Dantrolene inhibited slow inward currents and prolonged the action potential duration in isolated sinoatrial and atrioventricular nodes [9] and reduced arrhythmias in a murine model of exercise-induced ventricular tachycardia that contain a RyR2 mutation analogous to the human catecholaminergic polymorphic ventricular tachycardia (CPVT)[10]. This evidence concerns the gene RYR2 and catecholaminergic polymorphic ventricular tachycardia.