Wolff-Parkinson-White and Pre-excitation

Drawing apart the pattern from the syndrome shapes everything that follows. Many people have the WPW electrocardiogram pattern and never have an arrhythmia, others have recurrent palpitations from re-entry, and a small minority are at risk of the malignant atrial fibrillation scenario. The task is to work out which group an individual is in.

What matters most for danger is the conduction property of the accessory pathway. A pathway that can only conduct relatively slowly is generally low risk, because it cannot drive the ventricles dangerously fast during atrial fibrillation. A pathway that can conduct very rapidly carries more risk.

In specialist assessment, higher-risk features include very rapid conduction during atrial fibrillation, a pathway that recovers and conducts again very quickly, more than one accessory pathway, or readily provoked re-entrant tachycardia. The SEM doctor does not measure these, but should understand that this is what an electrophysiology assessment is trying to determine, and that an asymptomatic athlete found to have a WPW pattern therefore warrants assessment rather than simple reassurance.

The commonest symptomatic presentation is episodes of sudden, rapid, regular palpitations from re-entrant tachycardia, often starting and stopping abruptly, sometimes with light-headedness, breathlessness or chest discomfort. These can occur at rest or with exertion. Pre-excited atrial fibrillation tends to feel different, an irregular and very fast palpitation, and is a warning sign. Syncope is less common but is concerning, and rarely the first presentation is a cardiac arrest.

Many athletes, though, are entirely asymptomatic and come to attention only because a screening electrocardiogram shows the pattern; an incidental WPW pattern in a competitive athlete still needs prompt cardiology or electrophysiology assessment before clearance. Examination between episodes is usually normal, so a normal examination does not exclude the condition. In anyone over 16 with a blackout, give driving advice at the first visit: they should not drive while awaiting specialist assessment, following the Driver and Vehicle Licensing Agency rules.

The resting electrocardiogram (ECG) makes the diagnosis, showing the short PR interval, delta wave and broad QRS of pre-excitation. Specialist assessment should also exclude associated structural disease, particularly hypertrophic cardiomyopathy and Ebstein anomaly, for which echocardiography is commonly used.

The next step is risk assessment, combining non-invasive and specialist tests. An exercise test is useful: if pre-excitation disappears abruptly and completely as the heart rate increases, the pathway is likely to conduct poorly and to be lower risk. This is reassuring only when the loss is abrupt and complete, and it is not a guarantee of safety, so it should not be used by an SEM clinician alone to clear a competitive athlete.

Ambulatory monitoring helps capture symptomatic episodes and document the rhythm. The definitive assessment is an electrophysiology (EP) study, in which the conduction properties of the accessory pathway are measured directly, and which can be combined with treatment in the same procedure. Because interpretation and risk assessment are specialist tasks, athletes with pre-excitation are referred to cardiology, with a low threshold in those who compete.

Management is led by cardiology, and the SEM clinician's role is to recognise, refer and give sound first-line and activity advice. If an athlete has a stable, regular tachycardia, stop exercise, obtain a 12-lead electrocardiogram where possible, and use a modified Valsalva manoeuvre if trained and appropriate while arranging acute medical assessment, without same-day return to sport. Syncope, chest pain, severe breathlessness or a very fast irregular rhythm should be managed as an emergency.

In suspected atrial fibrillation with pre-excitation, the usual atrioventricular node-blocking drugs, such as adenosine, verapamil, diltiazem, beta-blockers and digoxin, are dangerous, because blocking the node can push more of the rapid atrial activity down the accessory pathway; unstable patients need urgent cardioversion and stable patients still need urgent specialist-led care. The definitive treatment for the accessory pathway is catheter ablation, which targets and interrupts the pathway and is frequently curative, removing both the arrhythmia and the future risk.

This is where WPW differs from many conditions in this area. Because a cure is often achievable, an athlete with symptomatic WPW syndrome, or an asymptomatic athlete whose pathway is shown to be higher risk, can usually return to full sport once a successful ablation has been confirmed, typically after specialist review and follow-up electrocardiograms rather than immediately.

Competitive athletes with asymptomatic pre-excitation usually warrant an electrophysiology study to assess risk, while recreational exercisers may begin with non-invasive assessment, but clearance stays specialist-led. Particular caution applies to activities where a blackout could be fatal, such as diving, motorsport or solo open-water swimming, while risk is unresolved. The overall message, though, is more optimistic than for the structural and other electrical diseases.

• •European Society of Cardiology guidance on supraventricular tachycardia informs the diagnosis, acute arrhythmia management and ablation indications for accessory pathways.
• •European sports cardiology guidance informs athlete-specific risk assessment, electrophysiology referral and return-to-sport decisions in pre-excitation.
• •National Institute for Health and Care Excellence (NICE) guidance on transient loss of consciousness supports the assessment of blackout, including activity restriction and driving advice.
• •Specialist arrhythmia and electrophysiology services, accessed through cardiology, provide risk assessment and catheter ablation, supported by charities such as Cardiac Risk in the Young (CRY) and the British Heart Foundation.

• •WPW is ventricular pre-excitation from an accessory pathway, and is one of the few curable causes of sudden cardiac death risk in athletes.
• •The pattern is a short PR interval, a delta wave and a broad QRS; the syndrome is the pattern plus arrhythmia symptoms.
• •Re-entrant tachycardia causes regular palpitations, while pre-excited atrial fibrillation is the dangerous, irregular, very fast rhythm.
• •Risk depends on how fast the accessory pathway conducts; abrupt, complete loss of pre-excitation on exercise suggests a lower-risk pathway.
• •Avoid atrioventricular node-blocking drugs, such as adenosine, verapamil, diltiazem, beta-blockers and digoxin, in pre-excited atrial fibrillation.
• •Catheter ablation is often curative, and a confirmed successful ablation usually allows return to full sport.