Drug-induced long QT syndrome and fatal arrhythmias in the intensive care unit

Abstract

Long QT syndrome (LQTS) is a genetic or acquired condition characterised by a prolonged QT interval on the surface electrocardiogram (ECG) and is associated with a high risk of sudden cardiac death because of polymorph ventricular tachyarrhythmia called Torsade de Pointes arrhythmia. Drug-induced LQTS can occur as a side effect of commonly used cardiac and non-cardiac drugs in predisposed patients, often with baseline QT prolongation lengthened by medication and/or electrolyte disturbances. Hospitalised patients often have several risk factors for proarrhythmic response, such as advanced age and structural heart disease. Patients in the intensive care unit (ICU) are particularly prone to develop drug induced LQTS because they receive several different intravenous medications. Additionally, they might have impaired drug elimination because of reduced kidney and/or liver function, and also drug-drug-interactions. The clinical symptoms and signs of LQTS range from asymptomatic patients to sudden death because of malignant arrhythmias, and it is therefore important to recognise the clinical characteristics and typical ECG changes. Treatment of acquired LQTS is mainly awareness, identification and discontinuation of QT prolonging drugs, in addition to eventually supplement of magnesium and potassium. Overdrive cardiac pacing is highly effective in preventing recurrences, and antiarrhythmic drugs should be avoided. Recent data suggest that QT prolongation is quite common in ICU patients and adversely affects patient mortality. Thus, high-risk patients should be sufficiently monitored, and the use of medications known to cause drug-induced LQTS might have to be restricted.