If the wiring in a house were installed incorrectly it would not function properly. It might even be dangerous. The same is true if there is a problem with the wiring in the heart. Abnormal heart wiring can cause abnormal heart rhythms, or arrhythmias. This usually results in a change in the rate at which the heart beats.
Some arrhythmias are merely an annoyance.
But, others can be serious and result in heartbeats that are too fast or too slow to pump blood effectively to the body. With SVT the atria beat too fast, often causing the ventricles to beat too quickly. Three common types or causes of SVT are described below. In WPW there is extra tissue connecting the atria and ventricles. It provides an extra pathway for electrical impulses to be conducted through the tissue that normally blocks electrical impulses between the atria and ventricles.