Effect of pacing and mexiletine on dispersion of repolarisation and arrhythmias in DeltaKPQ SCN5A (long QT3) mice.

Objective: It has been suggested that both pacing and treatment with mexiletine may reduce torsade de pointes (TdP) arrhythmias in patients with long QT syndrome 3 (LQT3), but it is not fully understood how these interventions could prevent TdP. We therefore studied the effects of pacing and mexiletine in mice with a heterozygous knock-in DeltaKPQ SCN5A(Delta/+) deletion (SCN5A-Tg), a murine LQT3 model.

Methods: Three right and left ventricular monophasic action potentials (MAPs) were simultaneously recorded in Langendorff-perfused hearts of SCN5A-Tg and wild type (WT) littermates.