Definition
The term WPW syndrome stands for a disorder known as Wolff-Parkinson-White syndrome. This is a disease from the group of cardiac arrhythmias. It is characterized by an additional pathway between the atrium and the ventricle, which is not present in a healthy heart. It is a congenital disease, but usually manifests itself after the age of 20. About 0.1 to 0.3% of the population is affected.
Type A
The WPW syndrome can be divided into a type A and a type B. The type assignment depends on the area in which the additional (accessory) pathway is located. In type A there is an additional pathway between the left atrium and the left ventricle. However, the distinction between type A and type B hardly plays a role in WPW syndrome nowadays.
Type B
The additional pathway in type B WPW syndrome is located between the right atrium and the right ventricle. The conduction pathway is called a Kent bundle in both type A and type B syndromes. There is no significant clinical difference between type A and type B. However, they do differ from each other, for example in their presentation on the ECG.
Causes of the WPW syndrome
The cause of WPW syndrome is, as briefly mentioned above, an additional conduction pathway in the heart. The heart functions by means of electrical excitation that is passed from one point to another. In the end, these electrical excitations cause a synchronized contraction of the heart muscle, i.e. the heartbeat.
So that the excitation can pass from one point to another, there are certain excitation conduction paths. For example, the excitation conduction from the atrium to the ventricle is made possible by the atrioventricular node (AV node). In a healthy heart, it is the only pathway on which electrical impulses can travel from the atrium to the ventricle.
In WPW syndrome there is another such pathway between the atrium and the ventricle in addition to the AV node. It is called a Kent bundle. In WPW syndrome, the electrical impulses that have been conducted from the atrium to the ventricle via the AV node can travel back to the ventricle via the Kent bundle and trigger renewed – early – excitation. This in turn leads to an early re-excitation of the ventricle and thus to an acceleration of the heartbeat (tachycardia). There are also variants in which the “normal” excitation runs via the Kent bundle from the atrium to the ventricle and the retrograde excitation from the ventricle back to the atrium via the AV node.
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