Most drug-induced torsade de pointes is preventable, and the steps are the same whatever the drug. The risk rises when a QT-prolonging agent meets a vulnerable patient, so both halves are worth checking before prescribing.
Correct potassium and magnesium before and during treatment, since low levels amplify the effect. Review the whole medication list for other QT-prolonging drugs and for agents that raise the culprit's levels, and avoid stacking them. Take extra care with bradycardia, older age, female sex, structural or ischaemic heart disease, and significant renal or hepatic impairment.
Where an at-risk patient needs a QT-prolonging drug, a baseline and follow-up electrocardiogram is reasonable; a QTc above about 500 milliseconds, or a rise of more than 60 milliseconds, should prompt a rethink.
- Check and correct potassium and magnesium before and during a QT-prolonging drug.
- Review the medication list for other QT-prolonging agents and avoid combining them.
- Weigh bradycardia, older age, female sex and structural heart disease as added risk.
- Take a baseline and follow-up ECG in at-risk patients.
- Reconsider the drug if QTc exceeds about 500 ms or rises by more than 60 ms.
Why it matters
The dangerous arrhythmia is largely preventable by fixing electrolytes and avoiding drug combinations.
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