Wolff-Parkinson-White Syndrome In Wolff-Parkinson-White syndrome, there is an extra electrical pathway in the heart — an abnormal bridge of heart muscle fibers that connects the upper chambers of the heart to the lower chambers. This extra pathway may allow electrical impulses to travel rapidly in the heart, causing an abnormally fast heartbeat, a form of supraventricular tachycardia . The extra electrical pathway may be seen on an electrocardiogram (EKG or ECG), causing an abnormal pattern known as a delta wave. In rare cases, the heart rhythm can be extremely rapid and potentially dangerous. The "normal" number of heartbeats per minute, called pulse rate, varies with age. The heart beats about 140 times a minute in a newborn, compared to 70 times a minute in an older child at rest. Heart rate is not constant, changing in response to many factors, such as activity, fever and fear. With Wolff-Parkinson-White syndrome, the heart beats too quickly — up