensate for an SA node that is no longer handling the pacemaking activity, and is one of a series of backup sites that can take over pacemaker function when the SA node fails to do so. This would present with a longer PR interval. A junctional escape complex is a normal response that may result from excessive vagal tone on the SA node. Pathological causes include sinus bradycardia, sinus arrest, sinus exit block, or AV block.[1]
Ventricles
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Allan B. Wolfson, ed. (2005). Harwood-Nuss' Clinical Practice of Emergency Medicine (4th ed.). p. 260. ISBN 0-7817-5125-X.
- ↑ Ward, Bryan G. (1992). "11". Athletic Heart Syndrome. Clinical Sports Medicine. p. 259. Unknown parameter
|coauthors=ignored (help) - ↑ "AV Junctional Rhythm Disturbances (for Professionals)". American Heart Association. 4 December 2008. Retrieved 15 December 2009.