Head-up tilt test induces T-wave alternans in long QT syndrome with KCNQ1 gene mutation: Case report CARE-compliant article

INTRODUCTION: Long QT syndrome (LQTS) is a congenital disorder characterized by a prolongation of the QT interval on electrocardiograms (ECGs) and a propensity to ventricular tachyarrhythmias, which may lead to syncope, cardiac arrest, or sudden death. T-wave alternans (TWA) refers to the periodic beat-to-beat alternation of T-wave shape, polarity and amplitude on surface ECG during regular heart rhythm. In this report, a case of long QT syndrome with KCNQ1 gene mutation induced TWA in the head-up tilt test (HUTT), which has not been reported yet. PATIENT CONCERNS: A 6-year-old boy presented with loss of consciousness twice, 5 months in duration. The boy's ECG showed prolonged QT interval (QTc = 600 ms, QTc = QT/RR(1/2)). During HUTT test, QT interval was significantly prolonged (QTc = 716 ms) based on macroscopic TWA. DIAGNOSIS: The patient was diagnosed with 1. Long QT syndrome type 1(LQT1); 2. Vasovagal syncope (VVS) INTERVENTIONS: Metoprolol 12.5 mg was given orally twice a day. The child was told avoid standing for a long time and strenuous exercises. OUTCOMES: There was no syncope or arrhythmia occurred during hospitalization and follow-up for 1 year. CONCLUSIONS: VVS may exist in patients with long QT syndrome. Increased sympathetic tone during the early stage of HUTT may induce macroscopic TWA in long QT syndrome with KCNQ1 gene mutation.