美国医学超声协会胎儿超声心动图操作指南-中文

美国医学超声协会胎儿超声心动图操作指南 I 简介 先天性心脏病是导致胎儿死亡的主要原因，死亡率约为 6‰。准确的产前诊断能够改善婴儿的预后，尤其在需要前列腺素来维持动脉导管通畅的病例中更为重要。胎儿超声心动图普遍认为是产前评价胎儿心脏畸形的最详 细的检查手段。其检查手段是在“基本”和“基本扩展”胎儿成像指南基础上延伸而出的，即胎儿心脏四腔心和流出道切面。胎儿超声心动图只有在有确切的原因的 情况下，并且最大限度的减少由于采集诊断信息而暴露在超声下的时间的情况下进行。有时，额外或特殊的检查手段比如彩色多普勒是必须的。但并不是所有的畸形 都能够检出，以下指南将最大限度的探查大部分临床严重的先心病。 II人员的资质及责任 参照AIUM官方文件《医师指南、诊断超声检查评估与解释、AIUM超声实践指南》 III指征 胎儿超声心动图指征基于先心病的亲代及胎儿危险因素。然而，大多数病例并没有明确的已知的高位因素。胎儿超声心动图的普通指征是（也不局限与此）： 母体指征 自身免疫抗体，抗Ro（SSA）/抗La（SSB） 家族遗传疾病（如：马凡综合症） 先心病家族史 试管婴儿 代谢性疾病（如：糖尿病和苯丙酮尿症） 至畸源接触（如：类视黄醇和锂） 胎儿指征 心脏显像异常 心脏心率心律异常 胎儿染色体异常 心外畸形 胎儿水肿 颈项透明层增厚 单绒毛膜双胎 无法解释的羊水过多 IV检查申请 书面或电子申请超声心动图检查应提供详细的信息以更好的完成检查。 检查申请必须由临床医生或其他有资格的健康中心出具，并提供相关临床资料，并且因遵守相关法律和当地健康结构规定。 V 检查说明 以下部分为胎儿超声心动图详细或选择性推荐。 A．综述 胎 儿超声心动图通常在孕18到22周进行。有些先心病可能在更早孕周发现。最佳的图像是胎儿心尖向前或朝向孕妇腹壁。由于声影（如：孕妇肥胖或胎儿俯卧体 位）使得全面的检查十分困难，特别是在晚孕期更是如此。所以由于心脏显像欠佳多次观察是必要的。检查者可以通过调节各种参数来获得最好的图像，比如焦点、 频率、增益、图像放大、时间分辨率、谐波成像及多普勒相关参数（比如：血流速度、壁滤波、帧频）。 B．心脏图像参数： 基本：胎儿超声心动图是对心脏结构及功能的全面评价。检查包括三个节段的分析：心房、心室、大动脉及其连接。节段分析法包括以下连接及关系： 心房位置 房室连接 心室与动脉流出到的连接 每个节段的异常都需要对其他伴随异常进行评价比如：心脏位置、心房异构、主动脉骑跨、房间隔缺损、室间隔缺损、心肌肥厚、体循环或肺静脉的异常连接、卵圆孔关闭、心室比例失调、动脉缩窄及二三尖瓣发育异常。 C．灰阶图像（推荐） 关键切面的获取有助于诊断信息的获得。应该获得以下切面： 四腔心 左室流出道 右室流出道 三血管及气管切面 短轴切面（心室及流出道） 主动脉弓 导管弓 上腔静脉 下腔静脉 D 多普勒检查（心脏血流异常时推荐） 使用光谱、连续、彩色和或能量多普勒来评价下列结构的血流或心律异常： 肺静脉 卵圆孔 房室瓣 房室间隔 主、肺动脉瓣 动脉导管 主动脉弓 E．M型超声心动图（心率或心律异常时推荐） M 型超声心动图显示一个薄的取样容积内结构随时间的变化。较高的时间分辨率有助于心室收缩的评价。能够分辨房性、室性心律失常，及它们之间的关系。其他方法如：脉冲多普勒或者组织多普勒也被用来评价胎儿心律失常。 F.心脏生物学测量（在结构异常时推荐） 胎儿心脏测量的正常范围根据不同孕周或胎儿大小而不同，数据已经以百分位数和z积分的形式公布。每个个体的测量应使用M型或二维图像，包括以下参数： 主动脉及肺动脉瓣环水平内径 主动脉弓及峡部内径 舒末期心室内径，紧贴房室瓣下 心室自由壁及室间隔的厚度，紧贴房室瓣下 额外测量按需要而定，包括： 心室收缩内径 心房的横径 肺动脉分支内径 G.补充切面（可选） 其他附属成像模式，比如3或4维超声，已经应用于心脏结构异常和定量胎儿血流参数（比如心输出量）的应用。多普勒超声和斑点追踪技术被用来描述心室的应变和心肌指数的测量。 VI．报告及存档 充足的存档对高质量病例管理是必要的。胎儿超声 心动图检查和说明应该永久存储。所用的图像包括正常和异常的都应该存档。异常时应该同时附有测量数据。图形应标注病人信息、仪器信息、检查日期、以及图像 左右方向。正式报告（最终报告）应收录在病人的医疗档案中。超声的检查应有临床适应症，并且遵守相关法律及当地健康结构的规定。报告应符合AIUM超声检 查标准。 VII．仪器要求 胎儿超声心动图检查应该使用实时探头扫查。因此 应使用扇形、凸阵及经阴道探头。尽量将探头频率调至最佳，值得注意分辨率与扫查深度是相互制约的。对目前设备而言，经腹壁探查时经常使用频率为 3.5MHz或更高，而经阴道扫查时频率为5MHz或更高。超声声影及母体体型肥胖均可限制高频探头的使用，从而限制了心脏高分辨率解剖信息的获得。 VIII．质量控制及提高、安全性、感染控制、患者教育 质量控制及提高、安全性、感染控制的执行应符合AIUM超声实践标准及指南。 仪器的工作辐射监控应符合AIUM超声实践标准及指南。 IX.ALARA 原则 每次检查的益处及风险应同时评估。在控制声能输出及扫查时间时应遵守ALARA原则（低声能、短时间）。更详细内容见AIUM发布的医学超声安全。 American Institute of Ultrasound in Medicine (AIUM) and the International Society of Ultrasound in Obstetrics and Gynecology outlined recent guidelines for sonographic evaluation of the fetal heart. The International Society of Ultrasound in Obstetrics and Gynecology guidelines include the “basic”cardiac examination that relies on a 4-chamber view.There are key features of this sonographic view that will be emphasized in this article. This society also included the “extended basic” examination that includes the right and left ventricular out-flow tracts (RVOTand LVOT, respectively). It is important to include imaging that demonstrates the relationship of the LVOT and the RVOT to detect conotruncal abnormalities. 美国超声医学协会（AIUM）和国际妇产科超声协会最近针对胎儿心脏超声检查出台了一项指南。国际妇产科超声协会指南包括了基于四腔心切面的最基本的心脏检查，其中重点强调了在此超声切面上的几个关键征象，同时指南还包括了“进一步”的检查，包括对左右心室流出道（RVOT和LVOT）的检查，明确两者的关系对于发现圆锥动脉干畸形非常重要。 Depending on technical factors, such as maternal body habitus, fetal age, or fetal position, demonstrating the relationship of the RVOT and the LVOT may be problematic. Alternatives to routine 2-dimensional (2-D) imaging of out-flow tracts include the use of 3-D imaging technologies including the use of dynamic multiplanar imaging. Even with advanced imaging and the ability to reconstruct images in different planes, the examiner must be familiar with routine cardiac views or failure of detection of CHD may still occur. Thus, understanding basic cardiac views is necessary to detecting CHD even with more advanced imaging. We will concentrate on a method to best understand these basic views, such as the 4-chamber or outflow tract views, as a springboard to more advanced cardiac imaging. An alternative to these views is a comprehensive examination of the fetal heart, which may be obtained using 4 to 5 short-axis views of the heart. These 5 planes include (1) the stomach; (2) the 4-chamber view of the heart; (3) the 5-chamber view of the heart; (4) the pulmonary artery (PA) bifurcation; and (5) the alignment of the 3 vessels, which are the PA, aorta, and superior vena cava (SVC). 由于一些技术上的原因，比如母体的体质、胎龄或者胎儿体位等因素的影响，有时显示ROVT和LOVT的关系比较的困难。除了可以通过常规二维图像来显示流出道外，还可以应用三维影像技术包括使用多维动态图像技术来显示流出道。即便是具备了先进的影像技术和不同平面图像重建的技能，检查者还必须要掌握常规的心脏切面，否则仍有可能无法发现先天性心脏病。因此，即便是有了很多先进的影像技术，但如果要发现先天性心脏病仍然需要掌握基本的心脏切面。我们概括了一种最好的方法来理解这些基本的切面比如四腔心切面和流出道切面，这种方法可以作为其他先进的心脏影像技术的跳板。除了这些切面之外，我们还需要对胎儿心脏进行其他的广泛细致的检查，我们可以通过4到5个短轴切面来获取，包括胃泡、四腔心切面、五腔心切面、肺动脉分叉以及三血管排列（肺动脉、主动脉和上腔静脉）。 A useful mnemonic to help In the basic evaluation of the fetal heart is PASSSS. Each letter is meant to serve as a memory aid as follows :position, axis, size, symmetry, septum, and squeeze. If each of these cardiac features is evaluated and considered normal, the examiner can evaluate the 4-chamber view of the fetal heart PASSSS as normal (Table 1). 在胎儿心脏的基础的检查中我们可以通过PASSSS这个词来进行记忆，每个字母可作为一个检查的要点：位置、轴向、大小、对称轴、间隔和节律。如果检查者能够发现心脏的每一个征象并认为正常，那么他可以认为在胎儿四腔心切面上它是正常的。 TABLE 1. The PASSSS Mnemonic for the 4-Chamber Vessel 四腔心切面的PASSSS记忆法 Position Determine correct situs 位置 确定位置是否正常，有无反位 Axis Determine that the interventricular septum is 40 to 45 degrees 轴：确定室间隔的角度在40-45度 Size Make sure that the heart is approximately one third of the fetal thorax 大小：确定心脏的大小是胎儿胸腔的三分之一左右 Symmetry Generally, the diameters of the right and left ventricles have a 1:1 ratio 对称性：通常情况下，左右心室的直径为1:1 Septum Check the entire septum for possible ductal defects 间隔：检查整个间隔明确是否存在可能的缺损 Sinus rhythm Check cardiac rate and rhythm 窦性节律：检查心律和心率。 In evaluating the fetal heart, the fetal presentation should first be documented. Then, the examiner must determine if the fetus’ left side is up or down. Lastly, the stomach side and its relationship to the heart side should be assessed. Simply put, situs solitus is the normal relationship, with the stomach on the left and the left atrium on the left side of the fetus. Situs inversus is the exact mirror image of situs solitus, with the stomach on the left but the left atrium on the right. Situs ambiguous is an anatomically indeterminate type of visceral situs, which is part of the heterotaxy syndromes. 胎儿心脏检查时首先我们要明确胎儿的胎位，然后必须要确定胎儿的左侧是在上还是在下，最后要明确胃泡在哪边以及胃泡和心脏的位置关系。简单的说，心房正位是正常的关系，胃泡和左心房位于胎儿的左侧。心房反位是心房正位的镜像面，胃泡位于左侧但左心房位于右侧。心脏不定位是一种解剖学上的心房位置不明确的类型，它属于器官变异综合症的一部分。 After determining the situs (or position), a 4-chamber view of the heart is obtained (Table 2). This is done by identifying the fetal thoracic spine, and a scan is obtained transverse to the thorax. Anatomically, the right ventricle is posterior to the sternum, and the left ventricle is to the left of the right ventricle or at the same side as the stomach. Identifying features unique to the right ventricle include its retrosternal location, lower insertion of the tricuspid valve compared with the mitral valve, and a thicker moderator band. The flap of the foramen ovale opens from the right atrium into the left atrium. 在明确了心房的位置之后我们可以来看一下四腔心切面（2）。我们可以通过辨认胎儿胸椎然后对胸腔进行横切面扫面获得四腔心切面。从解剖学上来说，右心室位于胸骨的后方，左心室在右心室的左侧或者和胃泡同在一侧。右心室独有的征象包括与胸骨的关系、三尖瓣的附着点比二尖瓣低以及粗大的调节束。卵圆孔瓣从右心房向左心房开放。 TABLE 2. Identification of Right and Left Ventricles From the 4-Chamber View View Right Ventricle Left Ventricle Position within thorax Right ventricle retrosternal Left border, same side as the stomach Flap of foramen ovale Present within the left atrium Insertion of AV valve leaflets on interventricular sternum Tricuspid valve inserted lower than the mitral valve Mitral valve inserted higher than the tricuspid valve Muscle Thicker moderator band Veins SVC + IVC Pulmonary veins IVC indicates inferior vena cava. Modified from DeVore and Polanko. 四腔心切面上鉴别左右心室 切面 右心室 左心室 胸腔内的位置 右心室位于胸骨后方 左心室位于左边和胃泡同处一侧 卵圆瓣 ---- 出现在左房内 房室瓣在室间隔上的附着点 三尖瓣的附着点低于二尖瓣 二尖瓣的附着点高于三尖瓣 肌层 可见调节束 --- 静脉 上下腔静脉 肺静脉 Axis 心轴 Once a 4-chamber view of the heart is obtained, a line is drawn from the spine to the anterior sternum. The interventricular septum intersects that line at 40 to 45 degrees. Shipp et al 13 found a normal cardiac axis of 43 degrees, with an SD of 7 degrees (Fig.. 1). Abnormal cardiac axis can be an indicator of extracardiac intrathoracic abnormalities, displacing the heart. Examples include pulmonary cystic adenomatoid malformation, diaphragmatic hernia, or intrathoracic pulmonary sequestration. Axis deviation is also seen in intracardiac abnormalities. Examples include Ebstein anomaly and tetralogy of Fallot. 在获取了四腔心切面后我们可以从脊柱到前面的胸骨画一条线，室间隔与之成40-45°的角。Shipping等人发现正常心轴为43°，SD为7°（图1）。心轴异常可能表明存在心外的胸腔内异常挤压心脏，比如肺脏的囊性腺瘤样畸形、膈疝或者胸腔隔离肺。心轴的偏转也可以是由于心内的异常导致，比如Ebstein畸形和Fallot四联征。 FIGURE 1. Four-chamber view of the heart. The 4-chamber view of the heart in the transaxial plane shows the spine noted posteriorly. A line is drawn from the spine to the anterior sternum. The interventricular septum intersects that line at approximately 45 degrees. Note that the RA lies to the right side of the spinal sternal line. The heart can be noted to occupy approximately one third of the fetal thorax. RA indicates right atrium. 图1 四腔心切面。在心脏轴向的四腔心切面上我们可以看到脊柱位于后方，从脊柱到前方的胸骨画一条线，室间隔与此线大约呈45°。我们可以看到RA位于脊柱胸骨线的右侧，心脏大约占整个胎儿胸腔的三分之一。 Size 大小 This is to assess the size of the fetal heart in relation to the fetal thorax. The cardiac area is approximately one third of the thoracic area (Fig. 1). Simply put, approximately 3 fetal hearts can normally fit into the fetal thorax. A small heart can be attributed to extrinsic mass compressing the heart. There are many causes for fetal cardiomegaly. Intrinsic cardiac anomalies include Ebstein anomaly, cardiomyopathies, or cardiac tumors, most commonly rhabdomyomas. 胎儿心脏的大小要看和胸腔的关系，心脏的面积大约是胸腔面积的三分之一（图1）。简单的说，正常情况下一个胸腔大约能放置三个心脏。心脏过小可能是由于心外的肿块挤压心脏，而心脏增大的原因很多，心内的异常有Ebstein畸形、心肌病变或者心脏肿瘤（最常见的是横纹肌瘤）。 Symmetry 对称性 This refers to the symmetric size of the ventricles. Generally, the diameters of the right and left ventricles maintain about a 1:1 ratio (Fig. 2). With the diameter of the right ventricle slightly larger than that of the left ventricle, real-time examination can be used as a rough estimate of ventricular chamber size. Most common anomalies are the hypoplasia of either the left or right side of the heart. Hypoplastic left heart syndrome is composed of findings including underdevelopment of the aorta, the aortic valve, the left ventricle, or the mitral valve. Right ventricle hypoplasia can be attributed to 1 of 2 anomalies: pulmonary atresia or tricuspid atresia with or without an intact ventricular septum. There are multiple other etiologies of chamber discrepancy beyond the scope of this review. 对称性是指心室大小对称，通常情况下，左右心室的直径保持大约1:1的比例（图2）。当右室直径比左室略大的话，实时检查可以大体的估测心室的腔径。最常见的异常是心脏左侧或右侧的发育不良，左心发育不全综合症包括有主动脉、主动脉瓣膜、左心室或二尖瓣的发育不全。右心发育不全可能是由于1-2种异常导致：肺动脉闭锁或三尖瓣闭锁合并或不合并室间隔完整。除此之外，还有很多种其他的原因导致腔径的不对称。 FIGURE 2. Four-chamber view of the heart. Note that the diameter of the RV is approximately equal to that of the LV at the AV valve level. RV indicates right ventricle; LV, left ventricle. 四腔心切面。在房室瓣水平RV的直径与LV大约是相等的 Septum 间隔 Evaluation for a septal defect is best performed on the 4-chamber heart view that is obtained perpendicular to the interventricular septum. This allows adequate visualization of the membranous portion of this septum, which can suffer from drop-out artifact if imaging is performed parallel to the interventricular septum. There are 3 basic types of septal defects. Ventricular septal defects (VSDs) can be small or large. The smaller ones are hard to detect and can occur in perimembranous location just below the aortic valve. Color Doppler may be helpful with this diagnosis. Atrial septal defects can be quite difficult to detect because of the normal foramen ovale. The atrioventricular (AV) canal defects result from the absence of the endocardial cushion. In this situation, the normal lower insertion of the tricuspid valve compared with the mitral valve is not observed, but rather there is a “T” configuration with the residual mitral and tricuspid valve inserting at the same level but with no interventricular septum (Fig.3). Color flow imaging allows easier recognition of ventricular defects. 检查室间隔时最好选取与室间隔垂直的四腔心切面，这样能非常清楚的看到室间隔的膜部，可以避免因声束与室间隔平行时出现的衰减伪像。间隔缺损有三种基本类型。室间隔缺损大小不一，较小的缺损难以发现，可发生在主动脉瓣下的膜周部。彩色多普勒有助于明确诊断。房间隔缺损非常难以发现，因为存在正常的卵圆孔。房室通道是由于心内膜垫缺损导致的，发生这种情况时我们看不到正常情况下的三尖瓣附着点低于二尖瓣，而是残存的二尖瓣和三尖瓣附着点在同一水平呈T型结构，但不与室间隔相连接（图3）。彩色血流图像可以很容易的看到室间隔的缺损。 FIGURE 3. Valve insertion. This diagram illustrates that the tricuspid valve lies closer to the apex than does the mitral valve. In an AV canal, these valves form a ‘‘T,’’ along with lack of the interventricular septum. 瓣膜附着点。示意图显示三尖瓣距离心尖要比二尖瓣近。当出现房室通道时，瓣膜与缺损的室间隔呈T型。 Squeeze 节律 This refers to assessing the normal fetal cardiac rhythm. The normal fetal cardiac rhythm is regular, with a 1:1 atrial-ventricular relationship. The heart rate increases rapidly in early gestation until it reaches the peak rate of 175 beats/min (SD, 20 beats/min) at approximately 8 weeks. Then, the heart rate gradually decreases to 140 beats/min (SD, 20 beats/min) at 20 weeks and 130 beats/min (SD, 20 beats/min) toward term. Fetal rhythm abnormalities include (1) irregularity of the cardiac rhythm, (2) abnormally slow or fast heart rate, or (3) combination of the two. M-mode ultrasound is most commonly used to document fetal cardiac rate and rhythm. M-mode line placement becomes important to simultaneously assess the atrial and ventricular walls to record the sequence of their systolic wall motions. The M-mode beam direction is placed through the atrial and ventricular walls immediately above and below the AV junction. At this location, the M-modes of the atrium and the ventricle are displayed together, allowing assessment of atrial contraction and conduction to the ventricles. In brief, most common causes of fetal arrhythmias include premature atrial contractions and brief sinus tachycardia/bradycardia. Less common arrhythmias include complete AV block and supraventricular tachycardia. Fetal rhythm abnormalities affect at least 2% of pregnancies and are a common reason for referral to fetal cardiologists. 这里指的是检查胎儿心律是否正常。正常的胎儿心律是规整的，房室比例为1:1。妊娠的早期心率会快速增高，8周的时候可以达到175bpm（SD，20bpm），到20周的时候逐渐的降到140bpm（SD，20bpm），足妊时为135bpm（SD，20bpm）。胎儿心律异常包括（1）心律不规整，（2）异常过缓或过速，或者（3）两者都存在。M型超声对于发现胎儿心律和心率异常非常有用，要注意M取样线放置的位置保证能同时监测心房和心室壁在收缩期的室壁运动的顺序。M型超声的取样线要在紧邻房室交界处的上方和下方并同时经过心房和心室壁，这样的话心房和心室的M波形才能同时显示出来从而能观察到心房的收缩和向心室的传导。简单的说，胎儿心律失常最常见的病因包括房性期前收缩和短暂的窦性心动过速和心动过缓，少见的情况还包括房室阻滞和室上性心动过速。胎儿心律失常至少出现在2%的妊娠中，也是常见的进行胎儿心脏检查的原因。 The PASSSS mnemonic is helpful as a basic evaluation of the 4-chamber heart view. PASSSS记忆法对于四腔心切面的基本检查有帮助。 OUTFLOW VIEWS 流出道切面 To improve sensitivity of CHD, long-axis views of the outflow tracts are obtained, with the interventricular septum perpendicular to the transducer beam. The left ventricular long-axis view of the fetal heart is obtained by rotating the transducer approximately 45 degrees from the 4-chamber view to angle from the fetal abdominal left upper quadrant toward the right shoulder (Fig. 4). This view will demonstrate the aorta originating from the left ventricle. 我们还可以通过观察流出道的长轴切面来提高CHD的检出率，在这个切面上，室间隔与探头的声束方向是垂直的。在四腔心切面上将探头旋转45度使得探头从胎儿上腹部指向右肩就可以获得左室长轴切面（图4）。在此切面上可以显示起源于左心室的主动脉。 This view is also useful in the visualization of the membranous portion of the interventricular septum. Once the aortic outflow tract is identified, the transducer is “rocked” slightly. This view should demonstrate the main PA exiting the right ventricle. The main PA and the ascending aorta should be perpendicular to each other, or demonstrated to “crisscross”, to exclude conotruncal anomalies such as transposition of the great arteries. When demonstrating the longaxis views of the outflow tracts, it is necessary to confirm crisscrossing of the vessels (Fig. 4). If this proves difficult, defining the anatomic features of the vessels is important. The aorta should be traced originating from the left ventricle to the proximal arch, with demonstration of the takeoffs of the great vessels to the head and neck. Similarly, the main PA should be demonstrated to arise from the right ventricle; it must be noted to bifurcate. 通过这个切面有助于显示室间隔的膜部。当我们看到主动脉流出道时将探头轻轻一动就可以显示出与右心室相连的主肺动脉。主肺动脉和升主动脉相互垂直或者说呈“十字交叉”就可以排除动脉圆锥的异常，比如大动脉转位。当显示出流出道的长轴切面时我们需要确定血管的十字交叉情况（图4）。如果有困难，那么我们可以根据血管的解剖特性来确定。主动脉与左心室相连然后延伸为主动脉弓，其分支走向头颈部。同时，主肺动脉起源于右心室，并且一定可以看到分叉。 FIGURE 4. A-E, Outflow tracts apex perpendicular to the ultrasound beam. A, Interventricular septum perpendicular to the ultrasound beam. B, Normal 4 chambers of the heart, with the interventricular septum perpendicular to the ultrasound beam. C, After performing a 4-chamber view of the heart, the transducer is placed at an angle between the left upper quadrant of the abdomen and the right shoulder. D, By changing from the 4-chamber view of the heart to a more oblique scan plane, the aorta is noted exiting the LV, which was noted exiting to the aorta (arrow). E, The transducer is rotated as the PA is seen to exit from the RV (arrow) and cross-perpendicular to the LVOT. 图4. A-E，流出道与声束垂直。A，室间隔与声束垂直。B，正常的四腔心切面，室间隔与声束垂直。C，在四腔心切面检查之后将探头由左上腹指向右肩部。D，从四腔心切面转变到倾斜的扫描平面上可以看到左心室与主动脉相互通联（箭头）。E，旋转探头可以看到起源于右心室的肺动脉（箭头）与左室流出道呈是十字交叉。 When the apex of the heart is “up” or pointed parallel to the ultrasound beam, then it may be more difficult to identify the outflow tracts to crisscross. In this situation, the LVOT is again obtained, but often short-axis view must be obtained to identify the RVOT. In this view, the aorta lies centrally, and the right ventricle and PA "wrap around" the aorta. It is important in this view to identify that the vessel originating from the right ventricle is the PA by noting that it bifurcates (Fig. 5). 如果心尖上翘或者是与声束平行的话就更难以确定流出道是否相互交叉排列，在这种情况下可以看到左室流出道，但常常是在短轴切面上才能看到右室流出道。在此切面上，主动脉位于中央，而右心室和肺动脉“环绕”在其周围，重要的是我们可以从此切面上通过观察与右室相连的血管是否分叉来确定是否为肺动脉（图5）。 In a review of transposition of the great vessels (TGA) findings, McGahan et al described the "baby bird’s beak" sign. This occurs when the main PA arising from the left ventricle is noted to bifurcate and thus is the PA. If the crisscrossing of the main PA and aorta is not demonstrated, then this view may be useful. When the main PA originating from the left ventricle is noted to bifurcate, the left branch makes a sharp angle with the main PA and ductus arteriosus, reminiscent of a baby bird’s head with an open beak. This is a critical clue that there is TGA. McGahan等人在对大动脉转位（TGA）的回顾中提出了“小鸟嘴征”，这种情况发生时肺动脉起源于左心室并且分叉所以可以确定它是肺动脉，如果我们不能发现主肺动脉和主动脉的十字交叉，那么可以通过这个切面来观察。当我们看到主肺动脉起源于左心室并且分叉时，左肺动脉与主肺动脉和动脉导管成锐角，构成了小鸟头部和张开的鸟嘴。这种征象强烈提示为TGA。 FIGURE 5. Outflow tracts-apex up. A, Interventricular septum is parallel to the ultrasound beam. B, The 4-chamber view of the heart with the apex up. Note that the tricuspid valve is closer to the apex (arrow) compared with the mitral valve, as illustrated in Figure 3. C, This long-axis view demonstrates the retrosternal location of the RV and the AO originating from LV. This view is also helpful to detect membranous VSDs. D, With the apex of the heart again pointed toward the transducer, the transducer is angled at almost 90 degrees from the long-axis plane. In this view, the circular aorta is noted centrally. The RV gives rise to the main PA. AO indicates aorta. 图5. 流出道-心尖上翘。A，室间隔与声束平行。B，四腔心切面显示心尖上翘，我们可以看到就像图3中所看到的三尖瓣（箭头）比二尖瓣更靠近心尖。C，长轴切面显示右心室位于胸骨后方，主动脉起源于左心室。此切面还有助于发现室间隔膜部缺损。D，在心尖指向探头的情况下，探头从左室长轴面调整90°。在这个切面上，圆形的主动脉位于中央，右心室延伸为主肺动脉。 COMPREHENSIVE 5 SHORT-AXIS VIEWS 更进一步的5个短轴切面 A comprehensive examination of the fetal heart using 5 short-axis views has been advocated. These are best obtained with the interventricular septum parallel to the transducer beam. These are 5 transverse planes (Figs. 6, 7). (1) The most caudal view begins with the fetal stomach, which is needed to assess the situs. (2) The 4-chamber view of the heart is then obtained. (3) The 5-chamber