Torsades de Pointes: Causes and Risk Factors

Introduction

Torsades de Pointes (TdP) is a specific type of polymorphic ventricular tachycardia (VT) that can lead to sudden cardiac arrest if not treated promptly. It is typically associated with a prolonged QT interval on the electrocardiogram (ECG). Understanding the causes of TdP is essential for its prevention and management.

Causes of Torsades de Pointes

TdP is most often triggered by conditions leading to QT interval prolongation. These causes can be categorized as congenital or acquired.

1. Congenital Causes (Genetic Long QT Syndromes)

Some people are born with mutations in genes regulating cardiac ion channels, predisposing them to a prolonged QT interval: - Long QT Syndrome (LQTS) Types 1-3 (Mutations in KCNQ1, KCNH2, and SCN5A genes) - Jervell and Lange-Nielsen Syndrome (Associated with congenital deafness) - Romano-Ward Syndrome (No associated deafness)

2. Acquired Causes

The most common form of QT prolongation is acquired due to external factors. The main triggers include:

#### a. Medications
Many drugs can prolong the QT interval, increasing the risk of TdP. These include: - Antiarrhythmic drugs (e.g., amiodarone, sotalol, quinidine, procainamide) - Antidepressants (e.g., tricyclic antidepressants, SSRIs such as citalopram) - Antipsychotics (e.g., haloperidol, ziprasidone) - Antibiotics (e.g., macrolides like erythromycin, fluoroquinolones) - Antiemetics (e.g., ondansetron)

#### b. Electrolyte Imbalances
Low levels of key electrolytes can predispose to TdP: - Hypokalemia (Low potassium) - Hypomagnesemia (Low magnesium) - Hypocalcemia (Low calcium)

#### c. Cardiac Conditions
- Bradyarrhythmias (e.g., sinus bradycardia, AV block) - Heart failure and cardiomyopathies - Myocardial ischemia or infarction

#### d. Other Factors
- Hypothermia (low body temperature) - Severe starvation or malnutrition - Endocrine disorders (e.g., hypothyroidism) - Drug overdose or toxicity (e.g., certain antidepressants)

Conclusion

Torsades de Pointes is a potentially life-threatening arrhythmia primarily caused by QT prolongation, which can be congenital or acquired. Prevention involves careful monitoring of medications, maintaining electrolyte balance, and managing underlying cardiac conditions. If left untreated, TdP can degenerate into ventricular fibrillation, leading to sudden cardiac death.

References

For further reading, refer to the following clinical guidelines:

Source recommendations

1. American Heart Association (AHA) Guidelines on Ventricular Arrhythmias and Sudden Cardiac Death

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
2. https://pubmed.ncbi.nlm.nih.gov/29097320/
3. https://www.sciencedirect.com/science/article/pii/S2405500X22010945
4. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000548
5. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/ventricular-fibrillation

2. European Society of Cardiology (ESC) Guidelines for the Diagnosis and Management of Ventricular Arrhythmias

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Ventricular-Arrhythmias-and-the-Prevention-of-Sudden-Cardiac-Death
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000549
3. https://www.escardio.org/static-file/Escardio/Guidelines/Documents/ehaa612.pdf
4. https://pubmed.ncbi.nlm.nih.gov/26320108/
5. https://www.jacc.org/doi/10.1016/j.jacep.2022.12.008