Wolff-Parkinson-White Syndrome

What is Wolff-Parkinson-White syndrome?

In Wolff-Parkinson-White (WPW) syndrome there is an extra connection (an accessory pathway) between the atria and ventricles. This means that as well as electrical impulses passing normally between the atria and the ventricles at the AV node, electrical impulses can also pass abnormally along the accessory pathway.

The accessory pathway in WPW syndrome is known as the bundle of Kent. It is a congenital problem which means that it is present from birth. The majority of people with WPW syndrome have no other heart abnormalities.

An electrical impulse that passes along the accessory pathway can arrive at the ventricles more quickly than normal. There is not the usual impulse delay that occurs at the AV node and no limiting of the electrical impulses that pass through. This can cause the heart rate to speed up. The accessory pathway can also sometimes transmit electrical impulses backwards from the ventricles to the atria.

So, in WPW syndrome, the normal electrical activity of the heart is disrupted. There is a risk of developing a fast heart rate (a tachycardia) from time to time and other heart rhythm disturbances (arrhythmias). WPW syndrome can lead to what is called a supraventricular tachycardia. Tachycardia is a heart rate over 100 beats per minute (bpm). 'Supra' means above and because the atria are above the ventricles, the tachycardia is supraventricular.

The common arrhythmia that occurs in WPW syndrome is a paroxysmal (intermittent) supraventricular tachycardia (SVT). Other arrhythmias that can also occur include atrial fibrillation (AF), atrial flutter and atrioventricular re-entrant tachycardia (AVRT). Rarely, another arrhythmia called ventricular fibrillation can develop.

How common is Wolff-Parkinson-White syndrome?

WPW syndrome probably affects somewhere between 1-3 in 1,000 people. It is more common in men. There does seem to be some genetic basis, as WPW syndrome can run in families. However, most cases of WPW syndrome occur in people with no known family history.

Symptoms

Symptoms are caused by the episodes of rapid heart rate (tachycardia). How often these episodes occur can vary from person to person. They can include:

• Palpitations.
• Dizziness or light-headedness.
• Chest pain or chest tightness.

In some people, symptoms can be more severe. An episode of a very rapid heart rate (up to about 250 bpm) can cause:

• Your blood pressure to drop and lead to collapse (blackout).
• A build-up of fluid in your lungs and shortness of breath.
• Your heart can stop beating altogether (a cardiac arrest). However, this is rare.

In some people, the rapid heart rate only ever occurs once or twice. In others, it can occur a few times per week. Each episode of tachycardia may last from less than a minute to a few hours. An episode of tachycardia may even last for a few days but this is rare.

Many people are not aware that they have WPW syndrome because their symptoms are mild or don't occur very often.

How is Wolff-Parkinson-White syndrome diagnosed?

• It may be diagnosed by doing a heart tracing (electrocardiogram, or ECG). There are classic changes on the ECG that can be seen in some people with WPW syndrome.
• Sometimes an ambulatory ECG may be suggested.
• Special tests called electrophysiology studies may be carried out in some people. They can help to find the precise area in the heart where the accessory pathway is located.

Treatment

Treating an episode of rapid heart rate

• Many episodes of SVT soon stop on their own and no treatment is needed.
• Simple measures, including drinking a cold glass of water, holding your breath or putting your face into cold water.
• If an episode of SVT lasts a long time or is severe, you may need to be admitted to hospital.
• Medicines can be used to stop an episode of SVT - eg, adenosine.
• Electric shock treatment (cardioversion) is sometimes used.

Prevention of episodes of rapid heart rate

• If you have no symptoms and are at low risk of complications you may need no treatment.
• Radiofrequency destruction (ablation) is the treatment of choice but other options are available.

Radiofrequency ablation

• A thin tube called a catheter is inserted into an artery near your groin. The tube is passed up to your heart.
• The small area in your heart that causes the fast heart rate (the accessory pathway) is destroyed using a type of energy called radiofrequency.
• Radiofrequency ablation can have very good results and can cure the condition in most people.

Medication treatment
Long-term treatment with a medicine may be advised if you don't want to have radiofrequency ablation, or if this has failed. One medicine used is called amiodarone.

Heart surgery

Heart surgery is still used in some cases - eg, if radiofrequency ablation has failed and you don't want to take medication for the rest of your life. Open heart surgery aims to find and destroy the accessory pathway that causes the fast heart rate.

What is the outlook?

WPW syndrome can be life-threatening during an acute episode of SVT but the outlook (prognosis) is otherwise very good. Catheter ablation usually cures WPW syndrome but some people with WPW aren't suitable for this treatment.