🫀 Torsades de Pointes (TdP)

High-Yield Medical Review

FreeMedsite

Definition	Polymorphic ventricular tachycardia characterized by shifting sinusoidal waveforms on ECG. The name translates to "twisting of the points" around the isoelectric baseline.
Prerequisite	⚠️ Prolonged QT Interval (Congenital or Acquired) Ventricular Action Potential & Mechanism Action Potential Phases Phase 0: Na⁺ Influx (Depolarization) Phase 1: Initial Repolarization Phase 2: Ca²⁺ In / K⁺ Out (Plateau) Phase 3: K⁺ Efflux (Repolarization) Phase 4: Resting Potential The TdP Trigger Delayed Phase 3 Repolarization leads to Early Afterdepolarizations (EADs)—extra depolarizations triggered before full repolarization is complete. 🔹 Pathophysiology (Step-by-Step) Prolonged repolarization → QT interval lengthens. Phase 3 delay → EADs (extra beats). EADs trigger polymorphic VT → "Twisting" QRS. Risk ↑ with bradycardia, drugs, or ↓ electrolytes. Progression → Ventricular Fibrillation (VF) → Sudden Death. 👁️ Visual Tip: Long QT → EADs → TdP → VF
Causes	1. Electrolyte Abnormalities: Hypokalemia (↓K⁺) Hypomagnesemia (↓Mg²⁺) Hypocalcemia (↓Ca²⁺) 2. Drug-Induced (ABCDEF Mnemonic): Antiarrhythmics (Class IA, III) Broad-spectrum (Macrolides, Quinolones) Chlorpromazine (Antipsychotics) Depressants (TCAs) Emetics (Ondansetron) Fungals (Azoles)
Management	Acute Management IV Magnesium Sulfate (Suppress EADs) Correct Electrolytes (K⁺, Mg²⁺, Ca²⁺) Withdraw QT-prolonging drugs Refractory / Unstable Isoproterenol (Shortens QT via ↑HR) Temporary Pacing Defibrillation if VF occurs

🎯 Student Recall Points

• 💎 Pathognomonic: Polymorphic VT with twisting QRS around the baseline in a patient with a long QT.
• 💎 Congenital: Romano-Ward (AD, No deafness) vs. Jervell-Lange-Nielsen (AR, sensorineural deafness).
• 💎 Key Fact: TdP is fundamentally a "disease of repolarization."