QTc-interval abnormalities and psychotropic drug therapy in psychiatric patients

Background Sudden unexplained death in psychiatric patients may be due to d rug-induced arrhythmia, of which lengthening of the rate-corrected QT inter val (QTc) on the electrocardiogram is a predictive marker. We estimated the point prevalence of QTc lengthening in psychiatric patients and the effect s of various psychotropic drugs. Methods Electrocardiograms were obtained from 101 healthy reference individ uals and 495 psychiatric patients in various inpatient and community settin gs and were analysed with a previously validated digitiser technique. Patie nts with and without QTc lengthening, QTc dispersion, and T-wave abnormalit y were compared by logistic regression to calculate odds ratios for predict ive variables. Findings Abnormal QTc was defined from the healthy reference group as more than 456 ms and was present in 8% (40 of 495) of patients. Age over 65 year s (odds ratio 3.0 [95% CI 1.1-8.3]), use of tricyclic antidepressants (4.4 [1.6-12.1]), thioridazine (5.4 [2.0-13.7]), and droperidol (6.7 [1.8-24.8]) were robust predictors of QTc lengthening, as was antipsychotic dose (high dose 5.3 [1.2-24.4]; very high dose 8.2 [1.5-43.6]). Abnormal QT dispersio n or T-wave abnormalities were not significantly associated with antipsycho tic treatment, but were associated with lithium therapy. Interpretation Antipsychotic drugs cause QTc lengthening in a dose-related manner. Risks are substantially higher for thioridazine and droperidol. The se drugs may therefore confer an increased risk of drug-induced arrhythmia.