Understanding Torsades de Pointes (TdP) on ECG

Introduction

Torsades de Pointes (TdP) is a specific type of polymorphic ventricular tachycardia associated with a prolonged QT interval. It can lead to serious complications, including sudden cardiac arrest, making early identification and management critical.

ECG Features of TdP

1. Prolonged QT interval: TdP is often preceded by a prolonged QT interval on ECG (> 450 ms in men, > 460 ms in women).
2. Polymorphic tachycardia: TdP appears as a unique ventricular tachycardia where the QRS complexes twist around the isoelectric line.
3. Irregular RR intervals: The ventricular rhythm is irregular due to varying cycle lengths.
4. Paroxysmal nature: TdP often occurs in bursts and may self-terminate or degenerate into ventricular fibrillation.

Causes of TdP

• Electrolyte imbalances: Hypokalemia, hypomagnesemia.
• Drugs: Medications that prolong the QT interval (e.g., antiarrhythmics, antipsychotics, certain antibiotics).
• Genetic conditions: Congenital Long QT Syndrome.
• Bradycardia-related TdP: Often seen in cases of heart block or severe sinus bradycardia.

Management of TdP

1. Immediate treatment:
   • Intravenous magnesium sulfate (even if magnesium levels appear normal).
   • Discontinuation of QT-prolonging drugs.
   • Correction of electrolyte imbalances.
2. In unstable patients with TdP leading to cardiac arrest:
   • Immediate defibrillation.
3. For recurrent cases:
   • Beta-blockers (in congenital Long QT Syndrome).
   • Consideration of a pacemaker or implantable cardioverter-defibrillator (ICD) in high-risk individuals.

Prevention and Risk Stratification

• Patients with a history of long QT syndrome or drug-induced TdP should avoid QT-prolonging medications.
• Routine ECG monitoring in high-risk patients.
• Genetic testing in suspected congenital cases.

Conclusion

TdP is a life-threatening ventricular arrhythmia that requires early recognition and intervention. Electrolyte correction, magnesium administration, and identifying underlying causes are key to treatment. In severe cases, defibrillation or device therapy may be required.

Source recommendations

1. American Heart Association Guidelines for Ventricular Arrhythmias

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
2. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/tachycardia--fast-heart-rate
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
4. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/ventricular-fibrillation
5. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms

2. European Society of Cardiology Guidelines on Ventricular Arrhythmias

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://academic.oup.com/eurheartj/article/43/40/3997/6675633
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
4. https://pubmed.ncbi.nlm.nih.gov/36017572/
5. https://www.sciencedirect.com/science/article/pii/S2405500X22010945