Wolff-Parkinson-White syndrome

Overview

In Wolff-Parkinson-White syndrome, there is an extra electrical pathway in the heart — an abnormal bridge of heart muscle fibers that connects the upper chambers of the heart to the lower chambers. This extra pathway may allow electrical impulses to travel rapidly in the heart, causing an abnormally fast heartbeat, a form of supraventricular tachycardia. The extra electrical pathway may be seen on an electrocardiogram (EKG or ECG), causing an abnormal pattern known as a delta wave. In rare cases, the heart rhythm can be extremely rapid and potentially dangerous.

The "normal" number of heartbeats per minute, called pulse rate, varies with age. The heart beats about 140 times a minute in a newborn, compared to 70 times a minute in an older child at rest. Heart rate is not constant, changing in response to many factors, such as activity, fever and fear. With Wolff-Parkinson-White syndrome, the heart beats too quickly — up to 300 beats per minute. The heart cannot fill completely with blood, preventing the body from receiving the blood volume it needs to function properly.

Signs & symptoms

Wolff-Parkinson-White syndrome may cause the following symptoms:

• Chest pressure or pain
• Fainting, also known as syncope, or near-syncope
• Fatigue
• Lightheadedness or dizziness
• Palpitations, which can be skipping, fluttering or pounding in the chest
• Shortness of breath

It is important to note that during an episode of Wolff-Parkinson-White syndrome, children may not know how to describe what they are feeling. They may have trouble keeping up with other children or realize they are having "spells" and want to sit down and rest. Sometimes, children do not experience any symptoms at all.

Wolff-Parkinson-White syndrome can exhibit in the following ways:

WPW Sinus Rhythm

This diagram illustrates the extra connection shown during a normal sinus rhythm, or the normal transmission of impulses through the heart.

WPW Orthodromic Reciprocating Tachycardia-Common

This diagram illustrates how the electrical impulse flows down the normal atrioventricular (AV) node from the atrium to the ventricle and then returns back to the atrium via the extra pathway, which acts as a "short circuit" perpetuating the arrhythmia.

Diagnosis

Wolff-Parkinson-White syndrome may occur spontaneously with unpredictable timing. Therefore, specialized tests may be needed to make an accurate diagnosis. If your doctor suspects that your child has an arrhythmia caused by Wolff-Parkinson-White syndrome, he or she may order one or more of the following diagnostic tests:

• Electrocardiogram (ECG or EKG) — An ECG records the heart's electrical activity. Small patches called electrodes are placed on your child's chest, arms and legs, and are connected by wires to the ECG machine. The electrical impulses of your child's heart are translated into a graph or chart, enabling doctors to determine the pattern of electrical current flow in the heart and to diagnose arrhythmias.
• Electrophysiology (EP) Study — In an EP study, doctors insert special electrode catheters — long, flexible wires — into veins and guide them into the heart. These catheters sense electrical impulses and also may be used to stimulate different areas of the heart. Doctors can then locate the sites that are causing arrhythmias. The EP study allows doctors to examine an arrhythmia under controlled conditions and acquire more accurate, detailed information than with any other diagnostic test.
• Exercise Stress Test — An exercise stress or treadmill test records the electrical activity of your child's heart during exercise, which differs from the heart's electrical activity at rest.
• Event Monitor — This is a small monitor about the size of a pager that your child can have for up to a month. Since the arrhythmia may occur at unpredictable times, this will help to record the abnormal rhythm when your child is experiencing symptoms. He or she can just push a button on the pager and record the heartbeat. The recording can then be transmitted by phone to the doctor.
• Holter Monitor — A Holter monitor is a small, portable machine that your child wears for 24 hours. It is about the size of a portable tape player and provides a continuous 24-hour recording of your child's heartbeat onto a tape. You will be asked to keep a diary of your child's activities and symptoms. This monitor may detect arrhythmias that might not show up on a resting electrocardiogram, which only records a heartbeat for a few seconds at rest.
• Tilt Table Test — If your child has a history of syncope, your doctor may perform a tilt table test to determine how your child's body responds to changes in position. During the test, your child will lie on a table that can be tilted upright to 70 degrees, with constant monitoring of blood pressure and heart rate.

Treatment

Treatment for Wolff-Parkinson-White syndrome will depend on the type and severity of your child's condition and the results of the diagnostic tests, such as the electrophysiology (EP) study. You and your child's doctor will decide which treatment is right for your child.

The following treatments may be considered:

Medications

Certain anti-arrhythmic drugs change the electrical signals in the heart and help prevent irregular or rapid heart rhythms from occurring. Medication may be used to convert the arrhythmia of Wolff-Parkinson-White syndrome to a normal rhythm, slow down the heart rate or prevent recurrences.

Follow-up Electrophysiology Study

On occasion, we admit children to the hospital and monitor their heart rhythm while we start their medication. To make sure that your child's medication is working properly, your child may be brought to the Electrophysiology Laboratory for an electrophysiology (EP) study. Our goal is to find the medication that works best for your child.

Radiofrequency Catheter Ablation (RFA)

Pioneered at UCSF Medical Center, radiofrequency catheter ablation (RFA) is a technique used to treat arrhythmias. For conditions like Wolff-Parkinson-White syndrome, in which a hair-thin strand of tissue creates an extra electrical pathway between the upper and lower chambers of the heart, RFA ablation offers a cure and has become the standard treatment for this condition.

RFA disrupts part of the electrical pathway causing irregular heart rhythms, providing relief for patients who may not respond well to medications, who prefer not to take medications or who can't take medications.

The procedure involves threading a tiny, metal-tipped catheter through a vein or artery in the leg and into the heart. Using fluoroscopy or X-ray, doctors guide the catheter through a blood vessel to the heart. Additional catheters, inserted through the vein in the leg and the neck, contain electrical sensors to find the area causing the arrhythmia. This is called mapping.

The metal-tipped catheter is maneuvered to each site in the heart that causes the irregular heartbeat. Radiofrequency waves or current is sent through the tip of the catheter, cauterizing or burning cells to destroy the extra electrical pathways that cause abnormal heart rhythms. In most cases, patients leave the hospital within 24 hours or the same day.

Cryoablation

Cryoablation, sometimes referred to as cryo, is similar to radiofrequency catheter ablation in that it is a procedure that disrupts the abnormal electrical pathway in the heart. Instead of burning cells, however, cryoablation destroys cells by freezing them. This newer technology has been used in the Electrophysiology Laboratory at UCSF Benioff Children's Hospital since March 2004.

Cryoablation has become the treatment of choice for children with arrhythmias. Your doctor will discuss this treatment and others with you to decide which method is the best option.

Like radiofrequency catheter ablation, cryoablation involves threading a tiny, metal-tipped catheter through a vein or artery in the leg and into the heart. Doctors guide the catheter through the blood vessel to the heart by using fluoroscopy or X-ray.