Journal of Pediatric Cardiology and Cardiac Surgery

Short QT syndrome (SQTS) is an inheritable cardiac electrical disease presenting both atrial and ventricular arrhythmias associated with abnormally short QT intervals on electrocardiograms (ECGs). SQTS is mainly associated with mutations of the genes encoding three different cardiac potassium channels. Among them, type 2 SQTS (SQT2) can be caused by gain-of-function of KCNQ1, resulting in accelerating ventricular repolarization. Several studies reported that patients with SQT2 bearing the KCNQ1 c.421G>A: p.V141M variant occasionally suffered from atrial fibrillation or bradycardia but rarely developed ventricular arrhythmias, and thus the variant has been considered as benign. However, when we observed an SQT2 family with the KCNQ1 p.V141M variant, one of the family members had developed ventricular fibrillation. The proband was referred to our hospital due to severe bradycardia (atrial standstill) and short QT intervals at the age of two and received a pacemaker implantation (PMI) using epicardial ventricular leads. The proband’s father also underwent a PMI at the age of 20 due to sick sinus syndrome. Genetic testing, performed to investigate familial bradycardia, identified a heterozygous KCNQ1 p.V141M variant in the proband and the father. Since the PMI, the father had been stable until at the age of 42 when he had a syncope due to ventricular fibrillation (VF). The VF was successfully terminated by an automated external defibrillator, and an implantable cardioverter-defibrillator was implanted. This is the first reported case of a patient with SQT2 bearing the KCNQ1 p.V141M variant showing lethal ventricular arrhythmia.