Also known as preexcitation syndrome, Wolff-Parkinson-White (WPW) syndrome is a condition in which there is an extra, abnormal electrical pathway in the heart that can cause an abnormal heart rhythm (arrhythmia). The condition is believed to be present from birth (a congenital heart defect). In most cases, WPW causes symptoms only when the heart rate is very fast (tachycardia). In other cases, the condition may cause no symptoms at all. However, some WPW patients carry a small risk of developing a potentially fatal heart rhythm known as ventricular fibrillation.
Some individuals do not need treatment for WPW, either because they have no symptoms or because the condition resolves on its own as patients get older. Other cases will require treatment, including an invasive procedure called catheter ablation that destroys the abnormal pathway. In rare cases, patients may need open-heart surgery. Medications (e.g., antiarrhythmics) may also be prescribed.
About Wolff-Parkinson-White syndrome
Also known as preexcitation syndrome, Wolff-Parkinson-White (WPW) syndrome is a condition in which the normal electrical signals in the heart travel along an extra electrical pathway. This can cause an abnormal heart rhythm (arrhythmia).
In a normal heart, electrical signals are generated in the upper right chamber of the heart (right atrium) and travel along a standard conduction system. These signals first stimulate the atria to contract, then pass through the atrioventricular node to the ventricles. This process causes the heart to contract in a rhythmic, predictable fashion. However, in patients with WPW syndrome, the electrical signals travel through an extra, abnormal pathway that bypasses the atrioventricular node. This pathway is known as the Kent bundles.
Because the electrical signals reach the ventricles via this abnormal route instead of through the heart’s normal conduction system, they may signal the ventricles to contract abnormally. This is usually because of a co-existing arrhythmia called atrial fibrillation, in which the atria beat very rapidly. It may also be due to a special kind of arrhythmia called an atrioventricular reentrant tachycardia (AVRT). An AVRT occurs when the electrical signal “loops” through the parallel conduction systems in the heart. In this action, the current travels down from the atrium to the ventricle through the normal AV node and back up to the atria through the accessory pathway. The process causes the ventricles to contract at a very rapid rate, known as reentrant tachycardia. As a result of either condition, the patient may experience rapid heart rhythms of over 100 beats per minute (tachycardias), along with palpitations, lightheadedness and/or loss of consciousness.
The vast majority of patients with WPW syndrome have a good prognosis, but the condition develops differently in different people. The condition may:
Go into dormancy, only to recur later in life.
Resolve on its own over time as the Kent bundles lose their ability to conduct electrical impulses.
Cause a potentially fatal arrhythmia such as ventricular fibrillation, in which the heart quivers rapidly instead of beating. This life-threatening complication is extremely rare, occuring in less than 1 percent of the individuals with WPW.
In 70 percent of WPW patients, there is no other sign of heart disease. The remaining 30 percent may have another heart condition in addition to WPW syndrome, including:
Mitral valve prolapse. A condition in which the two flaps of the mitral valve (which regulates blood flow between the left atrium and the left ventricle) cannot close properly. This may occur either because one of the flaps is larger than the other or because the “hinges” of the flaps are damaged. As a result, one or both of the flaps close in the wrong direction, and blood can leak back toward the upper chamber (regurgitation).
Cardiomyopathy. A type of heart disease in which the heart muscle is abnormally enlarged, thickened or stiffened.
Ebstein’s anomaly. A rare heart condition present from birth that involves a deformed and misplaced tricuspid valve (which regulates blood flow between the right atrium and the right ventricle).
The abnormal accessory pathways are believed to be present since birth and often the condition is first diagnosed in children and young adults. WPW is the leading cause of tachycardia among children and adolescents. There is interest in studying WPW’s genetic aspects, as there is an inherited form of the syndrome. It is felt that certain changes (mutations) are responsible for the tachycardia in WPW syndrome. Understanding the genetics of WPW syndrome may help toward making an early diagnosis and in offering the most effective therapies.
Signs and symptoms of WPW syndrome
Symptoms of Wolff-Parkinson-White (WPW) syndrome vary according to the nature and severity of the rapid heartbeat (tachycardia). Patients may have no symptoms until a tachycardia develops, after which patients may experience any or all of the following:
Palpitations (pounding or “galloping” heartbeat)
Mild to severe chest pain
Lightheadedness
Syncope (fainting)
Fatigue
Shortness of breath
Rarely, the person may go into cardiac arrest and lose consciousness as a result of ventricular fibrillation unless they are treated immediately by a defibrillator.
Diagnosis methods for WPW syndrome
To diagnose Wolff-Parkinson White (WPW) syndrome, the physician will begin by taking a complete medical history. This will include the patient’s family history, particularly for cardiovascular conditions and current symptoms. The physician will then give the patient a complete physical examination, during which blood pressure will be measured and the heart will be heard through a stethoscope. If a patient with Wolff-Parkinson-White (WPW) syndrome is having abnormal heart rhythms (arrhythmias), he or she will have normal or low blood pressure and a heart rate of approximately 150 to 250 beats per minute (about 90 to 150 beats faster than normal).
For individuals with suspected WPW, the physician is likely to order a painless test called an electrocardiogram (EKG). The EKG of someone with WPW syndrome will show a delta wave that signals the presence of an extra electrical pathway. This wave is visible even if the patient is in a normal heart rhythm. If signs of WPW are not immediately seen on an EKG, the patient may need to wear a small, continuous EKG Holter monitor for 24 hours to assess for the condition.
An electrophysiology study (EPS) is a minimally invasive test that may follow the EKG. The EPS is a procedure in which a thin tube (catheter) is inserted into a vein or artery (e.g., in the groin) and guided to the heart. Once in place, it can be used to perform specific, essential measurements of the heart’s electrical activity and pathways. The catheter can locate the extra electrical pathway and determine the extent to which electrical impulses are traveling through it. In some instances, the physician will also perform a catheter ablation, which is a catheter-based procedure that eliminates (ablates) the abnormal pathway.
Treatment and prevention for WPW syndrome
Many patients (e.g., those with no symptoms or only mild tachycardias) require no treatment. Other patients may need to take medications, such as antiarrhythmics, to control tachycardias. These medications must be carefully administered and monitored by a physician, as they can sometimes worsen the severity of an abnormal rhythm.
It is difficult to identify all patients with WPW who are at risk for sudden death due to ventricular fibrillation. This risk is determined by the ability of the accessory connection to conduct electrical signals at a rapid rate. In some cases, an exercise stress test can allow assessment of the electrical properties of the accessory pathway. In other individuals, an invasive electrophysiology study must be administered to definitively identify the condition. If the pathway has these characteristics then radiofrequency ablation should be performed.
In certain patients catheter ablation or radiofrequency ablation is necessary. These patients include those who cannot be successfully treated by medications or whose pathway places them at risk for sudden cardiac death. During ablation, an area of the patient’s body (usually the groin) is numbed, but the patient remains awake. The physician makes a cut (incision) in the area, through which a thin tube (catheter) is inserted into a major blood vessel. The catheter is guided all the way up to the heart. At the tip of the tube is a small wire, which can deliver radiofrequency energy to burn away the abnormal areas of the heart. Following successful ablation, the heart can beat normally again.
This catheter-based procedure is the preferred method of treating patients with Wolff-Parkinson-White (WPW) syndrome. It has a roughly 90 percent success rate of destroying the accessory pathways, and the risk of complications is low. Because the procedure’s success will eliminate the need to take medication, it is particularly valuable in treating younger patients who may not want, or be able, to take medications for the rest of their lives.
In rare cases, surgery will be necessary. Both surgical ablation and endocardial resection are types of open-heart surgery in which the surgeon selectively destroys the abnormal areas of the heart that are causing abnormal heart rhythms.
In an emergency situation where ventricular fibrillation develops and the person possibly loses consciousness (cardiac arrest), defibrillation is necessary.
Recurring tachycardias resulting from WPW syndrome can be controlled over the long term with drug therapy, but there is no effective way to prevent this condition entirely. It is recommended that individuals diagnosed with WPW syndrome carry a sample EKG printout and/or wear a medical bracelet to alert medical professionals of their condition should they experience cardiac arrest.
Variants of WPW syndrome
Wolff-Parkinson-White (WPW) syndrome is also known as preexcitation syndrome, and there are a number of variants of this syndrome. All of these variants are characterized by electrical impulses traveling through either an extra (accessory) pathway or abnormally through the heart’s normal electrical system, resulting in premature contraction of the ventricles. The premature contraction can lead to fast heart rhythms (tachycardias). Variants of WPW syndrome include:
Concealed accessory pathway. A common variant of WPW syndrome where the accessory pathway is not apparent by analysis of a surface electrocardiogram. This variant requires invasive electrophysiology testing for diagnosis and treatment.
Enhanced AV nodal pathway (formerly known as Lown-Ganong-Levine [LGL] syndrome). As recently as 1997, this condition was believed to be caused by an accessory pathway. Experts currently believe that the condition is caused by electrical signals that travel through the heart’s normal electrical system, but which are somehow sped up as they pass through the atrioventricular node (between the upper and lower chambers of the heart). This process is not well understood.
Nodoventricular fibers. A variant of WPW syndrome in which the electrical fibers pass through types of Mahaim fibers called nodoventricular fibers instead of through the heart’s normal electrical system.
Fasciculoventricular fibers. A variant of WPW syndrome in which the electrical fibers pass through types of Mahaim fibers called fasciculoventricular fibers instead of through the heart’s normal electrical system.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their doctor. Patients or parents may wish to ask their physicians the following questions related to Wolff-Parkinson-White (WPW) syndrome:
Why do you suspect WPW?
What tests will be used to diagnose the condition?
How urgently does my condition need to be treated?
What are my treatment options?
What are the risks assoicated with these treatments?
Is it possible that my condition will resolve on its own and not need treatment?
Will I need to take medications even if I undergo ablation?
Are there any lifestyle changes I can make that might improve my condition?
Do I have any restricitions due to WPW?
Do I have any other heart conditions in addition to WPW syndrome?
If I do require catheter ablation, how successful do you expect the procedure to be?
How will my condition be monitored during my life?
What are the chances my child will have WPW?
Do you recommend any genetic testing for my family members?
