What is Wolff-Parkinson-White syndrome?

Risk Factors

There are no known risk factors for WPW syndrome.

Etiology and Genetics

The etiology of Wolff-Parkinson-White syndrome is complex, involving both genetic and environmental determinants, most of which are not at all well understood. The great majority of cases are sporadic, and these individuals have no apparent family history of the disease. In a small minority of cases, mutations in the PRKAG2 gene, located on the long arm of chromosome 7 at position 7q36.1, have been shown to cause the condition. This gene encodes a protein known as protein kinase, AMP-activated, gamma 2 non-catalytic subunit (AMPK). An important cellular regulatory molecule, AMPK senses and responds to energy demands within the cell by helping to regulate the concentrations of the cell’s main energy source, adenosine triphosphate (ATP). AMPK is known to be active during heart development in the fetus, although its exact role in the process is not well understood. Mutations in the PRKAG2 gene may result in either an overactive or underactive AMPK protein, but in either case heart function is compromised.

The familial form of WPW syndrome, caused by mutations in the PRKAG2 gene, is inherited in an autosomal dominant fashion. This means that a single copy of the mutation is sufficient to cause full expression of the syndrome. An affected individual has a 50 percent chance of transmitting the mutation to each of his or her children. Many cases of familial WPW syndrome, however, result from a spontaneous new mutation, so in these instances affected individuals will have unaffected parents.

Symptoms

Some people with WPW syndrome never have tachyarrhythmia and its associated symptoms. In those who do, symptoms usually begin between ages eleven and fifty. The frequency and severity of the tachyarrhythmia varies from one person to another and may be associated with any or all of these symptoms: palpitations (sensation of a pounding heartbeat), chest pain or tightness, dizziness, fainting, and shortness of breath. In rare cases, a person will go into cardiac arrest (the heart stops pumping) and lose consciousness.

Screening and Diagnosis

The doctor will ask about a patient’s symptoms and medical history and will perform a physical exam. If the patient has a tachyarrhythmia due to WPW syndrome, he or she will have normal or low blood pressure and a heart rate of 150–250 beats per minute. (A normal heart rate is 60–100 beats per minute.)

If a patient is not having irregular heart rhythms during the exam, the results of the exam may be normal. In either case, an electrocardiogram (a test that records the heart’s activity by measuring electrical currents through the skin) will usually show a “delta wave” that signals an extra electrical pathway.

Other tests may include monitoring with a Holter monitor for twenty-four to forty-eight hours to check for any episodes of irregular heartbeat and an electrophysiology study, in which a catheter (a thin tube designed to be inserted into a blood vessel) is passed to the interior of the heart, where it takes detailed measurements of its electrical activity. This study will detect the extra pathway.

Treatment and Therapy

The goal of treatment is to reduce or eliminate episodes of tachyarrhythmia and associated symptoms. If a patient does not have symptoms, treatment is usually not necessary.

If a patient does need treatment, it may include medication. Antiarrhythmics may be given to coordinate the heart’s electrical signals. This can control or prevent episodes of rapid heartbeat. However, the patient must take the medicine carefully because it can sometimes make an abnormal heart rhythm worse.

Radio-frequency ablation is a procedure in which a catheter delivers energy at a particular radio frequency to the heart. This destroys (ablates) the abnormal electrical pathway. In most cases, ablation is successful and ends the need to take medicine.

Open-heart surgery is done to destroy the abnormal pathway. However, this procedure is rarely done.

Defibrillation is done in the case of cardiac arrest, which is rare. Defibrillation gives the heart a brief electric shock. This procedure converts a rapid, irregular heartbeat back into a normal heartbeat.

Prevention and Outcomes

There is no known way of preventing WPW syndrome. However, symptoms can be prevented with proper treatment.

Bibliography

Beers, Mark H., et al. The Merck Manual of Diagnosis and Therapy. 18th ed. Whitehouse Station: Merck Research Laboratories, 2006. Print.

Dugdale, David C., III, and Michael A. Chan. "Wolff-Parkinson-White Syndrome." MedlinePlus. US NLM/NIH, 4 June 2012. Web. 2 Sept. 2014.

Genetics Home Reference. "Wolff-Parkinson-White Syndrome." Genetics Home Reference. US NLM, 25 Aug. 2014. Web. 2 Sept. 2014.

Hollman, A. "The Wolff-Parkinson-White Syndrome: A Very Long Follow-Up." Amer. Jour. of Cardiology 113.10 (2014): 1751–1752. Print.

Rosenblum, Laurie. "Wolff-Parkinson-White Syndrome." Health Library. EBSCO, 14 Jan. 2014. Web. 2 Sept. 2014.