The SK4 channel blockers protected the CASQ2‐D307H KI and CASQ2 KO mice from harmful polymorphic ventricular tachycardia without being pro‐arrhythmic by themselves, since neither sinus arrest nor second‐order AV block was recorded in the animals, including WT mice. This evidence concerns the gene CASQ2 and polymorphic ventricular tachycardia.