Gu Beiyin, Liu Tingliang, Yang Lei, Zhang Haiyan, Xin Yili, Wang Jian
Department of Cardiology, Shanghai Children's Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai, China.
Medicine (Baltimore). 2020 May;99(20):e19818. doi: 10.1097/MD.0000000000019818.
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.
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). During HUTT test, QT interval was significantly prolonged (QTc = 716 ms) based on macroscopic TWA.
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.
There was no syncope or arrhythmia occurred during hospitalization and follow-up for 1 year.
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.
长QT综合征（LQTS）是一种先天性疾病，其特征是心电图（ECG）上QT间期延长，且易发生室性快速心律失常，这可能导致晕厥、心脏骤停或猝死。T波交替（TWA）是指在正常心律时体表心电图上T波形态、极性和振幅的逐搏周期性交替。在本报告中，1例KCNQ1基因突变所致长QT综合征患者在直立倾斜试验（HUTT）中出现TWA，此情况尚未见报道。
一名6岁男孩，5个月内出现两次意识丧失。该男孩的心电图显示QT间期延长（QTc = 600毫秒，QTc = QT/RR）。在HUTT试验期间，基于宏观TWA，QT间期显著延长（QTc = 716毫秒）。
患者被诊断为1. 1型长QT综合征（LQT1）；2. 血管迷走性晕厥（VVS）。干预措施：口服美托洛尔12.5毫克，每日两次。告知患儿避免长时间站立和剧烈运动。
住院期间及1年随访中未发生晕厥或心律失常。
长QT综合征患者可能存在VVS。HUTT早期交感神经张力增加可能在KCNQ1基因突变所致长QT综合征中诱发宏观TWA。
