Wolff–Parkinson–White syndrome
Template:Short description Template:Infobox medical condition
Wolff–Parkinson–White syndrome (WPWS) is a disorder due to a specific type of problem with the electrical system of the heart involving an accessory pathway able to conduct electrical current between the atria and the ventricles, thus bypassing the atrioventricular node.<ref name="GARD2012">Template:Cite web</ref><ref name="Bh2016" /> About 60% of people with the electrical problem develop symptoms,<ref name="Kim2017">Template:Cite journal</ref> which may include an abnormally fast heartbeat, palpitations, shortness of breath, lightheadedness, or syncope.<ref name="GHR2017">Template:Cite web</ref> Rarely, cardiac arrest may occur.<ref name="GHR2017" /> The most common type of arrhythmia (abnormal heart rate) associated with WPWS is paroxysmal supraventricular tachycardia.<ref name="GHR2017" />
The cause of WPW is typically unknown and is likely due to a combination of chance and genetic factors.<ref name=GARD2012/> A small number of cases are due to a mutation of the PRKAG2 gene which may be inherited in an autosomal dominant fashion.<ref name=GARD2012/> The underlying mechanism involves an accessory electrical conduction pathway between the atria and the ventricles.<ref name=GHR2017/> It is associated with other conditions such as Ebstein anomaly and hypokalemic periodic paralysis.<ref name=GHR2017/> The diagnosis of WPW occurs with a combination of palpitations and when an electrocardiogram (ECG) show a short PR interval and a delta wave.<ref name=Bh2016>Template:Cite journal</ref> It is a type of pre-excitation syndrome.<ref name="Bh2016"/>
WPW syndrome may be monitored or treated with either medications or an ablation (destroying the tissues) such as with radiofrequency catheter ablation.<ref name=BMJ2011>Template:Cite journal</ref> It affects between 0.1 and 0.3% in the population.<ref name=GHR2017/> The risk of death in those without symptoms is about 0.5% per year in children and 0.1% per year in adults.<ref name=Kim2017/> In some cases, non-invasive monitoring may help to more carefully risk stratify patients into a lower risk category.<ref name="Authority">Template:Cite web</ref> In those without symptoms ongoing observation may be reasonable.<ref name=Kim2017/> In those with WPW complicated by atrial fibrillation, cardioversion or the medication procainamide may be used.<ref name="Sim2010"/> The condition is named after Louis Wolff, John Parkinson, and Paul Dudley White who described the ECG findings in 1930.<ref name=Bh2016/>
Signs and symptoms
People with WPW are usually asymptomatic when not having a fast heart rate. However, individuals may experience palpitations, dizziness, shortness of breath, or infrequently syncope (fainting or near fainting) during episodes of supraventricular tachycardia. WPW is also associated with a very small risk of sudden death due to more dangerous heart rhythm disturbances.<ref name=":0">Template:Cite journal</ref>
Pathophysiology
Electrical activity in the normal human heart begins 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 travels 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.Template:Citation needed
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 the ventricles), which is usually shortened to less than 120 milliseconds in duration.Template:Citation needed
Individuals with WPW have an accessory pathway that communicates between the atria and the ventricles, in addition to the AV node.<ref name="Authority"/> 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. 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 contract at 300 beats per minute. Extremely rapid heart rates such as this may result in hemodynamic instability or cardiogenic shock. In some cases, the combination of an accessory pathway and abnormal heart rhythms can trigger ventricular fibrillation, a leading cause of sudden cardiac death.Template:Citation needed
WPW may be associated with PRKAG2, a protein kinase enzyme encoded by the PRKAG2 gene.<ref name=Gollob2008>Template:Cite journal</ref>
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.<ref name=Rosner1999>Template:Cite journal</ref><ref name=Sorbo1995>Template:Cite journal</ref><ref name=Munger1993>Template:Cite journal</ref> 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" in old, currently abandoned classification.<ref name=americanheart>Template:Cite web</ref> Problems arise when this pathway creates an electrical circuit that bypasses the AV node. The AV node is capable of slowing the rate of conduction of electrical impulses to the ventricles, whereas the bundle of Kent lacks this capability. When an aberrant electrical connection is made via the bundle of Kent, tachydysrhythmias may therefore result.Template:Citation needed
Diagnosis
WPW is commonly diagnosed on the basis of the electrocardiogram in an asymptomatic individual. In this case, it is manifested as a delta wave, which is a slurred upstroke in the QRS complex that is associated with a short PR interval. The short PR interval and slurring of the QRS complex are reflective of the impulse making it to the ventricles early (via the accessory pathway) without the usual delay experienced in the AV node.Template:Citation needed
If a person with WPW experiences episodes of atrial fibrillation, the ECG shows a rapid polymorphic wide-complex tachycardia (without torsades de pointes). This combination of atrial fibrillation and WPW is considered dangerous, and most antiarrhythmic drugs are contraindicated.Template:Citation needed
When an individual is in normal sinus rhythm, the ECG characteristics of WPW are a short PR interval (less than 120 milliseconds in duration), widened QRS complex (greater than 120 milliseconds in duration) with slurred upstroke of the QRS complex, and secondary repolarization changes (reflected in ST segment-T wave changes).Template:Citation needed
In individuals with WPW, electrical activity that is initiated in the SA node travels through the accessory pathway, as well as through the AV node to activate the ventricles via both pathways. Since the accessory pathway does not have the impulse slowing properties of the AV node, the electrical impulse first activates the ventricles via the accessory pathway, and immediately afterwards via the AV node. This gives the short PR interval and slurred upstroke of the QRS complex known as the delta wave.Template:Citation needed
In case of type A pre-excitation (left atrioventricular connections), a positive R wave is seen in V1 ("positive delta") on the precordial leads of the electrocardiogram, while in type B pre-excitation (right atrioventricular connections), a predominantly negative delta wave is seen in lead V1 ("negative delta").<ref name=americanheart/>
People with WPW may have more than one accessory pathwayTemplate:Sndin some cases, as many as eight abnormal pathways have been found. This has been seen in individuals with Ebstein's anomaly.<ref>Template:Cite web</ref>
Wolff–Parkinson–White syndrome is sometimes associated with Leber's hereditary optic neuropathy, a form of mitochondrial disease.<ref name=Mashima1996>Template:Cite journal</ref>
Risk stratification
WPW carries a small risk of sudden death, presumably due to rapidly conducted atrial fibrillation causing ventricular fibrillation. While the overall risk is approximately 2.4 per 1000 person years, the risk in an individual is dependent on the properties of the accessory pathway causing pre-excitation.<ref name=":0" />
A higher risk accessory pathway may be suggested by a history of syncope, but risk stratification is best performed by assessing how frequently a pathway can conduct impulse to the ventricles, usually via programmed electrical stimulation (PES) in the cardiac electrophysiology laboratory. This is an invasive but generally low-risk procedure during which the atria are stimulated to try to induce tachycardia. If a tachycardia involving the accessory pathway can be triggered, the cardiologist can then assess how rapidly the accessory pathway is able to conduct. The faster it can conduct, the higher the likelihood the accessory pathway can conduct fast enough to trigger a lethal tachycardia.Template:Citation needed
High-risk features that may be present during PES include an effective refractory period of the accessory pathway less than 250 ms, multiple pathways, septal location of pathway, and inducibility of supraventricular tachycardia (AVRT, atrial fibrillation). Individuals with any of these high-risk features are generally considered at increased risk for SCD or symptomatic tachycardia, and should be treated accordingly (i.e.: catheter ablation).<ref name=Pappone2003>Template:Cite journal</ref>
It is unclear whether invasive risk stratification (with PES) is necessary in the asymptomatic individual.<ref name=Cambell2003>Template:Cite journal</ref> While some groups advocate PES for risk stratification in all individuals under 35 years old, others only offer it to individuals who have history suggestive of a tachydysrhythmia, since the incidence of sudden cardiac death is so low (less than 0.6% in some reports).<ref name=Munger1993/><ref name=Fitzsimmons2001>Template:Cite journal</ref><ref name=Kenyon>Template:Cite web</ref>
Other methods of risk stratification include observing the ventricular rate during spontaneous atrial fibrillation on a 12-lead ECG. RR intervals of less than 250 ms suggest a higher risk pathway. During exercise testing, abrupt loss of pre-excitation as heart rate increases also suggest a lower risk pathway.<ref name=":0" /> However, this approach is hampered by the normal improvement in AV node conduction during exercise which can also mask pre-excitation despite ongoing conduction down the accessory pathway.<ref>Template:Cite bookTemplate:Page needed</ref>
Treatment
According to the ACLS protocol, patients with WPW who become symptomatic with a supraventricular tachycardia (SVT) with hemodynamic instability (along with a heart rate (HR) > 150 bpm during the SVT episode and the abnormal heart rhythm seen on a current ECG, hemodynamic instability is defined as hypotension with a systolic blood pressure (SBP) < 90 mm Hg or a rather-sudden drop in the SBP by > 40 mm Hg; other symptoms may include chest pain, palpitations, shortness of breath (SOB), confusion, delayed capillary refill, acute drop in urinary output (oliguria), lethargy with a change in mentation, or altered mental status and disorientation) requires emergent medical intervention with an automated external defibrillator (AED) for prompt electrical synchronized cardioversion in an attempt to bring the patient back into a normal sinus rhythm and/or prevent further decompensation, cardiac arrest, and mortality.<ref>Template:Cite journal</ref>
If the WPW patient is symptomatic but hemodynamically stable, antiarrhythmic drugs (e.g., amiodarone or procainamide) may be used in an attempt to chemically convert the patient back into normal sinus rhythm.<ref>Template:Cite journal </ref>
Medications
WPW pattern with hemodynamically stability and orthodromic AVRT leading to a regular narrow complex tachycardia may be managed similarly to other regular narrow complex supraventricular tachycardias: first with vagal maneuvers followed by a trial of adenosine (first-line therapy). The 2015 ACC/AHA/HRS guidelines recommend beta-blockers or calcium channel blockers as second-line agents, electric cardioversion is reserved for refractory arrhythmias. However, if there is any doubt about the diagnosis of orthodromic AVRT or if aberrant conduction leading to a wide complex QRS is observed, it may be prudent to manage as undifferentiated wide complex tachycardia.<ref name =wpw_ncbi>Template:Cite book</ref>
People with atrial fibrillation and rapid ventricular response may be treated with amiodarone<ref name=Sim2010>Template:Cite journal</ref> or procainamide<ref name=Fengler2007>Template:Cite journal</ref> to stabilize their heart rate. Procainamide and cardioversion are accepted treatments for conversion of tachycardia found with WPW.<ref name=Ritchie>Template:Cite book</ref> Amiodarone in atrial fibrillation with WPW, is linked to ventricular fibrillation, and thus may be worse than procainamide.<ref name=Sim2010/>
AV node blockers should be avoided in atrial fibrillation and atrial flutter with WPW or history of it; this includes adenosine, diltiazem, verapamil, other calcium channel blockers, and beta blockers.<ref name=Wald2009>Template:Cite book</ref> They can exacerbate the syndrome by blocking the heart's normal electrical pathway (therefore favoring 1:1 atrial to ventricle conduction through the pre-excitation pathway, potentially leading to unstable ventricular arrhythmias).<ref name=wpw_ncbi/>
Catheter ablation
The definitive treatment of WPW is the destruction of the abnormal electrical pathway by catheter ablation. Two main types of catheter ablation include radiofrequency ablation with heat or cryoablation with cold energy.<ref name="Authority"/> This procedure is performed by cardiac electrophysiologists and has high success rate in the hands of an experienced electrophysiologist.<ref name=Pappone1993>Template:Cite journal</ref> Findings from 1994 indicate success rates of as high as 95% in people treated with radiofrequency catheter ablation for WPW.<ref name=Thakur1994>Template:Cite journal</ref> If radiofrequency catheter ablation is successfully performed, the condition is generally considered cured. Recurrence rates are typically less than 5% after a successful ablation.<ref name=Pappone1993/> Some patients, such as ones with underlying Ebstein's anomaly and inherited cardiomyopathies, may have multiple accessory pathways.<ref>Template:Cite journal</ref>
History
The bundle of Kent is eponymously named for British physiologist Albert Frank Stanley Kent (1863Template:Ndash1958), who described lateral branches in the atrioventricular groove of the monkey heart (erroneously believing these constituted the normal atrioventricular conduction system).<ref name=Kent1893>Template:Cite journal</ref><ref name=Kent1914>Template:Cite journal</ref>
In 1915, Frank Norman Wilson (1890Template:Ndash1952) became the first to describe the condition later called Wolff–Parkinson–White syndrome.<ref name=Wilson1915>Template:Cite journal</ref> Alfred M. Wedd (1887Template:Ndash1967) was the next to describe the condition in 1921.<ref name=Wedd1921>Template:Cite journal</ref> Cardiologists Louis Wolff (1898Template:Ndash1972), John Parkinson (1885Template:Ndash1976) and Paul Dudley White (1886Template:Ndash1973) are credited with the definitive description of the disorder in 1930.<ref name=Wolff1930>Template:Cite journal</ref>
Notable cases
- LaMarcus Aldridge, American basketball player<ref name=Aldridge2007>Template:Cite web</ref>
- Michael Cera, Canadian actor<ref name="RStone-Nerd-2010">Template:Cite magazine</ref>
- Jonathon Cooper, American football player<ref>Template:Cite AV media</ref>
- Max Duggan, American football player<ref>Template:Cite web</ref>
- Nathan Eagleton, former Australian rules football player<ref name=Landsberger2008>Template:Cite web</ref>
- Jeff Garlin, American actor, writer, and comedian<ref name="earwolf.com"/>
- Quentin Groves, American football player who died of a heart attack at age 32<ref>Template:Cite news</ref>
- Dan Hardy, British UFC welterweight fighter,<ref>Template:Cite web</ref> turned analyst and commentator
- Alicia Hoskin, New Zealand Olympic canoeist.<ref>Template:Cite web</ref>
- Mitch Hurwitz, American television writer and producer, creator of Arrested Development<ref name="earwolf.com">Template:Cite web</ref>
- Jessie J, British musician<ref>Template:Cite news</ref>
- Marilyn Manson, American musician, painter, and actor<ref>Template:Cite web</ref>
- Meat Loaf, American musician<ref name=MeatLoaf2003>Template:Cite web</ref>
- Michael Montgomery, American football player<ref>Template:Cite web</ref>
- Montel Vontavious Porter, professional wrestler<ref name=IGNInt>Template:Cite web</ref>
- Michael Rupp, American ice hockey player<ref name=Chere2008>Template:Cite web</ref>
See also
References
External links
- Genetics Home Reference: Wolff-Parkinson-White syndrome (United States National Library of Medicine, Bethesda, Maryland)
- Wolff-Parkinson-White Syndrome Clinic, The University of Wisconsin - Madison
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