CHAPTER 11 • The Fetal Heart and Great Vessels
NTRODUCTION
Fetal cardiac examination in the first trimester focuses in general on the evaluation of
body situs, the four chambers, and the great vessels in order to confirm normal anatomy
and to rule out complex congenital heart defects (CHDs). Many CHDs can be detected
in the first trimester and are discussed in this chapter. First trimester ultrasound
evaluation of the fetal heart can also assess for the presence of indirect markers such as
tricuspid regurgitation (TR), abnormal cardiac axis, or an aberrant right subclavian
artery (ARSA), which can be clues to CHD or fetal aneuploidy. Ultrasound examination
of the fetal heart and great vessels can be a challenge in the first trimester as it requires
high-resolution images in two-dimensional (2D) gray scale and color Doppler and often
needs a combined transabdominal and transvaginal approach. In this chapter,
embryology of the fetal heart is first presented along with normal fetal cardiac anatomy
by ultrasound. Various fetal cardiac malformations that can be detected in the first
trimester are then presented. For a more comprehensive discussion on the sonographic
cardiac examination technique and a wide range of normal and abnormal fetal hearts,
we recommend our textbook “Practical Guide to Fetal Echocardiography: Normal and
Abnormal Hearts.”1
EMBRYOLOGY
The spectrum of congenital cardiac malformations is wide and is better understood with
a basic knowledge of cardiac embryology.
Starting in the third week postconception, clusters of angiogenic cardiac precursor
cells develop in the lateral splanchnic mesoderm and migrate anteriorly toward the
midline to fuse into a single heart tube. Heart tube pulsations are first recognized around
day 21 to 22 postconception (day 35 to 36 menstrual age, end fifth gestational week).
The heart develops according to well-defined major steps, namely (1) the formation of
the primitive heart tube; (2) the looping of the heart tube; and (3) the septation of atria,
ventricles, and outflow tracts (Fig. 11.1). The primitive heart tube is anchored caudallyby the vitello-umbilical veins and cranially by the dorsal aortae and pharyngeal arches,
and shows transitional folding zones such as the primary fold at the arterial pole and the
atrioventricular (AV) ring at the venous pole (Fig. 11.1). These transitional zones later
form the cardiac septa and valves. Figure 11.1 illustrates these developmental steps.1
With looping and bulging, the primitive ventricle moves downward to the right, whereas
the primitive atrium moves upward and to the left behind the ventricle. Within this tube
and at different sites, septations occur to differentiate the two atria, two ventricles, two
AV valves, and two separate outflow tracts. The paired branchial arteries with two
aortae progressively regress, resulting in a left aortic arch with its corresponding
bifurcations. On the venous side, different paired veins regress and fuse to develop the
systemic venous system with the hepatic veins and superior and inferior venae cavae.
The primitive atrium is divided into two by the formation of two septa, the septum
primum and the septum secundum. Both septa fuse except for the foramen primum,
which remains patent and becomes the foramen ovale with blood shunting from the right
to the left atrium. The formation of the ventricular septum is more complex and consists
of the fusion of septae of different spatial cardiac regions (interventricular septum, inlet
septum, and conal septum), thus explaining that ventricular septal defects (VSDs) are by
far the most common cardiac abnormalities (isolated and combined). The separation of
the outflow tracts involves a spiral rotation of nearly 180 degrees, leading to the
formation of a spiral aortopulmonary septum. This septum, resulting from the complete
fusion of both bulbus and truncus ridges, separates the outflow tract into two arterial
vessels, the aorta and pulmonary artery. Because of the spiraling of this septum, the
pulmonary artery appears to twist around the ascending aorta. The bulbar development
is responsible for incorporating the great vessels within their corresponding ventricle.
In the right ventricle, the bulbus cordis is represented by the conus arteriosus, which is
the infundibulum and in the left ventricle the bulbus cordis forms the walls of the aortic
vestibule, which is the septo-aortic and mitral-aortic continuity.1 For more details on
cardiac embryogenesis, we recommend monographs and review articles on this
subject.1–4Figure 11.1: Frontal views of the different stages of the developing heart: in A
the primitive heart tube stage, in B cardiac looping stage and in C view of the
looped heart during septation of atria, ventricles and great vessels. A: Two
transitional zones are identifiable: the atrioventricular ring (AVR) forming the
future atrioventricular valves and the primary fold (PF) forming the future
interventricular septum. B: The cardiac tube starts to loop with folding along the
long axis and rotation to the right and ventral, resulting in a D-looped heart.
Primitive cardiac chambers are better identified and are separated by
transitional zones as the sinoatrial ring (SAR), the AVR, and the PF. C: After
looping, several transitional zones can be identified separating the primitive
cardiac chambers, the AVR between the common atrium (blue) and common
ventricle (red), the PF between the primitive left (LV) and right (RV) ventricle,
and the VAR in the conotruncus (CT) region of the outflow tract of the heart.
RA, right atrium; LA, left atrium.
NORMAL SONOGRAPHIC ANATOMY AND
EXAMINATION TECHNIQUE
The steps for the examination of the fetal heart in the first trimester are no different from
the cardiac examination in the second and third trimesters. It is recommended to follow
a systematic step-by-step segmental approach to cardiac imaging. Although in the
second trimester the screening cardiac examination can be performed with gray-scale
ultrasound alone, in the first trimester, gray-scale ultrasound should be complemented
by color Doppler, especially for the evaluation of the great vessels.1 2D ultrasound
imaging with high resolution can now be achieved with transabdominal linear or
transvaginal transducers. In our experience, the transvaginal ultrasound approach is
recommended when the fetus is in transverse position low in the uterus, which providesfor the closest distance from the transvaginal transducer to the fetal chest (see Chapter
3). Furthermore, the transvaginal approach is helpful in fetuses at less than 13 weeks of
gestation or in the presence of suspected cardiac malformations.
The basic approach to fetal cardiac imaging by ultrasound is first performed in grayscale 2D ultrasound, with a focus on the fetal situs and the apical and transverse views
of the four-chamber heart (4CV) (Fig. 11.2). Ultrasound system optimization for the
gray-scale cardiac examination in the first trimester is shown in Table 11.1 . Although
the fetal abdomen and the 4CV can be reliably imaged in gray scale in the first trimester,
the anatomic orientation of the right and left ventricular outflow tracts is not commonly
seen in fetuses at less than 14 weeks of gestation because of their small size. We
therefore recommend the use of color or high-definition (power) Doppler as an adjunct
to gray-scale imaging for cardiac evaluation in the first trimester. Color Doppler in the
first trimester is therefore mostly used to indirectly evaluate the shape and size of
cardiac chambers and great vessels. The optimization of color Doppler is summarized
in Table 11.2 . Color Doppler application at the level of the four-chamber view (Fig.
11.3) is an important step for identifying normal and abnormal cardiac anatomy,
especially for fetuses at less than 14 weeks of gestation. Color Doppler demonstration
of the upper transverse views in the chest including the three-vessel-trachea (3VT) and
the transverse ductal views (Fig. 11.4) is essential for imaging of the great vessels and
is far superior to what can be achieved by gray-scale evaluation alone. Several cardiac
abnormalities involving the outflow tracts can be recognized in the first trimester in the
3VT view. The location, size, patency, and blood flow directions of the aortic and
ductal arches are more easily recognized in the first trimester on color Doppler
ultrasound (Fig. 11.4).
All ultrasound planes recommended for cardiac anatomic evaluation in the second
and third trimesters of pregnancy can be obtained in the first trimester under optimal
scanning conditions. Based upon our experience however, visualization in the first
trimester of four essential planes—(1) the axial view of the upper abdomen, (2) the
4CV in gray scale, (3) the 4CV in color Doppler, and (4) the 3VT in color Doppler
(Fig. 11.5)—provides enough information to rule out most major cardiac malformations.Figure 11.2: Typical planes displayed in gray scale during the first trimester
cardiac examination include the visualization of the abdominal situs (A) with
stomach (asterisk) and the four-chamber view, displayed in a transverse (B) or
in an apical view (C). LV, left ventricle; RV, right ventricle; R, right; L, Left.
Table 11.1 • Optimization of the gray-scale cardiac examination in the first
trimester
Fetus in dorsoposterior position (NT-position)
Image magnified
Narrow sector width
Fetal thorax to occupy one-third of ultrasound image
High contrast image settings
Mid- to high-resolution transducers
Ultrasound insonation from apical to right lateral of the fetal heart
NT-nuchal translucency
Table 11.2 • Optimization of Color Doppler Cardiac Examination in the
First Trimester
Optimize the gray-scale image before activating color Doppler
Narrow color Doppler box
Mid-velocity color Doppler range
Mid-filter levels
Mid-to-high persistenceLow color Doppler gain
Low power output
Bidirectional color Doppler if available
Figure 11.3: Color Doppler of an apical four-chamber view at 12 weeks of
gestation by transabdominal (A) and transvaginal (B) ultrasound examination
demonstrating diastolic flow from both right (RA) and left (LA) atrium into right
(RV) and left (LV) ventricle, respectively. Note that the heart in B is displayed
with a higher resolution due to the transvaginal approach.Figure 11.4: Transvaginal ultrasound of the outflow tracts in color Doppler in a
fetus at 13 weeks of gestation showing the five-chamber view (A), the short
axis view of the right ventricle (RV) (B), and the three-vessel-trachea view (C).
Ao, aorta; LV, left ventricle; PA, pulmonary artery; SVC, superior vena cava.Figure 11.5: Four essential planes in the first trimester cardiac examination
include the plane at the abdominal circumference level (A) to visualize
abdominal situs with the stomach (asterisk) on the left side, the four-chamber
view (B) in gray scale, as well as the four-chamber view in color Doppler in
diastole (C) and the three-vessel-trachea view in color Doppler in systole (D).
LV, left ventricle; RV, right ventricle; PA, pulmonary artery; Ao, aorta; R, right;
L, Left.
CONGENITAL HEART DISEASE IN THE FIRSTTRIMESTER
Congenital heart disease (CHD) is the most common severe congenital abnormality.5,6
About half of the cases of CHD are severe and account for over half of deaths from
congenital abnormalities in childhood.5 Moreover, CHD results in the most costly
hospital admissions for birth defects in the United States.7 The incidence of CHD is
dependent on the age at which the population is initially examined and the definition of
CHD used. An incidence of 8 to 9 per 1,000 live births has been reported in large
population studies.5,6 It is generally accepted that in the first trimester of pregnancy the
prevalence of CHD is higher, as many fetuses with complex anomalies die in utero,
especially when associated with extracardiac malformations or early hydrops. One of
the poor prognostic signs of CHD is its association with extracardiac anomalies
including genetic diseases. The detection of a fetal anomaly is therefore an indication
for fetal echocardiography. Even when isolated, CHD can be associated with
aneuploidy or syndromic conditions. Prenatal diagnosis of CHD in the first trimester
allows for pregnancy counseling and provides enough time for diagnostic options and
decision-making.1 CHD can be suspected in the first trimester by the presence of
indirect signs such as a thickened nuchal translucency (NT), by the presence of
extracardiac malformations, or by the direct observation of cardiac and great vessel
anatomic abnormalities.
ASSOCIATED EXTRACARDIAC MALFORMATIONS
Cardiac anomalies are often associated with extracardiac malformations either as part
of a defined genetic disease or in isolation. Cardiac anomalies may be found in
association with brain, abdominal, urogenital, or skeletal anomalies among others. Even
if CHD appears isolated, a careful follow-up should be performed in the second
trimester to look for associated extracardiac anomalies. Either isolated or in
combination with other extracardiac anomalies, the detection of a CHD is a major hint
for a possible association with aneuploidy or other syndromic conditions. The true
incidence of CHD association with aneuploidy is unknown but more than 20% of all
CHD detected in the first trimester are associated with chromosomal numeric
aberrations. This may represent an overestimation given that a significant percentage of
CHD in the first trimester is detected after a thickened NT is diagnosed. Aneuploidies
associated with CHD in the first trimester include trisomies 21, 18, and 13, as well as
with Turner syndrome and triploidy (see Chapter 6 for more details). Other
chromosomal anomalies are possible but rather accidental. One major chromosomal
anomaly is the association with deletion 22q11, testing for which has to be offered
when invasive procedure is performed, especially when a conotruncal anomaly is
detected (see below). Deletions and duplications are more commonly detected
nowadays given the widespread use of microarray as a diagnostic test followingchorionic villous sampling when CHD is diagnosed in the first trimester. Monogenic
diseases associated with cardiac defects are usually not detected in early gestation. For
more details on genetics of cardiac anomalies, we recommend monographs and review
articles on this subject.1,8
Deletion 22q11.2 Syndrome (DiGeorge Syndrome)
Deletion 22q11.2 syndrome (also called DiGeorge syndrome or CATCH 22) is the most
common deletion in humans and is the second most common chromosomal anomaly in
infants with CHD (second to trisomy 21). It has an estimated prevalence of 1:2,000 to
1:4,000 live births.9 The acronym CATCH-22 was used to describe features of
DiGeorge syndrome to include Cardiac anomalies, Abnormal facies, Thymus
hypoplasia, Cleft palate, Hypocalcemia, and the microdeletion on chromosome 22.8
Phenotypic abnormalities include cardiac anomalies, mainly outflow tract abnormalities
in combination with thymus hypoplasia or aplasia, cleft palate, velopharyngeal
insufficiency, and dysmorphic facial features.9 Disorders of the skeleton can affect the
limbs and the spine. Mental disorders are found in 30% of the adults with this deletion.8
Diagnosis of this deletion can be achieved by fluorescence in situ hybridization (FISH)
technique or with microarray analysis. In an affected fetus or infant, the parental
examination reveals, in approximately 6%, an affected parent with subtle signs of this
syndrome with a 50% transmission to future offspring.8 Cardiac anomalies that are
found in deletion 22q11.2 syndrome primarily include conotruncal anomalies such as an
interrupted aortic arch, common arterial trunk (CAT), absent pulmonary valve
syndrome, pulmonary atresia with VSD, tetralogy of Fallot (TOF), and conoventricular
septal defects.8,10,11 The presence of a right aortic arch either in isolation or in
combination with a cardiac anomaly increases the risk for deletion 22q11.2.12 Reports
on the detection of deletion 22q11.2 in the first trimester are scarce, but in our opinion,
this is primarily due to missed diagnosis of cardiac and extracardiac abnormalities
rather than due to the inability to make the diagnosis in the first trimester. Several
ultrasound features of deletion 22q11.2 that are seen in the second trimester such as a
small thymus,10 a dilated cavum septi pellucidi,13 or polyhydramnios14 are not seen in
the first trimester. Facial dysmorphism, as another feature of deletion 22q11.2, is too
subtle to be a reliable sonographic feature, even in the second trimester. In the presence
of a first trimester cardiac or extracardiac abnormality in the fetus, genetic counseling
for invasive diagnostic testing with chorionic villous sampling or amniocentesis is
recommended and with the widespread use of microarray, deletion 22q11.2 will be
more commonly detected in early gestation. Figure 11.6 shows a fetus at 13 weeks of
gestation with deletion 22q11.2 detected with targeted FISH performed due to the
presence of polydactyly and an interrupted aortic arch seen on the first trimester
ultrasound.Figure 11.6: Fetus at 13 weeks of gestation with deletion 22q11. Note in A the
presence of a normal facial profile with normal nuchal translucency (NT). Also
note in A the presence of hexadactyly (numbers 1–6), shown in hand. In B, the
four-chamber view demonstrates a ventricular septal defect (VSD). C:
Obtained at the three-vessel-trachea view and shows an interrupted aortic arch
(IAA) (arrows). Chorionic villous sampling with targeted FISH confirmed the
suspected deletion 22q11. AAO, ascending aorta; DA, ductus arteriosus; LV,
left ventricle; PA, pulmonary artery; RV, right ventricle.
INDIRECT SIGNS OF CARDIAC ANOMALIES IN THE
FIRST TRIMESTER
Several ultrasound markers associated with an increased risk for CHD have been
described in the first trimester and are today part of the indications for an early fetal
echocardiography as listed in Table 11.3. Four of these common ultrasound markers are
discussed in the following section.
Increased Nuchal Translucency Thickness
In addition to chromosomal anomalies, several reports have noted an association
between increased NT and major fetal malformations including cardiac defects (Fig.
11.7). Prospective studies in mixed low- and high-risk screening populations showed a
sensitivity of about 21% for a NT >99th percentile. Studies on the association of NT
with CHD have shown that the prevalence of major cardiac defects increases
exponentially with fetal NT thickness, without an obvious predilection to a specific
CHD.15,16 The underlying pathophysiologic mechanism relating the presence of a
thickened NT to fetal cardiac defect is not fully understood.Table 11.3 • Suggested Indications for Fetal Cardiac Imaging in the First
Trimester
Maternal indications Increased risk for aneuploidy (including maternal or
paternal balanced translocations)
Maternal poorly controlled diabetes mellitus
Maternal cardiac teratogen exposure
Previous child with complex cardiac malformation
Fetal indications Thickened nuchal translucency
Abnormal cardiac axis
Reverse flow in A-wave of ductus venosus
Tricuspid regurgitation
Extracardiac fetal malformations
Fetal hydrops in the first trimester
Reversed A-Wave in Ductus Venosus
Under normal conditions, ductus venosus (DV) waveforms show a biphasic pattern
throughout the cardiac cycle. Abnormal DV waveform pattern is typically characterized
by an absent or reversed A-wave during the atrial contraction phase of diastole (Fig.
11.8A). This flow pattern in the first trimester has been associated with an increased
risk of aneuploidy. In chromosomally normal fetuses, abnormal DV waveforms have
also been shown to be associated with structural cardiac anomalies.17 The underlying
pathophysiologic mechanism linking the reversed DV A-wave to fetal CHD is unclear,
but an increased right atrial preload as a result of an increase in volume, pressure, or
both in CHD could be one of the underlying mechanisms. Detecting a reversed A-wave
in the DV increases the risk for the presence of CHD in the fetus.16Figure 11.7: Relationship between increased nuchal translucency (NT)
thickness and risk of congenital heart disease (CHD) based on a meta-analysis
of 12 studies. Note that the prevalence of CHD increases with increased NT
thickness. (Adapted from Clur SA, Ottenkamp J, Bilardo CM. The nuchal
translucency and the fetal heart: a literature review. Prenat Diagn.
2009;29:739–748; copyright John Wiley & Sons, Ltd., with permission.)
Tricuspid Regurgitation
TR can occur in the fetus at all gestational ages and can be transient. TR at 11 to 13
weeks of gestation is a common finding in fetuses with trisomies 21, 18, and 13, and in
those with major cardiac defects.16 TR is found in about 1% of euploid fetuses, in 55%
of fetuses with trisomy 21, in one-third of fetuses with trisomy 18 and trisomy 13, and in
one-third of those with complex cardiac defects.18 A standardized approach to the
diagnosis of TR is important and includes the following (see also Chapter 1): the image
is magnified, an apical four-chamber view of the fetal heart is obtained, pulsed-wave
Doppler sample volume of 2.0 to 3.0 mm is positioned across the tricuspid valve, and
the angle to the direction of flow is less than 30 degrees from the direction of the
interventricular septum. A TR is thus diagnosed when it is seen for at least half of
systole with a velocity of over 60 cm per second. The detection of TR (Fig. 11.8B)
increases the risk for the presence of a complex cardiac defect.Figure 11.8: A: Pulsed Doppler of ductus venosus (DV) in a fetus at 13 weeks
of gestation with a cardiac defect, showing reversed flow in the A-waves (open
circle) during atrial contractions. The presence of this pattern suggests an
increased risk for associated cardiac abnormalities. B: Pulsed Doppler of the
tricuspid valve (long arrow) in a fetus with a tetralogy of Fallot. Note the
presence of tricuspid regurgitation on pulsed Doppler (opposing arrows). The
presence of tricuspid regurgitation increases the risk for the presence of
cardiac abnormalities. S, peak systolic velocity; D, peak diastolic velocity.
Cardiac Axis in Early Gestation
Several studies have established an association between an abnormal cardiac axis and
CHD in mid-second and third trimesters of pregnancy and also recently in early
gestation. Cardiac axis measurement in the first trimester can be challenging and
requires the use of high-definition color in order to clearly delineate the ventricular
septum (Fig. 11.9). In a case–control study design, we have recently reported on the
fetal cardiac axis in 197 fetuses with confirmed CHD between 11 0/7 and 14 6/7 weeks
of gestation, matched with a control group.19 In the control group, the mean cardiac axis
was 44.5 ± 7.4 degrees and did not significantly change in early pregnancy.19 In the
CHD group, 25.9% of fetuses had cardiac axis measurements within normal limits.19 In
74.1%, the cardiac axis was abnormal. The performance of cardiac axis measurement indetection of major CHD was significantly better than enlarged NT, TR, or reversed Awave in DV used alone or in combination.19
COMMON FETAL CARDIAC ANOMALIES
In the following sections, we will present CHD that can be diagnosed in the first
trimester of pregnancy. For each fetal cardiac abnormality, we will define the
abnormality, describe sonographic findings along with optimal planes for diagnosis in
the first trimester, and briefly list associated cardiac and extracardiac malformations.
Table 11.4 lists abnormal ultrasound findings and corresponding cardiac anomalies in
the first trimester of pregnancy. For more detailed information on prenatal cardiac
imaging and CHD in the first, second, and third trimesters of pregnancy, we refer the
readers to our book on this subject.1
Hypoplastic Left Heart Syndrome
Definition
Hypoplastic left heart syndrome (HLHS) is a group of complex cardiac malformations
involving significant underdevelopment of the left ventricle and the left ventricular
outflow tract, resulting in an obstruction to systemic cardiac output. In general, two main
classic forms of HLHS can be observed in the first trimester: one form involves atresia
of both the mitral and aortic valves, with practically no communication between the left
atrium and left ventricle and a nearly absent or severely hypoplastic left ventricle (Fig.
11.10A), and the other form involves a visible left ventricle, with hyperechoic wall,
globular shape, and poor contractility in association with severely dysplastic mitral
valve combined with a severe aortic stenosis or aortic atresia (Fig. 11.10B). The
reported birth incidence of HLHS is 0.1 to 0.25 per 1,000 live births.6
Ultrasound Findings
In HLHS, the four-chamber view appears abnormal in gray scale and in color Doppler.
Cases with a combined mitral and aortic atresia show an absent left ventricle, and can
be detected at 12 to 13 weeks of gestation (Figs. 11.11A and 11.12A). In gray scale, the
left ventricle appears small or absent in the 4CV (Figs. 11.11A and 11.12A), and color
Doppler shows an absence of flow into the left ventricle (Figs. 11.11B and 11.12B).
The classic appearance of a single ventricle on gray scale and color Doppler in the first
trimester is thus suggestive of HLHS. When suspected on the 4CV in the first trimester,
HLHS should be confirmed in the 3VT view, which reveals an enlarged pulmonary
artery with a small aortic arch with reverse flow on color Doppler (Figs. 11.11C and
11.12C). An echogenic globular left ventricle can occasionally be seen in the first
trimester in HLHS (Fig. 11.13) and represents left ventricular changes (fibroelastosis),
similar to that noted in the second and third trimesters of pregnancy. Of note is that the
presence of a “normal” four-chamber view in the first trimester cannot rule out HLHS,
as it has been shown to develop between the first and second trimesters of gestation.Figure 11.9: Cardiac axis (blue arrows) measurement in two fetuses at 13
weeks of gestation in color Doppler. In fetus A with a normal heart anatomy,
the cardiac axis is normal. In fetus B with an atrioventricular septal defect
(AVSD) and ventricle disproportion with aortic coarctation (CoA), the cardiac
axis is deviated with a wide angle. Cardiac axis is measured in a four-chamber
view of the heart by the angle of two lines; the first line starts at the spine (S)
posteriorly and ends in mid-chest anteriorly, bisecting the chest into two equal
halves, the second line runs through the ventricular septum. RV, right ventricle;
LV, left ventricle; L, left.
Table 11.4 • Abnormal Ultrasound Findings and Suspected Cardiac
Anomalies in the First Trimester
Four-chamber view in
gray scale and color
Doppler
Abnormal cardiac axis (left-sided in TOF, CAT—
mesocardia in TGA, DORV, dextrocardia in
heterotaxy)
Severe tricuspid insufficiency in Ebstein anomaly
Single ventricle in AVSD, univentricular heart, HLHS,
tricuspid atresia with VSD
Ventricle disproportion in coarctation of the aorta,
HLHS, HRHS, pulmonary atresia with VSD, mitral
atresia and tricuspid atresiaThree-vessel-trachea
view in color Doppler
Discrepant great vessel size with forward flow in the
small vessel in TOF, coarctation of the aorta,
Tricuspid atresia with VSD
Discrepant great vessel size with reversed flow in
the small vessel in HLHS, HRHS, PA with VSD
Single large great vessel in CAT, PA with VSD
Single great vessel of normal size in TGA or DORV
Interrupted aortic isthmus in interrupted aortic arch
Aortic arch right-sided to the trachea in right-sided
aortic arch with left ductus arteriosus, right-sided
aortic arch with right ductus arteriosus, and double
aortic arch
TOF, tetralogy of Fallot; CAT, common arterial trunk; TGA, transposition
of the great arteries; DORV, double outlet right ventricle; AVSD,
atrioventricular septal defect; HLHS, hypoplastic left heart syndrome; VSD,
ventricular septal defect; HRHS, hypoplastic right heart syndrome; PA,
pulmonary atresia.
Figure 11.10: Schematic drawings of hypoplastic left heart syndrome (HLHS).
Note in A the typical features of hypoplastic hypokinetic left ventricle (LV),
dysplastic mitral valve, atretic aortic valve, and hypoplastic aorta (Ao). B: The
infrequent type of HLHS in the first trimester with dilated, hyperechogenic left
ventricle (fibroelastosis), narrowing at the aortic valve level and obstruction to
left ventricular outflow, in association with critical aortic stenosis. RA, right
atrium; RV, right ventricle; PA, pulmonary artery; LA, left atrium.
Associated MalformationsHLHS is associated with a 4% to 5% incidence of chromosomal abnormalities,20 such
as Turner syndrome, trisomies 13 and 18, and others, and when HLHS is suspected in
the first trimester, counseling with regard to genetic testing should be performed.
Extracardiac malformations have been reported in 10% to 25% of infants with HLHS21
with associated genetic syndromes, such as Turner syndrome, Noonan syndrome, Smith–
Lemli–Opitz syndrome, and Holt–Oram syndrome.21 Fetuses with HLHS may develop
growth restriction in the late second and third trimesters of pregnancy probably due to a
20% reduction in combined cardiac output.22 When HLHS is diagnosed in the first
trimester, follow-up ultrasound examinations are recommended.
Figure 11.11: Hypoplastic left heart syndrome in a fetus at 13 weeks of
gestation demonstrated by transabdominal ultrasound. Note in A the absence
of a left ventricle (arrow) in the four-chamber view. In B, color Doppler shows
diastolic flow between right atrium (RA) and right ventricle (RV) with absent left
ventricular flow. In C, three-vessel-trachea view in color Doppler shows
antegrade flow in the pulmonary artery (PA) (blue arrow) and retrograde flow
into the aortic arch (AoA) (red arrow). LA, left atrium.Figure 11.12: Hypoplastic left heart syndrome in a fetus at 13 weeks of
gestation demonstrated by transvaginal ultrasound (different fetus than in Fig.
11.11). Note in A the absence of a left ventricle (LV) in the four-chamber view.
In B, color Doppler shows diastolic flow between right atrium (RA) and right
ventricle (RV) with absent left ventricular flow. In C, three-vessel-trachea view
in color Doppler shows antegrade flow in the pulmonary artery (PA) and
retrograde flow into the small aortic arch (AoA). Note the increased resolution
in the ultrasound images as compared to Figure 11.11 obtained
transabdominally. Compare with Figure 11.11. LA, left atrium.Figure 11.13: Four-chamber view in a fetus with hypoplastic left heart
syndrome (HLHS) at 13 weeks of gestation with gray-scale (A) and color
Doppler (B) imaging. Note the presence in A of a relatively small echogenic left
ventricular (LV) cavity. Color Doppler in B shows absence of mitral inflow
during diastole. The presence of an echogenic LV is unusually found in HLHS in
the first trimester in comparison with the second trimester. RA, right atrium;
RV, right ventricle; LA, left atrium.
Coarctation of the Aorta
Definition
Coarctation of the aorta (CoA) involves narrowing of the aortic arch, typically located
at the isthmic region, between the left subclavian artery and the ductus arteriosus (Fig.
11.14). CoA is a common anomaly, found in about 5% to 8% of newborns and infants
with CHD.6,23 CoA can be classified as simple when it occurs without important
intracardiac lesions and complex when it occurs in association with significant
intracardiac pathology.Figure 11.14: Schematic drawing of coarctation of the aorta. See text for
details. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle;
PA, pulmonary artery; Ao, aorta.
Ultrasound Findings
The presence of ventricular disproportion with a small left ventricle in the first
trimester is one of the markers for the presence of CoA. In gray scale, the ventricular
disproportion can be best demonstrated in a transverse view of the heart (Fig. 11.15).
Color Doppler demonstrates a difference in ventricular filling in the 4CV by showing
increased flow across the right ventricle when compared with the left ventricle (Fig.
11.15B). The diagnosis of CoA is confirmed in the 3VT by revealing a small aortic arch
in comparison with the pulmonary artery (Fig. 11.16). Typically, the aortic arch shows
antegrade flow in CoA (Fig. 11.16B), which enables its distinction from HLHS where
reversal flow is demonstrated on color Doppler (Fig. 11.12C). When the aortic arch
does not appear to be continuous with the descending aorta, the diagnosis of an
interrupted aortic arch should be suspected. It has to be borne in mind that confirming
the presence of CoA in the second trimester is critical because ventricular
discrepancies found in the first trimester of pregnancy may resolve with advancing
gestation. Making an accurate diagnosis of CoA is difficult in the first trimester and
commonly leads to false-positive diagnoses.
Associated MalformationsThe most common associated cardiac abnormalities in complex CoA include large
VSD, bicuspid aortic valve, aortic stenosis at the valvular and subvalvular levels,
mitral stenosis, and persistent left superior vena cava.24,25 These associated cardiac
abnormalities are difficult, if not impossible, to see on the first trimester ultrasound.
Chromosomal abnormalities are commonly associated with CoA, with Turner syndrome
representing the most common abnormality.26 If CoA is suspected in the presence of
other findings such as cystic hygroma and/or early fetal hydrops, Turner syndrome
should be considered in the diagnosis. CoA can also be found in association with other
chromosomal aberrations, such as trisomy 13 or trisomy 18, especially in the presence
of multiple extracardiac malformations. The presence of CoA with tachycardia,
impaired fetal growth, and/or multiple structural anomalies is suggestive of trisomy 13.
Figure 11.15: Four-chamber views in two fetuses (A and B) at 13 weeks of
gestation with suspected aortic coarctation. The axial gray-scale four-chamber
view in A and the apical color Doppler four-chamber view in B are abnormal
and show discrepant ventricular chamber size with a diminutive left ventricle
(LV). RV, right ventricle; L, left; R, right; LA, left atrium; RA, right atrium.
Pulmonary Atresia with Intact Ventricular Septum
Definition
Pulmonary atresia with intact ventricular septum (PA-IVS) is a group of cardiac
malformations having in common absent communication between the right ventricle and
the pulmonary arterial circulation (pulmonary atresia) in combination with an intact
ventricular septum. The right ventricular cavity is either hypoplastic with thickenedright ventricular myocardium (Fig. 11.17), or dilated with significant tricuspid valve
regurgitation and a dilated right atrium. A hypoplastic right ventricle occurs in the
majority of cases.27 PA-IVS is a rare condition with a prevalence of 0.042 to 0.053 per
1,000 live births.28
Figure 11.16: Color Doppler at the level of the four-chamber view (A) and
three-vessel-trachea view (B) in a fetus with coarctation of the aorta at 14
weeks of gestation. A diminutive left ventricle (LV) is noted in the four-chamber
view (A), and a small aortic arch is noted in the three-vessel-trachea view (B).
RV, right ventricle; RA, right atrium; LA, left atrium; PA, pulmonary artery.Figure 11.17: Schematic drawing of pulmonary atresia with intact ventricular
septum (PA-IVS). See text for details. RA, right atrium; RV, right ventricle; LV,
left ventricle; LA, left atrium; Ao, aorta; PA, pulmonary artery.
Ultrasound Findings
PA-IVS can be suspected in the first trimester with the detection of a small hypoplastic,
hypokinetic right ventricle at the 4CV (Fig. 11.18A). The anatomic depiction of the right
ventricle is similar to that of the left ventricle in HLHS. In most cases, this finding is
supported by color Doppler showing lack of right ventricular filling in the 4CV (Fig.
11.18B) and reverse flow in the ductus arteriosus and pulmonary artery in the 3VT view
(Fig. 11.18C). Often the dysplastic tricuspid valve is insufficient, and valvular
regurgitation can be demonstrated with color and pulsed Doppler.
Associated Malformations
One of the major associated findings in hearts with PA-IVS and hypoplastic right
ventricles is an anomaly of the coronary circulation, namely ventriculo-coronary arterial
communication, found in about one-third of cases of PA-IVS but typically not seen in
early gestation. Other associated cardiac findings include right atrial dilation, tricuspidvalve abnormalities, subvalvular obstruction of the aortic valve, atrial septal defects,
dextrocardia, and transposition of great arteries. Sequential evaluation into the second
trimester should be performed to rule out the association with heterotaxy, especially
with situs abnormalities. Extracardiac anomalies may be found but without an organspecific pattern. Chromosomal aberrations such as trisomy 21 or 22q11 microdeletion
are rare.
Figure 11.18: Four-chamber view in gray scale (A), color Doppler (B), and
three-vessel-trachea view (C) in a fetus with pulmonary atresia with intact
ventricular septum (PA-IVS) at 13 weeks of gestation. A: Gray scale of a
diminutive right ventricle (RV) with bulging of the interventricular septum into the
left ventricle (LV). B: Diastole in color Doppler in the absence of diastolic flow
into the right ventricle. C: The three-vessel-trachea view in color Doppler
indicates the typical pattern of antegrade flow in the aortic arch (Ao) (blue
arrow) in comparison with the retrograde flow across the ductus arteriosus
(DA) into the pulmonary artery (PA) (red arrow). RA, right atrium; LA, left
atrium.
Tricuspid Atresia with Ventricular Septal Defect
Definition
Tricuspid atresia with ventricular septal defect (TA-VSD) is characterized by the
absence of the right AV connection, resulting in lack of communication between the right
atrium and ventricle. The right ventricle is therefore diminutive in size. An inlet-type
VSD, typically perimembranous, is always present, and the size of the right ventricle isrelated to the size of the VSD. A large interatrial communication, in the form of a
widely patent foramen ovale or atrial septal defect, is necessary given an obstructed
tricuspid valve. TA-VSD is classified into three types based on the spatial orientation
of the great vessels.29 TA-VSD type 1 occurs in 70% to 80% of cases and is associated
with normally oriented great arteries. TA-VSD type 2 occurs in 12% to 25% of cases
and is associated with D-transposition of the great vessels. TA-VSD type 3, an
uncommon malformation, is seen in the remainder of TA cases and usually denotes
complex great vessel abnormalities such as truncus arteriosus or L-transposition. TAVSD is rare, with an incidence of 0.08 per 1,000 live births30 Figure 11.19 represents a
schematic drawing of type 1 TA-VSD.
Figure 11.19: Schematic drawing of tricuspid atresia with ventricular septal
defect (TA-VSD). See text for details. RA, right atrium; RV, right ventricle; LV,
left ventricle; LA, left atrium; Ao, aorta; PA, pulmonary artery.
Ultrasound Findings
TA-VSD can be detected in the first trimester on gray scale and color Doppler of the
4CV. Typically an enlarged left ventricle and a hypoplastic right ventricle is noted on
gray scale at the 4CV and color Doppler on transabdominal ultrasound reveals what
appears to be a single ventricular heart. With high-resolution transabdominal and
transvaginal transducers, the hypoplastic right ventricle is seen and the VSD is shown
with blood flow from the left to the right ventricle (Fig. 11.20A). In type 1 TA-VSD at
the 3VT view, the pulmonary artery is smaller than the aorta with antegrade flow in both
great arteries (Fig. 11.20B). TA-VSD has been associated with an enlarged NT in thefirst trimester.31 Because reversed A-wave in the DV has been reported in the second
and third trimesters in association with TA-VSD, this finding may be present in the first
trimester and may represent an early sign of right atrial increased preload.32
Figure 11.20: Transvaginal ultrasound of tricuspid atresia with ventricular
septal defect (TA-VSD) in color Doppler in a fetus at 13 weeks of gestation. A:
Obtained at the four-chamber view and shows blood inflow through the mitral
valve into the left ventricle (LV), with blood reaching the right ventricle (RV)
through the VSD (arrow). B: The three-vessel-trachea view with a narrow
pulmonary artery (PA) (associated pulmonary stenosis) as compared to the
aorta (Ao). LA, left atrium; RA, right atrium.
Associated Malformations
Associated cardiac findings include a large interatrial communication such as a patent
foramen ovale or an atrial septal defect, a VSD, transposition of the great vessels, and
various degrees of right ventricular outflow obstruction. Extracardiac anomalies can
also be found and fetal karyotyping should be offered despite a rare association with
chromosomal aberration including 22q11 microdeletion.33
Atrioventricular Septal Defect
Definition
Atrioventricular septal defect (AVSD) represents a cardiac abnormality characterized
by a deficient AV septation and abnormalities of the AV valves, primarily resulting in
the presence of a common AV junction. Common synonyms to AVSD include AV canal
defect or endocardial cushion defect. In the complete form of an AVSD, there is a
combination of an atrial septum primum defect and an inlet VSD with an abnormal
common AV valve, which connects to the right and left ventricles (Fig. 11.21). The
common AV valve usually has five leaflets. Partial AVSD includes an atrial septumprimum defect and a cleft in the mitral valve with two distinct mitral and tricuspid valve
annuli that attach at the same level on the interventricular septum. Partial AVSD is
difficult to detect in the first trimester. AVSDs can also be classified as balanced or
unbalanced. In unbalanced AVSD, the AV connection predominantly drains to one of the
two ventricles, resulting in ventricular size disproportion. Unbalanced AVSD is
typically found in association with heterotaxy syndrome. AVSDs are common cardiac
malformations found in 4% to 7.4% of all infants with CHD.34
Figure 11.21: Schematic drawing of a four-chamber view with a complete
atrioventricular septal defect (AVSD). LA, left atrium; RA, right atrium; LV, left
ventricle; RV, right ventricle.
Ultrasound Findings
AVSD may be recognized in the first trimester by demonstrating the defect in the center
of the heart during diastole on gray-scale ultrasound at the 4CV (Fig. 11.22A). In an
apical insonation of the 4CV in systole, the linear insertion of the AV valves can be
seen, albeit quite difficult in the first trimester. Color Doppler reveals the classic single
channel of blood flow entering the common AV (Figs. 11.22B and 11.23) instead of two
distinct channels over the tricuspid and mitral valves as is shown in normal hearts (Fig.
11.3). Occasionally, the defect is so large that the image resembles a univentricular
heart. A typical finding is the presence of valve regurgitation on color Doppler at the
common AV valve (Fig. 11.24). Often a thickened NT is found in association with
AVSD and this combination suggests the presence of trisomy 21 or trisomy 18. The
combination of AVSD with heart block or a right-sided position of the stomach raises
the suspicion of isomerism and heterotaxy syndrome.Figure 11.22: Apical four-chamber views in diastole in gray scale (A) and color
Doppler (B) in a fetus with complete atrioventricular septal defect (AVSD) at 12
weeks of gestation. AVSD is demonstrated by the star in A and B. Note the
presence in B of a single channel of blood on color Doppler entering the
ventricles over a common atrioventricular valve. LV, left ventricle; RV, right
ventricle.Figure 11.23: Apical four-chamber views during diastole in color Doppler in two
fetuses with complete atrioventricular septal defect (AVSD) at 12 weeks of
gestation. AVSD is demonstrated by the star in A and B. Note the presence in
diastole of a single channel of blood entering the ventricles over a common
atrioventricular valve. LA, left atrium; RA, right atrium; LV, left ventricle; RV,
right ventricle.
Associated Malformations
Associated cardiac abnormalities in AVSD include TOF, double outlet ventricle, right
aortic arch, and other conotruncal anomalies. Extracardiac anomalies in AVSD
primarily include chromosomal abnormalities, mainly trisomy 21 and much less
commonly trisomies 18 and 13. About 40% to 45% of children with Down syndrome
have CHD and of these, 40% are AVSD, commonly of the complete type. 34 Antenatal
diagnosis of AVSD, when isolated, is associated with trisomy 21 in 58% of cases. 35
When AVSD is associated with heterotaxy, the risk of chromosomal abnormality is
virtually absent, but the outcome is worsened due to the severity of the cardiac and
extracardiac malformations.
Ventricular Septal Defect
Definition
VSD is an opening in the ventricular septum, leading to a hemodynamic communication
between the left and right ventricles. VSDs are common CHDs, second only to bicuspid
aortic valve.36 Typically VSDs are reported based on their anatomic locations on theseptum. In prenatal series, muscular VSDs are most common and account for about 80%
to 90%, with perimembranous VSDs being the second most common.37 VSDs are
frequently associated with various cardiac anomalies.
Ultrasound Findings
VSDs are generally too small to be reliably detected as isolated anomalies in the first
trimester. Caution should be made in diagnosing VSDs in early gestation given a
significant false-positive diagnosis resulting from echo dropout in 2D ultrasound and
color overlapping when using color Doppler. In most cases, the VSD is reliably
demonstrated when it is associated with another cardiac anomaly (Fig. 11.25A) or when
the four-chamber view anatomy is abnormal. The presence of blood flow shunting
across the VSD confirms its presence in the first trimester (Fig. 11.25B). When a VSD
is suspected but cannot be confirmed in the first trimester, a follow-up examination is
recommended after 16 weeks of gestation with careful evaluation of the ventricular
septum.
Figure 11.24: A–C: Four-chamber views in color Doppler and during systole in
three fetuses with complete atrioventricular septal defect at 12, 13, and 14
weeks, respectively. Note the presence of valve regurgitation (faint arrows)
across the common atrioventricular valve in the three fetuses. LV, left ventricle;
RV, right ventricle.Figure 11.25: A: A five-chamber view in a fetus with tetralogy of Fallot at 13
weeks of gestation. Note the presence of a perimembranous ventricular septal
defect (VSD). B: A transverse four-chamber view in color Doppler at 12 weeks
of gestation with a muscular VSD. Note the presence of blood flow across the
VSD documented by color Doppler. LV, left ventricle; RV, right ventricle; Ao,
aorta.
Associated Malformations
Associated cardiac anomalies are common and are typically diagnosed prior to the
diagnosis of VSD in the first trimester. The association of an extracardiac abnormality
with a VSD increases the risk for the presence of a syndrome or chromosomal
aberration. VSDs are the most common abnormalities in many chromosomal defects,
such as trisomies 21, 18, and 13.36 An isolated muscular VSD has a risk of
chromosomal abnormalities similar to that of normal pregnancy.37
Ebstein Anomaly
Definition
In Ebstein anomaly, the septal and posterior leaflets of the tricuspid valve are displaced
inferiorly from the tricuspid valve annulus, toward the apex of the heart, and originate
from the right ventricular myocardium (Fig. 11.26). The anterior tricuspid leaflet
maintains its normal attachment to the tricuspid valve annulus. The proximal portion of
the right ventricle is then continuous with the true right atrium and forms an “atrialized”
portion of the right ventricle (Fig. 11.26). The spectrum of Ebstein anomaly is wide and
varies from a minor form, with minimal displacement of the tricuspid valves with mild
TR, to a severe form, with the “atrialization” of the entire right ventricle. Ebstein
anomaly is one of the less common cardiac abnormalities occurring in about 0.5% to1% of CHD in live births.6
Figure 11.26: Schematic drawing of Ebstein anomaly. See text for details. LA,
left atrium; RA, right atrium; LV, left ventricle; RV, right ventricle.
Ultrasound Findings
Ebstein anomaly is detected in the first trimester by the presence of significant TR.
Other main findings of Ebstein anomaly such as cardiomegaly and a dilated right atrium
are typically seen later in gestation. The displaced apical attachment of the tricuspid
valve in the right ventricle can be seen on gray-scale ultrasound in an apical or axial
4CV (Fig. 11.27A). Severe TR originating near the apex of the RV can be clearly
demonstrated on color and pulsed Doppler (Fig. 11.27B and C). In severe Ebstein
anomaly in the first trimester, the presence of cardiomegaly may be associated with a
thickened NT and fetal hydrops, a sign of impending fetal demise. Although some severe
cases of Ebstein anomalies may be suspected in the first trimester, mild Ebstein cases
can be missed and only detected in the second trimesters of pregnancy. The presence of
significant TR in the first trimester can be a marker of Ebstein anomaly, which is
typically confirmed in the second trimester of pregnancy.
Associated Malformations
Associated cardiac abnormalities include an obstruction of the right ventricular outflow
tract as pulmonary stenosis or atresia in more than 60% of fetuses diagnosed with
Ebstein anomaly prenatally.38 Atrial septal defect, which is not evident in the first
trimester, represents another common association and has been reported in up to 60% of
children with Ebstein anomaly. Most cases of Ebstein anomaly are isolated findings, butan association with chromosomal anomalies, such as trisomy 21 or trisomy 13, has been
reported in addition to familial cases. Long-term complications of Ebstein include
pulmonary hypoplasia in neonates and rhythm disorders in children.
Univentricular Heart
Definition
Univentricular heart or univentricular AV connection describes a group of cardiac
malformations where the AV connection is completely or predominantly to a single
ventricular chamber. Embryologically, this malformation is thought to result from failure
of the development of the bulboventricular loop stage. From a clinical point of view, a
CHD with a univentricular heart describes a heart with one functioning ventricle with
inflow from one or both atria. Within univentricular heart, three subgroups can be
identified: double inlet, where two atria connect to a single ventricle through two patent
AV valves; single inlet, where one atrium connects to a single ventricle through a single
AV valve; and common inlet, where both atria connect to a single ventricle through a
single AV valve. The morphology of the ventricle is generally a left ventricular
morphology with a rudimentary right chamber. Figure 11.28 represents a schematic
drawing of a univentricular heart with double inlet ventricle.
Figure 11.27: Gray scale (A) and color (B) in a fetus at 13 weeks of gestation
with Ebstein anomaly. Note the presence of generalized hydrops (asterisks) in
A and B. The displaced apical attachment of the tricuspid valve in the right
ventricle (RV) is shown in A (arrow). Severe tricuspid regurgitation originating
near the apex of the RV is shown in B (arrow). C: Pulsed Doppler of the
regurgitant jet across the dysplastic tricuspid valve. RA, right atrium; LV, leftventricle; L, left.
Figure 11.28: Schematic drawing of double inlet univentricular heart. See text
for details. LA, left atrium; RA, right atrium.
Ultrasound Findings
The detection of a univentricular heart in the first trimester is fairly common, not
because the condition itself is common, but rather because several severe cardiac
anomalies appear as a single ventricle on gray scale and color Doppler. Interestingly,
the classic univentricular heart is rarely detected in the first trimester and as shown in
Figure 11.29, this anomaly commonly escapes detection given the presence of two
inflow streams on color Doppler. Given the small size of the first trimester fetal heart,
several cardiac malformations such as HLHS, tricuspid atresia, mitral atresia, large
AVSD, and severe CoA may present as a single ventricle heart, especially on
transabdominal scanning with color Doppler (Figs. 11.11, 11.12, and 11.22). When a
single ventricle heart is suspected on color Doppler in the first trimester, a thorough
evaluation of the fetal heart with transvaginal ultrasound is recommended in order to
delineate the specific cardiac abnormality. It is preferred in such situations to examine
the fetal heart on transvaginal ultrasound in gray scale first and to assess in detail the
anatomy of the cardiac chambers and great vessels before switching to color Doppler.
Figure 11.30 shows other cardiac malformations that were initially suspected as
univentricular hearts on color Doppler evaluation.
Associated Malformations
Associated malformations in univentricular heart are atresia, hypoplasia, or straddlingof the AV valves, pulmonary (or subpulmonic) outflow obstruction, aortic (or subaortic)
outflow obstruction, and conduction abnormalities, primarily due to the anatomic
disruption of the conduction system.39 Many of these associated cardiac malformations
may not be evident or are difficult to detect in the first trimester of pregnancy.
The most important extracardiac abnormality to rule out is the presence of right or
left isomerism, especially in the presence of a common inlet ventricle.40 Chromosome
anomalies and other extracardiac anomalies are possible but rather unusual.
Figure 11.29: Fetus at 14 weeks of gestation with a double inlet univentricular
heart. Note that on gray-scale ultrasound (A) and color Doppler (B), both right
(RA) and left atrium (LA) drain through two atrioventricular valves into a single
ventricle (SV). Interestingly, in color Doppler (B), this can be easily
misdiagnosed as two-ventricular heart. L, left.Figure 11.30: Abnormal apical four-chamber views in color Doppler in three
fetuses (A–C) with cardiac anomalies suspicious for a “univentricular heart” at
12 to 13 weeks of gestation. In fetus A, a single chamber (right ventricle) is
perfused on color Doppler in a case of hypoplastic left heart syndrome (arrow
points to the absent left ventricle). Fetus B shows flow into one ventricle, which
is the left ventricle (LV), with absence of diastolic flow into the hypoplastic right
ventricle (RV) in a fetus with pulmonary atresia and dysplastic tricuspid valve. In
fetus C, a defect is seen in the center of the heart (star) (single color channel)
in a case of a large atrioventricular septal defect. RA, right atrium; LA, left
atrium.
Heterotaxy Syndrome, Atrial Isomerism, and Situs Inversus
Definition
Heterotaxy Syndrome (in Greek, heteros means different and taxis means arrangement)
is a general term that is used to describe the complete spectrum of abnormal organ
arrangement.41 The term right and left atrial isomerism (in Greek, iso means same and
meros means turn) has been suggested and used in heterotaxy syndrome as the atrial
morphology best describes organ arrangement.42 Isomerism of the thoracic organs is
characterized by a rather symmetric arrangement of the otherwise asymmetric structures
including the atria and lungs,43 thus allowing a classification into two main groups:
bilateral left-sidedness, also called left atrial isomerism and bilateral right-sidedness,
also called right atrial isomerism. Heterotaxy syndrome including right and left atrial
isomerism is found in between 2.2% and 4.2% of infants with CHD.6
Situs inversus is defined as a mirror-image arrangement of the thoracic and
abdominal organs to situs solitus (normal anatomy). Partial situs inversus can be either
limited to the abdominal organs and is generally called situs inversus with levocardia
or limited to the chest and is called dextrocardia.Ultrasound Findings
Right and left isomerism can be detected in the first trimester, owing to a thickened NT
in combination with cardiac anomaly or in the presence of hydrops with complete heart
block.43,44 Abnormal situs on ultrasound in the first trimester may represent the first clue
to the presence of right or left isomerism (Figs. 11.31 and 11.32). The cardiac axis can
be shifted thus revealing a suspicion for the presence of cardiac abnormality (Fig.
11.31).19 The presence of complete heart block in the first trimester should raise
suspicion for left atrial isomerism, as Sjögren antibodies are not typically associated
with bradyarrhythmia before 16 weeks. The detection of AVSD and univentricular heart
is feasible in the first trimester and the suspicion of such an anomaly, especially in
combination with a right-sided stomach, should suggest the presence of heterotaxy (Fig.
11.31). The arrangement of the abdominal vessels either as juxtaposition of the aorta
and inferior vena cava (right isomerism) or as interruption of the inferior vena cava
with azygos continuity (left isomerism) is difficult to diagnose in the first trimester. The
addition of color Doppler, however, may assist in the diagnosis of abnormalities in the
abdominal vessels. The assessment of pulmonary venous connections is also possible
but rather difficult in early gestation.
Partial and complete situs inversus can be detected in the first trimester. The
transvaginal approach to determining fetal situs may be challenging given the difficulty
inherent in the transvaginal probe orientation. Suspected situs abnormalities should be
confirmed at a later gestation.
Associated Malformations
Associated cardiac malformations are numerous in heterotaxy and primarily include
AVSD and univentricular heart. Associated extracardiac anomalies in heterotaxy are
typically not detected in the first trimester and include various gastrointestinal
anomalies and extrahepatic biliary atresia.45
Associated cardiac anomalies in situs inversus are on the order of 0.3% to 5% and
include VSD, TOF, double outlet right ventricle (DORV), and complete or corrected
transposition of the arteries.1 The presence of primary ciliary dyskinesia has also been
demonstrated in patients with heterotaxy and patients with complete situs inversus.46
Interestingly, chromosomal aberrations such as trisomies are nearly absent in this group.Figure 11.31: Transverse views of the fetal chest (A) and abdomen (B) in a
fetus at 13 weeks of gestation with isomerism, first suspected by the
discrepant positions of the heart in the left chest (A) and the stomach (St) in the
right abdomen (B). Note the presence of an abnormal cardiac axis and an
abnormal four-chamber view in A. L, left; R, right.
Tetralogy of Fallot
Definition
TOF is characterized by a subaortic (malaligned) VSD, an aortic root that overrides the
VSD, and infundibular pulmonary stenosis (Fig. 11.33). Right ventricular hypertrophy,
which represents the fourth anatomic feature of the “tetralogy,” is typically not present
prenatally. TOF with pulmonary stenosis is the classic form, but the spectrum of TOF
includes severe forms, such as TOF with pulmonary atresia and TOF with absent
pulmonary valve. TOF is one of the most common forms of cyanotic CHD and is found
in about 1 in 3,600 live births.5 The classic form of TOF with pulmonary stenosis
accounts for about 80% of all newborns with TOF.Figure 11.32: Transverse views of the fetal abdomen (A) and chest (B) and in
a fetus at 13 weeks of gestation with isomerism, first suspected by the
discrepant positions of the heart in the right chest (dextrocardia) (A) and the
stomach (asterisk) in the left abdomen (B). L, left; R, right.Figure 11.33: Schematic drawing of tetralogy of Fallot. See text for details.
LA, left atrium; RA, right atrium; LV, left ventricle; RV, right ventricle; VSD,
ventricular septal defect; PA, pulmonary artery; Ao, aorta.
Ultrasound Findings
In its classic form, TOF may be difficult to diagnose in the first trimester. The
sonographic anatomy of the four-chamber view in TOF can appear normal in the first
trimester, unless in association with cardiac axis deviation (Fig. 11.34A and B). Clues
to the diagnosis of TOF include a large aortic root in the five-chamber view on gray
scale and color Doppler ultrasound (Figs. 11.34C and 11.35A) with a small pulmonary
artery (Figs. 11.34D and 11.35B). Although the aortic override may not be easily noted
on the five-chamber view, the small pulmonary artery can be easily detected in the 3VT
in color Doppler (Figs. 11.34D and 11.35B). The discrepant size between the aorta and
pulmonary artery in the 3VT view with antegrade flow in both vessels on color Doppler
is an important sign for TOF in the first trimester (Figs. 11.34D and 11.35B). In our
experience, TOF in the first trimester is more commonly detected by the abnormal 3VT
view than by the five-chamber view demonstrating aortic override.Figure 11.34: Tetralogy of Fallot at 14 weeks of gestation examined
transvaginally. A and B: Axial planes of the chest at the four-chamber view in
gray scale and color Doppler, respectively. In A and B, the four-chamber view
appears normal with an axis deviation to the left (A) and with normal filling
during diastole (B). C: The five-chamber view in color Doppler. Note in C
overriding of the dilated aorta over the ventricular septal defect (star). D: The
three-vessel-trachea view in color Doppler. Note in D the discrepant vessel size
with a small pulmonary artery (PA) as compared to the dilated overriding aorta
(AO). Antegrade flow is noted in both great vessels in D. LV, left ventricle; RV,
right ventricle.Figure 11.35: Tetralogy of Fallot at 13 weeks of gestation. A: An axial plane at
the level of the five-chamber view in color Doppler. Note in A, the large
ventricular septal defect (VSD) with the overriding aorta (AO). B: The threevessel-trachea view in color Doppler. Note in B the discrepant vessel size with
a small pulmonary artery (PA) as compared to the AO. Antegrade flow is noted
in both great vessels in B. LV, left ventricle; RV, right ventricle.
Associated Malformations
Associated cardiac abnormalities with TOF include a right aortic arch, found in up to
25% of the cases or occasionally, an AVSD, which increases the risk of chromosomal
abnormalities. There is a high association of TOF with extracardiac malformations,
chromosomal anomalies, and genetic syndromes.47 The rate of chromosomal
abnormalities is around 30%, with trisomies 21, 13, and 18 accounting for the majority
of cases.47 The rate of microdeletion 22q11 is found in 10% to 15% of fetuses and
neonates with TOF,48 and this risk increases in the presence of thymic hypoplasia,10,49
right-sided aortic arch, extracardiac anomalies, or polyhydramnios in the second
trimester of pregnancy.
Pulmonary Atresia with Ventricular Septal Defect
Definition
Pulmonary atresia with ventricular septal defect (PA-VSD) is characterized by atresia
of the pulmonary valve, hypoplasia of the pulmonary tract, membranous or infundibular
VSD, and an overriding aorta (Fig. 11.36). Sources of pulmonary blood flow include
the ductus arteriosus and/or systemic–pulmonary collateral circulation. Systemic–pulmonary collateral circulation typically includes collateral arteries from the
descending aorta to the lungs, called major aortopulmonary collateral arteries
(MAPCAs).50 PA-VSD has a prevalence of 0.07 per 1,000 live births.6 A 10-fold
increased risk of PA-VSD is seen in infants of diabetic mothers.6
Figure 11.36: Schematic drawing of pulmonary atresia with ventricular septal
defect (PA-VSD). See text for details. LA, left atrium; RA, right atrium; LV, left
ventricle; RV, right ventricle; PA, pulmonary artery; Ao, aorta; DA, ductus
arteriosus.
Ultrasound Findings
The presence of an abnormal cardiac axis can be the first clue for the presence of PAVSD (Fig. 11.37A). The 4CV is commonly normal in PA-VSD and the five-chamber
view shows a dilated overriding aortic root (Fig. 11.37A) with an absence of a normalsized pulmonary artery in the right ventricular outflow tract view. Color Doppler at the
3VT view shows a dilated transverse aortic arch with absence of antegrade flow across
the pulmonary artery (Fig. 11.37B). Typically color Doppler demonstrates reverse flow
in a tortuous ductus arteriosus and pulmonary artery in an oblique view of the chest,
inferior to the aortic arch. The presence of MAPCAs is not detected in the first trimester
of pregnancy.Associated Malformations
A right-sided aortic arch can be present in 20% to 50% of all cases.51 Absence of the
ductus arteriosus is also reported in about half of the cases. MAPCAs are associated in
about 44% of cases50 and are typically diagnosed in the second trimester of pregnancy.
Associated extracardiac findings include a high incidence of chromosomal aberrations.
In the Baltimore–Washington Infant Study, 8.3% of children with PA-VSD had
chromosomal anomalies.6 The incidence of 22q11 microdeletion is high and is found in
18% to 25% of fetuses with PA-VSD,50 with an increased association in the presence of
MAPCAs and/or a right aortic arch or hypoplastic thymus.
Common Arterial Trunk
Definition
CAT is characterized by a single arterial trunk that arises from the base of the heart and
gives origin to the systemic, coronary, and pulmonary circulations (Fig. 11.38). A large
VSD is almost always present in this anomaly, resulting from the near absence of the
infundibular septum.52 The spectrum of the disease is wide and is mainly related to the
anatomic origin of the right and left pulmonary arteries, which may arise from a
pulmonary trunk or as direct branches from the CAT or the descending aorta. The root
of the CAT is large and has a biventricular origin in most cases (overrides the septal
defect). In up to a third of CAT cases, however, the root appears to arise entirely from
the right ventricle and, in rare cases, entirely from the left ventricle. The CAT valve has
three leaflets (tricuspid) in about 69% of cases, four leaflets (quadricuspid) in 22% of
cases, two leaflets (bicuspid) in 9% of cases, and, on very rare occasions, one, five, or
more leaflets.53 CAT is reported to occur in about 1.07 of 10,000 births.30
Ultrasound Findings
Demonstrating the direct origin of the pulmonary arteries from the CAT is difficult in the
first trimester and is facilitated by the application of color Doppler (Fig. 11.39). A
typical feature of CAT is the presence of truncal valve regurgitation, which can help to
differentiate CAT from other cardiac malformations involving an overriding aorta. A
differentiating feature of CAT from PA-VSD is that the pulmonary arteries arise directly
from the CAT rather than the right ventricle.
Associated Malformations
Associated cardiac malformations are common with CAT. The ductus arteriosus is
absent in 50% of the cases, and when present it remains patent postnatally in about twothirds of patients.54 Aortic arch abnormalities are common with CAT, with right-sided
arch noted in 21% to 36% of cases54 (Fig. 11.39). Truncal valve dysplasia with
incompetence is a common association. Extracardiac structural malformations are seen
in up to 40% of CAT cases and are typically nonspecific (10). Numerical chromosomal
anomalies are found in about 4.5% of the cases and include trisomies 21, 18, and 13.Microdeletion 22q11 is reported in 30% to 40% of cases.55
Figure 11.37: Transvaginal ultrasound at the level of the five-chamber view (A)
and the transverse ductal arch view (B) in a fetus at 12 weeks of gestation with
pulmonary atresia and ventricular septal defect. The five-chamber view (A)
shows a large overriding aorta (AO) (star) and an abnormal cardiac axis
(dashed lines). In the three-vessel-trachea view (B), reverse flow in the ductus
arteriosus (DA) is demonstrated on color Doppler (curved arrow). RV, right
ventricle; LV, left ventricle.Figure 11.38: Schematic drawing of common arterial trunk. See text for
details. LV, left ventricle; RV, right ventricle; VSD, ventricular septal defect; PA,
pulmonary artery; Ao, aorta.
Transposition of the Great Arteries
Definition
Complete transposition of the great arteries (TGA) is a common cardiac malformation
with AV concordance and ventriculoarterial discordance. This implies a normal
connection between the atria and ventricles; the right atrium is connected to the right
ventricle through the tricuspid valve and the left atrium is connected to the left ventricle
through the mitral valve, but there is a switched connection of the great vessels, the
pulmonary artery arising from the left ventricle, and the aorta arising from the right
ventricle. Both great arteries display a parallel course, with the aorta anterior and to the
right of the pulmonary artery (Fig. 11.40), hence the term D-TGA (D = “dexter”). DTGA is a relatively frequent cardiac anomaly with an incidence of 0.315 cases per
1,000 live births.56
Ultrasound Findings
In TGA, the great vessels assume a parallel course, which can be demonstrated in an
oblique axial view of the fetal chest (Fig. 11.41B). This oblique view of the fetal chestis not a standard plane of the obstetric ultrasound examination and thus is not displayed
on routine ultrasound scanning. The demonstration on color Doppler of a single great
vessel in the 3VT is often the first clue for the presence of TGA (Fig. 11.41A) in the
first trimester. Once TGA is suspected on the 3VT view, the diagnosis can then be
confirmed in the first trimester by demonstrating the parallel orientation of the great
vessels in the oblique view of the fetal chest (Fig. 11.41B). The 4CV is commonly
normal in TGA with the exception of an abnormal cardiac axis in some cases with
mesocardia.
Figure 11.39: Common arterial trunk (CAT) in a fetus at 13 weeks of
gestation. Note in planes A and B the bifurcation of the CAT into the aorta (AO)
and the pulmonary artery (PA). Also note that the aortic arch courses to the
right of the trachea, as a right-sided aortic arch. R, right; L, left.Figure 11.40: Schematic drawing of D-transposition of great arteries (D-TGA).
See text for details. LA, left atrium; RA, right atrium; LV, left ventricle; RV, right
ventricle; PA, pulmonary artery; Ao, aorta.
Associated Malformations
VSDs and pulmonary stenosis (left ventricular outflow obstruction) are the two most
common associated cardiac findings in D-TGA. VSDs are common and occur in about
40% of cases and are typically perimembranous but can be located anywhere in the
septum.56 Pulmonary stenosis coexists with a VSD in D-TGA patients in about 30% of
cases, and the stenosis is usually more severe and complex than in D-TGA with intact
ventricular septum.56 Extracardiac anomalies may be present but rare, and numerical
chromosomal aberrations are practically absent in D-TGA. Microdeletion of 22q11
could be present and should be ruled out, especially when extracardiac malformations
or a complex D-TGA is present.
Double Outlet Right Ventricle
Definition
DORV encompasses a family of complex cardiac malformations where both great
arteries arise primarily from the morphologic right ventricle (Fig. 11.42) but differ with
regard to the variable spatial relationship of the great arteries, the location of the VSD
that is commonly seen with DORV, and the presence or absence of pulmonary and less
commonly aortic outflow obstruction. In DORV, four types of anatomic relationships ofthe aorta to the pulmonary artery at the level of the semilunar valves and four anatomic
locations for the VSD have been described.57 The exact subtype of DORV may be hard
to characterize prenatally as the position of the VSD is difficult to establish with
accuracy in fetal echocardiography. DORV has an incidence of approximately 0.09 per
1,000 live births.5
Ultrasound Findings
DORV can occasionally be diagnosed in the first trimester due to the presence of an
abnormal 4CV or 3VT view. An abnormal cardiac axis is commonly found in DORV
and can be noted in the first trimester (Fig. 11.43A and B). The 3VT view typically
shows discrepant size of the great arteries, a single large vessel (Fig. 11.43C), or
parallel orientation of the great vessels (Fig. 11.44). When the 4CV is normal, DORV is
difficult to diagnose in the first trimester.
Figure 11.41: Color Doppler ultrasound at the three-vessel-trachea view (A)
and an oblique view of the chest (B) at 12 weeks of gestation in a fetus with
complete transposition of the great arteries (D-TGA). The three-vessel-trachea
view (A) demonstrates the presence of a single great artery of normal size,
representing the superiorly located aorta (Ao). The oblique view of the chest
(B) shows the parallel course of the great vessels arising in discordance with
the aorta (AO) from the right (RV) and the pulmonary artery (PA) from the left
ventricle (LV).Figure 11.42: Schematic drawing of double outlet right ventricle. See text for
details. LA, left atrium; RA, right atrium; LV, left ventricle; RV, right ventricle;
Ao, aorta; PA, pulmonary artery; VSD, ventricular septal defect.
Associated Malformations
Associated cardiac findings are common and include a full spectrum of cardiac lesions.
Pulmonary stenosis is the most common associated malformation and occurs in about
70% of cases.58 Extracardiac anomalies are very common in fetuses with DORV and
are nonspecific for organ systems.59 Chromosomal abnormalities are frequently found in
the range of 12% to 40% in fetuses with DORV and primarily include trisomies 18 and
13 and 22q11 microdeletion.60
Right and Double Aortic Arch
Definition
Right aortic arch is diagnosed when the transverse aortic arch is located to the right of
the trachea on transverse imaging of the chest. A right aortic arch is associated with
three main subgroups of arch abnormalities: right aortic arch with a right ductus
arteriosus, right aortic arch with left ductus arteriosus, and double aortic arch (Fig.
11.45). Right aortic arch can be part of a complex cardiac malformation, but can often
also be an isolated finding.61 A right aortic arch occurs in about 1 in 1,000 of the
general population,62 but the prevalence of right aortic arch is probably higher in thepresence of other cardiac anomalies.
Figure 11.43: Four-chamber views in gray scale (A), color Doppler (B), and
three-vessel-trachea view (C) in a fetus at 13 weeks of gestation with double
outlet right ventricle. In A and B, the ventricular septal defect (VSD) is
visualized in gray scale (A) and color Doppler (B). Note the abnormal location
of the heart in the chest with mesocardia in A and B. The three-vessel-trachea
view (C) shows the aorta (AO) as a single vessel (superior to the pulmonary
artery). In this case, the AO has a course to the right of the trachea (Tr),
representing a right aortic arch. RV, right ventricle; LV, left ventricle.
Figure 11.44: Oblique views (A and B) of the fetal thorax with color Doppler in
a fetus at 13 weeks of gestation with double outlet right ventricle (same fetus
as in Fig. 11.43). Note the presence of the ventricular septal defect (VSD) in A,and the origin of the aorta (AO) and pulmonary artery (PA) from the right
ventricle (RV) in A and B. Aortic and ductal arches are seen to the right of the
trachea (Tr) in A and B. LV, left ventricle.
Figure 11.45: Schematic drawings of the three-vessel-trachea view in a normal
fetus (A) where the transverse aortic arch (Ao) and isthmus merge with the
pulmonary artery (PA) and ductus arteriosus (DA) into the descending aorta in
a ‘‘V-shape’’ configuration to the left of the trachea (T). B: A right-sided aortic
arch with a right-sided DA in a ‘‘V-shape’’ configuration to the right side of the
trachea. C: A right aortic arch with the transverse aortic arch to the right side
of the trachea; the DA is left-sided and the connection of aortic and ductal
arches constitutes a vascular ring around the trachea in a ‘‘U-shape’’
configuration. D: A rare sub-form of right aortic arch with a left DA forming a
double aortic arch with the transverse aortic arch bifurcating into a right and a
left aortic arch (LAoA) surrounding the trachea and esophagus. L, left; R, right;
SVC, superior vena cava; RAoA, right aortic arch.
Ultrasound Findings
The diagnosis of a right aortic arch is possible in the first trimester and is enabled by
the use of color Doppler at the 3VT view (Figs. 11.46 and 11.47). It is commonly
suspected on transabdominal scanning when the relationship of the transverse aortic and
ductal arches is evaluated. Transvaginal scanning can help in confirming the diagnosis.
In recent years, we were able to diagnose right aortic arch with its three subgroups in
the first trimester. Differentiating between the U-sign right aortic arch and the double
aortic arch (lambda sign) may be difficult in the first trimester (Figs. 11.46 and 11.47).
When suspected in the first trimester of pregnancy, the identification of the actual
subtype of right aortic arch can be confirmed on follow-up ultrasound examination in the
second trimester of pregnancy.
Associated Malformations
Even if the right aortic arch appears as an isolated finding on ultrasound, fetalchromosomal karyotyping should be offered to rule out chromosomal aberrations,
primarily 22q11 microdeletion12 and occasionally trisomy 21 and other aneuploidies.
Associated intracardiac anomalies are more common when the aorta and ductus
arteriosus are on the right (V-sign) than with double aortic arch or with the U-sign right
aortic arch.1 Typical cardiac anomalies observed with a right aortic arch are TOF,
pulmonary atresia with VSD, CAT, absent pulmonary valve, tricuspid atresia, and
DORV.61,63 The presence of a right aortic arch in association with a conotruncal
anomaly increases the risk of 22q11 microdeletion.61,63
Anomalies of the Systemic and Pulmonary Veins
The systemic and pulmonary veins in the first trimester are generally too small in size to
be clearly evident on gray-scale ultrasound, making detection of venous malformations
extremely difficult. Anomalies of the abdominal venous vasculature are discussed in
Chapter 12. The presence of a left persistent superior vena cava may be rarely detected
in the first trimester. Anomalies of the pulmonary venous system are still considered not
diagnosable in the first trimester, unless in combination with isomerism, which provides
a clue to the presence of anomalous pulmonary venous return. A follow-up in the second
trimester of pregnancy is recommended when pulmonary venous malformations are
suspected in the first trimester.
Aberrant Right Subclavian Artery
ARSA can be demonstrated in the first trimester in the 3VT view in color Doppler by
reducing the velocity of flow in order to demonstrate the small subclavian artery. The
ability to image the ARSA is significantly enhanced when transvaginal fetal ultrasound
is performed (Fig. 11.48). ARSA has been associated with trisomy 21 and other
aneuploidies. The patient’s prior risk for aneuploidy should be taken into consideration
when counseling is performed for the diagnosis of an isolated ARSA.
Figure 11.46: Three-vessel-trachea views in two fetuses at 13 weeks of
gestation with a right aortic arch with a left ductus arteriosus (U-sign)
demonstrated on transabdominal (A) and transvaginal (B) color Doppler. PA,
pulmonary artery; Ao/AO, aorta; SVC, superior vena cava; TR, trachea; L, left.Figure 11.47: Transvaginal ultrasound in color Doppler in a fetus at 12 weeks
of gestation with double aortic arch (A,B). Note the left (LAO) and right (RAO)
aortic arches surrounding the trachea. Differentiating a RAO (see Fig. 11.46)
from a double arch is more commonly performed in the second trimester of
pregnancy. PA, pulmonary artery; DA, ductus arteriosus.1.
2.
3.
4.
5.
6.
7.
Figure 11.48: Transvaginal ultrasound of an axial view of the fetal chest at the
three-vessel-trachea view showing an aberrant right subclavian artery (ARSA)
in two fetuses (A and B), both at 13 weeks of gestation noted during the nuchal
translucency measurement. Ao, aorta; PA, pulmonary artery; L, left
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