Wolff Parkinson White Syndrome

A 25 year old male presents to the emergency department with sudden onset palpitations that began 30 minutes ago during exercise. He also reports lightheadedness, chest discomfort, and shortness of breath. There is no significant past medical history. Vital signs show blood pressure of 110/70 mm Hg, pulse rate of 158 beats per minute, respiratory rate of 18 breaths per minute, oxygen saturation of 98 percent on room air, and temperature of 96.9 F. Physical examination is unremarkable. ECG shows short PR interval less than 120 ms, widened QRS complex greater than 120 ms, and a delta wave, which is a slurred upstroke of the QRS complex. Diagnosis?

Diagnosis is Wolff Parkinson White syndrome with orthodromic atrioventricular reentrant tachycardia.

1. Definition

Wolff Parkinson White syndrome is a pre-excitation syndrome caused by an accessory conduction pathway between the atria and ventricles, known as the Bundle of Kent, which bypasses the AV node and leads to early ventricular depolarization.

2. ECG Features in Sinus Rhythm

1. Short PR interval less than 120 ms
2. Delta wave, a slurred upstroke of the QRS complex
3. Widened QRS complex greater than 120 ms

3. Pathophysiology

1. Presence of an accessory pathway allowing conduction outside the AV node
2. Formation of reentrant circuits
3. Leads to paroxysmal supraventricular tachyarrhythmias

4. Types of Tachyarrhythmias

1. Orthodromic atrioventricular reentrant tachycardia
• Conduction down the AV node and back via the accessory pathway
• Produces regular narrow complex tachycardia
2. Antidromic atrioventricular reentrant tachycardia
• Conduction down the accessory pathway and back via the AV node
• Produces regular wide complex tachycardia

5. Atrial Fibrillation in Wolff Parkinson White Syndrome

1. Accessory pathway has a short refractory period
2. Allows rapid conduction of atrial impulses to the ventricles
3. Leads to irregular wide complex tachycardia with very high ventricular rates
4. May degenerate into ventricular fibrillation

6. Management

6.1 Stable Orthodromic AVRT (Regular Narrow Complex)

1. Vagal maneuvers
2. Adenosine
3. Beta blockers or calcium channel blockers if needed

6.2 Antidromic AVRT (Regular Wide Complex)

1. Procainamide is the drug of choice
2. Treat as ventricular tachycardia if diagnosis is uncertain

6.3 Atrial Fibrillation with Wolff Parkinson White Syndrome

1. Procainamide or ibutilide
2. Avoid AV nodal blocking agents, including:
• Adenosine
• Beta blockers
• Calcium channel blockers
• Digoxin

These drugs increase conduction through the accessory pathway and may precipitate ventricular fibrillation

6.4 Hemodynamically Unstable Patient

1. Synchronized DC cardioversion

6.5 Definitive Treatment

1. Radiofrequency catheter ablation of the accessory pathway

7. Key Clinical Insight

Young patient with paroxysmal palpitations and ECG showing short PR interval, delta wave, and widened QRS strongly suggests Wolff Parkinson White syndrome

8. Exam Level Pearls

1. Short PR interval with delta wave is diagnostic of WPW pattern
2. Orthodromic AVRT is the most common arrhythmia and is narrow complex
3. Antidromic AVRT produces wide complex tachycardia
4. Irregular wide complex tachycardia suggests atrial fibrillation with WPW
5. Avoid AV nodal blockers in atrial fibrillation with WPW