Cortez Daniel, Bos J Martijn, Ackerman Michael J
Department of Electrophysiology, Penn State Milton S. Hershey Medical Center, Hershey, Pennsylvania; Clinical Sciences, Lund University, Lund, Sweden.
Departments of Cardiovascular Diseases, Pediatrics, and Molecular Pharmacology and Experimental Therapeutics, Divisions of Heart Rhythm Services and Pediatric Cardiology, Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, Minnesota.
Heart Rhythm. 2017 Jun;14(6):894-899. doi: 10.1016/j.hrthm.2017.03.003. Epub 2017 Mar 6.
Long QT syndrome (LQTS) and genotypic subtypes are associated with distinctive T-wave patterns, arrhythmogenic triggers, and corrected QT (QTc) interval risk associations. Twenty percent of patients with LQTS have normal QTc values, defined as electrographically concealed LQTS (ecLQTS). Vectorcardiography (VCG) has value for sudden cardiac death risk assessment.
The purpose of this study was to determine the use of VCG to identify patients with ecLQTS.
We performed a retrospective analysis in patients with ecLQTS with resting QTc values <440 ms. Computerized derivation of the spatial mean and peak QRS-T angles, QTpeak, Tpeak-Tend (angle between QRS and T-wave peak amplitudes in 3-dimensional space), and T-wave eigenvalues (TwEVs; amplitudes [in microvolts] for each of the first 4 TwEVs were derived from the 12-lead electrocardiogram) was performed. The results were compared with those for healthy controls. Intergenotype differences were analyzed.
Of 610 patients with LQTS, 169 patients (28%) had ecLQTS (86 (51%) men; mean age 22 ± 16 years; mean QTc interval 422 ± 14 ms). There were 519 healthy controls (44% men; mean age 19.8 ± 13.8 years) with a mean QTc interval of 426 ± 28 ms. Among VCG parameters, QTpeak and TwEVs significantly differentiated patients with ecLQTS from controls (P ≤ .01 for each) as well as differentiated KCNQ1-encoded type 1 LQTS (ecLQT1), KCNH2-encoded type 2 LQTS (ecLQT2), and SCN5A-encoded type 3 LQTS (ecLQT3) from controls (P < .01). ecLQT3 was differentiated from controls and ecLQT1 and ecLQT2 by the fourth TwEV (P < .01 for each). The fourth TwEV differentiated symptomatic patients with ecLQTS from asymptomatic patients with ecLQTS (P < .01).
ecLQTS can be distinguished from controls using QTpeak. ecLQT3 was best differentiated by the fourth TwEV. VCG may facilitate familial diagnostic anticipation of LQTS status before the completion of mutation-specific genetic testing even with normal resting QTc values.
长QT综合征（LQTS）及其基因型亚型与独特的T波形态、致心律失常触发因素以及校正QT（QTc）间期风险关联相关。20%的LQTS患者QTc值正常，被定义为心电图隐匿性LQTS（ecLQTS）。向量心电图（VCG）对心脏性猝死风险评估具有价值。
本研究的目的是确定VCG用于识别ecLQTS患者的效用。
我们对静息QTc值<440 ms的ecLQTS患者进行了回顾性分析。通过计算机推导得出空间平均和峰值QRS-T角度、QTpeak、Tpeak-Tend（三维空间中QRS与T波峰值振幅之间的角度）以及T波特征值（TwEVs；前4个TwEVs各自的振幅[以微伏计]由12导联心电图得出）。将结果与健康对照者的结果进行比较。分析基因型间差异。
在610例LQTS患者中，169例（28%）有ecLQTS（86例（51%）为男性；平均年龄22±16岁；平均QTc间期422±14 ms）。有519例健康对照者（44%为男性；平均年龄19.8±13.8岁），平均QTc间期为426±28 ms。在VCG参数中，QTpeak和TwEVs能显著区分ecLQTS患者与对照者（每项P≤0.01），也能区分KCNQ1编码的1型LQTS（ecLQT1）、KCNH2编码的2型LQTS（ecLQT2）和SCN5A编码的3型LQTS（ecLQT3）与对照者（P<0.01）。ecLQT3通过第四个TwEV与对照者以及ecLQT1和ecLQT2相区分（每项P<0.01）。第四个TwEV能区分有症状的ecLQTS患者与无症状的ecLQTS患者（P<0.01）。
可使用QTpeak将ecLQTS与对照者区分开来。ecLQT3通过第四个TwEV能得到最佳区分。即使静息QTc值正常，VCG也可能有助于在完成特定突变基因检测之前对LQTS状态进行家族性诊断预测。
