In Wolff-Parkinson-White, an accessory pathway leads to stimulation of the ventricles. The accessory pathway enables electrical conduction to bypass the AV node and stimulate the proximal ventricles prematurely (pre-excitation). This, in addition to normal electrical conduction through the AV node, leads to ‘double excitation’ of the ventricles.
The location and conduction through the accessory pathway varies between individuals. In most patients, conduction can move both anterograde (from the atria to the ventricles) and retrograde (from the ventricles to the atria).
In a smaller group (approx. 15% of patients), conduction moves in a retrograde manner only. Anterograde conduction by itself is rare.
Additionally, the accessory pathway may be left-sided or right-sided. This will affect the changes seen on the ECG (see investigations section).
The accessory pathway in Wolff-Parkinson-White Syndrome is sometimes referred to as the ‘bundle of Kent’.
Unlike normal conduction pathways in the heart, conduction through the accessory pathway in WPW is not regulated by the AV node and can therefore lead to tachyarrhythmias (the heart beating too fast).
Wolff-Parkinson-White Syndrome most commonly presents in males aged 30-40 years.2
The majority of WPW cases are sporadic, however, a small percentage of cases are thought to be due to an inherited mutation in the PRKAG2 gene.This genetic mutation is autosomal dominant.3
WPW Syndrome is also associated with congenital heart disease, such as Ebstein’s anomaly.
The clinical features of Wolff-Parkinson-White syndrome are caused by the associated tachyarrhythmias. Some patients may be asymptomatic and only diagnosed following a routine ECG.
Typical symptoms of tachyarrhythmias include:4
Other features may include chest pain, shortness of breath and sweating.4
The duration of these symptoms varies from person to person and can range from seconds to hours. The frequency of symptoms also varies considerably. Symptoms do not usually have any precipitating factors, however, episodes may be triggered by strenuous exercise, alcohol or caffeine.4
The main differential diagnoses for Wolff-Parkinson White syndrome are other tachyarrhythmias:5
Other conditions that may present in a similar way include valvular disease, Ebstein’s anomaly (a congenital malformation of the tricuspid valve) and hypertrophic cardiomyopathy.6
Key features of WPW on an ECG in sinus rhythm include:
Short PR interval <120ms
Delta wave: slurred upstroke of the QRS
Widened QRS complex >110ms
Incongruous ST segment and T waves changes
Prominent R waves in V1-3: this mimics a posterior infarction
Type A vs type B
Wolff-Parkinson-White syndrome can also be subdivided depending on which side the accessory pathway runs in the heart. Type A WPW pattern is a left-sided accessory pathway and type B WPW pattern is a right-sided accessory pathway.
ECG features will be different depending on whether a person has type A or type B WPW pattern:7
Type A (left-sided): positive delta wave in the precordial leads (I, II, III, aVL, aVR, aVF), R>S in V1
Type B (right-sided): negative delta wave in leads I and II
Blood tests may be useful in ruling out other (non-cardiac) causes of palpitations.
Relevant laboratory investigations include:
Full blood count
Urea and electrolytes
Liver function tests
Thyroid function tests
Relevant imaging investigations include:
Chest X-ray: to rule out other (non-cardiac) causes
Echocardiogram: to rule out structural heart disease (e.g. Ebstein’s anomaly, hypertrophic cardiomyopathy, valvular diseases) and assess left ventricular function.
Other relevant investigations may include:
Ambulatory ECG monitoring (e.g. 72-hour tape): this allows the ECG to detect periods of pre-excitation amongst normal sinus rhythm. This is often used to confirm the diagnosis of WPW syndrome.
Exercise stress test: may help to establish the relationship between exercise and tachyarrhythmias associated with WPW
Electrophysiology studies: may help identify accessory pathways for ablation
Often, episodes of pre-excitation are short, self-terminating and do not cause problems. In people who only experience occasional symptoms, no treatment is needed, and they are followed up regularly by a cardiologist.
In patients whose episodes are triggered by stress, exercise or alcohol, simple lifestyle changes may help to reduce the frequency of tachyarrhythmia episodes.
Management of tachyarrhythmias
During a symptomatic episode, Wolff-Parkinson-White syndrome is treated similarly to any other tachyarrhythmia.
Vagal manoeuvres are first-line and can be used by the patient at home. An example of a vagal manoeuvre is the Valsalva manoeuvre (forced expiration against a closed glottis) which slows the heart rate via stimulation of the vagus nerve.
If vagal manoeuvres are unsuccessful, intravenous adenosine may terminate the episode via blocking of conduction through the AV node.
Finally, cardioversion may be performed if adenosine is not successful.
Long-term, episodes may be prevented by catheter ablation of the accessory pathway, which is effective in 95% of patients. Alternatively, daily amiodarone may be used to slow the heart rate and prevent tachyarrhythmias.
Complications of Wolff-Parkinson-White syndrome are related to the periods of tachyarrhythmia. Complications may include palpitations, dizziness, syncope and sudden cardiac death.8
Sudden cardiac death in WPW Syndrome is rare, and the overall risk is approximately 0.1% in asymptomatic patients and 0.3% in symptomatic patients per year.9
Wolff-Parkinson-White syndrome is a congenital abnormality resulting in an abnormal accessory pathway in the heart
This accessory pathway causes pre-excitation of the ventricles and may result in tachyarrhythmias
The main diagnostic investigation is an ECG which has key features of a short PR interval, delta wave and broad QRS complex
Most cases do not require active management, however, during periods of tachyarrhythmia the main management options are vagal manoeuvres or adenosine
Complications of Wolff-Parkinson-White syndrome are related to the periods of tachyarrhythmia. Sudden cardiac death is rare, but more common in symptomatic patients.
Dr Chris Jefferies
Lovely Chhabra; Amandeep Goyal; Michael D. Benham. Wolff-Parkinson-White Syndrome. Published 2021. Available from: [LINK]
Rare Diseases. Wolff-Parkinson-White Syndrome. Published 2007. Available from: [LINK]
Vaughan CJ, Hom Y, Okin DA, McDermott DA, Lerman BB, Basson CT. Molecular genetic analysis of PRKAG2 in sporadic Wolff-Parkinson-White syndrome. J Cardiovasc Electrophysiol. 2003 Mar;14(3):263-8. Available from: [LINK]
Wolff-Parkinson-White Syndrome. Published August 2018. Available from: [LINK]
Marrakchi, S. Kammoun, I. Kachboura S. Wolff-Parkinson-White Syndrome mimics a conduction disease. Case Resp Med. Published July 2014. Available from: [LINK]
Dr C Tidy, Patient Info. Wolff-Parkinson-White Disease. Published 2020. Available from: [LINK]
Robert Buttner, Ed Burns. Pre-Excitation Syndromes. Life in the Fast Lane. Published December 2021. Available from: [LINK]
Wolff-Parkinson-White Syndrome Q&A. Published Jan 2017. Available from: [LINK]
Laaouaj J, Jacques F, O’Hara G, et al. Wolff–Parkinson–White as a bystander in a patient with aborted sudden cardiac death. HeartRhythm Case Reports2016;2:399. Available from: [LINK]
Figure 1. Tom Luck. Wolff-Parkinson-White Syndrome. License: [CC BY 3.0]. Available from: [LINK]
Figure 2. Robert Buttner, Ed Burns. Pre-Excitation Syndromes. Life in the Fast Lane. Published December 2021. Available from: [LINK]