Life-threatening cardiac arrhythmias due to drug-induced QT prolongation : A retrospective study over 6 years from a medical intensive care unit.

Abstract

Long QT syndrome (LQTS) can lead to ventricular arrhythmia, especially torsade de pointes (TdP) tachycardia and/or ventricular tachycardia (VT). The aim of this study is to characterize patients with life-threatening cardiac arrhythmias associated with drug-induced LQTS and to identify risk factors of distinct presenting arrhythmias. In this retrospective study, we present 33 consecutive cases of life-threatening cardiac arrhythmias associated with drug-induced long QT, which were direct admitted as emergency to a medical intensive care unit (MICU) during an observational time of 6 years. Of 33 identified cases, 55 % presented with TdP with the need of resuscitation and 45 % showed nonsustained VT, respectively. In the total cohort the mean corrected QT interval (QTc) was 532 ± 29ms, with 530 ± 31ms (n = 14) in men and 533 ± 28ms (n = 19) in women (p = 0.80), respectively. Cardiac drugs with QTc interval prolonging effect were reported in 24 % of cases, and the other 76 % involved noncardiac medications. Although hypokalemia is the most common risk factor for drug-induced malignant arrhythmias, a QTc interval of at least 500ms seems to be the major determinant of the risk of drug-induced proarrhythmias. Interestingly, patients with TdP exhibit more bradycardia as such with VT. This is the first study of patients with drug-induced life-threatening cardiac arrhythmias who were admitted as a case of emergency to a MICU. Physicians should be aware of drug-induced LQTS and be able to identify patients at risk and avoid specific drugs in such patients.