Previous studies on hiPSC-CMs from LQT1 asymptomatic mutation carriers have reported that β-adrenergic stimulation evoked arrhythmia at the single-cell level [25], whereas single hiPSC-CMs generated from LQT2 asymptomatic mutation carriers did not evoke arrhythmia [47]. The gene discussed is KCNH2; the disease is cardiac arrhythmia.