Also known as preexcitation syndrome, Wolff-Parkinson-White (WPW) syndrome is a condition in which the normal electrical signals in the heart travel along an extra electrical pathway. This can cause an abnormal heart rhythm (arrhythmia).

In a normal heart, electrical signals are generated in the upper right chamber of the heart (right atrium) and travel along a standard conduction system. These signals first stimulate the atria to contract, then pass through the atrioventricular node to the ventricles. This process causes the heart to contract in a rhythmic, predictable fashion. However, in patients with WPW syndrome, the electrical signals travel through an extra, abnormal pathway that bypasses the atrioventricular node. This pathway is known as the Kent bundles.

Because the electrical signals reach the ventricles via this abnormal route instead of through the heart’s normal conduction system, they may signal the ventricles to contract abnormally. This is usually because of a co-existing arrhythmia called atrial fibrillation, in which the atria beat very rapidly. It may also be due to a special kind of arrhythmia called an atrioventricular reentrant tachycardia (AVRT). An AVRT occurs when the electrical signal “loops” through the parallel conduction systems in the heart. In this action, the current travels down from the atrium to the ventricle through the normal AV node and back up to the atria through the accessory pathway. The process causes the ventricles to contract at a very rapid rate, known as reentrant tachycardia. As a result of either condition, the patient may experience rapid heart rhythms of over 100 beats per minute (tachycardias), along with palpitations, lightheadedness and/or loss of consciousness.

The vast majority of patients with WPW syndrome have a good prognosis, but the condition develops differently in different people. The condition may:

In 70 percent of WPW patients, there is no other sign of heart disease. The remaining 30 percent may have another heart condition in addition to WPW syndrome, including:

The abnormal accessory pathways are believed to be present since birth and often the condition is first diagnosed in children and young adults. WPW is the leading cause of tachycardia among children and adolescents. There is interest in studying WPW’s genetic aspects, as there is an inherited form of the syndrome. It is felt that certain changes (mutations) are responsible for the tachycardia in WPW syndrome. Understanding the genetics of WPW syndrome may help toward making an early diagnosis and in offering the most effective therapies.