Prolongation of myocardial repolarization, i.e. lengthening of the QTc interval on surface electrocardiogram, with increased risk of cardiac arrhythmias, has been recognized as a side effect of many drugs. Most conventional and atypical antipsychotic drugs can cause dose-related prolongation of QTc, although there are important differences in the potency of individual agents. Antipsychotic polipharmacy increases the risk for sever cardiac side effects.

In this prospective clinical investigation, we analyzed ECGs in 46 patients suffering from schizophrenic disorder who were treated with different antipsychotic drugs one week after the admission to the psychiatric hospital. Hearth rate, QT interval and QTc interval were assessed. the average daily dose of prescribed antipsychotic drugs was calculated and transformed to chlorpromazine units.

Average QTc interval in patients undergoing our clinical investigation was 417 msec, only 3 out of 46 (6,5%) patients had QTc over 450 msec and only one patient (2,2%) had QTc over 500 msec.

We found no differences in QTc interval between patients who were treated either with conventional or atypical antipsychotic or with combination of both, and no gender differences for QTc interval were found.

Our results raise the question of the clinical relevance of a single ECG for diagnostics of cardiac complications in schizophrenia patients and suggest the need to conduct ECG monitoring in patients with high risk for cardiac complications during antipsychotic treatment.