Accessory Pathway Condition
Wolff-Parkinson-White (WPW) Syndrome
WPW involves an additional electrical connection between the upper and lower chambers of the heart. It can change how electrical signals travel and may take part in episodes of fast heart rhythm.
On this page
Understanding WPW
What Is Wolff-Parkinson-White Syndrome?
In a typical heart, the electrical signal that starts each beat reaches the lower chambers only through one route, the AV node, which slows it slightly before passing it on.
In WPW there is an additional strand of tissue, called an accessory pathway, that also connects the upper and lower chambers. It lies outside the normal AV node route.
Because the signal can reach part of the ventricles early through this connection, the ECG may show a pattern called pre-excitation. The pathway can also form part of a circuit that sustains episodes of fast rhythm.
Accessory pathway outside the AV node route
Educational comparison
Normal Conduction vs Accessory Pathway
The two routes are shown side by side. The accessory pathway is an additional connection, not a replacement for the normal route.
Reference
Normal Conduction
The signal starts in the SA node, spreads through the atria, passes the AV node, travels along the His-Purkinje system and activates the ventricles.
Variation
WPW / Accessory Pathway
An additional atrial-to-ventricular electrical connection lets part of the ventricles be activated earlier than usual, alongside the normal route.
Mechanism
How WPW-Related Tachycardia Can Occur
Conceptual illustration of a re-entrant circuit
A fast rhythm can begin when an early beat finds one route ready to conduct and the other still recovering.
The signal then travels down one route and back up the other, forming a loop. If the loop repeats, the heart is driven rapidly. This is called re-entry.
When the circuit uses the AV node in one direction and the accessory pathway in the other, the rhythm is called atrioventricular re-entrant tachycardia (AVRT).
Relationship to SVT
WPW and Supraventricular Tachycardia
Accessory pathways can be associated with supraventricular tachycardia mechanisms. AVRT is one of them, and the SVT page describes it alongside other mechanisms such as AVNRT and atrial tachycardia.
This page focuses on the accessory pathway itself. For the wider picture of SVT, see the dedicated page.
What patients may notice
Symptoms
Presentation varies. Some people have no symptoms, and the pattern is found on an ECG done for another reason.
Palpitations
Awareness of a pounding or fluttering heartbeat.
Rapid heartbeat
A heartbeat that suddenly speeds up.
Dizziness
Feeling light-headed or unsteady.
Shortness of breath
Feeling breathless during an episode.
Chest discomfort
Pressure or discomfort in the chest.
Weakness
A feeling of tiredness or lack of strength.
Near-fainting or fainting
Occurs in some patients and needs medical assessment.
Fainting, chest pain or severe breathlessness need urgent medical care.
ECG
WPW on an ECG
- Pre-excitation: part of the ventricles is activated early
- A short PR interval in many cases
- A delta wave, a slurred early upstroke of the QRS
- Altered ventricular activation compared with a normal beat
These features do not look identical in every patient or on every ECG, and the pattern can come and go. Interpretation needs clinical context.
Assessment
How WPW Is Diagnosed
Diagnosis starts with the pattern and the story, and further tests are added where they are useful.
Clinical history
Symptoms, when they started and what they feel like.
ECG
Looks for the pre-excitation pattern.
Rhythm monitoring
Used where appropriate to record episodes.
Considered when clinically indicated.
Electrophysiology study
The Role of an Electrophysiology Study
Intracardiac recording during an electrophysiology study
An EPS records electrical signals from inside the heart. In WPW it can help to:
- Assess the properties of the accessory pathway
- Describe its conduction characteristics
- Establish where the pathway is located
- Clarify the mechanism of the arrhythmia
- Support treatment planning
Mapping
Accessory Pathway Mapping
Signals recorded from catheters placed inside the heart show the timing of activation at different points. Comparing that timing helps to localise where the connection crosses between the upper and lower chambers.
Mapping systems can add a three-dimensional view of the chamber. Whether mapping is used and how depends on the findings and the procedure planned.
Catheter ablation
Catheter Ablation for WPW
Catheter ablation treats the accessory pathway. Whether it is appropriate depends on clinical assessment.
EPS
The rhythm and pathway are studied from inside the heart.
Pathway localisation
The position of the connection is identified.
Target identification
The area to treat is selected.
Catheter ablation
Energy is delivered to the target.
Reassessment
Conduction is checked again.
Living With WPW
Exercise, Sport and Pregnancy
Advice for people with a pre-excitation pattern on the ECG is individual and depends on the accessory pathway, symptoms and any documented arrhythmia.
Exercise and sport. Many people with WPW exercise normally. Because exertion can provoke arrhythmia in some, an assessment of the pathway and its risk is generally advised before intensive or competitive sport, and ablation is sometimes recommended to allow safe participation.
Pregnancy. Pregnancy is possible for most women with WPW, and episodes may occasionally increase during pregnancy. Planning ahead with a cardiologist is helpful, including review of medicines, and where ablation is advisable it is ideally done before conception.
During an Episode
What to Do During a Fast Heartbeat
Sit or lie down
Stay calm and avoid exertion.
Vagal manoeuvres
Some patients are taught techniques that may stop certain regular tachycardias. They should be used only on the advice of your physician.
Record the rhythm
If possible, obtain an ECG or device recording during symptoms.
Seek urgent help
Call your emergency service for fainting, chest pain, severe breathlessness, or a very fast irregular heartbeat, which can be dangerous in WPW.
Some common anti-arrhythmic and AV-nodal-blocking medicines can be unsuitable for certain patients with WPW. Do not self-medicate; follow your cardiologist’s plan.
Treatment Options
Medication Context and Ablation
Observation
In selected people without symptoms and with a low-risk pathway profile.
Medication
May be used to reduce episodes, with choices guided by the type of rhythm and the patient.
Catheter ablation
Treats the accessory pathway directly and is often recommended when there are symptoms or when risk is a concern. See SVT Ablation.
After assessment or treatment
Follow-up
Follow-up depends on the individual situation and on whether treatment has been given. It may include a clinical review, an ECG and discussion of any symptoms.
Patients are told which symptoms need urgent medical care. For procedure preparation and recovery, see the patient information pages.
Questions