Marshall–White syndrome

Overview

Marshall–White syndrome, more commonly known today as Wolff–Parkinson–White (WPW) syndrome, is a congenital cardiac condition characterized by the presence of an abnormal extra electrical pathway in the heart. This pathway allows electrical signals to bypass the normal route, leading to episodes of rapid heart rate (tachycardia). Though the term "Marshall–White syndrome" was historically used in early cardiac literature, the condition is now universally referred to as Wolff–Parkinson–White syndrome, named after the three physicians who first described it in 1930.

WPW syndrome is one of the most common causes of supraventricular tachycardia (SVT) and can affect individuals of any age. In many cases, it is asymptomatic and discovered incidentally on an electrocardiogram (ECG), but in others, it can cause significant symptoms or, rarely, life-threatening arrhythmias.

Causes

Wolff–Parkinson–White syndrome is typically caused by the presence of an extra electrical conduction pathway between the atria and the ventricles, known as an accessory pathway. This pathway, often called the Bundle of Kent, allows electrical signals to bypass the atrioventricular (AV) node, leading to pre-excitation of the ventricles.

In most cases, WPW is a congenital condition, meaning individuals are born with the accessory pathway. The exact cause of this abnormality is unknown, but it is thought to result from improper development of the heart’s electrical system during fetal growth.

In rare cases, WPW can be associated with certain genetic conditions, such as Ebstein’s anomaly (a congenital heart defect affecting the tricuspid valve), or may be part of familial syndromes with an autosomal dominant inheritance pattern involving mutations in the PRKAG2 gene.

Symptoms

Symptoms of WPW syndrome can vary widely. Some individuals may remain asymptomatic throughout life, while others experience intermittent or frequent episodes of rapid heart rate. Common symptoms include:

• Palpitations: Sudden, rapid heartbeat that may feel like fluttering or pounding in the chest.

• Dizziness or lightheadedness

• Shortness of breath

• Chest discomfort or pain

• Fatigue or weakness

• Fainting (syncope): In severe cases due to reduced cardiac output during arrhythmias.

• Anxiety during episodes of tachycardia

In rare cases, WPW syndrome can lead to more dangerous arrhythmias such as atrial fibrillation with rapid conduction to the ventricles, which can degenerate into ventricular fibrillation and cause sudden cardiac arrest.

Diagnosis

Diagnosis of WPW syndrome is typically made through a combination of clinical evaluation and diagnostic testing. Key steps include:

• Electrocardiogram (ECG):

  • Hallmark features include a short PR interval, delta wave (a slurred upstroke in the QRS complex), and widened QRS complex.

• Holter monitoring: Continuous ECG recording over 24–48 hours to detect intermittent arrhythmias.

• Event recorder: For patients with infrequent symptoms, this device records the heart’s rhythm when activated during symptoms.

• Electrophysiological (EP) study: An invasive test that maps the heart's electrical system and precisely identifies the location of the accessory pathway.

• Echocardiography: To assess for structural heart defects, especially in suspected cases of Ebstein’s anomaly.

Diagnosis may be incidental during routine ECGs or while evaluating unexplained palpitations or syncope.

Treatment

Treatment of WPW syndrome depends on the severity of symptoms, frequency of tachycardia episodes, and the risk of dangerous arrhythmias. Common treatment approaches include:

• Lifestyle modifications: Avoiding stimulants like caffeine and certain medications that may trigger tachycardia episodes.

• Medications:

  • Antiarrhythmic drugs such as flecainide or propafenone

  • Beta-blockers or calcium channel blockers (used cautiously and avoided in atrial fibrillation with WPW)

• Vagal maneuvers: Techniques such as the Valsalva maneuver or carotid sinus massage may help terminate episodes of SVT.

• Catheter ablation (radiofrequency ablation):

  • The most definitive treatment for WPW

  • Involves destroying the accessory pathway using heat or cryotherapy via a catheter inserted into the heart

  • Success rates exceed 95% with low complication risk

• Emergency care: In cases of hemodynamic instability due to arrhythmia, immediate electrical cardioversion may be necessary.

Patients who have experienced life-threatening arrhythmias may require implantable defibrillators, though this is rare for isolated WPW.

Prognosis

The prognosis for individuals with Wolff–Parkinson–White syndrome is generally excellent, especially with timely diagnosis and treatment. Many people live completely normal lives without any limitations after successful catheter ablation.

However, untreated WPW carries a small risk of sudden cardiac death due to rapid arrhythmias, particularly in individuals with multiple accessory pathways or those who develop atrial fibrillation. This is why risk stratification through EP studies is crucial in certain cases, even in asymptomatic patients.

With proper management and regular follow-up, most patients experience complete resolution of symptoms and have a normal life expectancy.