Background and purpose
HERG blocking drugs known for their propensity to trigger Torsades de Pointes (TdP) were reported to induce a sympatho-vagal coactivation and to enhance High Frequency heart rate (HFHR) and QT oscillations (HFQT) in telemetric data. The present work aimed to characterize the underlying mechanism(s) leading to these autonomic changes. Experimental approach: Effects of 15 torsadogenic hERG blocking drugs (astemizole, chlorpromazine, cisapride, droperidol, ibutilide, dofetilide, haloperidol, moxifloxacin, pimozide, quinidine, risperidone, sotalol, sertindole, terfenadine, and thioridazine) were assessed by telemetry in beagle dogs. Haemodynamic effects on diastolic and systolic arterial pressure were analysed from the first doses causing QTc prolongation and/or HFQT oscillations enhancement. Autonomic control changes were analysed using the high frequency autonomic modulation (HFAM) model. Key
Purpose
HERG blocking drugs known for their propensity to trigger Torsades de Pointes (TdP) were reported to induce a sympatho-vagal coactivation and to enhance High Frequency heart rate (HFHR) and QT oscillations (HFQT) in telemetric data. The present work aimed to characterize the underlying mechanism(s) leading to these autonomic changes. Experimental approach: Effects of 15 torsadogenic hERG blocking drugs (astemizole, chlorpromazine, cisapride, droperidol, ibutilide, dofetilide, haloperidol, moxifloxacin, pimozide, quinidine, risperidone, sotalol, sertindole, terfenadine, and thioridazine) were assessed by telemetry in beagle dogs. Haemodynamic effects on diastolic and systolic arterial pressure were analysed from the first doses causing QTc prolongation and/or HFQT oscillations enhancement. Autonomic control changes were analysed using the high frequency autonomic modulation (HFAM) model. Key
Results
Except for moxifloxacin and quinidine, all torsadogenic hERG blockers induced parasympathetic activation or sympatho-vagal coactivation combined with enhancement of HFQT oscillations. These autonomic effects result from reflex compensatory mechanisms in response to mild haemodynamic side effects. These haemodynamic mechanisms were characterized by transient HR acceleration during HF oscillations. A phenomenon of concealed QT prolongation was unmasked for several torsadogenic hERG blockers under β-adrenoceptor blockade with atenolol. Resulting enhancement of HFQT oscillations was shown to contribute directly to triggering dofetilide-induced ventricular arrhythmias.