Department of Cardiology and Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute for Surgical Research, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Department of Cardiology and Center for Cardiological Innovation, Oslo University Hospital, Rikshospitalet, Oslo, Norway; Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
JACC Cardiovasc Imaging. 2015 May;8(5):501-510. doi: 10.1016/j.jcmg.2014.12.023. Epub 2015 Apr 15.
This study aimed to explore systolic and diastolic function and to investigate genotype-specific differences in subjects with long QT syndrome (LQTS).
LQTS is an arrhythmogenic cardiac ion channelopathy that traditionally has been considered a purely electrical disease. The most commonly affected ion channels are the slow potassium channel, IKs (KCNQ1 gene/LQT1), and the rapid potassium channel, IKr (KCNH2 gene/LQT2). Recent reports have indicated mechanical abnormalities in patients with LQTS.
We included 192 subjects with genotyped LQTS (139 LQT1, 53 LQT2). Healthy persons of similar age and sex as patients served as controls (n = 60). Using echocardiography, we assessed systolic function by left ventricular (LV) ejection fraction (EF), global longitudinal strain (GLS), and contraction duration (16 LV segments). Mechanical dispersion was calculated as standard deviation of contraction duration. Time difference between contraction duration and QT interval from electrocardiography (ECG) was defined as electromechanical time difference. We assessed diastolic function by transmitral filling velocities, early diastolic myocardial velocity (e'), and left atrial volume index (LAVI). Heart rate corrected QT interval (QTc) was assessed from 12-lead ECG.
Systolic function by GLS was reduced in subjects with LQTS compared with healthy controls (-22.1 ± 2.1% vs. -23.0 ± 2.0%, p = 0.01), and GLS was worse in subjects with LQT2 compared with subjects with LQT1 (p = 0.01). Subjects with LQTS had longer contraction duration (426 ± 41 ms vs. 391 ± 36 ms, p < 0.001) and more dispersed contractions (33 ± 14 ms vs. 21 ± 7 ms, p < 0.001) compared with healthy controls. Diastolic function was also reduced in subjects with LQTS compared with healthy controls; e' was lower (10.7 ± 2.7 cm/s vs. 12.5 ± 2.0 cm/s, p < 0.001), and LAVI was increased (30 ± 8 ml/m(2) vs. 26 ± 5 ml/m(2), p = 0.01), also when adjusted for age and other possible confounders.
Subjects with LQTS had a consistent reduction in both systolic and diastolic function compared with healthy controls. Differences in myocardial function between subjects with LQT1 and subjects with LQT2 may indicate that mechanical alterations in LQTS are genotype specific.
本研究旨在探讨长 QT 综合征（LQTS）患者的收缩和舒张功能，并研究基因型特异性差异。
LQTS 是一种心律失常性心脏离子通道病，传统上被认为是一种纯粹的电疾病。最常受影响的离子通道是缓慢钾通道，IKs（KCNQ1 基因/LQT1）和快速钾通道，IKr（KCNH2 基因/LQT2）。最近的报告表明，LQTS 患者存在机械异常。
我们纳入了 192 名基因分型的 LQTS 患者（139 名 LQT1，53 名 LQT2）。年龄和性别与患者相似的健康人作为对照（n=60）。使用超声心动图，我们通过左心室（LV）射血分数（EF）、整体纵向应变（GLS）和收缩持续时间（16 个 LV 节段）评估收缩功能。机械离散度计算为收缩持续时间的标准差。心电图（ECG）从收缩持续时间和 QT 间期定义为电机械时间差。我们通过二尖瓣充盈速度、舒张早期心肌速度（e'）和左心房容积指数（LAVI）评估舒张功能。从 12 导联心电图评估心率校正 QT 间期（QTc）。
与健康对照组相比，LQTS 患者的 GLS 收缩功能降低（-22.1±2.1% vs.-23.0±2.0%，p=0.01），LQT2 患者的 GLS 比 LQT1 患者更差（p=0.01）。与健康对照组相比，LQTS 患者的收缩持续时间更长（426±41 ms vs.391±36 ms，p<0.001），收缩更离散（33±14 ms vs.21±7 ms，p<0.001）。与健康对照组相比，LQTS 患者的舒张功能也降低；e'更低（10.7±2.7 cm/s vs.12.5±2.0 cm/s，p<0.001），左心房容积指数（LAVI）更高（30±8 ml/m² vs.26±5 ml/m²，p=0.01），即使在调整年龄和其他可能的混杂因素后也是如此。
与健康对照组相比，LQTS 患者的收缩和舒张功能均有一致降低。LQT1 患者和 LQT2 患者之间心肌功能的差异可能表明 LQTS 的机械改变具有基因型特异性。
