Bipolar electrogram and monophasic action potential recordings from the ventricles of Langendorff-perfused Scn3b−/− hearts demonstrated significantly shorter ventricular effective refractory periods (VERPs), larger ratios of electrogram duration obtained at the shortest and longest S1–S2 intervals, and ventricular tachycardias (VTs) induced by programmed electrical stimulation. This evidence concerns the gene SCN3B and ventricular tachycardia.