Your son, who is approaching his teen years like other children, regularly goes out to play during free time at school. The teacher then informs you based on observations made during basketball sessions, that he frequently takes rest in between, and sits down to catch his breath. Your child has not mentioned anything to you, but you too observe a similar thing when you see him run around with his friends in the neighborhood. This prompts you to take him to a physician. On performing certain tests on his heart, a rare condition known as Wolff-Parkinson-White Syndrome (WPW) is diagnosed, where there is an extra electrical pathway in the heart, leading to changes in the pattern of the heart beating. This change in heart beat rhythm is known as an arrhythmia and in cases of WPW, a fast heartbeat or tachycardia is often experienced. This condition, you learn, is a common cause of fast heart rate disorders in infants and children.
About Wolff Parkinson White Syndrome
WPW is a disorder of the heart, present at birth, but the arrhythmias usually become apparent only later during teenage years or early twenties. However, the complications may arise at any age, and about 80 percent of people develop the first signs between the ages of 11 and 50 years. Some individuals born with WPW never experience any health problems, and it is known to affect around 1 to 3 in 1,000 people worldwide, with men having a higher incidence than women. In the majority of cases, episodes of tachycardia that occur are not life-threatening, but treatment may be required to stop or prevent these episodes.
Causes
The heart is made up of four chambers, the upper chambers are called the atria that receive and collect blood, while the lower chambers, are called the ventricles, which pump blood throughout the body. Located in the right atrium, is the sinus node, a natural pacemaker that controls the heart rhythms. Electrical impulses travel from the sinus node, across the atria to the ventricles via the atrioventricular node (AV node). With the help of electrical impulses these chambers work together, to pump blood efficiently throughout the body. In WPW, an extra electric pathway, connects the atria and ventricles, that bypasses the AV node, resulting in early contraction of ventricles or preexcitation arrhythmia. The rapid heart rate that results is called supraventricular tachycardia. The exact cause for this extra pathway to develop is still unknown, but it may be attributed to:
- Congenital factors (present at birth)
- Random or sporadic factors
A small percentage of cases are due to inheritance, while most of the cases are a result of random or sporadic factors. Parents having such extra pathways may pass them onto their children, with an incidence as high as 5.5 in 1,000 with respect to first-degree relatives. It has also been observed that around 7 to 20 percent of patients with WPW have congenital heart defects. Other factors resulting in rapid heartbeat are looped electrical impulses, where impulses are sent to the ventricles at a very rapid rate, resulting in very fast pumping. Atrial fibrillation can be another cause for WPW, where electrical impulses travel in a haphazard manner across the atria, causing them to beat very quickly. This is less common, but can be life-threatening.
Symptoms
People with WPW may have only few episodes of tachycardia, while others may develop it once or twice a week.
General symptoms seen are a result of rapid heart rate and include:
- Pounding heartbeats (palpitations)
- Dizziness
- Fainting
- Easily tired on exertion
- Anxiety
Often, teenagers and people in their early twenties develop sudden palpitations when exercising, lasting for a few seconds or persisting for several hours.
In infants, WPW can cause the following signs:
- Shortness of breath
- Poor eating
- Fast heartbeats visible on chest
- Not alert or active
When there is an underlying heart problem along with WPW, more severe symptoms can result such as:
- Chest tightness and pain
- Breathing difficulty
- Sudden death
At times, a person experiences no symptoms in spite of having an extra electrical pathway, and it may be discovered by chance during a routine cardiac check up. In such case, the condition is known as Wolff-Parkinson-White pattern.
Tests and Diagnosis
Normally, an electrocardiogram (ECG) that shows the heart’s electrical activity record is used for diagnosing the condition. Electrodes are placed on the chest, arms and legs, which are connected by wires to the ECG machine. Any extra pathway that exists between the atria and ventricles will be seen.
Other methods include using portable ECG devices to keep a track of the patient’s heart rate such as:
- Holter monitor
- Event recorder
A Holter monitor is carried in the pocket or worn on a belt or shoulder strap. This records the heart activity for a 24-hour period thus providing the physician a full detail of the heart rhythms. An event recorder is used to monitor the heart activity over a few weeks or months and the patient has to activate it when symptoms of tachycardia are setting in. On pushing a button, an ECG strip of few minutes preceding and following the time is recorded. Several questions on history of fainting, cardiac arrests in the family, sport and physical activities may be asked during diagnosis.
An electrophysiological testing may be carried out to confirm the diagnosis or to find the exact location of the extra pathway.
Treatment and management
The goal of treatment is to slow down the heart rate and prevent future episodes of tachycardia. This includes stimulating the vagus nerve (the tenth cranial nerve), to help regulate the heart rate. This is known as vagal maneuvering, which includes coughing, bearing down like having a bowel movement and applying an icepack on the face. Anti-arrhythmic medications such as adenosine as an injection maybe administered or oral medications such as flecanide or propafenon maybe prescribed when vagal maneuvering does not help. When neither of the above helps, cadioversion is done, where shock is applied to the heart through paddles or patches on the chest, to restore regular rhythm.
Other than regulating the heart rate to maneuvering and medication, there are procedures to correct the syndrome such as:
- Radiofrequency or catheter ablation
- Surgery
In radiofrequency ablation, the extra electrical pathway is destructed by using an electrode catheter inserted in the heart. This is a very successful (85 to 95%) and common procedure, with the risk of death being less than 1 in 1,000. This is useful in young people, where the option of life long treatment with anti-arrhythmic drugs can be avoided. Surgery can also be performed for ablation purpose, but being an invasive procedure, is reserved for people who are having a heart surgery for other reasons. In infants and children younger than 10 years, digoxin is given to suppress the tachycardia. There is probably no need for treatment when symptoms are absent, and in such people, the extra pathway may spontaneously disappear over time.
Being safe
It will help to be educated about dealing with an episode of tachycardia, so that you have control over the situation. Having discussions with the doctor on knowing when to seek emergency care and how to perform vagal maneuvering can avoid a dangerous situation. Having a healthier lifestyle and avoiding substances like caffeine, alcohol, tobacco, which can affect the heart rate, will help manage the syndrome.
