Wolff-Parkinson-White (WPW) Syndrome
(See also Overview of Abnormal Heart Rhythms.)
Wolff-Parkinson-White syndrome is a disorder in which an extra electrical connection between the atria and the ventricles is present at birth. People may have episodes of a very rapid heartbeat.
Wolff-Parkinson-White syndrome is the most common of several disorders that involve an extra (accessory) electrical pathway between the atria and the ventricles. (Such disorders are called atrioventricular reciprocating supraventricular tachycardias.) This extra pathway makes fast arrhythmias more likely to occur. Wolff-Parkinson-White syndrome is present at birth, but the arrhythmias it causes usually become apparent during the teens or early twenties. However, arrhythmias may occur during the first year of life or not until after age 60.
When infants develop arrhythmias due to this syndrome, they may become short of breath or lethargic, stop eating well, or have rapid, visible pulsations of the chest. Heart failure may develop.
Typically, when teenagers or people in their early 20s first experience an arrhythmia due to this syndrome, it is an episode of palpitations that begins suddenly, often during exercise. The episode may last for only a few seconds or may persist for several hours. For most people, the very fast heart rate is uncomfortable and distressing. A few people faint.
In older people, episodes of paroxysmal supraventricular tachycardia due to Wolff-Parkinson-White syndrome tend to cause more symptoms, such as fainting, shortness of breath, and chest pain.
Atrial fibrillation may be particularly dangerous for people with Wolff-Parkinson-White syndrome. The extra pathway can conduct the rapid impulses to the ventricles at a much faster rate than the normal pathway (through the atrioventricular node) can. The result is an extremely fast ventricular rate that may be life threatening. Not only is the heart very inefficient when it beats so rapidly, but this extremely fast heart rate may also progress to ventricular fibrillation, which is fatal unless treated immediately.
Because Wolff-Parkinson-White syndrome changes the pattern of electrical activation in the heart, it can be diagnosed using electrocardiography (ECG), which records the electrical activity of the heart.
Episodes of paroxysmal supraventricular tachycardia due to Wolff-Parkinson-White syndrome can often be stopped by one of several maneuvers that stimulate the vagus nerve and thus slow the heart rate. The maneuvers are most effective when they are used shortly after the arrhythmia starts. When these maneuvers are ineffective, drugs such as verapamil or adenosine are usually given intravenously to stop the arrhythmia. Antiarrhythmic drugs may then be continued indefinitely to prevent episodes of a fast heart rate (see Table: Some Drugs Used to Treat Arrhythmias).
In infants and children younger than 10 years, digoxin may be given to suppress episodes of paroxysmal supraventricular tachycardia due to Wolff-Parkinson-White syndrome. However, adults with the syndrome should not take digoxin because it can facilitate conduction by the extra pathway and increase the risk that atrial fibrillation will degenerate into ventricular fibrillation. For this reason, digoxin is usually stopped before people with this syndrome reach puberty.
Destruction of the extra conduction pathway by radiofrequency ablation (delivery of energy of a specific frequency through an electrode catheter inserted in the heart) is successful in more than 95% of people. The risk of death during the procedure is less than 1 in 1,000. Radiofrequency ablation is particularly useful for young people who might otherwise have to take antiarrhythmic drugs for a lifetime.