Wolff-Parkinson-White syndrome pathophysiology: Difference between revisions

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{{Wolff-Parkinson-White syndrome}}
{{Wolff-Parkinson-White syndrome}}
{{CMG}}; {{AE}} {{CZ}}
{{CMG}}; {{AE}} {{Sara.Zand}}  {{CZ}}


==Overview==
==Overview==
In normal individuals, electrical activity in the heart is initiated in the [[sinoatrial node|sinoatrial]] (SA) node (located in the [[right atrium]]), propagates to the [[atrioventricular node|atrioventricular]] (AV) node, and then through the [[bundle of His]] to the ventricles of the heart. (See [[electrical conduction system of the heart]]).
In normal individuals, electrical activity in the heart is initiated in the [[sinoatrial node|sinoatrial]] ([[SA]]) node (located in the [[right atrium]]), propagates to the [[atrioventricular node|atrioventricular]] ([[AV]]) node, and then through the [[bundle of His]] to the ventricles of the heart. Individuals with [[Wolf-parkinson-White]] ([[WPW]]) have an [[accessory pathway]], known as the [[bundle of Kent]], that communicates between the [[atria]] and the [[ventricles]].  The conduction through the accessory pathway can be bidirectional (most commonly), only retrogarde (less common), or only antegrade (least common).  The most common type of tachycardia associated with WPW is [[atrioventricular reciprocating tachycardia]] ([[AVRT]]).  The accessory pathway does not share the rate-slowing properties of the [[AV node]]; therefore, the combination of an accessory pathway and cardiac [[arrhythmia]] can trigger [[ventricular fibrillation]], a leading cause of [[sudden cardiac death]].


==Pathophysiology==
==Pathophysiology==
*The AV node acts as a gatekeeper, limiting the electrical activity that reaches the ventricles of the heart.
===Accessory Pathway===
*This function of the [[AV node]] is important, because if the signals generated in the atria of the heart were to increase in rate (as they do during [[atrial fibrillation]] or [[atrial flutter]]), the AV node will limit the electrical activity that conducts to the ventricles.  For instance, if the atria are electrically activated at 300 beats per minute, half those electrical impulses are blocked by the AV node, so that the ventricles are activated at 150 beats per minute (giving a [[pulse]] of 150 beats per minute).  
* Individuals with WPW have a congenital [[accessory pathway]] that communicates between the [[atria]] and the [[ventricles]], in addition to the [[AV node]].
*Another important property of the [[AV node]] is that it slows down individual electrical impulses.  This is manifest on the [[electrocardiogram|ECG]] as the PR interval, the time from activation of the atria (manifest as the P wave) and activation of the ventricles (manifest as the QRS complex).
* This [[accessory pathway]] is known as the [[bundle of Kent]].
*Individuals with WPW syndrome have an accessory pathway that connects the atria and the ventricles, in addition to the AV node. This accessory pathway is known as the [[bundle of Kent]].  This accessory pathway does not share the rate-slowing properties of the AV node, and may conduct electrical activity at a significantly higher rate than the AV node.
* The [[bundle of Kent]] is an abnormal extra or [[accessory pathway|accessory conduction pathway]] between the atria and ventricles that is present in a small percentage (between 0.1% and 0.3%) of the general population.<ref name=Sorbo1995>{{cite journal|author=Sorbo MD, Buja GF, Miorelli M, Nistri S, Perrone C, Manca S, Grasso F, Giordano GM, Nava A|title=The prevalence of the Wolff–Parkinson–White syndrome in a population of 116,542 young males|journal=Giornale Italiano di Cardiologia|volume=25|issue=6|year=1995|pages=681–7|pmid=7649416|language=Italian}}</ref><ref name=Munger1993>{{cite journal|author=Munger TM, Packer DL, Hammill SC, Feldman BJ, Bailey KR, Ballard DJ, Holmes DR Jr, Gersh BJ|title=A population study of the natural history of Wolff–Parkinson–White syndrome in Olmsted County, Minnesota, 1953–1989|journal=Circulation.|volume=87|issue=3|year=1993|pages=866–73|pmid=8443907|doi=10.1161/01.CIR.87.3.866}}</ref>
*For instance, in the example above, if an individual had an atrial rate of 300 beats per minute, the accessory bundle may conduct all the electrical impulses from the atria to the ventricles, causing the ventricles to activate at 300 beats per minute.
* This pathway may communicate between the [[left atrium]] and the [[left ventricle]], in which case it is termed a "type A pre-excitation", or between the [[right atrium]] and the [[right ventricle]], in which case it is termed a "type B pre-excitation".<ref name=americanheart>[http://www.americanheart.org/presenter.jhtml?identifier=563 americanheart.org Atrial and Ventricular Depolarization Changes] Last updated 11/24/2008.</ref>
*Extremely fast heart rates are potentially dangerous, and can cause hemodynamic instability. In some cases, the combination of an accessory pathway and cardiac arrhythmias can trigger ventricular fibrillation, a leading cause of [[sudden cardiac death]].
[[Image:WPW.png|thumb|center|300px|A atrioventricular tachycardia through the accessory bundle. The electrical signal travels from the ventricles via the accessory bundle to the atria and returns to the ventricles via the AV node]]


===Genetics===
The accessory pathway is characterized by:<ref name="pmid9717020">{{cite journal| author=Obel OA, Camm AJ| title=Accessory pathway reciprocating tachycardia. | journal=Eur Heart J | year= 1998 | volume= 19 Suppl E | issue=  | pages= E13-24, E50-1 | pmid=9717020 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=9717020 }} </ref>
A small percentage of all cases of WPW syndrome are caused by mutations in the gene PRKAG2. PRKAG2 gene encodes a protein that is a part of the enzyme AMP-activated protein kinase (AMPK), which plays an important role in the energy processes of the cell.  This enzyme plays an unknown role in the development of heart before birth. Studies have shown that mutations in the PRKAG2 gene lead to alteration in the AMPK enzyme activity causing a build up of abnormal levels of glycogen in the heart muscle cells.  Other studies have found that altered AMPK activity is related to changes in the regulation of certain ion channels in the heart which play an important role in maintaining the heart rhythm.
* Conducting electrical stimulus faster than the [[AV node]]
* Longer refractory period compared to the [[AV node]]
* A non-decremental conduction in response to an increased paced rates


Most cases of WPW syndrome are sporadic in origin and only a small percentage of cases are of familial origin.
===Electrical Activity===
====Normal Electrical Activity====
* The electrical activity in the normal human [[heart]] is initiated when a cardiac [[action potential]] arises in the [[SA node|sinoatrial]] (SA) node, which is located in the [[right atrium]].
* From there, the electrical stimulus is transmitted via internodal pathways to the [[AV node|atrioventricular]] (AV) node.
* After a brief delay at the [[AV node]], the stimulus is conducted through the [[bundle of His]] to the left and [[right bundle branches]] and then to the [[Purkinje fibers]] and the [[endocardium]] at the apex of the[[ heart]], then finally to the [[ventricular]] [[myocardium]].
 
Shown below is an image depicting the conduction system in the normal [[heart]].
 
[[File:Conduction system in the heart.png|400px|center|The conduction system in the normal heart]]
 
* The [[AV node]] serves an important function as a "gatekeeper", limiting the [[ electrical activity]] that reaches the [[ventricle]]s.
* In situations where the [[atria]] generate excessively rapid electrical activity (such as [[atrial fibrillation]] or [[atrial flutter]]), the [[AV node]] limits the number of signals conducted to the ventricles.
* For example, if the [[atria]] are electrically activated at 300 beats per minute, half those electrical impulses may be blocked by the [[AV node]], so that the [[ventricle]]s are stimulated at only 150 beats per minute—resulting in a pulse of 150 beats per minute.
 
 
* Another important property of the [[AV node]] is that it slows down individual electrical impulses.
* This is manifested on the [[electrocardiogram]] as the [[PR interval]] (the time from electrical activation of the atria to electrical activation of the[[ ventricle]]s), which is usually shortened to less than 120 milliseconds in duration.
 
====Electrical Activity in WPW====
 
* The accessory pathway communicates between the [[atria]] and [[ventricle]]. 
* The accessory pathway can remain a bystander; however, problems may arise when this pathway creates an [[Electrical network|electrical circuit]] that bypasses the [[AV node]].  When an aberrant electrical connection occurs via the [[bundle of Kent]], [[tachyarrhythmia]] may therefore result.
 
Shown below is an image depicting the normal conduction of electrical signals in the [[ heart]] versus that in the presence of an [[accessory pathway]].
 
[[File: Abnormal [[electrical pathway]] in [[WPW]].jpeg|center| The normal conduction of electrical signals in the normal[[ heart]] versus that in the presence of an [[accessory pathway]]
 
* The conduction through the accessory pathway can be:
* Bidirectional (most commonly): retrogarde (also known as concealed) as well as antegrade (also known as manifest, responsible for the [[ ECG]] findings of [[delta wave]] and short [[PR interval]])
* Only retrogarde (less common)
* Only antegrade (least common)
 
* When [[arrhythmia]] occurs in a patient with an [[accessory pathway]], it defines as [[WPW syndrome]].
* The most common type of tachycardia associated with [[WPW]] is [[atrioventricular reciprocating tachycardia]] ([[AVRT]]).
** [[AVRT]] in [[ WPW]] can be derived as follows:
* [[Orthodromic]] (~95%): the antegrade electrical signal moves from the [[atria]] to the [[ventricles]] through the [[AV node]], whereas the retrograde electrical signal moves from the [[ventricle]]s to the [[atria]] through the [[accessory pathway]].
* [[Antidromic]] (~5%): the antegrade electrical signal moves from the [[atria]] to the [[ventricle]]s through the [[accessory pathway]], whereas the retrograde electrical signal moves from the [[ventricle]]s to the [[atria]] through either the [[AV node]] or a second [[accessory pathway]].
 
 
 
* Other [[ supraventricular tachyarrhythmia]] may occur in patients with [[ WPW]], such as [[atrial tachycardia]], [[atrial flutter]], [[atrial fibrillation]],[[AVNRT]].
* In these [[arrhythmia]], the [[accessory pathway]] may act as a bystander.
* The [[accessory pathway]] does not share the rate-slowing properties of the [[AV node]], and may conduct [[electrical activity]] at a significantly higher rate than the [[AV node]].
* The combination of an [[accessory pathway]] and [[tachyarrhythmia]] can trigger [[ventricular fibrillation]] and [[sudden cardiac death]].
* If an individual had an [[atrial]] rate of 300 beats per minute, the accessory bundle may conduct all the electrical impulses from the [[atria]] to the [[ventricles]], causing the [[ventricles]] to contract at 300 beats per minute. Extremely rapid [[heart rates]] such as this may result in [[hemodynamic instability]] or [[cardiogenic shock]].
* The [[missense Mutation]] in PKRAG2 has been associated with the development of familiar [[ WPW syndrome]] and [[cardiac hypertrophy]] , involving the gamma-2 subunit of AMPK pathway<ref name="pmid16943919">{{cite journal |vauthors=Sidhu J, Roberts R |title=Genetic basis and pathogenesis of familial WPW syndrome |journal=Indian Pacing Electrophysiol J |volume=3 |issue=4 |pages=197–201 |date=October 2003 |pmid=16943919 |pmc=1502052 |doi= |url=}}</ref>
 
===Associated Conditions===
WPW syndrome is associated with the following disorders:
* [[Ebstein's anomaly]]<ref name="pmid21570234">{{cite journal |author=Rao MP, Panduranga P, Al-Mukhaini M, Al-Jufaili M |title=Ebstein anomaly in an adult presenting with wide QRS tachycardia: diagnostic and therapeutic dilemmas |journal=Am J Emerg Med |volume=30 |issue=5 |pages=834.e1–4 |year=2012 |month=June |pmid=21570234 |doi=10.1016/j.ajem.2011.03.001 |url=}}</ref><ref name="pmid20150013">{{cite journal |author=Bayar N, Canbay A, Uçar O, Aydoğdu S, Diker E |title=[Association of Gerbode-type defect and Wolff-Parkinson-White syndrome with Ebstein's anomaly] |language=Turkish |journal=Anadolu Kardiyol Derg |volume=10 |issue=1 |pages=88–90 |year=2010 |month=February |pmid=20150013 |doi= |url=}}</ref><ref name="pmid20924185">{{cite journal |author=Legius B, Van De Bruaene A, Van Deyk K, ''et al.'' |title=Behavior of Ebstein's anomaly: single-center experience and midterm follow-up |journal=Cardiology |volume=117 |issue=2 |pages=90–5 |year=2010 |pmid=20924185 |doi=10.1159/000318041 |url=}}</ref>
* [[Mitral valve prolapse]]: This cardiac disorder, if present, is associated with left-sided accessory pathways.<ref name="pmid7970027">{{cite journal |author=Savini E, Capone PL |title=[Wolff-Parkinson-White, a study on the prevalence of the site of accessory pathways: relations between stability of pre-excitation, symptoms, cardiac arrhythmias and association of mitral valve prolapse with localization of pre-excitation] |language=Italian |journal=Minerva Cardioangiol |volume=42 |issue=7-8 |pages=339–43 |year=1994 |pmid=7970027 |doi= |url=}}</ref>
* [[Hypertrophic cardiomyopathy]]: This disorder is associated with familial/inherited form of WPW syndrome.<ref name="pmid22839583">{{cite journal |author=Kruchina TK, Vasichkina ES, Egorov DF, Tatarskiĭ BA |title=[Asymptomatic ventricular pre-excitation in children: a 17 year follow-up study] |language=Russian |journal=Kardiologiia |volume=52 |issue=5 |pages=30–6 |year=2012 |pmid=22839583 |doi= |url=}}</ref>
* [[Hypokalemic periodic paralysis]]<ref name="nlm">{{Cite web  | last =  | first =  | title = Wolff-Parkinson-White syndrome - Genetics Home Reference | url = http://ghr.nlm.nih.gov/condition/wolff-parkinson-white-syndrome | publisher =  | date =  | accessdate = 15 April 2014 }}</ref>
* [[Pompe disease]]<ref name="nlm">{{Cite web  | last =  | first =  | title = Wolff-Parkinson-White syndrome - Genetics Home Reference | url = http://ghr.nlm.nih.gov/condition/wolff-parkinson-white-syndrome | publisher =  | date =  | accessdate = 15 April 2014 }}</ref>
* [[Tuberous sclerosis]]<ref name="nlm">{{Cite web  | last =  | first =  | title = Wolff-Parkinson-White syndrome - Genetics Home Reference | url = http://ghr.nlm.nih.gov/condition/wolff-parkinson-white-syndrome | publisher =  | date =  | accessdate = 15 April 2014 }}</ref>


==References==
==References==

Latest revision as of 19:40, 9 November 2020

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Cafer Zorkun, M.D., Ph.D. [3]

Overview

In normal individuals, electrical activity in the heart is initiated in the sinoatrial (SA) node (located in the right atrium), propagates to the atrioventricular (AV) node, and then through the bundle of His to the ventricles of the heart. Individuals with Wolf-parkinson-White (WPW) have an accessory pathway, known as the bundle of Kent, that communicates between the atria and the ventricles. The conduction through the accessory pathway can be bidirectional (most commonly), only retrogarde (less common), or only antegrade (least common). The most common type of tachycardia associated with WPW is atrioventricular reciprocating tachycardia (AVRT). The accessory pathway does not share the rate-slowing properties of the AV node; therefore, the combination of an accessory pathway and cardiac arrhythmia can trigger ventricular fibrillation, a leading cause of sudden cardiac death.

Pathophysiology

Accessory Pathway

The accessory pathway is characterized by:[4]

  • Conducting electrical stimulus faster than the AV node
  • Longer refractory period compared to the AV node
  • A non-decremental conduction in response to an increased paced rates

Electrical Activity

Normal Electrical Activity

Shown below is an image depicting the conduction system in the normal heart.

The conduction system in the normal heart
The conduction system in the normal heart
  • The AV node serves an important function as a "gatekeeper", limiting the electrical activity that reaches the ventricles.
  • In situations where the atria generate excessively rapid electrical activity (such as atrial fibrillation or atrial flutter), the AV node limits the number of signals conducted to the ventricles.
  • For example, if the atria are electrically activated at 300 beats per minute, half those electrical impulses may be blocked by the AV node, so that the ventricles are stimulated at only 150 beats per minute—resulting in a pulse of 150 beats per minute.


  • Another important property of the AV node is that it slows down individual electrical impulses.
  • This is manifested on the electrocardiogram as the PR interval (the time from electrical activation of the atria to electrical activation of theventricles), which is usually shortened to less than 120 milliseconds in duration.

Electrical Activity in WPW

Shown below is an image depicting the normal conduction of electrical signals in the heart versus that in the presence of an accessory pathway.

[[File: Abnormal electrical pathway in WPW.jpeg|center| The normal conduction of electrical signals in the normalheart versus that in the presence of an accessory pathway

  • The conduction through the accessory pathway can be:
  • Bidirectional (most commonly): retrogarde (also known as concealed) as well as antegrade (also known as manifest, responsible for the ECG findings of delta wave and short PR interval)
  • Only retrogarde (less common)
  • Only antegrade (least common)


Associated Conditions

WPW syndrome is associated with the following disorders:

References

  1. ↑ Sorbo MD, Buja GF, Miorelli M, Nistri S, Perrone C, Manca S, Grasso F, Giordano GM, Nava A (1995). "The prevalence of the Wolff–Parkinson–White syndrome in a population of 116,542 young males". Giornale Italiano di Cardiologia (in Italian). 25 (6): 681–7. PMID 7649416.
  2. ↑ Munger TM, Packer DL, Hammill SC, Feldman BJ, Bailey KR, Ballard DJ, Holmes DR Jr, Gersh BJ (1993). "A population study of the natural history of Wolff–Parkinson–White syndrome in Olmsted County, Minnesota, 1953–1989". Circulation. 87 (3): 866–73. doi:10.1161/01.CIR.87.3.866. PMID 8443907.
  3. ↑ americanheart.org Atrial and Ventricular Depolarization Changes Last updated 11/24/2008.
  4. ↑ Obel OA, Camm AJ (1998). "Accessory pathway reciprocating tachycardia". Eur Heart J. 19 Suppl E: E13–24, E50–1. PMID 9717020.
  5. ↑ Sidhu J, Roberts R (October 2003). "Genetic basis and pathogenesis of familial WPW syndrome". Indian Pacing Electrophysiol J. 3 (4): 197–201. PMC 1502052. PMID 16943919.
  6. ↑ Rao MP, Panduranga P, Al-Mukhaini M, Al-Jufaili M (2012). "Ebstein anomaly in an adult presenting with wide QRS tachycardia: diagnostic and therapeutic dilemmas". Am J Emerg Med. 30 (5): 834.e1–4. doi:10.1016/j.ajem.2011.03.001. PMID 21570234. Unknown parameter |month= ignored (help)
  7. ↑ Bayar N, Canbay A, Uçar O, Aydoğdu S, Diker E (2010). "[Association of Gerbode-type defect and Wolff-Parkinson-White syndrome with Ebstein's anomaly]". Anadolu Kardiyol Derg (in Turkish). 10 (1): 88–90. PMID 20150013. Unknown parameter |month= ignored (help)
  8. ↑ Legius B, Van De Bruaene A, Van Deyk K; et al. (2010). "Behavior of Ebstein's anomaly: single-center experience and midterm follow-up". Cardiology. 117 (2): 90–5. doi:10.1159/000318041. PMID 20924185.
  9. ↑ Savini E, Capone PL (1994). "[Wolff-Parkinson-White, a study on the prevalence of the site of accessory pathways: relations between stability of pre-excitation, symptoms, cardiac arrhythmias and association of mitral valve prolapse with localization of pre-excitation]". Minerva Cardioangiol (in Italian). 42 (7–8): 339–43. PMID 7970027.
  10. ↑ Kruchina TK, Vasichkina ES, Egorov DF, Tatarskiĭ BA (2012). "[Asymptomatic ventricular pre-excitation in children: a 17 year follow-up study]". Kardiologiia (in Russian). 52 (5): 30–6. PMID 22839583.
  11. ↑ 11.0 11.1 11.2 "Wolff-Parkinson-White syndrome - Genetics Home Reference". Retrieved 15 April 2014.

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