Wolff-Parkinson-White syndrome pathophysiology: Difference between revisions
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__NOTOC__ | __NOTOC__ | ||
{{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. 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]]. | 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== | ||
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* 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]]. | * 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. | * 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]]. | * 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. | 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]] | [[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 | * 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. | * 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 | * 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. | * 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 | * 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==== | ====Electrical Activity in WPW==== | ||
* The accessory pathway communicates between the atria and ventricle. | * 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. | * 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 heart versus that in the presence of an accessory pathway. | 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]] | [[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: | * 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]]) | * 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 retrogarde (less common) | ||
* Only antegrade (least common) | * Only antegrade (least common) | ||
* When [[arrhythmia]] occurs in a patient with an accessory pathway, it defines as WPW syndrome . | * 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]]). | * The most common type of tachycardia associated with [[WPW]] is [[atrioventricular reciprocating tachycardia]] ([[AVRT]]). | ||
** AVRT in WPW can be derived as | ** [[AVRT]] in [[ WPW]] can be derived as follows: | ||
* Orthodromic (~95%): the antegrade electrical signal moves from the [[atria]] to the [[ | * [[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]]. | * [[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]] | * 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. | * 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 [[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]]. | * 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. | * 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> | * 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=== | ===Associated Conditions=== | ||
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
- Individuals with WPW have a congenital accessory pathway that communicates between the atria and the ventricles, in addition to the AV node.
- This accessory pathway is known as the bundle of Kent.
- The bundle of Kent is an abnormal extra or 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.[1][2]
- 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".[3]
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
- The electrical activity in the normal human heart is initiated when a cardiac action potential arises in the sinoatrial (SA) node, which is located in the right atrium.
- From there, the electrical stimulus is transmitted via internodal pathways to the 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 theheart, then finally to the ventricular myocardium.
Shown below is an image depicting 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
- 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 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 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)
- 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).
- 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 ventricles to the atria through the accessory pathway.
- Antidromic (~5%): the antegrade electrical signal moves from the atria to the ventricles through the accessory pathway, whereas the retrograde electrical signal moves from the ventricles 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[5]
Associated Conditions
WPW syndrome is associated with the following disorders:
- Ebstein's anomaly[6][7][8]
- Mitral valve prolapse: This cardiac disorder, if present, is associated with left-sided accessory pathways.[9]
- Hypertrophic cardiomyopathy: This disorder is associated with familial/inherited form of WPW syndrome.[10]
- Hypokalemic periodic paralysis[11]
- Pompe disease[11]
- Tuberous sclerosis[11]
References
- ↑ 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.
- ↑ 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.
- ↑ americanheart.org Atrial and Ventricular Depolarization Changes Last updated 11/24/2008.
- ↑ Obel OA, Camm AJ (1998). "Accessory pathway reciprocating tachycardia". Eur Heart J. 19 Suppl E: E13–24, E50–1. PMID 9717020.
- ↑ 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.
- ↑ 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) - ↑ 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) - ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 11.0 11.1 11.2 "Wolff-Parkinson-White syndrome - Genetics Home Reference". Retrieved 15 April 2014.