People with Wolff-Parkinson-White syndrome are born with an extra connection in the heart, called an accessory pathway, that allows electrical signals to bypass the atrioventricular node and move from the atria to the ventricles faster than usual. The accessory pathway may also transmit electrical impulses abnormally from the ventricles back to the atria. This extra connection can disrupt the coordinated movement of electrical signals through the heart, leading to an abnormally fast heartbeat (tachycardia) and other changes in heart rhythm. Resulting symptoms include dizziness, a sensation of fluttering or pounding in the chest (palpitations), shortness of breath, and fainting (syncope). In rare cases, arrhythmias associated with Wolff-Parkinson-White syndrome can lead to cardiac arrest and sudden death. The most common arrhythmia associated with Wolff-Parkinson-White syndrome is called paroxysmal supraventricular tachycardia.
The symptoms of WPW syndrome result from the presence of an alternate electrical pathway. The normal heart has one conduction pathway (the Bundle of His) along which electrical impulses are transmitted from the small chambers of the heart (the atria) to the large chambers (the ventricles). These electrical impulses induce the muscles of the atria and then the ventricles, to contract and relax, pumping blood throughout the body. Individuals with WPW syndrome have a second abnormal conduction pathway, the Bundle of Kent, which sends extra electrical impulses from the muscles of the atria to those of the ventricles. These extra electrical impulses bypass the normal route and disrupt the normal rhythm of heartbeats and generate irregularities, usually exceptionally rapid heartbeats known as “atrial flutter, atrial fibrillation, or paroxysmal supraventricular tachycardia.” The exact cause of alternate pathways is unknown.