With aging, Scn5a+/− mice with a severe phenotype had an increased propensity to develop spontaneous ventricular arrhythmias under anesthesia (5/10) in comparison to Scn5a+/− mice with a mild phenotype (0/8; p<0.05) and WT mice (0/12; p<0.05). The gene discussed is SCN5A; the disease is Ventricular arrhythmia.