lable at ScienceDirect

Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182

Contents lists avai

Taiwanese Journal of Obstetrics & Gynecology

journal homepage: www.t jog-onl ine.com

Original Article

Continuous transverse scanning of the fetal heart using across-sectional image database of common fetal congenitalheart deformities

Zhen-Juan Yang, Qiu-Yan Pei*, Yun-Tao Li, Jun-Xue GaoDepartment of Obstetric Ultrasound, Peking University People's Hospital, Peking, 100044, China

a r t i c l e i n f o

Article history:Accepted 7 April 2015

Keywords:anatomical databasecongenital heart deformitycontinuously transverse scancross sectionsfetus

* Corresponding author. Department of Obstetric UPeople's Hospital, Beijing 100044, China.

E-mail address: qiuyanpeicn@163.com (Q.-Y. Pei).

http://dx.doi.org/10.1016/j.tjog.2016.02.0051028-4559/Copyright © 2016, Taiwan Association of O(http://creativecommons.org/licenses/by-nc-nd/4.0/).

a b s t r a c t

Objective: To provide an anatomical basis for continuous transverse scanning of the fetal heart byanalyzing the typical cross-sectional characteristics of different types of congenital heart deformities(CHDs) using an anatomical image database.Materials and methods: The database consisted of cross-sectional images obtained from 45 cases ofcommon fetal CHDs, which were continuously displayed by the three-dimensional software Amira 5.3.1.The following anatomical parts were observed from the database of heart samples in a bottom-to-topmanner: the coronary sinus, four chambers, left ventricular outflow tract, right ventricular outflowtract, and transverse ductal and aortic arches. The anatomical characteristics of these sections wereanalyzed and compared with the ultrasonic transverse views obtained from the same fetuses.Results: During the display of the anatomical database of 45 cases of common fetal CHDs, the afore-mentioned typical cross sections were successively revealed, along with the corresponding pathologicalfeatures. These sections also exhibited a very good correspondence with the ultrasonic transverse viewsof the same cases.Conclusion: The database of cross-sectional anatomical images of fetal CHDs provided an anatomicalbasis for continuous transverse scanning of the fetal heart.Copyright © 2016, Taiwan Association of Obstetrics & Gynecology. Published by Elsevier Taiwan LLC. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/

4.0/).

Introduction

Fetal cardiac malformations are the most common congenitalanomalies [1,2], with an incidence of 6.8% to 10.0% among livebirths [3]. The incidence of these malformations is 6.5 and 4 timeshigher than those of chromosomal anomalies and neural tube de-fects, respectively. In addition, 4% of live births are expected to beaffected by severe congenital cardiac malformations; this figureaccounts for 20% of total neonatal deaths and up to 50% of infantdeaths attributed solely to congenital anomalies [4]. The prenataldetection of congenital heart disease may improve the outcome offetuses with specific types of cardiac lesions [5e8].

Fetal echocardiography (FECG) is the only prenatal diagnosticapproach for congenital heart deformity (CHD) [9,10]. Although

ltrasound, Peking University

bstetrics & Gynecology. Published

FECG was reportedly first used in 1980 [11], prenatal ultra-sonologists prior to that time used to observe the fetal cardiacstructure using the views of adult echocardiography (AECG)[12e14], such as the long-axis left and right ventricular outflowtract (LVOT and RVOT, respectively) views. However, these viewsare technically more difficult to obtain through FECG than throughAECG because of the effect of fetal position and other circulatoryissues [15]. Consequently, FECG has not been widely applied, andprenatal detection rates still vary considerably [16].

In contrast to images seen in adults, the acoustic shadow of theribs and sternum is not obvious in images of the fetal heart ob-tained in the second trimester. The lack of gas in the lungs, how-ever, facilitates FECG.

In 2001, Yagel et al [4] introduced amethod for a comprehensivecardiac evaluation of the fetal heart through five short-axis views:upper abdomen transverse, four-chamber, LVOT, RVOT, and trachea[three vessels and trachea (3VT)] views. This method is completedthrough a continuous transverse scan along the fetal thorax. In2013, the International Society of Ultrasound in Obstetrics and

by Elsevier Taiwan LLC. This is an open access article under the CC BY-NC-ND license

Table 1Sections reflecting the pathological features of various kinds of fetal CHD.

CHD (n) CSS FCS LVOTS RVOTS TDAS TAAS

TOF (6) � � þ þ þ þTOF þ ECD (1) � þ þ þ þ þTOF þ PAA þ A-PCA (1) � þ þ þ þ þTGA (3) � � þ þ þ þTGA þ TA þ VSD (1) � þ þ þ þ þTGA þ TA þ HLHS þ MA (1) � þ þ þ þ þPTA (2) � � þ þ þ þCOA þ VSD þ HLHS (1) � þ þ þ þ þDORV (1) � þ þ þ þ þECD (3) � þ þ þ � �ECD þ TOF þ APVD (1) � þ þ þ þ �ECD þ APVD (1) � þ þ þ þ �APVD (1) � þ � � � �EA (3) þ þ � � þ �EA þ NVM (1) � þ þ þ � �EA þ VSD (1) � þ þ þ � �TA þ VSD (1) � þ þ þ � �MA þ VSD (1) � þ þ � � �HLHS (2) � þ � � � �Dextrocardia þ HLHS þ ECD (1) � þ þ þ � �HRHS (1) � þ þ þ þ �NVM þ PLSVC (1) þ þ þ þ � �HCM (1) � þ þ þ � �AM (1) � þ � � � �SA þ SV (1) � þ þ þ þ þSV þ PTA (1) � þ þ þ þ þVR þ TOF (1) � þ þ þ þ þIAA (1) � � � � þ þDA (1) � � � � þ þIVCI (1) � þ þ þ þ �PLSVC (2) þ þ þ þ � �

e ¼ normal in the section; þ ¼ visible lesions in the section; AM ¼ atrial myxoma;A-PCA ¼ aortopulmonary collateral artery; APVD ¼ anomalous pulmonary venousdrainage; CHD ¼ congenital heart deformity; COA ¼ coarctation of the aorta;CSS ¼ coronary sinus section; DA ¼ dextroaortic arch; DORV ¼ double-outlet rightventricle; EA ¼ Ebstein's anomaly; ECD ¼ endocardial cushion defect; FCS ¼ four-chamber section; HCM ¼ hypertrophic cardiomyopathy; HLHS ¼ hypoplastic leftheart syndrome; HRHS ¼ dextrocardia, hypoplastic right heart syndrome;IAA ¼ interruption of aortic arch; IVCI ¼ inferior vena cava interruption;LVOTS ¼ left ventricular outflow tract section; MA ¼ mitral atresia; n ¼ Number ofCHD; NVM ¼ noncompaction of ventricular myocardium; PAA ¼ pulmonary arteryatresia; PLSVC ¼ persistent left superior vena cava; PTA ¼ persistent truncus arte-riosus; RVOTS ¼ right ventricular outflow tract section; SA ¼ single atrium;SV ¼ single ventricle; TA ¼ tricuspid atresia; TAAS ¼ transverse aortic arch section;TDAS ¼ transverse ductal arch section; TGAs ¼ transposition of the great arteries;TOF ¼ tetralogy of Fallot; VR ¼ vascular ring; VSD ¼ ventricular septal defect.

Z.-J. Yang et al. / Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182 177

Gynecology [17] further highlighted the transverse sweep tech-nique, which has become popular and increasingly accepted inrecent years [18e23].

Understanding the cross-sectional anatomical views of differenttypes of CHDs is important when using the transverse sweeptechnique. This study represents the first attempt to establish across-sectional anatomical image database of various types ofcommon CHDs, which provides an anatomical foundation for thecontinuous transverse scan of a fetal heart.

Materials and methods

Specimen

A total of 45 fetal CHD samples were collected in this study from2006 to 2013. The samples were obtained from CHD cases diag-nosed in our prenatal diagnosis center following maternal induc-tion of labor, either due to poor prognosis or combined with otherserious malformations. The five ultrasonic short-axis views wereobtained during FECG from all 45 cases. This study was conductedin accordance with the declaration of Helsinki and with approvalfrom the Ethics Committee of Peking University People's Hospital(IRB no. 2012-30). Written informed consent was obtained from allparticipants.

Construction of fetal CHD database

The CHD fetal samples were fixed in a solution containing 4%formaldehyde for 4 weeks. The thymus, lungs, heart, trachea,esophagus, diaphragm, part of the descending aorta, and tissuesfrom the inferior vena cava and cervix were separated andremoved from the fetal samples and were continuously fixed inthe same solution for 2 to 4 weeks. The heart sample wasremoved with a 0.2- to 0.5-cm-thick border of lung tissue on thesides to maintain the maximum size that fits the freezingmicrotome. The bottom of the heart sample consisted of a crosssection of the chest along the apical edge. The top of the heartsample consisted of a transverse section of the cervix along thelower edge of the thyroid gland. Two to four logo bars wereimplanted and the heart samples were cut transversely into a 60-mm-thick layer from bottom to top. Each section was micro-photographed with a digital camera (Canon EOS 5D Mark II;camera lens, EF180 mm f/3.5 L Macro, Japan).

The original database of the anatomical, ultra-thin cross-sectional images of different CHDs was constructed. The CHDsincluded the tetralogy of Fallot, complete endocardial cushiondefect, pulmonary artery atresia, transposition of the great arteries,persistent truncus arteriosus, Ebstein's anomaly, hypoplastic leftheart, pulmonary stenosis, atrial myxoma, anomalous pulmonaryvenous drainage, noncompaction of the ventricular myocardium,rhabdomyoma of the heart, and kollonema.

Each database contained 500 to 700 cross-sectional images witha resolution of 3744 pixels � 5616 pixels. The images were origi-nally saved in JPEG format. Each image had two to four identifica-tion points produced by the logo bar, which was used for thereconstruction.

Analysis of anatomical characteristics

Using the identification points in each image as reference points,Photoshop or MATLAB software was used to register each image,which eliminated the shift and rotation caused by photography. TheJPEG format was converted into PNG format, and the database ofdifferent kinds of fetal CHD was imported into Amira 5.3.1, a three-dimensional (3D) software, and displayed continuously. The

anatomical characteristics of the typical cross sections wereanalyzed during the continuous display and compared with the fiveultrasonic short-axis views, which were obtained during the FECGof the same fetuses.

Results

General information

The 45 cases included in the cross-sectional database of fetalCHD not only clearly represented the atrioventricular cavity andgreat vessels, but also distinctly showed the cardiac valves, chordaetendineae, papillary muscle (musculus papillaris), coronary sinus,and coronary artery and its branches.

During the continuous display of the typical cross sections fromthe anatomical database, the following were observed from thebottom to the top of the heart samples: coronary sinus section (CSS),four-chamber section (FCS), left ventricular outflow tract section(LVOTS), right ventricular outflow tract section (RVOTS), transverseductal arch section (TDAS), and transverse aortic arch section (TAAS).These sections reflected the pathological features of various kinds of

Z.-J. Yang et al. / Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182178

fetal CHD and exhibited a very good correspondence with the ul-trasonic transverse views. However, the ultrasonic transverse viewsdid not always show the CSS, and the cross-sectional database didnot show the upper abdomen transverse view. Table 1 shows the 45CHD cases and their relevant sections.

For example, in the tetralogy of Fallot, the LVOTS showed signsof aortic enlargement and the aorta over-riding the ventricularseptum, whereas the RVOTS showed pulmonary stenosis. BothTDAS and TAAS exhibited ductal arch stenosis and a broadenedand longer aortic arch, respectively. These findings are consistentwith the ultrasonic transverse sections (Figure 1). The FCS

Figure 1. (A) Parts of typical cross-sectional images of tetralogy of Fallot (TOF), in which situis normal, but the left ventricular outflow tract section (LVOTS) shows aortic enlargement(TDAS) shows ductal arch stenosis. The transverse aortic arch section (TAAS) shows broadentract section (RVOTS), (d) LVOTS, (e) FCS, and (f) coronary sinus section. (B) Ultrasonic tranTDAS, (c) RVOTS, (d) LVOTS, (e) FCS, and (f) upper abdomen transverse views. AA ¼ aorticDAO ¼ descending aorta; ESO ¼ esophagus; IVC ¼ inferior vena cava; LA ¼ left atrium; LVRA ¼ right atrium; RV ¼ right ventricle; St ¼ stomach; TRA ¼ trachea.

revealed all the anatomical characteristics of the different typesof atrioventricular structural anomalies. The complete endocar-dial cushion defects presented atrioventricular septal disconti-nuity and a group of atrioventricular valves. Ebstein's anomalyresulted in a tricuspid valve septal leaflet depression (Figure 2).Other common atrioventricular structure anomalies are alsoshown in Figure 2. In some cases of atrioventricular structureanomalies, such as the Ebstein anomaly and hypoplastic leftheart, the LVOTS, RVOTS, TDAS, and TAAS exhibited abnormalitiescaused by secondary lesions. In the dextroaortic arch, TAASshowed that the aortic arch moved to the right and that the

s solitus and the right ventricular loop are shown. The four-chamber section (FCS) viewand the aorta over-riding the ventricular septum. The transverse ductal arch sectioning and lengthening of the aortic arch. (a) TAAS, (b) TDAS, (c) right ventricular outflowsverse views corresponding to the typical cross-sectional images of TOF: (a) TAAS, (b)arch; AAO ¼ ascending aorta; AO ¼ aorta; CS ¼ coronary sinus; DA ¼ arterial duct;

¼ left ventricle; LVOT ¼ outflow tract of left ventricle; MPA ¼ main pulmonary artery;

Z.-J. Yang et al. / Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182 179

trachea and esophagus were located between the ductal andaortic arches (Figure 3). When the venous drainage wasabnormal, the pathological features were also reflected in theaforementioned multisections. One of these cases was an infra-cardiac type of total anomalous pulmonary venous drainage,combined with inferior vena cava interruption, endocardialcushion defect (ECD), and venous catheter absence. The FCS,LVOTS, RVOTS, and TDAS all showed an abnormal azygous veinlocated behind the descending aorta and then drawn into thesuperior vena cava in the TAAS. The common vein cavity, whichcollects all four pulmonary vein blood flows, was located behindthe four-cavity heart and goes downward into the portal systemof the abdominal cavity (Figure 4).

Discussion

The application of the 3D software on the 45 cases of the cross-sectional image database of common fetal CHD successivelyrevealed CSS, FCS, LVOTS, RVOTS, TDAS, and TAAS. These sectionsalso revealed the pathological features of different fetal CHDs.

Figure 2. The four-chamber sectional view of different atrioventricular structural anomalieand the right ventricular is dysplastic. (B) Hypoplastic right heart: the diameter of the right vdysplasia, and right atrial enlargement. (C) Complete endocardial cushion defects: atriovcompaction of the ventricular myocardium: many papilla criss-cross myocardial trabeculaetrabecular interval of different sizes connecting with the ventricular cavity. LA ¼ left atrium

We propose using the five short-axis views, that is, the upperabdomen transverse, four-chamber, LVOT, RVOT, and 3VT viewswhile examining the fetal heart [17]. Given the effect of the freezingmicrotome cutting volume, the database does not include the up-per abdomen transverse view. However, similar to the four-chamber view, the upper abdomen transverse view is one of thesections that can easily be obtained provided that the transversescanning along the stomach is horizontal. The changes in thenumber and position of vascular malformation in these views oftenprovide clues to diseases, such as atrial reverse, inferior vena cavainterruption, or anomalous pulmonary venous drainage. The upperabdomen transverse view, as one of continuous transverse views,therefore has an important clinical value and is convenient in theprenatal diagnosis of fetal CHD.

The 3VT viewdid not appear during the transverse display of thedatabase in this study. Instead, the TDAS and TAAS views weredisplayed after the RVOT view. This result is mainly due to thedissimilar levels of the aortic and ductal arches. However, duringthe continuous horizontal scan of the fetal heart in the TDAS level,the probe was slightly inclined toward the head. The obtained 3VT

s. (A) Tricuspid atresia: the tricuspid valve (TV) is atretic, the left ventricle is enlarged,entricle is significantly narrowed; also seen are ventricular wall hypertrophy, tricuspidentricular septal discontinuity and only a group of atrioventricular valves. (D) Non-, multiple and excessive papillose myocardial trabeculae, intervening fossae, countless; LV ¼ left ventricle; RA ¼ right atrium; RV ¼ right ventricle.

Z.-J. Yang et al. / Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182180

view showed that the TDAS and TAAS views are synchronous. The3VT view is more likely to display large vascular malformationsthan the TDAS and TAAS views. The 3VT view can therefore be usedin lieu of the TDAS and TAAS views as the observation section of thecontinuous transverse scan of the fetal heart.

The CSS was not included in the proposed five sections, but itconstantly appeared during the continuous display of the database.The CSS is normally very difficult to reveal because of the narrowfetal coronary sinus. However, when the venous return is abnormal,such as in the intracardiac type of pulmonary vein abnormalities,the coronary sinus, which is connected to the persistent left su-perior vena cava, abnormally expands and is therefore easilyrevealed during ultrasound examination. In this study, three casesof persistent left superior vena cava and one case of the intracardiactype of total anomalous pulmonary venous drainage were found,

Figure 3. (A) Parts of typical cross-sectional images of the dextroaortic arch. (B) Ultrasonicarch to the right side with the trachea and esophagus lying between the ductal arch and thebranches, (c) section of AA and LBT, (d) section of AAO and LBT, (e) section of DA, and (f) sESO ¼ esophagus; LBT ¼ left brachiocephalic trunk; LCCA ¼ left common carotid artery; LSCAartery; RPA ¼ right pulmonary artery; RSCA ¼ right subclavian artery; SVC ¼ superior ven

and all these conditions caused coronary sinus expansion. The CSSis normally unobservable during the continuous horizontal scan ofthe fetal heart. Malformation becomes a possibility when the cor-onary sinus distinctly expands.

The database established in this research not only provided ananatomical basis for the continuous horizontal scanning of thefetal heart, but also can be used to recognize the pathoanatomicalcharacteristics of multiple types of fetal CHD during the displayof the anatomical database of the 45 cases of common fetal CHDby Amira 5.3.1. Ultrasonologists can simply use continuoustransverse scanning method for fetal cardiac screening to detectmany types of fetal CHD, thereby improving the prenatal diag-nosis rate.

During the construction of the database, the fetal samples werefixed with formaldehyde, and the heart specimens were cut such

transverse views corresponding to the images in (A) show the movement of the aorticaortic arch: (a) section of the head and neck artery branch, (b) section of the AA and LBTection of three vessels. AA ¼ aortic arch; AAO ¼ ascending aorta; DA ¼ arterial duct;¼ left subclavian artery; MPA ¼main pulmonary artery; RCCA ¼ right common carotid

a cava; TRA ¼ trachea.

Figure 4. (A, aed) Parts of typical cross-sectional images of infracardiac type of total anomalous pulmonary venous drainage in combination with inferior vena cava interruption,ECD, and absence of venous catheter. The common vein cavity collects blood flow from the four pulmonary veins, and is located behind the heart. (eeh) Ultrasonic transverse viewscorresponding to the typical cross-sectional images of this case. (B) An ultrasonic view showing the common vein cavity going downward into the portal system of the abdominalcavity. CV ¼ common vein cavity; DAO ¼ descending aorta; HV ¼ hepatic vein; LHV ¼ left hepatic vein; LLPV ¼ left low pulmonary vein; LUPV ¼ left upper pulmonary vein;MHV ¼ medial hepatic vein; PS ¼ portal system; RA ¼ right atrium; RHV ¼ right hepatic vein; RLPV ¼ right low pulmonary vein; RUPV ¼ right upper pulmonary vein; RV ¼ rightventricle; St ¼ stomach.

Z.-J. Yang et al. / Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182 181

that part of the thoracic cavity was retained to maintain the naturalstate of the heart as much as possible. Meanwhile, the databasewith the 60-mm-thick layer is the thinnest part of the heart sectiondatabase that clearly displays the valve, chordae tendineae, andother tiny structures. However, this study has its limitations. Theheart as a specimen is different from a live beating heart. Forexample, changes occur in the atrioventricular cavity and vasculardiameter due to the difference in the elasticity of thewall and bloodloss during the preparation of the specimens. Thus, the physio-logical state of the heart anatomy cannot be fully replicated. Thesedifferences should always be considered when using the con-structed database.

In summary, this study established a database of cross-sectionalimages of various types of common fetal CHDs. A typical crosssection revealed the anatomical characteristics of different CHDsand provided an anatomical basis for the continuous horizontalscanning of the fetal heart.

Conflicts of interest

The authors have no conflicts of interest relevant to this article.

Acknowledgments

This work was supported by funds from The Capital Project ofFund Development (2011-4022-07) and Peking University People'sHospital Research and Development (RDC2012-01). The authors ofthis article have made enough contributions including collectingthe specimens, acquiring primary digital images, reviewing themanuscript, and its approval.

References

[1] Zhang Y, Riehle-Colarusso T, Correa A, Li S, Feng X, Gindler J, et al. Observedprevalence of congenital heart defects from a surveillance study in China.J Ultrasound Med 2011;30:989e95.

[2] Yu Z, Xi Y, Ding W, Han S, Cao L, Zhu C, et al. Congenital heart disease in aChinese hospital: pre- and postnatal detection, incidence, clinical character-istics and outcomes. Pediatr Int 2011;53:1059e65.

[3] Yang XY, Li XF, Lü XD, Liu YL. Incidence of congenital heart disease in Beijing,China. Chin Med J (Engl) 2009;122:1128e32.

[4] Yagel S, Cohen SM, Achiron R. Examination of the fetal heart by five short-axisviews: a proposed screening method for comprehensive cardiac evaluation.Ultrasound Obstet Gynecol 2001;17:367e9.

Z.-J. Yang et al. / Taiwanese Journal of Obstetrics & Gynecology 55 (2016) 176e182182

[5] Tworetzky W, McElhinney DB, Reddy VM, Brook MM, Hanley FL,Silverman NH. Improved surgical outcome after fetal diagnosis of hypoplasticleft heart syndrome. Circulation 2001;103:1269e73.

[6] Andrews R, Tulloh R, Sharland G, Simpson J, Rollings S, Baker E, et al. Outcomeof staged reconstructive surgery for hypoplastic left heart syndrome followingantenatal diagnosis. Arch Dis Child 2001;85:474e7.

[7] Franklin O, Burch M, Manning N, Sleeman K, Gould S, Archer N. Prenataldiagnosis of coarctation of the aorta improves survival and reduces morbidity.Heart 2002;87:67e9.

[8] Tworetzky W, Wilkins-Haug L, Jennings RW, van der Velde ME, Marshall AC,Marx GR, et al. Balloon dilation of severe aortic stenosis in the fetus: potentialfor prevention of hypoplastic left heart syndrome: candidate selection, tech-nique, and results of successful intervention. Circulation 2004;110:2125e31.

[9] Rajiah P, Mak C, Dubinksy TJ, Dighe M. Ultrasound of fetal cardiac anomalies.Am J Roentgenol 2011;197:W747e60.

[10] Votino C, Jani J, Damry N, Dessy H, Kang X, Cos T, et al. Magnetic resonanceimaging in the normal fetal heart and in congenital heart disease. UltrasoundObstet Gynecol 2012;39:322e9.

[11] Allan L. Fetal cardiac scanning today. Prenat Diagn 2010;30:639e43.[12] Ogg�e G, Gaglioti P, Maccanti S, Faggiano F, Todros T. Prenatal screening for

congenital heart disease with four-chamber and outflow-tract views: amulticenter study. Ultrasound Obstet Gynecol 2006;28:779e84.

[13] Lee W, Riggs T, Amula V, Tsimis M, Cutler N, Bronsteen R, et al. Fetal echo-cardiography: z-score reference ranges for a large patient population. Ultra-sound Obstet Gynecol 2010;35:28e34.

[14] International Society of Ultrasound in Obstetrics & Gynecology. Cardiacscreening examination of the fetus: guidelines for performing the ‘basic’ and‘extended basic’ cardiac scan. Ultrasound Obstet Gynecol 2006;27:107e13.

[15] Pei Q, Liang M, Huang X, Wei Y. Construction of a three-dimensionalanatomical database of the human fetal heart. Pediatr Cardiol 2010;31:234e7.

[16] Simpson LL. Screening for congenital heart disease. Obstet Gynecol Clin NorthAm 2004;31:51e9.

[17] International Society of Ultrasound in Obstetrics and Gynecology, Carvalho JS,Allan LD, Chaoui R, Copel JA, DeVore GR, et al. ISUOG practice guidelines(updated): sonographic screening examination of the fetal heart. UltrasoundObstet Gynecol 2013;41:348e59.

[18] Lee W, Allan L, Carvalho JS, Chaoui R, Copel J, Devore G, et al. ISUOG consensusstatement: what constitutes a fetal echocardiogram? Ultrasound ObstetGynecol 2008;32:239e42.

[19] Yagel S, Arbel R, Anteby EY, Raveh D, Achiron R. The three vessels and tracheaview (3VT) in fetal cardiac scanning. Ultrasound Obstet Gynecol 2002;20:340e5.

[20] Vi~nals F, Heredia F, Giuliano A. The role of the three vessels and trachea view(3VT) in the diagnosis of congenital heart defects. Ultrasound Obstet Gynecol2003;22:358e67.

[21] Carvalho JS, Ho SY, Shinebourne EA. Sequential segmental analysis in complexfetal cardiac abnormalities: a logical approach to diagnosis. Ultrasound ObstetGynecol 2005;26:105e11.

[22] Tongsong T, Tongprasert F, Srisupundit K, Luewan S. The complete three-vessel view in prenatal detection of congenital heart defects. Prenat Diagn2010;30:23e9.

[23] Zalel Y, Wiener Y, Gamzu R, Herman A, Schiff E, Achiron R. The three-vesseland tracheal view of the fetal heart: an in utero sonographic evaluation.Prenat Diagn 2004;24:174e8.