PITX2 and cardiac arrhythmia: After administration of flecainide, for the control and four Pitx2-deficient LA cases, CV and the differences between RA and LA remained (Fig 4E and S5E Fig), while prolongation of WL occurred in both the LA and RA (Fig 4F and S5F Fig), thereby reducing the incidence of arrhythmias induced by Pitx2 deficiency.