Unique ECG presentations and clinical management of a symptomatic LQT2 female carrying a novel de novo KCNH2 mutation

A 26-year-old woman, 12 days in postpartum, developed recurrent syncope and cardiac arrest. Her ECG revealed QT-prolongation associated with LQT2-specific T-U wave patterns, T wave alternans, long QT-dependent torsade de pointes (TdP) and ventricular fibrillation (VF). She also had intermittent LBBB (80 bpm) on alternate beats and RBBB at sinus tachycardia (113 bpm). Family genotyping revealed a novel de novo missense mutation G604C of KCNH2. Propranolol slowed heart rate and further prolonged QT interval (610 ms) that caused TdP recurrence. Mexiletine combined with magnesium and potassium supplements prevented TdP/VF recurrence. This patient has remained event-free after 9-month follow-up.