WPW syndrome

Definition: What is WPW Syndrome?

Wolf Parkinson White syndrome (or WPW syndrome in short) is a disorder of the heart that may trigger a cardiac arrhythmia. The condition entails a "short circuit" within the heart's electrical conduction of impulses in the region of the junction between the atria and ventricles.

Prevalence of WPW syndrome

WPW syndrome has the potential to develop symptoms in any age group. The condition is an overall rare disease affecting 0.1-0.3% of the population.

Causes of WPW Syndrome

Normally, there is only a single electrical pathway connecting the right atrium to the ventricles, since the so-called SA node which is responsible for the heart's rhythm is located in the right atrium. Before the electrical impulse is transmitted to the ventricles, the AV node acts as a control. With WPW syndrome, there is an additional pathway, also known as the "Kent bundle". Due to this extra pathway, reverse electrical signals can pass from the ventricles back to the atria. This is referred to as atrioventricular reentry tachycardia (AVRT), a circular excitation that causes palpitations.

The special and dangerous feature of this bundle is the fact that it cunducts faster than the regular pathway. This allows an electrical impulse to reach the ventricles through this rapid conduction. In a healthy heart, however, this is not dangerous and may not even be noticed by the patient. However, WPW syndrome may lead to complications, if the patient already suffers from atrial fibrillation. This involves the generation of far more electrical impulses and therefore heart muscle contractions in the atrium than in a healthy person. However, said AV node permits only a small number of these electrical signals to cross to the ventricles, and therefore functions as a filter for fibrillation. The Kent bundle has no such gatekeeper though and allows any excitation to pass from the atrium to the ventricles without restriction, causing a dangerous condition referred to as ventricular fibrillation. In other words, the heart contracts so rapidly it can no longer pump out blood and a functional cardiac arrest ensues.

Symptoms of WPW Syndrome

Bouts of palpitations are the most common manifestations of WPW syndrome. The onset and termination of these are sudden and virtually "out of the blue". Further symptoms may be dizziness, malaise, feeling faint or even syncope. The patient may also experience nausea and an increased urge to urinate.

Diagnosis: How can WPW syndrome be diagnosed?

To start with, the physician will gather the most relevant facts such as history of previous cardiovascular diseases, exact symptomatology and family history. Electrocardiogram (ECG) is the most important tool available for diagnosing WPW syndrome. An ECG reads and records the electrical activity of the heart by means of electrodes attached to the chest, hands and feet. This provides a large amount of data regarding the heart's excitation pattern and the functional state of the heart.

In case the ECG is not enough, an electrophysiological examination (EPU) needs to be carried out. This involves advancing a special catheter with electrodes via the groin to the heart. Electrical signals can be measured directly within the heart.

Therapy of WPW Syndrome

The choice of therapy takes into account the patient's symptoms as well as their general health status. Initially medications can be prescribed to improve the symptoms and reduce the palpitations. However, catheter ablation is the only cure available for WPW syndrome. It is an invasive procedure that involves piercing a blood vessel in the groin with an electrode and advancing it to the heart. Following this, the Kent bundle is coagulated and the electrical circuit is permanently interrupted.