Strand Sarah, Strasburger Janette F, Lutter William J, Wakai Ronald T
Department of Medical Physics, University of Wisconsin-Madison; Madison, WI.
Division of Cardiology, Department of Pediatrics, Children's Hospital of Wisconsin, Medical College of Wisconsin, Milwaukee, WI.
Heart Rhythm O2. 2020 Aug;1(3):200-205. doi: 10.1016/j.hroo.2020.05.003. Epub 2020 May 21.
Diagnosis of fetal long QT syndrome (LQTS) using fetal magnetocardiography (fMCG) is straightforward in cases of overt QTc prolongation accompanied by LQTS rhythms; however, cases of isolated QTc prolongation can be challenging.
To characterize repolarization in normal and phenotype-positive LQTS fetuses with the goal of utilizing additional parameters of repolarization to improve the accuracy of fMCG diagnosis of LQTS.
FMCG recordings were taken from 37 phenotype-positive fetuses with confirmed LQTS and 132 normal controls. The normal fetuses were grouped into those with T-and U-waves and those with only T-waves. We compared the repolarization characteristics of normal fetuses with only T-waves with those of LQTS fetuses. We also compared the repolarization characteristics of normal fetuses with T-and U-waves with those of LQTS fetuses with two-component T-waves.
Late-peaking T-waves were strongly associated (35/37= 95%) with LQTS. No normal fetuses showed both QTc prolongation (QTc> 500 ms) and a late-peaking T-wave. U-waves were seen in 11 normal fetuses (8%) and resulted in waveforms that often mimicked those of the 19 LQTS fetuses with two-component T-waves; however, in normal fetuses the polarities of the T-and U-waves were the same, whereas in LQTS fetuses with two-component T-waves the polarity of the components was usually opposite.
A late-peaking T-wave in association with QTc prolongation is a distinctive, reliable indicator of fetal LQTS. U-waves confound assessment of QTc; however, normal U-waves can usually be distinguished from LQTS T-waves based on polarity.
对于伴有长QT综合征（LQTS）节律且QTc明显延长的病例，使用胎儿心磁图（fMCG）诊断胎儿长QT综合征较为直接；然而，孤立性QTc延长的病例可能具有挑战性。
描述正常胎儿和表型阳性的LQTS胎儿的复极化特征，目的是利用复极化的其他参数提高fMCG诊断LQTS的准确性。
对37例确诊为LQTS的表型阳性胎儿和132例正常对照进行fMCG记录。正常胎儿分为有T波和U波的胎儿以及只有T波的胎儿。我们比较了只有T波的正常胎儿与LQTS胎儿的复极化特征。我们还比较了有T波和U波的正常胎儿与有双成分T波的LQTS胎儿的复极化特征。
晚期峰值T波与LQTS密切相关（35/37 = 95%）。没有正常胎儿同时出现QTc延长（QTc>500毫秒）和晚期峰值T波。11例正常胎儿（8%）出现U波，其波形常与19例有双成分T波的LQTS胎儿相似；然而，在正常胎儿中，T波和U波的极性相同，而在有双成分T波的LQTS胎儿中，各成分的极性通常相反。
与QTc延长相关的晚期峰值T波是胎儿LQTS的一个独特、可靠的指标。U波会干扰QTc的评估；然而，通常可以根据极性将正常U波与LQTS的T波区分开来。
