In several case reports, proarrhythmic effects of
antipsychotic drugs have been reported. The aim of the present study was to investigate if application of
risperidone or
quetiapine has the potential to provoke polymorphic
ventricular tachycardia in a sensitive model of proarrhythmia. In 24 isolated rabbit hearts,
risperidone (5 and 10 μM, n = 12) or
quetiapine (5 and 10 μM, n = 12) was infused after obtaining baseline data. Eight endocardial and epicardial monophasic action potentials and a simultaneously recorded 12-lead ECG showed a significant QT prolongation after application of
risperidone as compared with baseline (5 μM: +29 ms, 10 μM: +35 ms, p < 0.01) accompanied by an increase of action potential duration. Administration of
risperidone also significantly increased spatial dispersion of repolarization (5 μM: +16 ms, 4 μM: +19 ms; p < 0.05) as well as temporal dispersion of repolarization. Lowering of
potassium concentration in bradycardic AV-blocked hearts provoked early afterdepolarizations (EADs) in 8 of 12 hearts and polymorphic
ventricular tachycardia resembling
torsade de pointes in 6 of 12 hearts (10 μM, 49 episodes). The results were compared with hearts treated with
quetiapine (5 and 10 μM).
Quetiapine led to an increase in QT interval (5 μM: +10 ms; 10 μM: +28 ms; p < 0.05) and a similar increase of APD90. However, treatment with
quetiapine did not result in significant alterations of spatial and temporal dispersion of repolarization. No ventricular arrhythmias were observed in this group. In the present study,
quetiapine demonstrated a safe electrophysiologic profile despite significant QT prolongation. In contrast,
risperidone led to a more marked prolongation of myocardial repolarization combined with a more marked increase of dispersion of repolarization.