孕11⁺⁰至13⁺⁶周时的二尖瓣间距：21三体综合征的标志物还是假象？

Maiz N, Dagklis T, Huggon I, Allan L, Nicolaides K H

Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, UK.

Ultrasound Obstet Gynecol. 2007 Nov;30(6):813-8. doi: 10.1002/uog.5170.

OBJECTIVES

To investigate the possible association between a particular pulsed Doppler waveform pattern, mitral gap, and trisomy 21 at 11 + 0 to 13 + 6 weeks.

METHODS

We performed two studies. The first was a retrospective analysis of pulsed Doppler velocity waveforms of the mitral valve inflow, recorded during specialist fetal echocardiography in 291 chromosomally normal and 144 trisomy 21 fetuses with a nuchal translucency (NT) thickness of 3.5 mm or more. We examined each waveform in each trace to determine whether there was a gap between the E-wave (early diastolic filling) and A-wave (atrial contraction) in the waveform across the mitral valve. We also examined each trace that contained at least one waveform with a mitral gap and, first, noted the order of waveforms with a mitral gap relative to those without and, second, measured the A-wave peak velocity in a representative waveform with a mitral gap and in one without. The second study was a prospective investigation in which Doppler velocity waveforms of the mitral valve inflow were assessed in 227 singleton pregnancies immediately before chorionic villus sampling.

RESULTS

A mitral gap was observed in 16 (5.5%) of the chromosomally normal and in 25 (17.4%) of the trisomy 21 fetuses. The incidence of mitral gap was significantly associated with the presence of cardiac defects but not with thickness of NT. The median number of waveforms per recorded image was 6 (range, 3-7) and in 32 (78%) of the 41 traces with a mitral gap only one or two of the waveforms was abnormal. The abnormal waveforms were in the middle or at the end of the trace in 95% of cases and had a lower mean A-wave peak velocity than did the normal waveforms (mean difference 3.7 cm/s; 95% CI, 0.3-7.0 cm/s; P = 0.03). In a prospective study of 10 normal fetuses we could produce a mitral gap deliberately by moving the sample volume out of the center of flow in the atrioventricular valve. In the prospective study of 227 pregnancies undergoing chorionic villus sampling a mitral gap was observed in 26/197 (13.2%) in which the fetal karyotype was subsequently found to be normal, 4/20 (20%) with trisomy 21 and 1/10 with other chromosomal defects.

CONCLUSIONS

At 11 + 0 to 13 + 6 weeks, a mitral gap may be more common in fetuses with trisomy 21 than in fetuses with a normal karyotype. However, it is possible that a mitral gap does not reflect an underlying hemodynamic abnormality, but is rather the result of suboptimal positioning of the Doppler sample volume as the fetus moves during acquisition.

目的

研究在孕11⁺⁰至13⁺⁶周时，一种特定的脉冲多普勒波形模式（二尖瓣间隙）与21三体之间可能存在的关联。

方法

我们进行了两项研究。第一项是对二尖瓣流入道脉冲多普勒速度波形的回顾性分析，这些波形记录于291例染色体正常胎儿和144例21三体胎儿的专科胎儿超声心动图检查过程中，这些胎儿的颈部透明带（NT）厚度为3.5毫米或更厚。我们检查每条记录中的每个波形，以确定二尖瓣波形中E波（舒张早期充盈）和A波（心房收缩）之间是否存在间隙。我们还检查了每条至少包含一个有二尖瓣间隙波形的记录，首先记录有二尖瓣间隙波形相对于无间隙波形的顺序，其次测量一个有二尖瓣间隙的代表性波形和一个无间隙波形中的A波峰值速度。第二项研究是一项前瞻性调查，在227例单胎妊娠中，于绒毛取样前即刻评估二尖瓣流入道的多普勒速度波形。

结果

在染色体正常的胎儿中，16例（5.5%）观察到二尖瓣间隙；在21三体胎儿中，25例（17.4%）观察到二尖瓣间隙。二尖瓣间隙的发生率与心脏缺陷的存在显著相关，但与NT厚度无关。每个记录图像的波形中位数为6（范围3 - 7），在41条有二尖瓣间隙的记录中，32条（78%）仅有一两个波形异常。在95%的病例中，异常波形位于记录的中间或末尾，其平均A波峰值速度低于正常波形（平均差异3.7厘米/秒；95%CI，0.3 - 7.0厘米/秒；P = 0.03）。在对10例正常胎儿的前瞻性研究中，我们通过将取样容积移出房室瓣血流中心，可刻意制造出二尖瓣间隙。在对227例接受绒毛取样的妊娠进行的前瞻性研究中，在197例胎儿核型随后被发现正常的妊娠中，26例（13.2%）观察到二尖瓣间隙；在21三体妊娠中，4例（20%）观察到二尖瓣间隙；在其他染色体缺陷妊娠中，10例中有1例观察到二尖瓣间隙。