Electrical signals in the heart normally pass through a pathway that helps the heart beat regularly. It is the only path they use and is called the atrio-ventricular or A-V node. As the signals move from the heart's upper chambers (the atria) to the lower chambers (the ventricles), they cause the heart to beat. The way the normal heart is "wired" prevents extra beats from occurring and keeps the next beat from coming too soon.
If you have WPW, you have an extra, or accessory, pathway -- a shortcut -- that may cause a very rapid heart rate. This is called supraventricular tachycardia.
Congenital Heart Defect
WPW is thought to be a congenital heart defect.