Wolff-Parkinson-White syndrome

In Wolff-Parkinson-White (WPW) syndrome, the heart beats abnormally fast.

The syndrome is congenital (present at birth) and is caused by an extra electrical connection in the heart.

WPW syndrome is one of the most common causes of an abnormally fast heart rate in infants and children. However, the syndrome is sometimes not detected until later in life.

The heart of a person with the syndrome will suddenly start racing before stopping or slowing down abruptly. This rapid heart rate is called supraventricular tachycardia (SVT).

Episodes can last for seconds, minutes, hours or, in rare cases, days. The frequency with which episodes occur can vary from person to person. Some people may have episodes on a daily basis, whereas others may only experience them occasionally.

When someone with WPW syndrome has SVT, their heart rate may be as high as 230 beats per minute (bpm). At rest, a normal heart rate in adults is 60-100 bpm, and in babies and children up to 150 bpm.

Children with the syndrome will often report having symptoms such as:

• chest pain
• palpitations
• difficulty breathing

Adults often experience symptoms such as:

• a pounding heartbeat that occurs suddenly
• a pulse that's too fast to count
• a reduced ability to tolerate activity

In rare cases of WPW syndrome, a person's heart rate can increase significantly when a heart rhythm called atrial fibrillation occurs. The combination of the syndrome and atrial fibrillation can be life threatening.

What happens?

When the heart beats normally, its muscular walls contract (tighten and squeeze) to force blood out and around the body. They then relax, allowing the heart to fill with blood again.

In WPW syndrome, electrical signals in the heart can travel round and round in a loop, causing the heart to beat very fast. The heart muscle contracts at such a fast rate that it has very little time to relax and fill with blood in between contractions.

This reduces the amount of blood being pumped around the body, which can make you feel short of breath, dizzy, light-headed and faint.

You should dial 999 to request an ambulance if a person with WPW syndrome collapses or faints.

Someone with the syndrome may have heart palpitations, where the heart feels like it's pounding, fluttering or beating irregularly for a few seconds or minutes.

Others may not experience heart palpitations, and the syndrome may only be picked up if they have an electrocardiogram (ECG) for another reason.

Why it happens

The fast heart rate of WPW syndrome is caused by an extra electrical connection in the heart. This allows electrical signals to bypass the usual route and form a short circuit, resulting in an abnormally fast heart rhythm. 

The extra electrical circuit is caused by a strand of muscle that grows from the atria to the ventricle when a foetus develops in the womb. The syndrome rarely runs in families and usually occurs randomly in some babies.

A few people with WPW syndrome also have a structural problem with their heart or underlying heart disease. For example, the syndrome is sometimes associated with a heart valve problem called Ebstein's anomaly.

In Ebstein's anomaly the tricuspid valve, which separates the lower right chamber (ventricle) from the upper right chamber (atrium), doesn't develop properly.

Diagnosis

If your GP thinks you might have WPW syndrome after assessing your symptoms, they'll probably recommend that you have an ECG and refer you to a cardiologist (heart specialist).

An ECG is a test that records your heart's rhythm and electrical activity. Small discs called electrodes are stuck on your arms, legs and chest and connected by wires to an ECG machine. The machine records the tiny electrical signals produced by your heart each time it beats.

If you have WPW syndrome, the ECG will record a "delta wave", which is an unusual wave pattern on the ECG that isn't usually present in people who don't have the condition. 

Capturing an episode of a racing heart and palpitations using a normal ECG can often be difficult. You may therefore be asked to wear a small portable ECG recorder, which will trace your heart rate continuously over 24 hours or when you switch it on at the start of an episode.

Treatment

In many cases, episodes of abnormal heart activity associated with WPW syndrome are harmless, don't last long and settle down on their own without treatment.

You should go to your nearest hospital's accident and emergency (A&E) department if your heart beats abnormally fast for 20 minutes. You'll be given an injection to correct this abnormal heart rhythm.

Anti-arrhythmic medicine or medication such as adenosine can often be used to prevent or manage a rapid heartbeat. If medication proves ineffective, a type of electric shock therapy called electrical cardioversion may be recommended.

However, the most effective long-term treatment for WPW syndrome is a keyhole surgical procedure called catheter ablation. It involves inserting a narrow tube (catheter) into an artery or vein through a hollow needle, which is passed through the skin at the top of your thigh and fed up to your heart.

When the tip of the catheter reaches the correct place in your heart, the area of tissue that's causing the abnormal heart rate is either destroyed using a type of energy called radiofrequency or by freezing the tissue (cryotherapy).

Catheter ablation is successful in more than 90% of cases of WPW syndrome.