CausesBy Mayo Clinic staff
The extra electrical pathway of Wolff-Parkinson-White syndrome is present at birth. An abnormal gene (gene mutation) is the cause of a small percentage of cases of the disorder. Wolf-Parkinson-White syndrome is associated with some forms of congenital heart disease, such as Ebstein's anomaly. Otherwise, little is known about why this extra pathway develops.
Normal heart electrical system
Your heart is made up of four chambers — two upper chambers (atria) and two lower chambers (ventricles). The rhythm of your heart is normally controlled by a natural pacemaker — the sinus node — located in the right atrium. The sinus node produces electrical impulses that initiate each heartbeat.
From the sinus node, electrical impulses travel across the atria, causing the atria muscles to contract and pump blood into the ventricles. The electrical impulses then arrive at a cluster of cells called the atrioventricular node (AV node) — usually the only pathway for signals to travel from the atria to the ventricles.
The AV node slows down the electrical signal before sending it to the ventricles. This slight delay allows the ventricles to fill with blood. When electrical impulses reach the muscles of the ventricles, they contract, causing them to pump blood either to the lungs or to the rest of the body.
Abnormal electrical system related to Wolff-Parkinson-White syndrome
In Wolff-Parkinson-White syndrome, an extra electrical pathway connects the atria and ventricles. This means that an electrical signal can bypass the AV node. When electrical impulses use this detour through the heart, the ventricles are activated too early — a condition known as preexcitation.
Abnormal rhythm or fast heartbeat in patients with WPW:
Two major types of rhythm disturbances can be related to the presence of the extra electrical pathway:
- Looped electrical impulses. The problem with a fast heartbeat usually occurs in Wolff-Parkinson-White syndrome because electrical impulses travel down either the normal or the extra pathway and up the other one, creating a complete electrical loop of signals. This condition, called AV reentrant tachycardia, sends impulses to the ventricles at a very rapid rate. The ventricles, as a result, pump very quickly, causing symptoms.
- Disorganized electrical impulses. If electrical impulses don't begin correctly in the right atrium, they may travel across the atria in a disorganized way, causing them to beat very quickly and out of step with each other. This condition is called atrial fibrillation. These disorganized signals also increase the pumping rate of the ventricles to some extent. If there's an extra electrical pathway, as with Wolff-Parkinson-White syndrome, the ventricles can beat even faster. The ventricles don't have time to fill up with blood and don't pump enough blood to the body. This less common condition can be life-threatening.
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