Makindo Medical Notes

🧠 Pathophysiology & Mechanisms

• Normally ➝ AV node delays conduction ⏱.
• In WPW ➝ accessory pathway conducts in both directions ➝ reentry circuits 🔄.
• 🚨 AF with WPW: rapid conduction down accessory pathway can cause VF (life-threatening).

🫀 Associations

• ASD (septum secundum)
• Ebstein anomaly
• HCM
• MVP

👨‍⚕️ Clinical Presentation

• May be asymptomatic despite classic ECG findings 📈.
• Symptoms: 💓 palpitations, 😵 syncope, dizziness.
• 🚨 Rarely → sudden cardiac death (rapid AF → VF).

📈 ECG Findings

• Resting ECG:
  • 🙈 Concealed pathway: Normal ECG, no delta wave.
  • 👀 Manifest pathway: Short PR + slurred delta wave.
• Arrhythmias:
  • 🔄 AVRT (SVT): usually narrow complex.
  • ⚡ AF with pre-excitation: irregular wide rhythm + delta waves → risk of VF.

📊 ECG Examples - WPW

📊 ECG Example - AVNRT

🔬 Investigations

• 🧪 Bloods: FBC, U&E, TFTs, CRP
• 📈 ECG: look for pre-excitation, delta waves
• 🫀 Echo/MRI: check structural heart disease
• ⚡ EP studies: localise accessory pathway, plan ablation

🚨 Atrial Fibrillation in WPW

🏥 Acute Management Scenarios

• Regular Narrow Complex Tachycardia (AVRT SVT):
  • 🧘 Vagal manoeuvres first.
  • 💉 Adenosine if stable. 🚨 If unstable → DC cardioversion.
• Pre-excited AF:
  • 📈 Irregular wide rhythm, delta waves, HR >200 bpm.
  • 🚨 If unstable → immediate DC shock.
  • 💊 Options: IV Procainamide, Ibutilide, Propafenone, Flecainide.
  • ❌ Avoid AV nodal blockers (Digoxin, BB, CCB, Adenosine).

🔧 Definitive Management

• 🎯 Radiofrequency catheter ablation → first-line in recurrent SVT/pre-excited AF.
• ✅ Success rate ~95%, reduces symptoms & SCD risk.
• ⚠️ Rare complication (1%): AV block → pacemaker required.

🩺 Case 1 — Symptomatic Tachycardia

A 24-year-old man presents with sudden-onset palpitations and light-headedness after exercise. Pulse is 180 bpm, BP 120/80 mmHg. ECG during the episode shows a narrow-complex tachycardia, and a previous ECG demonstrated a short PR interval and delta wave consistent with WPW. Management: 💊 Stable SVT in WPW is managed with procainamide or flecainide; radiofrequency ablation offers a curative option. Avoid: ❌ AV nodal blockers (adenosine, verapamil, beta-blockers, digoxin) as they can worsen conduction down the accessory pathway.

🩺 Case 2 — Pre-excited AF

A 32-year-old woman presents with palpitations and chest tightness. ECG shows atrial fibrillation with irregular broad-complex tachycardia and varying QRS morphology — consistent with AF in WPW. She is haemodynamically stable. Management: ⚡ Procainamide or ibutilide are preferred; cardioversion if unstable. Electrophysiology referral for ablation. Avoid: ❌ Never use AV nodal blockers (adenosine, verapamil, beta-blockers, digoxin) in pre-excited AF — can trigger VF.

🩺 Case 3 — Incidental Finding

A 19-year-old student attends for a routine health check before joining the army. He is asymptomatic, but ECG shows a short PR interval and delta wave. Management: 🩺 No acute treatment needed; counsel regarding risk of arrhythmias. Refer to cardiology/electrophysiology for risk stratification (exercise testing, EP study). Ablation may be considered in high-risk occupations or competitive athletes. Avoid: ❌ Ignoring the finding in high-risk settings (e.g. pilots, military, professional athletes). Avoid AV nodal blockers if arrhythmia occurs.