Intraperitoneal injection (20 mg/kg) of SK4 channel blockers, TRAM‐34 or clotrimazole, elicited bradycardia and noticeably reduced the ECG arrhythmic features recorded in vivo from CASQ2‐D307H KI and CASQ2 knockout (KO) mice at rest and following treadmill exercise. The gene discussed is CASQ2; the disease is Bradycardia.