Wolff-Parkinson-White Syndrome (WPW)

What is Wolff-Parkinson-White (WPW) Syndrome?

Doctors Louis Wolff, Sir John Parkinson, and Paul Dudley White, first described the cardiac syndrome in 1930 when they observed changes in a person’s heart rate. In a normal heart, electrical conduction of the heartbeat that travels from the atrium to the ventricle (the upper and lower chambers of the heart, respectively) passes through the atrioventricular node (AVN). When the electrical conduction passes through the AV node to the ventricle, the number of electrical signals are controlled and the next transmission (the refractory period) is delayed giving the cells of the ventricle time to get ready for the next impulse. This feature is absent in WPW patients.

In the WPW syndrome, the electrical connection passes through another accessory pathway called the bundle of Kent between the atrium and the ventricle of the heart. This pathway does not cut down the electrical activity nor does it delay the electrical transmission going to the ventricles. This leads to extremely rapid heartbeats.

Although WPW syndrome is present at birth, the symptoms may appear only in adulthood between the ages of 20 and 40. The WPW syndrome affects 1 to 3 individuals out of 1000. Mortality due to the WPW syndrome affects 4% of the affected population.

The most common type of irregular heartbeat caused in the WPW syndrome is known as paroxysmal supraventricular arrhythmia.

What are the Causes of Wolff-Parkinson-White Syndrome?

Not much is known on how the extra electrical connection (accessory pathway) develops in the heart. In hereditary WPW, scientists have attributed a region on chromosome 7 as responsible for the syndrome, and they have also identified a gene responsible for the syndrome. However, the association between the gene and the pathophysiology of the condition is still not clear.

The accessory pathway bypasses the standard AVN that is the standard route for electrical conduction of the heart rate. There are 5 types of accessory pathways between the atrium and ventricle.

There are risk factors for sudden death associated with WPW syndrome. They are:

• Ebstein anomaly
• Numerous accessory pathways
• Very short pre-excitation periods in the ventricle
• Hereditary WPW syndrome
• History of tachycardia (rapid heart rate)

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The WPW syndrome is also associated with other congenital conditions, such as Ebstein anomaly. It is also observed as part of other genetic conditions, such as Pompe disease, tuberous sclerosis complex, Danon disease, and hypokalemic periodic paralysis.

What are the Symptoms of Wolff-Parkinson-White Syndrome?

Not everyone exhibits the same symptoms. There are some who experience rapid heart beats once or twice a week, and others experience only a few instances of tachycardia. There are those who experience no symptoms. The following characterize the symptoms of WPW syndrome:

• Palpitations (pounding or fluttering sensation in the chest)
• Fainting (syncope)
• Dizziness
• Shortness of breath
• Chest pain
• Feeling light in the head

How do you Diagnose Wolff-Parkinson-White Syndrome?

Diagnosing WPW patients is based on the presence of tachyarrhythmias and pre-excitation. Men are more frequently diagnosed compared to women. The gender distinction is not observed in children.

Electrocardiogram (ECG) or a continuous- or person-triggered ambulatory (portable) ECG monitoring e.g. a Holter monitor may help diagnose and distinguish between WPW alone and WPW with AF.

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A normal heart rate for an adult ranges between 60 to100 beats per minute while in infants and children it is less than 150 beats per minute. During an episode of tachycardia, the heart rate is more than 100 beats per minute.

Electrophysiologic (EPS) study that uses catheters to assess the heart can help to detect the accessory pathway. A negative EPS indicates low risk of getting future ventricular fibrillation (VF – an extremely rapid heartbeat causing death), atrioventricular re-entrant tachycardia (AVRT), or pre-excited atrial fibrillation (AF)

How do you Treat Wolff-Parkinson-White Syndrome?

Combined diagnosis and treatment is a good strategy to manage the condition. The goal in treating WPW syndrome is to extend the refractory period of the accessory pathway (AP) compared with that of the traditional AVN. This gives the ventricle more time to transmit the next electrical impulse through the AP. In this way, the heart rate is stabilized.

Radiofrequency (RF) catheter ablation is used to treat Wolff-Parkinson-White syndrome combined with AF. This procedure helps to destroy the tissue that is causing the rapid heartbeat. The procedure has an 85% to 95% success rate. However, RF ablation leads to complications, such as sudden death, stroke, cardiac surgery, and myocardial infarction.

Open heart surgery is an effective treatment for WPW but is performed only in the case of a heart surgery for an associated condition.

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Medications:

There are 4 drugs that are used to treat WPW:

• Flecainide increases the interval between heartbeats as it blocks the sodium channels in the heart, which conduct electrical potential. Tachyarrhythmia is controlled. However, Flecainide negatively affects the contractility of the ventricular muscles. Hence, this drug cannot be prescribed to those who have any structural defects in their heart along with WPW syndrome.
• IV procainamide (17 mg/kg) is used in the chemical cardioversion (shock) of stable patients with WPW.
• Amiodarone blocks potassium channels in the heart muscle and prolongs the transmission of electrical impulses. The drug is effective in patients who are not experiencing pre-excitation in the heart. In the presence of existing pre-excitation, the drug accelerates the heart rate resulting in VF.
• Ibutilide is a drug that may be used but has many side effects.

Electrical cardioversion (shock) can be used to immediately treat patients with WPW and AF, who are unstable.

Vagal maneuvers are postures that slow the heart rate by affecting the vagus nerve, such as putting an ice pack on the face or bending down while coughing.

How do you Prevent Wolff-Parkinson-White Syndrome?

Patients with WPW and AF should not be treated with drugs that prolong electrical conduction through the AVN. This will only accelerate electrical conduction through the AP and result in degeneration to VF.

Patients should avoid alcohol or exercise that trigger the rapid heartbeat.