Preexcitation syndrome

Definition

Wolff-Parkinson-White syndrome involves episodes of rapid heart rate (tachycardia) and baseline abnormal ECG caused by abnormal electrical pathways (circuits) in the heart.

Alternative Names

Causes

Normally, electrical signals in the heart go through the atrioventricular (AV) node, the pathway connecting the two top chambers of the heart (atria) to the two bottom chambers (ventricles).

In people with Wolff-Parkinson-White syndrome, there is an extra, or accessory, AV pathway.  This can lead to a condition of pre-excitation. Pre-excitation occurs when electrical activity bypasses the AV node and goes thru the extra pathway. In some patients, the extra pathway may result in re-entry supraventricular tachycardia, which is a rapid heart rate that starts above the two bottom chambers of the heart.

The location of the extra electrical pathway in Wolff-Parkinson-White can often be precisely identified.Wolff-Parkinson-White occurs is one of the most common causes of fast heart rate disorders (tachyarrhythmias) in infants and children.

How often the rapid heart rate occurs depends on the patient. Some people with Wolff-Parkinson-White may have just a few episodes of rapid heart rate, others may experience the rapid heart rate once or twice a week. In some cases, the patient has no symptoms. In this case, the extra pathway is often found when a doctor has requested an ECG for some other purpose.

Symptoms

A person with WPW syndrome may have:

• Palpitations (a sensation of feeling your heart beat)
• Light-headedness
• Fainting
• Dizziness
• Shortness of breath
• Chest pain or chest tightness

Exams and Tests

An exam performed during a tachycardia episode will reveal a heart rate greater than 150 (normal is 60 to 100 beats per minute), and blood pressure that is normal or low. If  the patient is currently not having tachycardia, the physical exam may be completely normal. Wolff-Parkinson-White syndrome may be revealed by the following tests:

• ECG (electrocardiogram)
• Continuous ambulatory monitoring (Holter monitor)
• EPS, an intracardiac electrophysiologic study

Treatment

The goal of treatment is to reduce symptoms by reducing the episodes of tachycardia (rapid heart rate).

Medication may be used to control or prevent rapid heart beating. These include adenosine, antiarrhythmics, and amiodarone. Digoxin, verapamil, and beta-blockers (other drugs commonly used to treat other types of tachycardia) can increase the frequency of tachycardia episodes for some people with Wolff-Parkinson-White.

Other treatments to stop a persistent episode of tachycardia may include electrical cardioversion (shock) or catheter ablation with a special type of energy called radiofrequency. This destroys the accessory pathway using a catheter (tube) inserted into the body to reach the heart. The success rate for this procedure ragnes between 85 - 95%, depending on the location of the extra pathway.

Surgery may provide a permanent cure for Wolff-Parkinson-White. This involves ablation (destruction) of the accessory pathway using open heart surgery. Surgery may be a good approach to cure symptomatic Wolff-Parkinson-White syndrome, but it is usually only done if the patient must undergo surgery for other reasons.

Outlook (Prognosis)

Possible Complications

• Reduced blood pressure (caused by continous rapid heart rate)
• Heart failure
• Side effects of medications
• Complications of surgery

The most severe form of tachyarrhythmia is atrial fibrillation. It may rapidly lead to shock, and  requires emergency treatment (cardioversion).

When to Contact a Medical Professional

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