Makindo Medical Notes

⚡ Torsades de Pointes (Polymorphic VT): Occurs in repetitive, non-sustained paroxysms but can degenerate into VF. 💉 First-line: IV magnesium 8 mmol (2 g) bolus over 10–15 mins in 50–100 ml 5% dextrose or saline. ❌ Avoid amiodarone. Correct K/Mg/Ca. Consider pacing, isoprenaline (except congenital LQTS), and defibrillation if unstable.

📖 About

• Coined by Dessertenne in 1966.
• A polymorphic ventricular tachycardia with the QRS axis “twisting around the baseline.”
• Commonly associated with prolonged QTc >460 ms.
• Drug-associated risk varies — see www.qtdrugs.org.

📌 Definition

• Polymorphic VT with continuously changing QRS axis.
• Seen in congenital or acquired Long QT syndrome.
• Often due to inhibition of the HERG potassium channel.

🖥️ Electrocardiogram

🧬 Genetics

• LQT1 & LQT2 → slow potassium channels.
• LQT3 → sodium channel defects.
• LQT4–12 → rarer subtypes.
• Congenital long QT: autosomal dominant, more pronounced in females.

📊 Epidemiology

• Females 2–3x more likely to develop TdP.
• Drug-induced QT prolongation more common in women.

🩺 Clinical

• Occurs in bursts, often self-terminating.
• Symptoms: presyncope, syncope, hypotension, pulmonary oedema.
• May deteriorate to sustained VT/VF → cardiac arrest.

⚠️ Risk Factors

• Congenital: Romano-Ward (AD), Jervell-Lange-Nielsen (AR + deafness).
• Acquired: electrolyte disorders (↓K, ↓Ca, ↓Mg), medications, bradycardia.
• Other: baseline ECG abnormalities, renal or liver impairment, female sex.

💊 Causes of Acquired Long QT

• Electrolyte/metabolic: hypokalaemia, hypocalcaemia, hypomagnesaemia, hypothyroidism, hypothermia.
• Drugs: amiodarone, disopyramide, flecainide, erythromycin, terfenadine, TCAs, quinidine, lithium, phenothiazines. 👉 Always check in BNF.

🔎 Investigations

• FBC, U&E, Mg, Ca, TFTs, troponin if ACS suspected.
• ECG: twisting QRS, prolonged QTc often >500 ms.
• Echocardiogram: rule out structural heart disease.

🛠️ Management

• Stop offending drugs (esp. amiodarone, class I/III antiarrhythmics).
• IV magnesium sulphate: 8 mmol (2 g) bolus → then 72 mmol (18 g) over 24 hrs.
• Pacing (atrial > ventricular) if bradycardia-dependent TdP.
• IV isoprenaline: useful for acquired TdP but contraindicated in congenital LQTS.
• Defibrillation if unstable.
• Congenital LQTS: beta-blockers mainstay; consider ICD or left stellate ganglion block for refractory cases.
• Acquired LQTS: beta-blockers contraindicated (bradycardia worsens risk).

📚 References

• AHA/ACC: Prevention of Torsades in Hospital Settings

💡 Teaching Pearl: TdP is always a “red flag rhythm.” Think: correct electrolytes, stop QT-prolonging drugs, give magnesium, pace or shock if needed.