Torsades de pointes and congenital long QT syndrome

Neumar, 2010Thomas, 2015

Torsades de pointes (‘twisting of the points’) is a type of polymorphic ventricular tachycardia in which the QRS axis on the electrocardiogram (ECG) constantly shifts; it occurs most often in patients with a prolonged QT interval (usually more than 0.5 seconds). Torsades de pointes is frequently self-limiting; however, it can be life threatening if it progresses to sustained ventricular tachycardia or ventricular fibrillation (cardiac arrest). QT-interval prolongation may be present from birth (ie congenital long QT syndrome) or acquired (usually secondary to drugs or bradycardia).

To determine whether a drug is likely to prolong the QT interval, refer to Drugs highly associated with QT-interval prolongation and torsades de pointes and, for more detail, the CredibleMeds website (registration required).

For information on QT-interval prolongation due to drug poisoning, see Treatment for QT-interval prolongation and torsades de pointes.

Initial treatment of congenital long QT syndrome involves immediately stopping any drug suspected of causing QT-interval prolongation, and correcting electrolyte abnormalities. Urgently check serum magnesium and potassium concentrations; for dose recommendations to correct serum imbalances see Treatment for electrolyte abnormalities in QT-interval prolongation. If intravenous potassium chloride is required, aim to maintain a serum potassium concentration of 5 to 5.5 mmol/L.

Refer all patients with congenital long QT syndrome for specialist management. Implantable cardioverter defibrillator (ICD) therapy or left cardiac sympathetic denervation may be indicatedSchwartz, 2020.

The only beta blockers with evidence of benefit for treating congenital long QT syndrome are propranolol and nadololSchwartz, 2020. If there are no contraindications, beta-blocker therapy should be given to both symptomatic and asymptomatic patients to reduce the risk of syncope and sudden cardiac deathAl-Khatib, 2018. Suitable regimens are:

Atenolol or metoprolol are not recommended for use in congenital long QT syndrome because of a lack of efficacy Schwartz, 2020; seek specialist advice if the patient has another indication for atenolol or metoprolol (eg metoprolol succinate for heart failure).