DAY 25: Pre-excitation Syndromes – WPW Syndrome 🩺

Welcome back! Today, we’re diving into a fascinating group of conditions called pre-excitation syndromes, focusing specifically on Wolff-Parkinson-White (WPW) syndrome. This lesson will equip you with the knowledge to recognize WPW on an ECG and understand its underlying mechanisms. Let’s get started! 🚀

Learning Objectives 🎯

• 💡 Define pre-excitation and explain the mechanism behind WPW syndrome.
• 📝 Identify the key ECG features of WPW syndrome: short PR interval, delta wave, and widened QRS complex.
• 🩺 Understand the clinical significance of WPW syndrome and its potential complications.
• 🔍 Differentiate WPW syndrome from other conditions that may mimic its ECG features.
• 📚 Describe the common treatment strategies for WPW syndrome.

Step-by-Step Content 📝

What is Pre-excitation? Pre-excitation occurs when the ventricles are activated earlier than normal due to an accessory pathway that bypasses the AV node. In WPW syndrome, this accessory pathway is called the Bundle of Kent. ⚡

WPW Syndrome Explained: Normally, electrical impulses travel from the atria to the ventricles through the AV node, which slows down the conduction to allow the atria to contract and fill the ventricles before ventricular contraction. However, the Bundle of Kent allows impulses to bypass the AV node and directly excite the ventricles. This causes the ventricles to partially depolarize early, before the normal impulse arrives. 💫

Key ECG Features of WPW Syndrome:

• Short PR Interval: Due to the impulse bypassing the AV node, the PR interval is shorter than 0.12 seconds (less than 3 small squares). ⏱️
• Delta Wave: This is a slurred upstroke of the QRS complex, representing the early ventricular activation via the accessory pathway. It’s the most distinctive feature! 🌊
• Widened QRS Complex: The QRS complex is wider than 0.12 seconds (more than 3 small squares) because the ventricles are being activated by two separate pathways. 📈
• Secondary ST-T wave changes: Often seen as repolarization abnormalities opposite the delta wave polarity.

Example ECG Interpretation: Imagine an ECG with a PR interval of 0.10 seconds, a slurred upstroke to the QRS complex (delta wave), and a QRS duration of 0.14 seconds. This is classic WPW! 🥳

Clinical Significance: WPW syndrome can cause palpitations, dizziness, syncope, and, in rare cases, sudden cardiac death. The risk comes from the potential for rapid conduction of atrial fibrillation down the accessory pathway, leading to ventricular fibrillation. 🚨

Treatment: Treatment options include medications to slow conduction in the AV node or accessory pathway, and catheter ablation to eliminate the accessory pathway. 🔥

Quiz Time ❓

1. What is the most characteristic ECG finding in WPW syndrome?
   A. Prolonged PR interval
   B. Delta wave (Correct)
   C. Narrow QRS complex
   D. Peaked T waves
2. Which accessory pathway is responsible for WPW syndrome?
   A. Bundle of His
   B. Bundle of Kent (Correct)
   C. AV node
   D. SA node
3. What is a possible complication of WPW syndrome?
   A. Hypertension
   B. Ventricular fibrillation (Correct)
   C. Bradycardia
   D. Atrial flutter
4. A patient with WPW has a PR interval of 0.15 seconds. Is this typical for WPW?
   A. Yes
   B. No (Correct)
   C. Only if the QRS is prolonged.
   D. Only if the T wave is inverted.
5. The QRS complex in WPW syndrome is usually:
   A. Narrow
   B. Prolonged (Correct)
   C. Absent
   D. Normal

Summary: Today, we learned about WPW syndrome and its hallmark ECG features: short PR interval, delta wave, and widened QRS complex. We also discussed its clinical significance and treatment options. ✅

Review and Practice: Review the ECG criteria for WPW syndrome. Practice identifying WPW on sample ECG strips. Look for examples online or in your textbook. 📚

Next Day Preview: Tomorrow, we will explore other pre-excitation syndromes and delve into the differential diagnosis of wide QRS complexes. Stay tuned! ➡️