Predictive factors for QTc prolongation in schizophrenic patients taking antipsychotics

Background and Purpose: The rate-corrected electrocardiographic QT (QTc) interval may significantly increase in schizophrenic patients taking antipsychotics. QTc prolongation is a risk factor for development of arrhythmia. The objective of this study was to assess the predictors of QTc prolongation in schizophrenic patients taking antipsychotic medication. Methods: Electrocardiograms were obtained from 138 controls and 412 schizophrenic inpatients taking antipsychotics. QTc prolongation was defined as a mean value of 2 standard deviations above the controls. Predictors were analyzed with a logistic regression model. Results: Based on data obtained from controls, QTc prolongation was defined as a QTc greater than 421 ms. Logistic regression analysis showed that significant predictors for QTc prolongation were: female gender (odds ration, 3.355 [95% CI, 1.767-6.371]); increased age (1.040 [1.01-1.069]); and increased doses of some antipsychotics, including clozapine (1.006 [1.003-1.008]), chlorpromazine (1.003 [1.002-1.005]), thioridazine (1.007 [1.003-1.011]), and sulpiride (1.001 [1.001-1.002]). Conclusions: Predictors of the QTc prolongation in schizophrenic patients taking antipsychotic medications were female gender, old age, and treatment with clozapine, chlorpromazine, thiroridazine, or sulpiride.