--- title: Wolff-Parkinson-White syndrome (WPW) description: What WPW syndrome and ventricular pre-excitation are, why an accessory pathway can be dangerous, how it is detected, which treatment approaches clinical guidelines describe and when urgent help is needed. type: disease preset: wpw-syndrome aliases: - WPW - WPW syndrome - WPW pattern - ventricular pre-excitation - pre-excitation syndrome - accessory pathway sources: - tier: guideline org: minzdrav-rf title: Наджелудочковые тахикардии year: 2025 doi: 10.15829/1560-4071-2025-6448 url: https://cr.minzdrav.gov.ru/view-cr/619_3 - tier: guideline org: esc title: 2019 Рекомендации ESC по лечению пациентов с наджелудочковыми тахикардиями year: 2020 doi: 10.15829/1560-4071-2020-3864 url: https://doi.org/10.15829/1560-4071-2020-3864 - tier: reference org: msd-manuals title: Wolff-Parkinson-White Syndrome (WPW Syndrome) year: 2024 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/specific-cardiac-arrhythmias/wolff-parkinson-white-syndrome-wpw-syndrome - tier: reference org: msd-manuals title: Atrial Fibrillation and Wolff-Parkinson-White Syndrome (WPW Syndrome) year: 2024 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/specific-cardiac-arrhythmias/atrial-fibrillation-and-wolff-parkinson-white-syndrome-wpw-syndrome - tier: guideline org: nice title: Transient loss of consciousness ('blackouts') in over 16s (CG109) year: 2023 url: https://www.nice.org.uk/guidance/cg109 sources_checked: 2026-10-12 review: null --- Wolff-Parkinson-White (WPW) syndrome is a condition in which an extra (accessory) pathway between an atrium and a ventricle conducts the electrical impulse, bypassing the atrioventricular (AV) node. Through this pathway the impulse reaches part of the ventricles earlier than usual. This is called ventricular pre-excitation, and it can be seen on an [ECG](../../diagnostic/ecg/). Doctors speak of WPW syndrome when pre-excitation comes with recurrent episodes of tachycardia; if the ECG signs are present but there are no episodes, it is called the WPW pattern (phenomenon). The WPW pattern is found on the ECG in 0.15–0.25% of people, and in 0.55% of first-degree relatives.

Normally the impulse travels across the atria to the atrioventricular (AV) node, which holds it back for a moment, and only then excites the ventricles through the normal conduction system. The muscle of the atria and the ventricles is completely separated, and the impulse has no other way through.

In WPW there is an accessory pathway between an atrium and a ventricle: a strand of heart muscle cells that bypasses the AV node. The impulse passes through it without the AV node delay and excites one part of the ventricle before the rest, which the impulse reaches by the usual route. On the ECG this shows as a short PR interval (under 120 ms), a delta wave at the start of the QRS complex and a wide QRS (over 120 ms).

## Why it happens An accessory pathway is a thin strand of heart muscle cells that connects an atrium directly to a ventricle. It forms before birth: normally the muscle of the atria and the ventricles becomes completely separated, but here the separation stays incomplete. Otherwise the heart is usually normal. Pre-excitation syndromes can run in families, and they are usually found at a young age. An accessory pathway can cause two kinds of problems. Most often these are episodes of tachycardia: the impulse starts to circle through the AV node and the accessory pathway (see the article on [supraventricular tachycardia](../supraventricular-tachycardia/)). Less common but more dangerous is [atrial fibrillation](../atrial-fibrillation/): the rapid impulses from the atria then reach the ventricles without passing through the AV node, which normally holds them back, and a very fast ventricular rhythm can turn into ventricular fibrillation and cause sudden death. Accessory pathways (APs; the Russian Ministry of Health guideline calls them accessory atrioventricular connections) are single or multiple strands of myocardial cells that bypass the physiological conduction system; their presence reflects incomplete embryological development of the AV annulus. About 60% of APs run along the mitral valve, 25% are septal and about 15% run along the right free wall. Antegrade conduction over an AP can be persistent (a manifest AP, including the WPW pattern or syndrome) or intermittent (an intermittent AP); APs that conduct only retrogradely are called concealed. With a concealed pathway the ECG shows no WPW pattern, and these patients are not at risk of rapidly conducted supraventricular arrhythmias. Most APs underlying WPW syndrome occur in a structurally normal heart; rare familial forms of pre-excitation have been described. ## Symptoms The main sign is episodes of a fast, regular heartbeat that start suddenly and stop suddenly; during an episode there may be breathlessness, chest discomfort or light-headedness. An episode can last from a few seconds to several hours, and fainting is uncommon. Between episodes a doctor's examination usually finds nothing abnormal. Most people with a WPW pattern on the ECG never have any symptoms from it in their lifetime; about one in five is thought to develop episodes of tachycardia over time. The most serious complication is sudden cardiac arrest: it is rare, but it is sometimes the first sign of WPW, especially in teenagers. In atrioventricular re-entrant tachycardia (AVRT) the mean age at onset of symptoms is 23 years. Orthodromic AVRT accounts for more than 90% of AVRT: the impulse travels to the ventricles through the AV node and the His–Purkinje system and returns to the atria over the AP; the heart rate is above 150 per minute but rarely exceeds 220, and the QRS complex is narrow. Antidromic AVRT occurs in 3–8% of patients with WPW syndrome, and its QRS is wide (fully pre-excited). The life-threatening arrhythmia in manifest WPW syndrome is atrial fibrillation (AF) or atrial flutter: if the AP has a short antegrade refractory period, rapid conduction to the ventricles can lead to ventricular fibrillation. The rate of sudden cardiac death (SCD) in WPW syndrome is 0.15–0.39% over 3–10 years of follow-up; a high risk of SCD is associated with young age, inducibility of AVRT at an electrophysiology study (EPS), multiple APs and the ability of the AP to conduct rapidly to the ventricles. ## How it is diagnosed The main test is an ECG: the signs of pre-excitation show on it even between episodes. If episodes are rare, the doctor may arrange a longer heart rhythm recording, such as [Holter monitoring](../../diagnostic/holter-monitoring/) or a wearable recorder. A heart ultrasound (echocardiogram) shows the size and function of the heart chambers. Sometimes an electrophysiology study (EPS) is needed, either non-invasive or from inside the heart. If a WPW pattern is found on an ECG by chance and there have been no episodes, the doctor assesses the risk of sudden cardiac arrest. For people who do competitive sport or work in high-risk occupations (for example pilots and professional drivers), guidelines recommend an EPS to assess the risk. The typical resting ECG of a manifest AP shows a short PR interval (under 120 ms), a delta wave in the initial part of the QRS complex and a wide QRS (over 120 ms). In asymptomatic pre-excitation, an EPS for SCD risk stratification is recommended for those who do competitive sport or have occupations that could potentially provoke arrhythmia episodes (class I B); in other patients with asymptomatic pre-excitation an EPS should be considered (class IIa B). High-risk EPS criteria are a shortest pre-excited RR interval ≤250 ms, an AP effective refractory period ≤250 ms, multiple APs and inducible AP-mediated tachycardia. Abrupt and complete normalisation of the PR interval with loss of the delta wave during exercise or a drug test was regarded as a marker of low risk. Even invasive tests are not absolutely accurate in assessing risk. In people over 16 with transient loss of consciousness, NICE lists ventricular pre-excitation on the ECG among the abnormalities that require urgent referral for cardiovascular assessment, with the referral reviewed by a specialist within 24 hours. ## How it is treated If the condition is unstable during an episode, the rhythm is restored with an electric shock; this is called electrical cardioversion. If the condition is stable and the tachycardia is the usual (orthodromic) kind, doctors start with vagal manoeuvres and, if these do not work, give medicines into a vein. In WPW some of the usual medicines for tachycardia are dangerous: in atrial fibrillation with pre-excitation, doctors do not use medicines that slow conduction through the AV node, because these can help it turn into ventricular fibrillation. This is why the choice of treatment is always the doctor's. To get rid of episodes in the long term, catheter ablation is used: a catheter is passed through a blood vessel to the heart and the accessory pathway is targeted precisely. This is the treatment of choice for recurrent episodes with symptoms and after atrial fibrillation conducted over the accessory pathway; ablation is usually effective, and serious complications are rare. If ablation is not wanted or not possible, the doctor may prescribe medicines to prevent episodes. If there is a WPW pattern but there have been no episodes, ablation is recommended when an EPS shows a high risk, and follow-up when the risk is low; with a low risk, ablation is also possible at the patient's wish in an experienced centre. The doctor and the patient decide together which way to go. Synchronised electrical cardioversion is recommended for haemodynamically unstable patients with AVRT, and for haemodynamically unstable patients with irregular wide-QRS tachycardia when accessory pathways are present. In stable patients with AVRT vagal manoeuvres are recommended; drug therapy in orthodromic and antidromic tachycardia targets one of the components of the circuit, the AV node or the AP; in antidromic AVRT, which runs over a rapidly conducting AP, drugs acting on the AP are used. In pre-excited AF, drugs acting on the AV node (including beta-blockers, non-dihydropyridine calcium channel blockers and cardiac glycosides) must be avoided because they may promote the transition of AF into ventricular fibrillation. The Russian Ministry of Health and ESC guidelines classify them as not recommended and potentially harmful in this setting (class III B); the same list includes one class III antiarrhythmic drug, which also slows AV node conduction and so favours conduction over the AP. Catheter ablation of the AP is recommended for all patients with symptomatic recurrent AVRT (class I B) and is the treatment of choice in symptomatic recurrent AVRT or AF conducted over the AP. If ablation is not desired or not feasible, class IC antiarrhythmic drugs may be used in patients with pre-excitation and symptomatic AVRT without structural heart disease and/or chronic heart failure; beta-blockers and calcium channel blockers in orthodromic AVRT are acceptable only in patients without manifest pre-excitation. In asymptomatic pre-excitation, ablation is recommended when high-risk EPS criteria are present (class I B) and when left ventricular dysfunction is presumed to be caused by electrical dyssynchrony (class IIa C). ## When to call an ambulance Call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK) if an episode of palpitations comes with fainting, feeling faint (sudden darkening of vision, weakness, dizziness, cold sweat) or a drop in blood pressure (the upper, systolic, reading below 100 mm Hg). According to the guidelines, hospital admission is also required when an episode comes with chest pain, fluid on the lungs (acute left ventricular failure) or impaired blood flow to the brain, and when a heart attack is suspected. Atrial fibrillation in a person with WPW is an emergency, because the ventricles can start to beat very fast.