ISUOG 实用指南（更新版）：胎儿心脏超声筛查指南解读

二、胎儿心脏筛查
    依据最新的文献报告，目前胎儿心脏超声筛查应包括四腔观和左右心室流出道观[29-37]。
（一）心脏四腔观
    1. 心脏位置：胎儿心脏四腔观涉及特殊标准的详细评估，而非几个简单心腔的计数。图1~6 显示四腔观筛查的主要基础。评估心脏的位置，须鉴别胎儿左右两侧，首先确定胎儿左右，确定胃泡和心脏都在胎儿左侧，正常心脏面积不超过胸腔面积的1/3。一些观可能显示胎儿心脏周边小的低回声，会被误诊为心包积液，但这种单独存在的表现通常是正常变异[38-39]。
心脏主要位于左侧胸腔，心脏长轴指向左侧并成角，平均为（45±20）° [40]（图1~4）。即使在四腔观显示不满意时[41]，也应观察心脏长轴和位置。当胎儿心脏和（或）胃泡不在胎儿左侧时应怀疑心脏位置异常。心轴异常（尤其左右心室流出道异常）时心脏畸形的风险增加。心轴异常还与染色体异常相关。心脏由正常左前位异常移位可能因膈疝或占位性病变所致，如肺囊腺瘤。心脏位置异常也可继发于胎儿肺发育不良或发育不全。心轴移动提示可能存在胎儿腹裂和脐膨出。
    2. 胎心率：正常胎心率在120~160 次/min。孕中期正常胎儿可能存在轻微短暂的心动过缓。持续心动过缓，尤其心率持续低于110 次/min[42] 可能存在心脏传导阻滞，需经胎儿心脏学专家进行实时评估。在孕晚期反复出现胎心率减速可能胎儿缺氧。偶发心率异常与胎儿心脏结构异常的风险无直接关系，常可自行恢复。伴发严重节律异常，需行超声心动图筛查[43-44]。增加多普勒听诊次数并有针对性扫查以排除心包积液，确定胎儿心脏观的正常。轻微的心动过速（＞ 160 次/min）可能是胎动时胎心的正常变异。而持续心动过速（≥ 180 次/min）则需要进一步评估，以除外存在胎儿缺氧或严重的快速型心律失常[45]。
    3. 四腔观结构：正常情况下两侧心房大小基本一致，卵圆孔瓣开放于左心房内。房间隔下缘为原发隔。心脏十字交叉处房间隔下段与室间隔上段连接，并有两侧房室瓣附着。通常可观察到肺静脉进入左心房，当仪器条件允许时建议至少观察到两条肺静脉进入左心房。
    调节束接近心尖部，为一条明显的肉柱横穿右心室腔，有助于鉴别形态学右心室。左心室心尖部光滑，构成心脏心尖部。正常情况下两心室大小相近，无室壁增厚表现。孕晚期可能出现左右心室腔轻微不对称，属于正常变异，但在孕中期发现明显左右心不对称应进一步筛查[46]。左心梗阻性病变，如主动脉缩窄，左心发育不良，是造成左右心室腔不对称的重要原因[47-48]。
    室间隔缺损诊断较困难，应仔细检查室间隔，从心尖部到十字交叉处。当声束垂直于室间隔时易于观察室间隔；当超声束平行于室壁时可能将回声失落误认为室间隔缺损。当超声图像不能提供足够的侧向分辨率，尤其当胎儿大小和位置不利于筛查时，小的室间隔缺损（1~2 mm）诊断非常困难。这些小缺损临床意义不大，常可在宫内自然闭合[49-50]。二尖瓣及三尖瓣分别自如开启、关闭。三尖瓣隔叶在室间隔的附着点较二尖瓣更靠近心尖部。房室瓣排列异常是心脏异常的重要超声表现，如房室间隔缺损。
（二）左右心室流出道观
    左右心室流出道观是胎儿心脏超声筛查的必要部分。主动脉和肺动脉这两条血管的筛查非常重要，包括血管与心室的连接关系、大小和位置关系及动脉瓣的开放程度。如不能确定，推荐行进一步评估。要求至少应观察到流出道从相应的心室发出，血管的大小径线相似，起始部互相交叉。
    还可以在左右心室流出道观上增加三血管观和三血管气管观。与单纯四腔观相比，增加左右心室流出道筛查可提高严重心脏畸形的诊断率[31，33，51-52]。左右心室流出道观有利于圆锥动脉畸形的诊断，如法洛四联征、大动脉转位、右心室双出口和共干畸形[34-37，53-58]。
    1. 超声筛查技术：从胎儿腹部（标准的腹围切面）横向向头侧进行移动扫查，从心脏四腔观到纵隔，连续评估各个不同的观：左心室流出道观，右心室流出道观，三血管观，三血管气管观（图7~12）[59]。在理想的条件下筛查，左右心室流出道观较容易获得。但由于机器等条件的影响，并不是每一个受筛查者在常规筛查过程中都能获得这些观。
    从心脏四腔观开始，将探头向胎儿头侧滑动（或转动角度）就能获得左心室流出道观和右心室流出道观（图13，14），获得主动脉和主肺动脉在起始处的交叉观，还可显示肺动脉分叉处。另外，描述评估胎儿流出道另一种方法是旋转技术[32]：从心脏四腔观开始，将探头向胎儿的右肩旋转。当声束与室间隔垂直时更容易进行此项筛查，但需要一些技巧。左心室流出道观，在扫查过程中可显示完整的升主动脉。
    应用胎儿心脏超声筛查技术获得左心室流出道观后，将探头向头侧倾斜，直至超声束几乎垂直于主动脉时可以观察到肺动脉。将探头从右心室流出道观继续向头侧滑动或倾斜，可获得主动脉和肺动脉的其他观。这些观与三血管观和三血管气管观是一致的，其中显示了两个动脉与上腔静脉和气管的关系，这一观中既可显示主动脉弓，又可显示动脉导管弓[53-56]。
    2. 左心室流出道观：左心室流出道观可以确定主动脉起源于形态左心室（图15~18）观察室间隔和主动脉前壁之间的连续性，主动脉瓣启闭自如，无增厚。追踪主动脉弓处向颈部方向发出3 条动脉。

三、彩色多普勒
    虽然彩色多普勒血流在指南中不是必须筛查的项目，但在胎儿心脏筛查中推荐用于常规筛查[60]，彩色多普勒可用于心脏结构成像及显示异常血流类型。彩色多普勒血流技术有助于肥胖孕妇的胎儿心脏结构的评估[61]，并能提高低危孕妇中胎儿严重先天性心脏畸形的检出率[37，62]。

四、胎儿超声心动图
    当胎儿心脏筛查时不能获得正常心脏四腔观和左右心室流出道观，或有先天性心脏病风险增高的指标而疑有先天性心脏畸形时，应行胎儿超声心动图筛查。这些筛查步骤的具体细节此前曾发布过[18]。在无任何风险因素和心外畸形的胎儿中，产前诊断出的先天性心脏病并不少见，产前胎儿心脏筛查非常重要[58]。然而，医疗保健医师应掌握胎儿超声心动图筛查的指征[63]。如在妊娠11~14 周时胎儿颈项透明层厚度大于3.5 mm，即使后来的测量值在正常范围内[64-67]，也提示应行详细的心脏筛查。
    胎儿超声心动图筛查应由熟悉先天性心脏畸形的产前诊断专家完成。除基本筛查信息外，还应包括心脏结构和功能的详细分析，进一步描述内脏心房位置、体静脉、肺静脉的连接、卵圆孔、房室连接、心室大动脉连接、大血管的关系和主动脉弓、动脉导管弓的矢状观[68-70]。
其他传统的超声技术也可用于胎儿心脏筛查中，包括多普勒超声测量血流速度，鉴别通过瓣膜和心室的异常流量类型。M 型超声心动图是分析心脏节律、心功能和心肌壁厚度的一种重要方法。新技术，如组织多普勒与容积超声（三维- 时间空间关联成像技术），用于对胎儿心脏解剖结构和功能进行更详细的评估。三维- 时间空间关联成像技术有助于对复杂心脏畸形胎儿诊断评估，包括圆锥动脉干畸形、主动脉弓畸形和异常肺静脉反流。其他超声模式，如斑点追踪目前主要用于研究方面，可能成为评估胎儿心脏功能的一个重要临床方法。总之，在胎儿心脏超声筛查常规中增加左右心室流出道观，必要时增加三血管观和三血管气管观，能弥补单纯胎儿心脏超声四腔观筛查的不足，可明显提高胎儿先天性心脏病产前超声检出率。
（本文图1~26 见光盘）

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[ 译自：International Society of Ultrasound in Obstetrics and Gynecology, Carvalho JS, Allan LD, et al. ISUOG Practice Guidelines (updated): sonographic screening examination of the fetal heart[J]. Ultrasound Obstet Gynecol, 2013, 41(3): 348-359.]