Antipsychotics and prolongation of the QTc interval: a clinical study

Introduction. In the 1990s, pre-marketing studies of new antipsychotic drugs reported prolongation of the heart rate-corrected QT interval (QTc) on the electrocardiogram (ECG) and cases of sudden cardiac death. In the past QT interval prolongation, associated with increased risk of mortality, had already been observed in association with use of other classes of drugs, but renewed attention followed the introduction of new antipsychotic drugs. Objective. The aim of this study was to evaluate ECG changes of the QT interval in patients hospitalized in an acute psychiatric ward and to evaluate a possible correlation with use of antipsychotic drugs. Methods. Over a six months period we carried out an ECG in all patients in our psychiatric ward. The ECG was recorded with the assessment of the QT interval corrected using Bazett's method (QTc). We recruited 105 patients (53 females and 52 males). A descriptive statistical evaluation and measures for qualitative phenomena between QTc and antipsychotic drug were used. Results. QTc values were divided into three classes (440<; 441 >= 500 <=; 501 !) respectively indicating: no risk, intermediate risk and high risk. Therapies were divided as follows: monotherapy, combined therapy with 2 antipsychotics and combined therapy with 3 antipsychotics. In the majority of patients (n=65,62%), the QTc value was less than 441 msec, in 34 patients (32%), the QTc value was less than 500 msec and in 6 patients (5.7% of the total observed population) the QTc value was greater than 500 msec. Conclusions. In the present study there was no direct correlation between drug usage and QTc changes, but 5.71% of the studied patients had a QTc value greater than 500 msec, which is considered a risk value. Evaluation of QTc must become a routine tool during therapy with antipsychotic drugs, even if other factors could cause increased mortality in psychiatric patients.