Welcome to the Rare Classroom, a new series from Patient Worthy. Rare Classroom is designed for the curious reader who wants to get informed on some of the rarest, most mysterious diseases and conditions. There are thousands of rare diseases out there, but only a very small number of them have viable treatments and regularly make the news. This series is an opportunity to learn the basics about some of the diseases that almost no one hears much about or that we otherwise haven’t been able to report on very often.

Eyes front and ears open. Class is now in session.

The disease that we will be learning about today is:

Wolff-Parkinson-White Syndrome

Also WPW pattern, ventricular pre-excitation with arrhythmia, or auriculoventricular accessory pathway syndrome

What is Wolff-Parkinson-White Syndrome?

• This is a disorder characterized by an abnormality that impacts the electrical function of the heart and leads to symptoms.
• Not all people with this problem experience symptoms.
  • In those with symptoms, they often only occur when the person’s heartrate is high
• Irregular heartbeat is the most common symptom and rarely, cardiac arrest can occur.
• It is associated with other conditions, such as hypokalemic periodic paralysis, Leber’s hereditary optic neuropathy, and Ebstein anomaly.
  • WPW syndrome is also associated with the protein kinase enzyme PRKAG2, encoded by a gene of the same name.

How Do You Get It?

• In most cases, the cause of WPW syndrome is unknown. However, the latest research suggests that a combination of random chance and genetic factors play a role.
• In a few cases, a mutation impacting the PRKAG2 gene is inherited from the parents. This occurs in a autosomal dominant fashion.
• In people with WPW syndrome, an extra accessory pathway called the bundle of Kent is present.
  • The bundle of Kent sends electrical signals at an abnormally fast rate
• The disease is typically diagnosed based on the results of an electrocardiogram.

What Are The Symptoms?

• Around 40 percent of patients with this abnormality do not experience symptoms
• Symptoms generally occur when the heart is under strain and beating rapidly.
  • These symptoms can include:
    • Abnormal heart rhythms
      • Usually, this occurs as an unusually rapid heartrate. The most common form is called paroxysmal supraventricular tachycardia.
    • Low blood pressure
    • Altered mental state
    • Syncope (fainting)
    • Heart palpitations
    • Shortness of breath
    • Dizziness
    • Lightheadedness
• WPW syndrome does carry a slight risk of sudden death as a result of cardiac arrest
  • This is typically the result of atrial fibrillation which triggers ventricular fibrillation
  • This risk is also dependent on the properties of the accessory pathway
    • High risk characteristics include a shorter refractory period, septal location of the pathway, the presence of multiple pathways, and atrial fibrillation.

How Is It Treated?

• Patients with these high risk features are those that need to be treated most urgently
• Those displaying serious abnormal heart rhythms are treated with electrical cardioversion
  • This process converts the rhythm to a regular rhythm using electricity
• Cardioversion using medication may be employed if the patient appears to be more stable.
  • Common medications to treat these symptoms include procainamide and amiodarone.
  • AV node blockers are not recommended as these can worsen atrial fibrillation symptoms.
• The most effective therapy for WPW syndrome is catheter ablation. This procedure destroys the abnormal electrical pathway.
  • Radiofrequency ablation is the most common approach and can have a success rate as high as five percent.
  • A successful ablation generally results in the condition being cured; however, this may not be true for patients with multiple pathways.

Where Can I Learn More???

• Check out our cornerstone on this disease here.
• Learn more about this condition from the SADS Foundation.