The aim of our study was to assess the impact of psychiatric medications and concomitant risk factors on the prevalence of QTc prolongation and torsades de pointes (TdP) in hospitalized subjects. We examined the association between individual risk scores and QTc prolongation and proposed an evidence-based protocol for electrocardiogram monitoring on psychotropic medications.
Electrocardiograms (ECGs) of subjects hospitalized over a 1-year period were analyzed for QTc prolongation, associated risk factors, and use of medications. Analysis was performed using logistic regression to identify independent predictors of QTc prolongation, and the Pearson χ2 test was used for risk score assessment.
A total of 1249 ECGs of 517 subjects were included in this study. Eighty-seven subjects had QTcB intervals greater than 470 milliseconds for females and greater than 450 milliseconds for males. Twelve (2.3%) subjects had QTcB of 500 milliseconds or greater, or greater than 60 milliseconds of change from baseline. Of these subjects, only 1 case of QTc interval change was related to routine use of psychiatric medications. There were no incidents of TdP. Age, diabetes, hypokalemia, overdose, diphenhydramine, and haloperidol were significant independent predictors of QTc prolongation. Risk scores were significantly correlated with QTc prolongation (P = 0.001).
Our retrospective review study found that the occurrence of TdP and QTc prolongation was low in this subject population. QT abnormalities were associated with known risk factors, and risk scores correlated well with QTc prolongation. Providers can use the protocol proposed in this study, which incorporates risk scores and the CredibleMeds classification system to determine the need for ECG monitoring and to guide treatment.