Fig. 1.

(A) Pedigree of Case 1. Arrow indicates the proband; squares indicate male family members; circles indicate female members; black filled indicate family members diagnosed with LQTS; (B) KCNQ1 c.749T > C were identified through WES and validated with Sanger sequencing; (C) The ECG of the proband in Case 1 before the β-blocker therapy showed the prolonged QTc interval(577ms); (D) The ECG of the proband showed significantly shortened QTc interval after propranolol therapy; (E) Treadmill exam of the proband’s father showed prolonged QTc up to 550ms at 3 min of the recovery phase