Wolff-Parkinson-White syndrome Wolff-Parkinson-White syndrome is characterised by attacks of rapid heart rate (tachycardia),which is shown in an electrocardiogram (ECG). In some people the ECG abnormality may bepresent without any symptoms such as tachycardia. The heartbeat is regulated by electrical impulses that travel through the atria (upper chambers ofthe heart) to a knot of tissue known as the atrioventricular node, and then to the ventricles (lowerchambers of the heart). Usually electrical impulses pause at the atrioventricular node beforeprompting the ventricles to contract.

In Wolff-Parkinson-White syndrome, an extra pathway conducts the electrical impulses to theventricles without the normal delay. This extra pathway does not usually have seriousconsequences. However sometimes the extra (“accessory”) pathway may “bounce” the electricalimpulses back to the atria after each beat. This creates a circuit in which each atrial (upperchamber) beat is followed by a ventricular (lower chamber) beat, which is then followed by anotheratrial beat and so on. The heart rate can reach over 200 beats per minute, when the normalresting heart rate is around 70 to 80 beats per minute.