Electrophysiologic Characterization of the Antipsychotic Drug Sertindole in a Rabbit Heart Model of Torsade de Pointes: Low Torsadogenic Potential Despite QT Prolongation

Abstract

There is growing concern that antipsychotic drugs that prolong the QT interval almost always increase the risk for patients to develop life-threatening ventricular tachyarrhythmias (VTs) of the torsade de pointes type. We therefore sought to compare the electrophysiologic effects of the psychotropic agent sertindole, which prolongs cardiac repolarization by inhibiting the rapid component of the delayed rectifier potassium current (I_Kr) but has a low torsadogenic potential to the antiarrhythmic agent dl-sotalol. In 18 Langendorff-perfused rabbit hearts, sotalol (10 μM,n = 8) and sertindole (0.5, 1.0, and 1.5 μM;n = 10) led to significant and comparable QT prolongation. In the presence of sotalol, torsade de pointes reproducibly occurred in atrioventricular node-blocked hearts after lowering the potassium concentration to 1.5 mM. High doses of sertindole (1.5 μM) only caused monomorphic VT (n= 4) and nonsustained polymorphic VT (n = 2) in the presence of QRS prolongation. Multiple simultaneous epi- and endocardial monophasic action potentials and a volume-conducted ECG demonstrated widening of the T/U wave, early afterdepolarizations, and increased dispersion of repolarization in the presence ofdl-sotalol. In contrast to sotalol, QT and monophasic action potential prolongation were cycle length-independent in the presence of sertindole. Sertindole had no significant effect on transmural or interventricular dispersion of repolarization. Early afterdepolarizations did not occur. Despite comparable QT prolongation, sertindole did not display the proarrhythmic profile typical of other blockers of I_Kr such asdl-sotalol. It is likely that a different mode of interaction between sertindole and the channel and/or additional pharmacological effects of sertindole, e.g., its ability to inhibitI_Na and/or its ability to block α₁-receptors, play a role.