Monitoring of QT interval in patients treated with psychotropic drugs

Background Psychotropic drugs have the potential for QT interval prolongation, the frequency is not known. The aim of this study was to monitor the occurrence of QT interval prolongation in a non-selected population of patients treated with psychotropic drugs with proarrhythmic potential. Methods In consecutive patients hospitalized at psychotic wards at the Department of Psychiatry treated with antipsychotic and antidepressant drugs with known or unexplored proarrhythmic potential a 12-lead ECG was recorded (50 mm/s, 20 mm/mV) on therapy; the QT interval was measured manually, corrected according to Bazett and Fridericia. QTc intervals of 470 ms (females) and 450 ms (males) were considered borderline, longer QTc intervals were considered pathologic. Results ECGs were recorded in 452 patients (187 females, 265 males, aged 43 ± 16 years). Using Bazettʹs correction, abnormal QTc values were observed only in 2% of the whole group and in 1.8% of the patients treated with drugs associated with QT prolongation (the greatest QTc value is 490 ms in female and 480 ms in male). With Fridericiaʹs correction, there was only 1 case of borderline QTc in the whole group (the greatest QTc value is 450 ms in both sex groups). Conclusions Our 2-year real-life experience shows that occurrence of QTc prolongation in present psychiatric patients is low. Values associated with high risk of arrhythmias (QTc > 500 ms) were not observed. This might be related to the recent changes of spectrum of antipsychotic therapy used, the general trend to use lower doses, and increasing awareness about the drug-induced long QT syndrome.