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{{Bradycardia}} | {{Bradycardia}} | ||
{{CMG}}; {{AE}} {{ | {{CMG}}; {{AE}} | ||
==Overview== | |||
[[Bradycardia]] is a decrease in the [[heart rate]] due to abnormalities in the [[atria]], [[AV node]] or [[ventricle]]s. | |||
==Classification== | |||
===Classification of Bradycardia According to The Origin of Impulse=== | |||
{{familytree/start |summary=Bradyarrhythmia}} | |||
{{familytree | | | | | | | | | | | A01 | | | | | | A01= '''[[Bradyarrhythmia]]'''}} | |||
{{familytree | | | | | |,|-|-|-|-|-|^|-|v|-|-|-|.| | | | }} | |||
{{familytree | | | | | B01 | | | | | | B02 | | B03 | | | B01= '''<u>The origin of the impulse:</u><br>Atria'''| B02= '''<u>The origin of the impulse:</u><br>AV junction'''| B03= '''<u>The origin of the impulse:</u><br> Ventricles'''}} | |||
{{familytree | |,|-|-|-|+|-|-|-|.| | | |!| | | |!| |}} | |||
{{familytree | C01 | | C02 | | C03 | | C04 | | C05 | | | C01= '''[[Sinus node dysfunction]]:'''<br>[[Respiratory sinus arrhythmia]]<br>[[Sinus bradycardia]]<br> [[Sinoatrial block]] <br> [[Sinus arrest]] <br> [[Sick sinus syndrome]] <br><br> '''Normal variant:'''<br>[[Respiratory sinus arrhythmia]]| C02= '''Abnormality in the atria:'''<br>[[Low atrial focus bradycardia]]<br> [[Atrial bigeminy]]| C03= '''[[AV block|AV node dysfunction]]:'''<br>[[First Degree AV Block|First degree AV block]] <br> [[Second Degree AV Block|Second degree AV block]] <br> [[Complete or Third-Degree AV Block|Complete or third-degree AV block]]|C04= [[Junctional bradycardia|Junctional escape rhythm]] <br> [[Junctional bigeminy]]| C05=[[Isorhythmic A-V dissociation]] <br> [[Slow VT]] ([[idioventricular rhythm]])<br>[[Ventricular escape rhythm]]<br> [[Escape capture bigeminy]]}} | |||
{{familytree/end}} | |||
===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. | |||
*The [[heart rate]] increases during [[inhalation]] and decreases during [[exhalation]]. | |||
*This is thought to be caused by changes in the [[vagal tone]] during [[respiration]].<ref name="HN">{{cite book|title=Harwood-Nuss' Clinical Practice of Emergency Medicine|editor=Allan B. Wolfson|year=2005|edition=4th|page=260|isbn=0-7817-5125-X}}</ref> | |||
*If exhalation is associated with a drop in the [[heart rate]] below 60 [[bpm]] with each breath, this type of [[bradycardia]] is usually deemed benign and is considered 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-[[Athletic heart syndrome|conditioned athletes]]. | |||
*Studies have found 50-85% of conditioned athletes have [[benign]] sinus bradycardia, as compared to 23% of the general population studied. | |||
*The heart muscle of athletes has become conditioned to have a higher [[stroke volume]], so it requires fewer contractions to circulate the same volume of blood.<ref name="HN" /> | |||
====Sick Sinus Syndrome==== | |||
*[[Sick sinus syndrome]] covers conditions that include: | |||
**Severe sinus bradycardia, [[sinoatrial]] block, sinus arrest, and [[bradycardia]]-[[tachycardia]] syndrome ([[atrial fibrillation]], [[flutter]], and [[Paroxysmal supraventricular tachycardia|paroxysmal supraventricular]] [[tachycardia]]).<ref name="HN" /> | |||
== | ===AV Junction=== | ||
*An [[atrioventricular nodal bradycardia]] or [[junctional escape rhythm]] is usually caused by the absence of the electrical impulse from the [[sinus node]].<ref>{{cite journal|title=CrossRef Listing of Deleted DOIs|journal=CrossRef Listing of Deleted DOIs|year=2008|issn=00000000|doi=10.1007/BF00400429}}</ref> | |||
*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]].<ref name="HN" /> | |||
*An AV junctional escape is a delayed heartbeat originating from an [[Ectopic beat|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]].<ref name="HN" /> | |||
*[[Dysrhythmia]] also may occur when the electrical impulses from the [[SA node]] fail to reach the [[AV node]] because of SA or [[AV block]].<ref name="Sharma2003">{{cite journal|last1=Sharma|first1=Sanjay|title=Physiological Society Symposium - the Athlete's Heart|journal=Experimental Physiology|volume=88|issue=5|year=2003|pages=665–669|issn=09580670|doi=10.1113/eph8802624}}</ref> | |||
*This is a protective mechanism for the heart, to compensate for an [[SA node]] that is no longer handling the [[Pacemaker|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]].<ref name="HN" /> | |||
===Ventricles=== | |||
*[[Ventricular bradycardia]], also known as ventricular escape rhythm or [[Idioventricular rhythm|idioventricular]] rhythm, is a heart rate of less than 50 bpm. | |||
*This is a safety mechanism when there is a lack of electrical impulse or stimuli from the [[atrium]]. Impulses originating from or below the His bundle, also known as ventricular, will produce a wide QRS complex with heart rates between 20 and 40 bpm.<ref name="HN" /> | |||
*Those above the His bundle, also known as junctional, will typically range between 40 and 60 bpm with a narrow QRS complex. | |||
*In a [[third degree heart block]], approximately 61% take place at the bundle branch-[[Purkinje System|Purkinje system]], 21% at the AV node, and 15% at the His bundle. | |||
*AV block may be ruled out with an EKG indicating "a 1:1 relationship between P waves and QRS complexes. [[Ventricular|Ventricular bradycardias]] occurs with [[sinus bradycardia]], [[sinus arrest]], and [[AV block]]." | |||
*Treatment often consists of the administration of [[atropine]] and [[cardiac pacing]].<ref name="HN" /> | |||
==Infantile Bradycardia== | |||
*For infants, [[bradycardia]] is defined as a heart rate of less than 100 bpm (normal is around 120-160).<ref name="pmid4056971">{{cite journal |vauthors=Rein AJ, Simcha A, Ludomirsky A, Appelbaum A, Uretzky G, Tamir I |title=Symptomatic sinus bradycardia in infants with structurally normal hearts |journal=J. Pediatr. |volume=107 |issue=5 |pages=724–7 |date=November 1985 |pmid=4056971 |doi=10.1016/s0022-3476(85)80400-5 |url=}}</ref><ref name="pmid21411136">{{cite journal |vauthors=Fleming S, Thompson M, Stevens R, Heneghan C, Plüddemann A, Maconochie I, Tarassenko L, Mant D |title=Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies |journal=Lancet |volume=377 |issue=9770 |pages=1011–8 |date=March 2011 |pmid=21411136 |pmc=3789232 |doi=10.1016/S0140-6736(10)62226-X |url=}}</ref> | |||
*[[Premature]] babies are more likely than full-term babies to have [[apnea]] and [[bradycardia]] spells; their cause is not clearly understood. | |||
*Some researchers think the spells are related to centers inside the brain, that regulate breathing, which may not be fully developed. | |||
*Touching the baby gently or rocking the incubator slightly will almost always get the baby to start breathing again, which increases the [[heart rate]]. | |||
*Medications ([[theophylline]] or [[caffeine]]) can be used to treat these spells in babies if necessary. | |||
*[[NICU]] standard practice is to electronically monitor the [[heart]] and [[lungs]] for this reason. | |||
==References== | ==References== | ||
{{ | |||
{{Reflist|2}} | |||
[[Category:Up-to-Date]] | |||
Latest revision as of 13:48, 21 September 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
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 | |||||||||||||||||||||||||||||||||||||||||
| Sinus node dysfunction: Respiratory sinus arrhythmia Sinus bradycardia Sinoatrial block Sinus arrest Sick sinus syndrome Normal variant: Respiratory sinus arrhythmia | Abnormality in the atria: Low atrial focus bradycardia Atrial bigeminy | AV node dysfunction: First degree AV block Second degree AV block Complete or third-degree AV block | Junctional escape rhythm Junctional bigeminy | Isorhythmic A-V dissociation Slow VT (idioventricular rhythm) Ventricular escape rhythm Escape capture bigeminy | |||||||||||||||||||||||||||||||||||||||
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.
- The 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 exhalation is associated with a drop in the heart rate below 60 bpm with each breath, this type of bradycardia is usually deemed benign and is considered 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.
- The heart muscle of athletes has become conditioned to have a higher stroke volume, so it 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 fibrillation, flutter, and paroxysmal supraventricular tachycardia).[1]
AV Junction
- An atrioventricular nodal bradycardia or junctional escape rhythm is usually caused by the absence of the electrical impulse from the sinus node.[2]
- 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]
- 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
- Ventricular bradycardia, also known as ventricular escape rhythm or idioventricular rhythm, is a heart rate of less than 50 bpm.
- This is a safety mechanism when there is a lack of electrical impulse or stimuli from the atrium. Impulses originating from or below the His bundle, also known as ventricular, will produce a wide QRS complex with heart rates between 20 and 40 bpm.[1]
- Those above the His bundle, also known as junctional, will typically range between 40 and 60 bpm with a narrow QRS complex.
- In a third degree heart block, approximately 61% take place at the bundle branch-Purkinje system, 21% at the AV node, and 15% at the His bundle.
- AV block may be ruled out with an EKG indicating "a 1:1 relationship between P waves and QRS complexes. Ventricular bradycardias occurs with sinus bradycardia, sinus arrest, and AV block."
- Treatment often consists of the administration of atropine and cardiac pacing.[1]
Infantile Bradycardia
- For infants, bradycardia is defined as a heart rate of less than 100 bpm (normal is around 120-160).[4][5]
- Premature babies are more likely than full-term babies to have apnea and bradycardia spells; their cause is not clearly understood.
- Some researchers think the spells are related to centers inside the brain, that regulate breathing, which may not be fully developed.
- Touching the baby gently or rocking the incubator slightly will almost always get the baby to start breathing again, which increases the heart rate.
- Medications (theophylline or caffeine) can be used to treat these spells in babies if necessary.
- NICU standard practice is to electronically monitor the heart and lungs for this reason.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Allan B. Wolfson, ed. (2005). Harwood-Nuss' Clinical Practice of Emergency Medicine (4th ed.). p. 260. ISBN 0-7817-5125-X.
- ↑ "CrossRef Listing of Deleted DOIs". CrossRef Listing of Deleted DOIs. 2008. doi:10.1007/BF00400429. ISSN 0000-0000.
- ↑ Sharma, Sanjay (2003). "Physiological Society Symposium - the Athlete's Heart". Experimental Physiology. 88 (5): 665–669. doi:10.1113/eph8802624. ISSN 0958-0670.
- ↑ Rein AJ, Simcha A, Ludomirsky A, Appelbaum A, Uretzky G, Tamir I (November 1985). "Symptomatic sinus bradycardia in infants with structurally normal hearts". J. Pediatr. 107 (5): 724–7. doi:10.1016/s0022-3476(85)80400-5. PMID 4056971.
- ↑ Fleming S, Thompson M, Stevens R, Heneghan C, Plüddemann A, Maconochie I, Tarassenko L, Mant D (March 2011). "Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies". Lancet. 377 (9770): 1011–8. doi:10.1016/S0140-6736(10)62226-X. PMC 3789232. PMID 21411136.