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Wolff-Parkinson-White Syndrome (WPW) – Types, and Treatment

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What is Wolff-Parkinson-White Syndrome?

Wolff-Parkinson-White syndrome is characterised by attacks of rapid heart rate (tachycardia), which is shown in an electrocardiogram (ECG). In some people the ECG abnormality may be present without any symptoms such as tachycardia. The heartbeat is regulated by electrical impulses that travel through the atria (upper chambers of the heart) to a knot of tissue known as the atrioventricular node, and then to the ventricles (lower chambers of the heart). Usually electrical impulses pause at the atrioventricular node before prompting the ventricles to contract.

In Wolff-Parkinson-White syndrome, an extra pathway conducts the electrical impulses to the ventricles without the normal delay. This extra pathway does not usually have serious consequences. However sometimes the extra (“accessory”) pathway may “bounce” the electrical impulses back to the atria after each beat. This creates a circuit in which each atrial (upper chamber) beat is followed by a ventricular (lower chamber) beat, which is then followed by another atrial beat and so on. The heart rate can reach over 200 beats per minute, when the normal resting heart rate is around 70 to 80 beats per minute. Between one and two people per 1000 are thought to have Wolff-Parkinson-White syndrome. The condition can be managed with medications and a procedure to get rid of the extra pathway, which usually does not require surgery.

ECG pattern of Wolff-Parkinson-White syndrome

Types of Wolff-Parkinson-White Syndrome

The WPW syndrome has been divided into two types (A and B) on the basis of the direction of the dominant QRS deflection in lead Vi.

Type A

In type A the delta wave and the remainder of the QRS complex are primarily upright in lead V, which shows R, RS, Rs, RSr’, and Rsr’ patterns. A negative delta wave is seen in lead I.

Type B

In type B the delta wave and the QRS complex are usually negative in lead V,, which shows QS or rS patterns. Lead I show a positive delta wave.

Intermediate forms

In addition, there are cases with intermediate forms which cannot be clearly classified in either of the above two types. Recently, a third group, AB, has been suggested for the cases with intermediate forms.

Epidemiology

The natural history of asymptomatic WPW patients has been speculated from the available data on symptomatic WPW patients and from those who have been incidentally discovered to have a WPW ECG pattern. In large-scale population-based studies involving pediatric and adult populations, the general prevalence of WPW has been estimated between 1 to 3 per 1000 individuals (0.1 to 0.3 %). Identification of the truly asymptomatic patients with WPW pattern is difficult, as these individuals by definition are those who have no clinical symptoms. A general estimate by experts suggests that about 65% of adolescents and 40% of individuals over 30 years with a WPW pattern on a resting ECG are asymptomatic. The incidence of patients with the WPW pattern progressing to arrhythmia is thought to be around 1% to 2% per year, and WPW syndrome prevalence peaks from age 20 to 24.

Familial studies have shown a slightly higher incidence of WPW, about 0.55% among first-degree relatives of an index patient with WPW. A familial form of WPW syndrome has been observed with a missense mutation in the PRAKAG2 gene leading to an increase in prevalence to 3.4% in first-degree relatives, and the condition is associated with congenital structural heart disease including Ebstein anomaly and hypertrophic cardiomyopathy.

Pathophysiology

WPW ECG pattern is caused by abnormal electrical conduction through an accessory pathway that bypasses the normal cardiac conduction system. This accessory pathway allows cardiac electrical activity to bypass the atrioventricular node conduction delay, and arrive early at the ventricle, leading to premature ventricular depolarization. This preexcitation also bypasses the fast conducting His-Purkinje system and results in early but slowly propagated ventricular depolarization, which gives rise to the ECG pattern of a short PR interval with a “slurred” start to the QRS complex termed a delta wave. The remainder of a normal QRS obliterates this delta wave as the normal cardiac conduction catches up following AV node delay and fast conduction through the His-Purkinje system.

There are two ways in which an accessory pathway can lead to WPW syndrome. The pathway can either initiate and maintain an arrhythmia or allow conduction of an arrhythmia generated elsewhere. The first type occurs when a circuit is formed between the normal conduction system of the heart and the accessory pathway (or two or more accessory pathways), allowing for atrioventricular reentrant tachycardia (AVRT). An incorrectly timed extra electrical impulse can lead to a recurring cycle between the atria, AV node, ventricles, and the accessory pathway. Orthodromic AVRT occurs when conduction progresses from the atria with antegrade conduction through the AV node to the ventricle and retrograde conduction through the accessory pathway. This will usually result in a narrow complex QRS as the His-Purkinje system is used unless aberrant conduction is present. Antidromic AVRT is the opposite with antegrade conduction passing from the atria through the accessory pathway to the ventricle and retrograde conduction back up the AV node and is usually associated with a wide complex QRS.

The other way an accessory pathway can lead to arrhythmia is by allowing conduction of an arrhythmia that is generated elsewhere to propagate to a portion of the heart that would normally be electrically insulated from this arrhythmia. The accessory pathway is typically comprised of myocardial tissue and usually has non-decremental or non-delayed conduction allowing immediate ventricular activation. This non-decremental conduction property predisposes patients with WPW syndrome to sudden cardiac death. This occurs due to rapid ventricular rates in conditions with rapid atrial depolarization, such as atrial fibrillation (AF) or atrial flutter. These fast ventricular rates can degenerate into ventricular fibrillation (VF) and cardiac arrest.

Causes

The extra electrical connection found in Wolff- Parkinson-White syndrome develops early in pregnancy, while the baby is developing in the womb. One theory is that additional muscle fibre strands develop between the atrium and ventricle, causing the extra connection.

Wolff-Parkinson-White syndrome is the most common cause of abnormal heart rhythms (arrhythmia). It occurs more frequently in males than females and in the majority of cases happens ‘out of the blue’. In a very small number of cases, it is passed on from parent to child.

Symptoms of Wolff-Parkinson-White Syndrome

Some people don’t experience any symptoms. They have WPW pattern but haven’t experienced a fast heart rate (tachycardia).

If people do get symptoms, they can include:

Symptoms will affect people differently. They can affect people for minutes, seconds or hours. In a few cases they can last for days. How often they happen can vary, with some people being affected daily, while others only experience them a few times a year, or never.

They can sometimes be triggered by strenuous exercise, stress, caffeine or drinking alcohol.

Risk factors

Complications

Complications may include:

The most severe form of a rapid heartbeat is ventricular fibrillation (VF), which may rapidly lead to shock or death. It can sometimes occur in people with WPW, particularly if they also have atrial fibrillation (AF), which is another type of abnormal heart rhythm. This type of rapid heartbeat requires emergency treatment and a procedure called cardioversion.

Diagnosis of Wolff-Parkinson-White Syndrome

If you have a fast heartbeat, your health care provider will likely recommend tests to check for WPW syndrome, such as:

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.

Artificial pacemaker

Patients suffering from irregular heartbeat after treatment are implanted with an artificial pacemaker to regulate their heart rhythm.

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.

Prevention of Wolff-Parkinson-White Syndrome

There is no way to prevent WPW, but you can prevent complications by learning as much as you can about the disease. Work closely with your cardiologist (healthcare provider who specializes in diseases of the heart) to find the best treatment. Ask them to teach you how to do a Valsalva maneuver.

Here are some helpful lifestyle suggestions:

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