Wolff-Parkinson-White (WPW) syndrome is a type of heart problem present at birth (congenital heart defect). WPW syndrome may occur with other types of congenital heart disease, such as Ebstein anomaly.
Rarely, WPW syndrome is passed down through families (inherited). The inherited, or familial, type is associated with a thickened heart muscle. This is a form of hypertrophic cardiomyopathy.
To understand the causes of WPW syndrome, it may be helpful to know how the heart typically beats.
How does the heart beat?
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In a typical heart rhythm, a tiny cluster of cells at the sinus node sends out an electrical signal. The signal then travels through the atria to the atrioventricular (AV) node and into the ventricles, causing them to contract and pump blood.
The heart is made of four chambers — two upper chambers (atria) and two lower chambers (ventricles).
The heart's rhythm is controlled by a natural pacemaker (the sinus node) in the right upper chamber (atrium). The sinus node sends electrical signals that typically start each heartbeat. These electrical signals move across the atria, causing the heart muscles to squeeze (contract) and pump blood into the ventricles.
Next, the heart signals arrive at a cluster of cells called the AV node, where the signals slow down. This slight delay allows the ventricles to fill with blood. When the electrical signals reach the ventricles, the chambers contract and pump blood to the lungs or to the rest of the body.
In a typical heart, this heart signaling process usually goes smoothly, resulting in a resting heart rate of 60 to 100 beats a minute.
In WPW syndrome, an extra electrical pathway connects the upper and lower heart chambers, allowing heart signals to bypass the AV node. As a result, the heart signals don't slow down. The signals become excited, and the heart rate gets faster. The extra pathway can also cause heart signals to travel backward, causing an uncoordinated heart rhythm.