2. • CHD is the most common birth defect and the most
lethal.
• In fetal life, the incidence of CHD is likely to be even
higher due to affected fetuses undergoing an early
spontaneous loss, stillbirth, or elective termination
of pregnancy.
• Therefore, Early Gestation Fetal Cardiac Evaluation
and Screening for Fetal Cardiovascular Disease is
necessary.
3. Foetal circulation
• Gas exchange occurs in the placenta
• PREFERENTIAL STREAMING : Delivery of highly
oxygenated blood to the metabolically active
tissues(brain & heart) and of less oxygenated blood to
the placenta
• SHUNT-DEPENDENT’ circulation - the presence of
intracardiac and extracardiac shunts
• PARALLEL CIRCULATION : various organs receive
portions of their blood supply from either ventricles
4. Foetal circulation
• deoxygenated blood arrives at the placenta via the umbilical
arteries and is returned to the fetus in the umbilical vein.
• partial pressure of oxygen in the umbilical vein is around 4.7
kPa and fetal blood is 80–90% saturated.
• 50–60% of this placental venous flow bypasses the hepatic
circulation via the ductus venosus (DV) to enter the inferior
vena cava (IVC).
• In the IVC, the better oxygenated blood flow from the DV
tends to stream separately from the extremely desaturated
systemic venous blood, which is returning from the lower
portions of the body with an of around saturation 25–40%.
5. • At the junction of the IVC and the right atrium (RA) is a tissue flap
known as the Eustachian valve. Which tends to direct the more
highly oxygenated blood, streaming along the dorsal aspect of the
IVC, across the foramen ovale (FO) and into the left atrium (LA).
• In the LA, the oxygen saturation of fetal blood is 65%
• This better oxygenated blood enters the left ventricle (LV) and is
ejected into the ascending aorta.
• The majority of the LV blood is delivered to the brain and coronary
circulation thus ensuring that blood with the highest possible
oxygen concentration is delivered to these vital structures
6. • Desaturated blood ( 25–40%), from the superior vena cava (SVC)
and the coronary sinus, in addition to the IVC's anteriorly streamed
flow (comprised mainly of venous return from lower body and
hepatic circulation), is directed across the tricuspid valve and into
the right ventricle (RV).
• This blood is then ejected into the pulmonary artery (PA).
• Because of the high pulmonary vascular resistance (PVR) only about
12% of the RV output enters the pulmonary circulation, the
remaining 88% crossing the ductus arteriosus (DA) into the
descending aorta.
• The lower half of the body is thus supplied with relatively
desaturated blood.
7.
8. Combined ventricular output (CVO)
• In the adult circulation
circulatory system is in series and there are no shunts,
stroke volume of the RV should equal that of the LV
cardiac output can be defined in terms of the volume of blood ejected
by one ventricle in 1 min.
• In the fetus-
intracardiac and extracardiac shunting
the stroke volume of the fetal LV is not equal to the stroke volume of
the RV.
RV receives about 65% of the venous return and the LV about 35%.
so cardiac output of the fetus-the total output of both ventricles (the
combined ventricular output ).
About 45% of the CVO is directed to the placental circulation with
only 8% of CVO entering the pulmonary circulation.
9. The fetal circulation in transition
• Gas exchange must be transferred from the
placenta to the lungs
• the fetal circulatory shunts must close
• the left ventricular output must increase.
10. • umbilical vessels are reactive and constrict in
response to longitudinal stretch and the increase in
blood
• external clamping of the cord will augment this
process
• with the placental circulation removed there is a
dramatic fall in the flow through the ductus venosus
and a significant fall in the venous return through the
IVC
• ductus venosus closes passively 3–10 days after birth
11. • During late gestation there is a gradual reduction in PVR.
• At birth: After expansion of the lungs, there is a dramatic fall
in PVR and an 8–10-fold increase in pulmonary blood flow.
lung expansion and opening up pulmonary vessels.
stimulation of pulmonary stretch receptors resulting in reflex
vasodilatation.
better oxygenation of neonatal blood also reverses the
pulmonary vasoconstriction caused by hypoxia
12. • increase in pulmonary blood flow leads to a massive rise in
pulmonary venous return to the LA.
• decrease in IVC flow results in a fall in venous return to the RA.
• these two factors allow the pressures in the LA and RA to equalize
• the flap of the foramen ovale is pushed against the atrial septum and
the atrial shunt is effectively closed.
• initial closure of the foramen ovale occurs within minutes to hours
of birth.
• anatomical closure occurs later via tissue proliferation
13. • Concomitant with the drop in PVR, the shunt at the level of the
DA becomes bi-directional.
• exact mechanism of ductal closure is not known
• increased PO2 in neonatal blood produces direct constriction
of smooth muscle within the duct
• concentrations of PGE2 (produced in the placenta, fall rapidly
after birth) adding to ductal constriction.
• ductal tissue itself may become less sensitive to the dilating
influences of the prostaglandins.
14. • Closure of the ductus takes place in two stages.
full term newborns, functional ductal closure
occurs by 96 h.
followed later by anatomical closure via
endothelial and fibrous tissue proliferation
18. FETAL INDICATIONS
Increased Nuchal Translucency
a fluid-filled appearance of the back of the fetal neck
11 and 13 weeks 6 days of gestation
≥3.5 mm ( >95% of expected)
Suspected CHD on Routine Obstetric Ultrasound
Extracardiac Birth Defects-omphalocele, duodenal atresia,
diaphragmatic hernia
Risk of High Output Failure-
monochorionic diamniotic twins with twin-to-twin
transfusion syndrome (TTTS), twin reversed arterial
perfusion sequence
fetal anemia
chorioangioma.
19. MATERNAL INDICATIONS
Diabetes
Phenylketonuria Maternal phenylketonuria (PKU) -
phenylalanine level >15 mg/dL have a 10- to 15-fold increase
risk
Maternal Autoimmune Disease-
Complete heart block (CHB) occurs in ∼4% of pregnancies when
maternal autoimmune antibodies
Family History of Congenital Heart Disease
maternal heart disease are 5.7%
paternal heart disease 2.2%,
prior child with heart disease ∼2% to 6%
20. Timing of the Fetal Echocardiogram
• 18 to 22 weeks of gestation
• may miss cases in which disease is progressive or occurs late in
gestation, for example, maternal diabetes-associated ventricular
hypertrophy .
• If fetal heart disease is suspected later in pregnancy, fetal
echocardiography should be performed promptly to aid decision-
making about delivery and potentially to guide in utero therapy.
• This is especially true for fetal arrhythmias, which often do not
manifest before 25 to 26 weeks of gestation and, in some cases, only
in the third trimester
22. Four-Chamber View
• Near transverse/axial view
• fetal heart superior to the diaphragm and inferior
to the bronchial bifurcation
• cardiac position and the sizes of the atria,
ventricles, and atrioventricular valves, pulmonary
venous return to the left atrium can be visualized.
• Color Doppler should be used to assess
atrioventricular valvar regurgitation and to
confirm pulmonary venous return.
23.
24.
25. Left-Ventricular and Right-Ventricular
Outflow Tract Views
• by sweeping slightly cephalad from the four-
chamber view
• ventriculoarterial
• narrowing of the outflow tracts
• semilunar valves
• supravalvar areas can be detected by 2D imaging
• valvar regurgitation
• lack of flow in cases of semilunar valve atresia.
27. Three-Vessel and Tracheal View
• By sweeping even further cephalad from the
outflow tract views
• the side of the superior vena cava (SVC) and the
aortic arch can be defined.
• The transverse arch and ductal arch are
visualized, and by color Doppler, flow reversal in
the arch or the duct may be seen if present
28. Bicaval View
• The bicaval view is obtained by sagittal imaging of the
fetal chest, just to the left of midline
• This view will confirm that the suprahepatic portion of
the inferior vena cava is intact (it may be interrupted in
heterotaxy), and that a right SVC is present.
• he best to visualize the foramen ovale.
• Color Doppler should be used to assess the direction of
flow across the foramen ovale which is normally from
right to left, but may be reversed in cases of HLHS or
other complex lesions.
29.
30. Long Axis View of the Aortic Arch
• The long axis view of the aortic arch, the so-
called “candy-cane” view, is obtained by sagittal
imaging of the fetal thorax and angling slightly
leftward.
• it can also be obtained by aligning the transverse
arch with the ultrasound beam in the three-
vessel and trachea view, and turning the probe
90 degrees
31. • The arch should be assessed for
• Hypoplasia
• Coarctation
• measurements can be performed and compared
with those normal for age.
• Flow should be toward the descending aorta.
Reversal of flow in the arch indicates that the ductus
arteriosus is supplying some of the flow to the head
and upper extremity, and may be seen when there
are hypoplastic left-sided structures or an atrial
septal aneurysm obstructing mitral valve inflow
32. Long Axis View of the Ductal Arch
• The long axis view of the ductal arch, the so-called “hockey stick”
view, is usually obtained from a direct sagittal view of the fetal
thorax, just left of center.
• The ductus should be assessed for restriction and direction of flow.
• By spectral Doppler, a restrictive ductus arteriosus typically has a
peak velocity greater than 2 m/s and an abnormal flow pattern with
continuous flow, as opposed to the normal pulsatile flow.
• Continuous high-velocity flow is also usually evident by color
Doppler imaging.
• Flow reversal in the ductus arteriosus is present with severe right-
sided obstructive lesions, such as severe pulmonary stenosis or
pulmonary atresia (PA).
33. High Short Axis View of the Great
Arteries
• Imaging in cross-section of the heart can be very useful in assessing
the outflow tracts, the ventricular septum, cardiac function, and the
anatomy of the atrioventricular valves.
• the aortic valve en face, surrounded by the pulmonary artery
wrapping around it
• The pulmonary arteries can also be seen bifurcating, and the
tricuspid valve is usually well seen
• best for demonstrating obstruction to the RVOT and for
differentiating types of VSDs that involve the outlet portion of the
ventricular septum
• Tricuspid valve regurgitation can also be assessed from this view
34.
35. low short axis
• The low short axis is the best view to assess
ventricular function, and for muscular VSDs
• As muscular VSDs are often very small, the use of
color Doppler to show flow across the septum is
usually necessary to detect or confirm these defects
• morphology of the atrioventricular valves can be
assessed and a common atrioventricular valve or
mitral valve cleft can be detected.
36. Assessment of Cardiovascular
Performance
• Even in the structurally normal fetal heart, there is a variety of
cardiac and noncardiac pathologies that may affect the ability of the
heart to deliver oxygen to the brain and other organ systems
• These include
• perinatal infection,
• maternal diabetes,
• exposure to toxins,
• anemia,
• autoimmune disease,
• a mass effect due to congenital anomalies,
• arrhythmias,
• inherited or idiopathic cardiomyopathies, and
• increased fetal preload or afterload due to vascular anomalies,
placental abnormalities, vascular tumors, or humoral factors
37. • cardiac output is a function of stroke volume and heart rate.
• Stroke volume, in turn, is determined by the preload, afterload, and
contractility of the ventricles
• The fetal circulation operates in parallel compared to the postnatal
circulation, which operates in series
• The fetal LV, instead of supporting the entire systemic circulation, is
responsible only for the head and upper body
• The fetal RV, on the other hand, is responsible for supporting the lower
body and placental circulation
• Because of this difference, the fetal RV typically has a slightly larger cross-
sectional dimension as well as a larger estimated output compared to the lef
38. • The determinants of cardiac output also appear to vary dramatically
between fetal and postnatal circulations.
• The fetal myocardium has a markedly reduced compliance
compared to the postnatal, and thus responds poorly to volume
loading.
• Fetal cardiac output is also highly sensitive to afterload.
• In cases of placental insufficiency, increases in the afterload to the
fetal RV may result in a significant reduction in output of that
ventricle.
• The sole source of metabolic energy of the fetal myocardium is
glucose, and the fetal sarcoplasmic reticulum accumulates calcium
at a slower rate compared to adult myocardium.
39. • These findings may explain the dramatic
decompensation seen in fetuses with
uncontrolled tachycardia.
40. • In the fetus, congestive heart failure can be defined
as an inadequate oxygen delivery for normal end-
organ function, higher extracellular water content,
diminished calcium stores in the sarcoplasmic
reticulum, lower albumin concentration, higher
heart rate, and lower systemic arterial pressure
result in a propensity for elevated ventricular filling
pressures with alterations in fetal hemodynamics.
• Therefore, regardless of the etiology, indices of
diastolic dysfunction tend to precede those of
systolic dysfunction.
41. • Markers of diastolic dysfunction in the fetus include
• atrioventricular valvar regurgitation
• umbilical venous pulsations
• flow reversal in the ductus venosus
• monophasic atrioventricular valve inflow.
• As heart failure progresses in the fetus, fluid may
accumulate in the pericardial space, in the pleural space,
in the peritoneal cavity, and in the soft tissues.
• Fluid accumulation in two or more compartments
clinically defines hydrops fetalis, a risk factor for
morbidity and mortality in a variety of disease states
42. • Finally, systolic dysfunction is a late and ominous
finding in fetal cardiac dysfunction.
• While measurement of ejection fraction of the LV is
possible using the area-length method, fetal systolic
function is currently most often assessed by simple
single plane assessment of shortening fraction.
• A shortening fraction of <28% is considered
abnormal regardless of gestational age.
43. Cardiovascular Profile Score (CPS)
• incorporates cardiac and extra cardiac aspects of
fetal cardiovascular function
• The CPS encompasses five categories
hydrops
umbilical venous Doppler
heart size
abnormal myocardial function
arterial Doppler
• each worth 2 points
44.
45. • predictor of adverse fetal outcome in a variety of
disease processes, including
• CHD
• high-output extra cardiac lesions
• TTTS, idiopathic hydrops fetalis, and primary
fetal cardiomyopathy
• The heart failure score is 10 if there are no
abnormal signs
46.
47.
48. • The MPI, or Tei Index, is a commonly used
measure of cardiac function on the fetal
echocardiogram.
• The MPI is obtained by measuring the AV valve
closure time to opening time (systole), and the
semilunar valve ejection time
49. • The ejection time is then subtracted from the AV valve closure
to opening time in order to arrive at the sum of isovolumetric
contraction and relaxation.
• This sum is then divided by the ejection time.
• Normal values of the MPI change slightly throughout
gestation.
• Generally, values of less than 0.43 to 0.45 are considered to be
normal .
• Elevated MPI values can reflect an alteration in both systolic
and diastolic function
51. Ventricular Septal Defects
• Medium to large VSDs can be detected in the fetus with careful
imaging.
• VSDs are among the most commonly missed lesions by prenatal
imaging, presumably due to the wide variation in size, and equal
ventricular pressures precluding easy observation of shunting
• In both early and later gestation, a combination of 2D
ultrasonography and Doppler color imaging can help to identify
VSDs and to minimize false positives
• Although large defects can often easily be visualized by 2D imaging,
the diagnosis should always be confirmed by color Doppler imaging,
which usually demonstrates bidirectional flow across the defects
52. Perimembranous VSDs
• Perimembranous VSDs are seen from several
views, including the left ventricular outflow tract
view and high short axis views
53. • False positives are high, as the membranous septum is the thinnest
part of the septum, and can appear to be missing even when present.
• A perimembranous defect should always be confirmed by color
Doppler.
• Perimembranous defects may be missed if redundant tricuspid valve
tissue covers the defect, preventing visualization of shunting.
• With normal segmental anatomy, the aortic valve and/or tricuspid
valve will always be in the image as a border of the defect.
• If one starts from a four-chamber view, and sweeps cephalad, the
defect is visible just as aortic valve comes into view
54. • Muscular outlet extension of a perimembranous
VSD associated with malalignment of the
infundibular septum is frequently seen as part of
TOF (anterior malalignment) or interrupted
aortic arch (posterior malalignment).
• There is also a higher association with a right
aortic arch which can be detected and may
trigger further genetic workup
55. • Isolated defects in the inlet septum that border the
atrioventricular valves are termed perimembranous
inlet type by Anderson (atrioventricular canal type
VSDs by Van Praagh). This type of defect is best
diagnosed in the four chamber view
• One should carefully inspect for a primum ASD,
common atrioventricular valve, or zone of
apposition in the left atrioventricular valve to ensure
that the defect is not a component of an AVSD.
56. Muscular VSDs
• Muscular VSDs are the most difficult to detect
on fetal imaging, as they are often small and may
have irregular borders.
• They are typically detected by color sweeps using
a low Nyquist limit in the four-chamber and low
short axis views, but may also be noted by 2D
imaging without color
57. Doubly Committed Subarterial VSDs
• Doubly committed subarterial VSDs are the least common
type of VSD and may be confused with a membranous defect
during fetal evaluation, as they are most easily seen sweeping
from the four-chamber view superiorly/anterior to the
outflow tracts.
• Some keys on fetal imaging are to remember that although
one border is the aortic valve (like a perimembranous VSD),
this VSD is not bordered by the tricuspid valve, but is typically
bordered by the pulmonary valve, so that the aortic and
pulmonary valves share a hinge point.
• High short axis imaging is the best view to distinguish doubly
committed subarterial from perimembranous defects
58. • Both muscular and perimembranous VSDs may
close spontaneously, and this may occur in utero
• Studies suggest that between 2% and 31% of
muscular defects close during fetal life, with
another 19% to 75% closing during the next 12
months.
• Up to 15% of muscular defects discovered in
utero will require surgery
59. • For perimembranous defects, studies suggest
• 4% to 35% of these close in fetal life,
• and another 1% to 23% in first 12 months, with
an estimated 42% needing surgery
• Malalignment VSDs and doubly committed
subarterial defects rarely close spontaneously,
and most often require surgical repair.
60. Atrioventricular Septal Defects
• Atrioventricular septal defects (AVSDs) are most
easily demonstrated in the four-chamber view.
This allows easy visibility of the atrioventricular
valve attachments, primum atrial septal defects,
as well as any ventricular septal component.
• Short-axis imaging across the atrioventricular
valves also allows for close inspection of the left
atrioventricular valve for evidence of a common
valve or zone of apposition/cleft
61. • Color Doppler should always be used, as this
may allow better detection of the degree of
ventricular level shunting, as this will
significantly affect counseling.
• Color Doppler can also be used to assess the
degree of fetal atrioventricular valvar
regurgitation, which has been shown to correlate
closely with the degree of postnatal regurgitation
62.
63. • When AVSD is diagnosed in utero, there must be a high
suspicion of genetic abnormalities.
• In one study, the frequency of genetic disorders in
nonheterotaxy AVSD was 74%
• The most common diagnosis was Trisomy 21 (34 of 53
tested fetuses with AVSD), but Trisomy 18 and Turner
syndrome were also associated.
• One study has reported spontaneous in utero closure of
the VSD component in four fetuses with complete AVSD
64. Transposition of the Great Arteries
• Fetal TGA is a malformation often undetected
due to a normal appearing fetal four-chamber
view.
• Of the major congenital heart lesions, it is the
least commonly detected in utero.
• Recently, the addition of outflow tract evaluation
to routine screening has improved its detection
65.
66. • The patent foramen ovale (PFO) and the patent
ductus arteriosus (PDA) are two very important
structures to evaluate in the fetus with TGA and
a functionally intact ventricular septum.
• Abnormal flow in either a PDA and/or an
abnormal or a restrictive PFO may be predictive
of severe neonatal hypoxemia associated with an
increased morbidity and mortality.
67. • In the fetus with TGA the highly oxygenated blood from the placenta
is directed into the left heart crossing through lungs and PDA, which
results in pulmonary vasodilation, deceased pulmonary vascular
resistance, increased pulmonary blood flow, and increased left atrial
filling pressure that can shift the atrial septum to the right or restrict
the PFO.
• In late gestation, abnormal constriction of the PDA may occur due
to the higher oxygen content of the blood traversing it.
• A restrictive PDA is associated with an anatomic constriction or
narrowing and high velocity, turbulent, continuous antegrade flow
through it.
• Retrograde holodiastolic laminar flow into the PDA is abnormal and
also associated with neonatal hypoxemia
68. • In the fetus with TGA, several features of the atrial septum are
considered to be predictive of neonatal hypoxemia because of
inadequate mixing of blood at the atrial level, necessitating
urgent newborn balloon atrial septostomy.
• These concerning findings include a restrictive PFO that is flat
or protruding toward the right atrium, the PFO bowing into
the LA greater than 50% of its width, or a hypermobile PFO
undulating between the left and right atrium.
• Appropriate parental counseling and multidisciplinary
delivery planning is required when a fetus is diagnosed with
TGA and may require an urgent neonatal intervention
69. Congenitally Corrected Transposition
of the Great Arteries
• Congenitally corrected transposition of the great arteries
(CCTGA) is frequently not diagnosed prenatally, possibly
because of the relatively normal chamber sizes on the four-
chamber view
• CCTGA is most easily diagnosed in the fetus utilizing sweeps
in multiple directions to confirm the discordant
atrioventricular and ventriculoarterial relationships
• In the fetus with CCTGA, coexisting lesions are very common,
and include VSD (62% to 79%), pulmonary outflow tract
obstruction (35% to 50%), and tricuspid (systemic AV valve)
valve abnormalities, for example, Ebstein anomaly and
dysplasia (25% to 36%)
70. • Thus careful inspection of the ventricular
septum, atrioventricular valves, and outflow
tracts is important CHB may be present in 6% to
10% of fetuses with CCTGA; thus the fetal heart
rhythm should be evaluated in detail.
• CCTGA in the fetus is also associated with
cardiac malposition, heterotaxy, ventricular
hypoplasia or valvar atresia.
71. • Only 1% to 2% of CCTGA patients have no
additional cardiac anomaly.
• In two fetal series of CCTGA, spontaneous
intrauterine fetal demise (IUFD) was rare,
occurring on 0/14 and 1/30 fetuses; however in
one study of 34 fetuses, 3 had IUFD (9%),
including one with CHB
72. Tetralogy of Fallot and Pulmonary
Atresia with VSD
• Conotruncal defects, reviewed in depth separately, can
represent a challenge to prenatal diagnosis. TOF, double
outlet right ventricle (DORV), PA with a VSD, and interrupted
aortic arch are all thought to result from a disturbance in the
development of the conotruncus.
• These defects may involve abnormal septation of the aorta
and pulmonary outflow tracts, abnormal alignment between
the outflow tracts and the ventricles, and the presence of a
VSD.
• The link between these defects is further highlighted by the
common association with 22q11.2 deletion syndrome, many
with the DiGeorge phenotype
73. • In the long-axis view of the LV, the appearance of a
VSD and overriding of a great vessel can signal the
presence of any of the above lesions.
• In addition, even in a fetus with an isolated VSD
and no conotruncal abnormalities, the aorta may
appear to be overriding in certain views.
• Distinguishing these lesions and searching for
known associated lesions is of the utmost
importance
74. • TOF is the most common cyanotic cardiac defect,
with a birth prevalence of approximately 0.5 per
1000 live births
• Anterior and superior deviation of the infundibular
septum is a pathognomonic feature. An aorta that
overrides the ventricular septum is present ,
although this same characteristic may be present in
truncus arteriosus, PA with VSD, or DORV with
subaortic VSD
75. • The RVOT view, with attention paid to the relationship
between the infundibular and trabecular septum, is crucial to
making the diagnosis.
• Color and spectral Doppler interrogation of the PV and of the
ductus arteriosus, as well as measurement of the PV and main
pulmonary artery can aid in predicting the postnatal outcome,
as retrograde flow in the ductus is associated with a need for
postnatal patency of the ductus arteriosus to maintain
adequate pulmonary flow.
• The presence of associated cardiac anomalies, such as
additional VSDs, a right-sided aortic arch, or pulmonary
artery hypoplasia should be excluded.
76. • PA with a ventricular septal defect (PA-VSD) is viewed by
many to be the most severe form of TOF, with complete
obliteration of the RVOT.
• From the outflow tract views, an overriding aorta is visualized,
and it can be indistinguishable from TOF.
• Determining whether the pulmonary arteries are confluent,
and the source of pulmonary flow are crucial.
• In the case of pulmonary flow fed by a ductus arteriosus,
prostaglandin initiation will be necessary at birth, as will
neonatal surgery to establish a stable source of pulmonary
blood flow
77. • Where pulmonary flow is provided by aortopulmonary
collateral arteries, flow is typically stable at birth.
• In the case of pulmonary flow supplied by a ductus arteriosus,
the ductus is often small and tortuous. A right-sided aortic
arch is common in PA-VSD, and can be detected prenatally
• Just as TOF may be associated with an AVSD, especially in
Trisomy 21, PA-VSD may be associated with an AVSD
• In cases of PA-VSD with an AVSD, careful attention must be
paid to systemic and pulmonary venous return, as this
combination is common in heterotaxy
78. Truncus Arteriosus
• Truncus arteriosus (also known as common arterial
trunk) is a conotruncal defect characterized by a single
outlet from the heart which gives risk to both the
systemic and pulmonary blood flow.
• Truncus arteriosus can be mistaken for PA with a VSD
given a similar LVOT view
• Determining the source of pulmonary blood flow is
essential to distinguishing these two lesions.
• Additionally, the identification of a dysplastic,
regurgitant, truncal valve can aid in making this
distinction.
• The ductus arteriosus is absent in the majority of cases
79. • When the ductus arteriosus is present, arch
interruption and ductal origin of a pulmonary artery
should be excluded.
• Identifying aortic arch interruption is crucial, as this
would signal the need for prostaglandin
administration upon delivery and neonatal surgery
to establish stable systemic blood flow.
• Follow up prenatal echocardiography is important,
as progressive truncal regurgitation, fetal hydrops
and in utero death may develop
80. Double Outlet Right Ventricle
• DORV occurs when both of the great arteries arise from the RV
• The ventriculoarterial alignment results in both the great arteries
positioned at least 50% over the RV
• There is usually a loss of fibrous continuity between the mitral valve
and the posterior semilunar valve.
• DORV is associated with a broad spectrum of intracardiac defects
and great artery relationships, all of which impact on the clinical
presentation and surgical management.
• In DORV, the outlet from the LV is via the VSD DORV types are
classified based upon VSD location.
81. • In subaortic VSD with normally related great arteries, LV output is
directed to the aorta and often there is associated subpulmonary
obstruction.
• The physiology is either that of pulmonary over circulation due to
the VSD or depending on the degree of pulmonary outflow tract and
pulmonary arterial obstruction, physiology akin to TOF.
• When the VSD is subpulmonary, the LV output is directed to the PA
and the physiology is usually similar to TGA with a VSD.
• A subpulmonary VSD may be associated with a subaortic
obstruction, coarctation of the aorta, aortic valvar stenosis or arch
hypoplasia.
82. • Typically when the defect is subpulmonary the
great arteries are side-by-side
• DORV with an uncommitted or doubly
committed VSD are the least common types.
• A perimembranous inlet VSD (atrioventricular
canal type VSD in Van Praagh nomenclature),
which is typically uncommitted is commonly
associated with heterotaxy
83. • DORV can be undetected in the fetus when the four-
chamber view appears normal.
• Recent inclusion of outflow track visualization to routine
screening has significant potential to improve detection
rates
• The location of the VSD and the relationships of the
great arteries can usually be accurately determined on
fetal echocardiography.
• Genetic abnormalities are found in 14% to 20% of fetuses
with DORV, although 22q11 deletion syndrome is rare
84. • DORV can be undetected in the fetus when the four-chamber view
appears normal.
• Recent inclusion of outflow track visualization to routine screening
has significant potential to improve detection rates
• The location of the VSD and the relationships of the great arteries
can usually be accurately determined on fetal echocardiography.
• Genetic abnormalities are found in 14% to 20% of fetuses with
DORV, although 22q11 deletion syndrome is rare
• Fetuses with DORV and multiple extracardiac anomalies have the
worst outcomes
85. • Given this, prenatal counseling for DORV is
highly variable and is based on the intracardiac
anomalies, the great artery relationships and the
presence of extracardiac or chromosomal
abnormalities
86. Aortopulmonary Window
• Aortopulmonary window is a rare condition in which
there is a communication between the ascending aorta
and pulmonary trunk proximal to its bifurcation
• Common associations include interrupted aortic arch,
arch hypoplasia, and VSD. Prenatal diagnosis of
aortopulmonary window is uncommon, but has been
reported
• Two-dimensional sweeps and use of color Doppler allow
visualization of an aortopulmonary window in utero
87. Pulmonary Atresia with Intact
Ventricular Septum
• Pulmonary atresia with an intact ventricular septum
(PA-IVS) is a morphologically heterogeneous lesion
characterized in which there is right ventricular
outflow tract obstruction (RVOTO) either due to an
atretic PV or muscular infundibular atresia
• It is often accompanied by hypoplasia of the right
ventricular cavity, due in part to increased
muscularization of the RV
• Fetal critical PV stenosis may evolve into atresia in
utero
• RV size and growth potential is variable and is
related to the size of the tricuspid (TV) annulus
88. • Fetal PA-IVS with TV/RV hypoplasia exhibits impaired growth as
the pregnancy progresses.
• At mid-gestation the RV may be tripartite with a well-developed
infundibulum. Where the RV is tripartite, the TV z score >−3 and
the RVOT is patent, a biventricular repair is anticipated
• A bipartite RV is a hypoplastic, hypertrophied RV which is nonapex
forming.
• Fetus with PA-IVS and TV z score ≤−3 are more likely to undergo
univentricular repair.
• This group with TV annular hypoplasia also have a high prevalence
of RV to coronary artery fistulae
89. • Fetuses with coronary artery fistulae have a worse long-term
prognosis due to possible RV-dependent coronary flow
• In another study, a fetal score using four measurements in
PAIVS were predictive for a univentricular repair: TV/MV
annulus ratio ≤0.83; PV/AV annulus ratio ≤0.75 RV/LV
length ≤0.64, and TV inflow duration/cardiac cycle length
≤36.5%
• A univentricular repair was performed in all fetuses in whom
four criteria were present and in 92% of those with three
criteria.
• Another study found that while TV annular size was a good
predictor of outcome at all gestational ages, the best
echocardiographic predictors varied by gestational age
90. • Fetal counseling is based upon RV and TV size and
the absence or presence of coronary artery fistulae.
• When fistulae are present, prenatal counseling
should include increased risk of fetal death,
coronary artery insufficiency after delivery, and
possible need for cardiac transplantation.
• Fetal pulmonary valvuloplasty has been shown to
result in improved growth of the RV in selected
fetuses with PA-IVS, and is discussed further in
Section XIII
91. Aortic Arch Hypoplasia and Coarctation
of the Aorta
• Coarctation of the aorta is suspected in the fetus in whom the size of the RV
and pulmonary artery are greater than those of the LV and aorta (Ao) but
with both ventricles apex-forming
• However, a relatively larger RV resulting in an RV:LV size discrepancy is
also a normal finding in late gestation
• At times, the presence of abnormal angulation of the aortic arch or severe
hypoplasia may be clear
• However, more often, ventricular size discrepancy is present without clear
arch hypoplasia.
• Thus, clearly defining coarctation in the fetus is challenging and false
positives are common. n the human fetus ∼41% to 47% of CCO is through
the PDA, while only 35% to 40% of CCO is through the ascending aorta
92. • Given the lower flow in the ascending aorta, the aortic isthmus will appear relatively small
due to the large fetal PDA. The LV output increases by 240 mL/min/kg in the first 2 hours
of life
• The increased LV output and flow through the aortic isthmus along with closure of the PDA
in the newborn will typically unmask a neonatal coarctation if present.
• A posterior shelf or indentation seen at the aortic isthmus in the longitudinal aortic arch
view is observed in some but not all fetuses with coarctation of the aorta
• Monitoring the dimensions and z scores of the RV, PA, LV, and aorta can detect
disproportionate growth of the right heart and decreased growth of the left heart, which
may be a harbinger of neonatal coarctation
• A recent series reported that an aortic isthmus z-score of less than -2 in the fetus was most
predictive of coarctation requiring surgery, followed by visualized of a posterior aortic shelf.
Least predictive was continuous flow throughout systole and diastole in the fetal aortic
isthmus
93. Hypoplastic Left Heart Syndrome,
Hypoplastic Left Heart Complex, and
Fetal Aortic Stenosis
• HLHS has been defined as a spectrum of cardiac malformations,
characterized by a severe underdevelopment of the left heart–
aorta complex, consisting of aortic and/or mitral valve atresia,
stenosis, or hypoplasia with marked hypoplasia or absence of the
LV, and hypoplasia of the ascending aorta and of the aortic arch
• Given inadequate prograde aortic flow, there is obligatory
retrograde flow in the aortic arch
• While this pattern may be seen early in fetal life, it is not
uncommon to see other patterns of left ventricular disease that
may be treated as HLHS in the newborn period. Ultimately, there
are likely several mechanisms which may predispose to left-sided
hypoplasia
94. • Understanding this process has been easier since fetal imaging has
been developed
• Most mechanisms appear to be related to the so-called “no flow, no
grow” phenomena, such that when flow is impaired, growth of the
affected fetal heart structures slows or halts.
• Excluding where there are abnormalities of the cardiac connections
or severe hypoplasia at baseline, fetal left ventricular hypoplasia
may evolve in two general left ventricular phenotypes: reduced
short-axis dimension with normal length, or reduced length with
globular shape
• If the left-sided cardiac structures are not clearly small enough to
meet the criteria for HLHS, the anatomy may be referred to as a
“borderline LV” or “borderline left heart”
95. • The pattern in which the LV is narrow in the short-axis dimension but apex-
forming is most commonly seen when arch hypoplasia is present, and is
often first recognized as left-right ventricular asymmetry
• Mitral valve abnormalities including mitral annular hypoplasia and
parachute mitral valve are common, as is bicommissural aortic valve.
• While subaortic obstruction and aortic annular hypoplasia are commonly
seen in this pattern, moderate to severe AS is not typically seen.
• Endocardial fibroelastosis and ventricular dysfunction are typically not
present.
• This pattern is often referred to as Shone complex, although Shone and
colleagues described a very specific set of anatomic features that are not
always present in this pattern of findings
96. • The Congenital Heart Surgery Nomenclature and Database Project
proposed using the term “Hypoplastic left heart complex” for this pattern of
left heart disease, as first introduced in 1998 by Tchervenkov et al
• For those with a long and thin LV, a main etiology is likely obstruction of
inflow into the LV, as this pattern of hypoplasia has been described with
abnormal or small foramina ovale, aneurysmal atrial septa obstructing
mitral valve flow, 115 and leftward malattachment of the atrial septum
• For most of these patients, the LV actually expands with improved filling
after birth.
• Many children with a long thin LV pattern will require aortic arch repair, as
well as possible mitral valve surgery and/or subaortic or aortic surgery.
Severe cases of this type of left ventricular hypoplasia may require single
ventricle palliation
97. • The second pattern associated with left ventricular
hypoplasia, in which the ventricle does not develop along
its long axis and as a result is globular—“short and fat”—
is almost universally noted with severe fetal AS.
• In fetal AS, the LV first becomes dilated and severely
dysfunctional
• Endocardial fibroelastosis develops, and the pressure
generated by the LV decreases.
• Left ventricular growth halts, any rightsided structures
grow around the left heart
98. • Fetal AS with a dilated LV detected before 30 weeks of
gestation will likely result in HLHS, although the prognosis
when the dilated LV is detected later in gestation is unclear
• Endocardial fibroelastosis and ventricular dysfunction are
nearly universal in late-gestation fetal AS.
• Mitral valve abnormalities and arch obstruction are also very
common.
• Fetal AS is particularly easy to miss during cardiac screening,
as the LV may appear normal on the four-chamber view after
a period of dilation and ongoing growth arrest, although
dysfunction is severe
99. • Clues for development of HLHS in the fetus with
AS in the absence of a severely small LV are
severe LV dysfunction, endocardial fibrosis (an
echobright lining of the LV endocardium)
monophasic mitral inflow retrograde flow in
aortic arch and left to right flow across the atrial
septum
100. • A portion of patients with HLHS, HLHC, and AS will develop
severe restriction at the atrial septum or closure of the
foramen ovale which confers a much worse prognosis as there
is inadequate exit of pulmonary venous flow
• For this reason, fetal intervention or emergent postnatal
intervention may be offered, as discussed in section XIII of
this chapter
• In these cases the pulmonary veins often appear dilated, and
pulmonary venous flow is both prograde and retrograde.
• The pattern of pulmonary venous flow serves as a key to
postnatal severity of disease
101. • The ratio of prograde to retrograde flow in the
pulmonary vein has also been shown to be useful
, with ratios being associated with a high
likelihood of need for urgent postnatal
intervention
• One study has demonstrated that a decreased
fetal pulmonary vascular response
102. Cardiomyopathy
• Fetal cardiomyopathy, when defined as systolic
dysfunction or significant hypertrophy, is a
relatively common finding in utero and accounts for
11% of cardiac disease diagnosed in the fetus.
• Therefore, upon diagnosis a thorough evaluation of
the fetus for reversible underlying causes must be
undertaken.
• This is crucial, as outcomes of fetuses with
cardiomyopathy is generally poor, and worsens if a
cause is not found and treated
103. • The fetal myocardial response to volume loading,
pressure loading, and/or inflammation can be
indistinguishable from an intrinsic myocardial
abnormality.
• A recent review of fetuses diagnosed with left ventricular
noncompaction demonstrated that the majority (92%)
had coincident structural heart disease.
• This group of patients represents a particularly high-risk
cohort, as 81% of patients with known followup died or
underwent heart transplantation
104. • A single institution review from The Hospital for Sick
Children in Toronto, Canada represents the largest
review of primary fetal cardiomyopathy to date.
• In addition to those without any identifiable cause of
cardiomyopathy, this review included fetuses with
infectious, inflammatory and genetic/metabolic disease,
as well as those with anemia and with dysrhythmias.
• Their findings suggest that predictors of poor outcome
include CPS ≤6, cardiomegaly, evidence of diastolic
dysfunction, increased ventricular thickness, and fetal
hydrops.
105. • A smaller series from Texas Children's Hospital included only fetuses without any
identifiable cause of cardiomyopathy.
• This series also identified that hydrops was a strong predictor of fetal death.
• While no patient with CPS >6 sustained fetal or neonatal demise, a low CPS score was not
found to be a useful predictor of perinatal outcome.
• Importantly, both series found elevated MPI to be a common finding in fetuses with
cardiomyopathy, but limited in its ability to predict outcome.
• Overall reported survival for fetal cardiomyopathy has improved dramatically over time,
potentially related to improved rates of diagnosis in the less severe cases.
• In contrast to earlier reports, in which the majority of fetuses had severe cardiomyopathy
with accompanying hydrops, recent series have reported survival to infancy to be as high as
89%, and survival to 1 and 5 years to be as high as 85% and 75%, respectively
106. Tumors
• Cardiac tumors are a rare indication for fetal
echocardiography.
• Regardless of the type, the primary concern in the
evaluation should be for obstruction to ventricular
inflow or outflow and for dysrhythmia
• Fetal dysrhythmia, large tumor size, and fetal
hydrops are strongly associated with in utero or
neonatal death, irrespective of treatment strategy
107. • The majority of intracardiac tumors diagnosed in fetal
life are rhabdomyomas, marked by their heterogeneous,
echogenic appearance, and origin from the ventricular
septum or free wall
• Rhabdomyomas may increase in size during fetal life,
and they typically regress during postnatal life.
• While over half of fetuses diagnosed with
rhabdomyomas are ultimately diagnosed with tuberous
sclerosis, factors associated with a diagnosis of tuberous
sclerosis include multiple cardiac tumors and a family
P.163 history of tuberous sclerosis
108. • Other cardiac tumors diagnosed in fetal life include
fibromas, myxomas, teratomas, and hemangiomas.
• Hemangiomas are markedly heterogeneous, with cystic
and solid components.
• Teratomas are typically located in the pericardial cavity,
associated with a pericardial effusion, and are high-risk
lesions.
• Fibromas, in contrast, are homogeneous in appearance,
and are frequently associated with a benign course.
109. Pericardial Effusions
• Pericardial effusions are rarely seen in isolation
and are typically associated with a primary
abnormality, including structural heart disease,
dysrhythmias, chromosomal abnormalities, or
extracardiac defects.
• While a pericardial effusion associated with
these defects is generally regarded to convey
high risk, outcomes for fetuses with isolated
pericardial effusions are generally favorable
111. Twin–Twin Transfusion Syndrome
• TTTS affects 8% to 20% of monochorionic diamniotic
pregnancies, and is the major cause for fetal death in
these pregnancies
• Prevailing theories concerning the pathophysiology of
TTTS include an imbalance of blood volume and
circulating hormonal mediators due to placental vascular
connections.
• This imbalance results in a larger, “recipient” twin with
polyhydramnios and varying degrees of cardiomyopathy,
and a smaller, “donor” twin with oligohydramnios which
is typically free of cardiac findings
112. • In 1999, Quintero et al. published a staging system to stratify TTTS
risk based on the obstetric ultrasound.
• Despite the lack of cardiac functional parameters in this system, it
remains the most commonly used tool in clinical and research
practice.
• The presence of TTTS is defined by polyhydramnios in the large
(recipient) twin and oligohydramnios in the small (donor) twin.
• Advancing Quintero stage is defined by: absence of fluid in the
donor bladder, abnormal Doppler studies of the umbilical cord
and/or ductus venosus, the presence of fetal hydrops, and the
presence of fetal death.
113. • Laser coagulation of the vascular connections has proven
superior to amnioreduction alone for the management of
TTTS although both donor and recipient fetuses remain at
risk for development of structural cardiac defects,
cardiomyopathy, fetal and postnatal death, and postnatal
neurologic disability despite laser therapy.
• To date, published outcomes for laser ablation are highly
variable.
• Survival of both fetuses varies from 35% to 74%, survival of at
least one fetus varies from ∼82% to 88%, and overall
perinatal survival is approximately 65% following laser
therapy
114. • While the Quintero system has been useful in identifying those fetuses with advanced-stage
TTTS and predicting outcome after amnioreduction, its ability to predict outcome at lower-
stage TTTS and after laser therapy is limited
• The application of more sophisticated cardiac scoring systems to those fetuses with stage I
or stage II TTTS has identified subpopulations within these groups with relatively
significant cardiomyopathy
• These scoring systems involve the incorporation of cardiac specific findings of systolic or
diastolic dysfunction into the evaluation of fetuses with TTTS.
• These findings include elevated MPI, ventricular hypertrophy, valvar regurgitation,
cardiomegaly, monophasic AV valve inflow, and systolic dysfunction.
• Furthermore, emerging data have identified diastolic abnormalities in monochorionic
diamniotic twins who do not yet meet criteria for TTTS based on standard ultrasonographic
criteria at the time of evaluation but who eventually develop TTTS
115. • These data, in addition to the relatively common
incidence in monochorionic diamniotic
pregnancies and the high-risk nature of TTTS,
have led to the recommendation that all
monochorionic diamniotic gestation pregnancies
receive a thorough fetal cardiovascular
evaluation
116. Twin Reversed Arterial Perfusion
• Twin reversed arterial perfusion (TRAP) sequence refers to a rare complication of
monochorionic twin gestations with an incidence of ∼1 in 35,000 pregnancies.
• In this condition, one twin without functional cardiac activity fails to fully develop, and its
blood supply is fed by the normally developed “pump” twin.
• Owing to its rare nature, specific outcome measures and predictors of death are lacking.
• Despite these limitations, it is well regarded that this disease carries high-risk, with less
than 50% of the “pump twins” surviving in utero without intervention and a high risk for
severe prematurity and neonatal death in liveborns
• A recent metaanalysis of retrospective studies of fetal laser treatment for TRAP sequence
suggests improved survival of the pump twin with treatment. Overall neonatal survival in
treated cases was 80% in the studied group
117. Congenital Diaphragmatic Hernia
• n congenital diaphragmatic hernia (CDH), the presence of
abdominal contents in the thorax results in varying degrees of
pulmonary hypoplasia and pulmonary hypertension.
• Typically, the degree of pulmonary parenchymal and vascular
disease is the primary factor that determines prognosis.
• However, in approximately 18% to 30% of infants born with CDH,
coincident structural heart disease is seen
• The presence of structural heart disease has been associated with
increased mortality in CDH in a number of retrospective reviews
• More recently, studies have identified an association between the
severity of heart defects and mortality, with major cardiac defects
associated with increased risk for mortality
118. • Separate from coincident structural heart disease, CDH can be associated
with hypoplasia of left-sided cardiac structures
• This is likely due to a combination of a mass effect on the left atrium and
LV, as the degree of hypoplasia tends to improve upon reduction of
abdominal contents. Other proposed mechanisms of left-sided hypoplasia
are diminished pulmonary flow and diminished flow across the foramen
ovale owing to abnormal geometry of the IVC and cardiac mass
• In fact, one report which examined the effects of balloon occlusion of the
fetal trachea to improve pulmonary development demonstrated larger
postnatal left-sided cardiac structures in fetuses who did not undergo
tracheal occlusion
• While the majority of patients with CDH and left-sided hypoplasia in utero
do not have pathologic left heart hypoplasia postnatally, more severe left-
sided hypoplasia may contribute to the development of coarctation of the
aorta
119. Sacrococcygeal Teratoma/Vascular
Malformation
• High-flow vascular malformations such as
sacrococcygeal teratoma, chorioangiomas, and
arteriovenous malformations have been associated
with increased estimated CCO, cardiomegaly,
worsened CPS, hydrops, and fetal death
• When associated with fetal hydrops at a previable
gestational age, high-flow malformations are almost
universally fatal. Evaluation of fetuses with these
malformations has progressed significantly in the
last decade owing to the recognition that early, in
utero intervention for many may improve outcomes
120. Ectopia Cordis/Pentalogy of Cantrell
• Ectopia cordis is an extremely rare and often lethal condition
• It is marked by displacement of all or part of the heart outside of the thorax and is further
categorized into cervical, thoracocervical, thoracic, thoracoabdominal, and abdominal
forms
• Coincident congenital heart defects are common.
• While various structural defects have been reported, conotruncal abnormalities such as
DORV, TOF, and TGA seem to predominate
• The diagnosis of ectopia cordis can be subtle, and missed in utero where there is only mild
displacement outside the thorax.
• Coincident defects in the abdominal wall should prompt careful inspection of the position
of the heart. Fetal and postnatal death is common in the setting of ectopia cordis, although
cases of survival following repair of the thoracic defect have been reported
121. • Complete pentalogy of Cantrell is a condition in
which there is an anterior diaphragmatic deficiency,
midline abdominal wall defect, diaphragmatic
pericardial defect, and a lower sternal defect.
Incomplete cases are also reported.
• Associated intracardiac defects are common,
including atrial and VSDs, TOF, and Ebstein
anomaly
• Mortality is common particularly in complete cases
and in those with coincident extracardiac anomalies
122. Omphalocele and Gastroschisis
• Abdominal wall defects are defined by extrusion of intestinal contents
outside of the abdomen.
• Gastroschisis is an isolated defect in the abdominal wall, and is typically
located to the right of the umbilical cord insertion site.
• Gastroschisis most commonly occurs in isolation, and is rarely associated
with genetic or cardiac disease
• Omphalocele, in contrast, typically includes the umbilical cord insertion
site.
• It may include liver, and is commonly associated with syndromic,
chromosomal, and/or cardiac disease.
• While the concurrent diagnoses of omphalocele and cardiac structural
disease typically carries a poor prognosis, coincident genetic disease and
pulmonary hypertension may also play a significant role
123. Fetal Arrhythmia
• Abnormalities of fetal cardiac rhythm are an important aspect of
fetal cardiology, accounting for 12% to 20% of referrals for fetal
echocardiography.
• Ectopy is estimated to occur in at least 1% to 3% of pregnancies
• however, only about 10% of those evaluated fetal arrhythmias have
the potential to be life threatening .
• Fetal rhythm disturbances may occur in isolation or in association
with a variety of other conditions affecting the fetus or mother such
as intrauterine growth retardation, TTTS, hydrops, infections, fetal
hypoxia, fetal cardiomyopathy or CHD, maternal medications,
stimulant exposure, or thyroid perturbations..
124. • The fetal cardiologist must evaluate the type,
mechanism, and etiology of the arrhythmia,
assess its hemodynamic effects, screen for
associated CHD, and decide on the optimal
management strategy.
• The fetal cardiologist must communicate and
work closely with the obstetrician and maternal
fetal medicine specialist to provide optimal, safe,
and efficacious fetal therapy
125. • Fetal echocardiography currently remains the most readily available and
widely used tool to assess fetal arrhythmias.
• The chronology and temporal relationship of atrial and ventricular
contractions demonstrated by fetal echocardiography allows one to infer
the electrical activation of the heart and thus the mechanism of the
arrhythmia.
• Spectral and color Doppler and M-mode recordings are routinely utilized,
and tissue Doppler has also been reported.
• The mechanical analog of the PR interval is measured from the onset of
flow with atrial contraction to the onset of ventricular systolic flow.
• Normal values for gestational age have been reported, and are longer than
the measured electrical PR interval
126. • Pulsed spectral Doppler across inflow/outflow: The A wave of tricuspid or
mitral inflow correlates with flow from atrial contraction, and prograde flow
across the aortic or PVs correlates with ventricular systole.
• 2. SVC/ascending aorta or pulmonary vein/pulmonary artery simultaneous
spectral Doppler: Retrograde flow in the SVC or pulmonary vein represents
atrial systole and aortic or pulmonary artery flow represents ventricular
systole.
• 3. M-mode allows recording of the sequence and time relationship of atrial
and ventricular systolic wall movements. The M-mode cursor should
traverse the most mobile region of the atria and ventricles to optimally
display muscle contraction.
• 4. Tissue Doppler: Allows examination of simultaneous atrial and
ventricular segmental wall motion. The time interval from the onset of Aa to
the onset of IV correlates well with the electrical PR interval
127. • Transmaternal fetal electrocardiogram (ECG)
can permit measurement of electrical intervals
during stable rhythm in the early gestation fetus
and normal values for gestational age have been
published by Taylor and coworkers.
• However, fetal ECGs are limited in their clinical
utility by low signal to noise ratios and, in later
gestation, to the attenuation of the electrical
signal secondary to the vernix caseosa
128. Irregular Rhythm
• Premature atrial contractions (PACs) are the most frequent cause of
ectopy in the fetus, occurring 10 times more frequently than
premature ventricular contractions (PVCs).
• They have been associated with the presence of a floppy, aneurysmal
septum primum .
• Although most often benign, approximately 0.5% to 1% of fetuses
ultimately develop supraventricular tachycardia (SVT) .
• The risk for SVT appears to be significantly higher in those with
couplets or blocked atrial bigeminy.
• Fetuses with infrequent ectopy persisting >1 to 2 weeks as well as
those with frequent ectopy, defined as bigeminy, trigeminy, or
>every 3 to 5 beats, should be referred for an echocardiogram .
129. • The initial study should confirm the mechanism
of the arrhythmia, observe for tachycardia, and
assess for any abnormalities of cardiac structure
or function.
• By examining the relationship of mechanical
atrial and ventricular contractions, PACs may be
distinguished from other more concerning
causes of irregular rhythm including PVCs or
second-degree atrioventricular block (AVB)
130. • Being of atrial origin, PACs “reset” the sinus
node, so there is a pause in atrial activity before
the next sinus beat.
131. PVC
• When a PVC occurs, the atrial rhythm usually remains unaffected, exhibiting a regular
cadence from the sinus node.
• PVCs can occur in fetuses with long QT syndrome, myocarditis, or cardiomyopathy (299).
• The risk for development of ventricular tachycardia (VT) in the fetus with PVCs is
unknown.
• If the fetal cardiologist does not detect any tachycardia, or evidence to raise the suspicion
for tachycardia outside of the scan time (such as tricuspid regurgitation, pericardial
effusion, ventricular dysfunction, abnormal fetal vessel flow), then serial fetal
echocardiograms may not be necessary.
• However, the obstetrician or maternal–fetal medicine specialist should follow fetuses with
PVCs or frequent PACs weekly to monitor the heart rate and rhythm as long as the
arrhythmia persists
132. Bradycardia
• Fetal echocardiography is recommended to
determine the cause of bradycardia and assess for
associated ventricular dysfunction or CHD.
• Subsequent serial examinations are recommended
to monitor rate, rhythm, and ventricular function if
bradycardia is persistent.
• The mechanisms for bradycardia in the fetus include
sinus bradycardia, blocked atrial bigeminy, and
AVB.
133. Sinus Bradycardia
• Persistent fetal sinus bradycardia may be
autoimmune mediated or infectious.
• Evaluation should therefore include
• maternal IgG and IgM for parvovirus
• TORCH diseases
• maternal anti-SSA(anti-Ro) and SSB (anti-La)
antibodies .
• Fetal distress or abnormalities of the nervous
system may also result in sinus bradycardia.
134. • Secondary sinus bradycardia may be related to
• maternal medications (e.g., beta-blockers)
• maternal conditions such as hypothyroidism.
• With heterotaxy syndrome, ectopic or low atrial foci
generate fetal bradycardia typically in the range of
77 to 130 bpm, but can become lower as pregnancy
progresses .
• These fetuses can be at risk for the development of
hydrops, cardiac dysfunction, and fetal death.
135. • Persistent mild sinus bradycardia below the third
percentile for fetal age in an normal heart should raise
concern for congenital long QT syndrome.
• Although fetuses are typically asymptomatic from the
mild sinus bradycardia, it is important to monitor
serially for the development of VT or second-degree AV
block.
• Drugs that prolong the fetal QT interval and electrolyte
abnormalities such as hypomagnesemia or hypocalcemia
should be avoided in these expectant mothers
136. Bradycardia Due to Blocked Atrial
Bigeminy
• In blocked atrial bigeminy, the PAC is not conducted as the AV node
is still refractory from the previous sinus beat.
• This rhythm can be distinguished from 2:1 or complete AVB by
examining the atrial and ventricular contraction patterns
• In AVB, the atrial rate is consistently regular and faster than the
ventricular rate.
• In blocked atrial bigeminy, the atrial rate is regularly irregular, with
a short A-A interval (sinus beat to PAC) followed by a longer A-A
interval (PAC to delayed beat from “reset” sinus node)
• The first atrial (sinus) beat is followed by a ventricular contraction
with a consistent AV interval. The subsequent early premature beat
will demonstrate no corresponding ventricular contraction
137. • Assessing isovolumic contraction times has been reported to aid in
differentiating blocked PACs from immune-mediated AVB, with
AVB fetuses demonstrating longer ICTs (60.9 ms vs. 13.6 ms for the
blocked PACs).
• Blocked atrial bigeminy typically results in ventricular rates between
75 and 90 bpm.
• Rates below 65 should increase suspicion for AVB. Fetuses with
normal hearts are usually asymptomatic, thus blocked atrial
bigeminy does not require antiarrhythmic therapy.
• Expectant mothers should be advised to avoid stimulants such as
caffeine. While atrial ectopy persists, the fetal heart rate should be
monitored weekly, as blocked atrial bigeminy increases the risk for
SVT more than random isolated PACs
138. Bradycardia due to atrioventricular
block
• Between 90% and 95% of fetal AVB is related to either an
isoimmune process (40%) or a structural abnormality of the
conduction system in complex CHD (50% to 55%).
• Management in either situation includes close serial assessment of
the fetal heart rate and observation for the development of heart
failure.
• If the fetal heart rate drops below 55 bpm or if there are signs of
fetal heart failure, hydrops or underlying severe CHD, maternal
treatment with beta-sympathomimetics may be used to augment the
escape ventricular rate .
• Terbutaline is a commonly used, generally well-tolerated agent
139. • Structural defects associated with AVB include CCTGA,
heterotaxy with LAI, DORV, and AVSD.
• The prognosis for fetuses with congenital AVB and
structural heart disease is generally poor. In one study
from two tertiary referral centers, only 9 of 16 such
pregnancies intended to carry to term resulted in live
births, and only 3 were still alive at 1 year of age.
• In a more recent and optimistic study at a single
institution, 5 of 7 fetuses (71%) with AVB and LAI
survived to live birth, and remained alive at a year of age
140. • The true prevalence of anti-SSA anti-SSB maternal autoantibodies
in the general population is not known, but fetal AVB may develop
regardless of the presence or absence of overt maternal symptoms of
lupus or Sjogren Syndrome.
• High SSA levels (≥50 U/mL) appear to correlate with increased fetal
risk
• In pregnancies of known serology positive mothers with no
previously affected children, between 1% and 5% of fetuses develop
AVB).
• If a previous child had AVB or neonatal lupus, the risk increased
strikingly to between 11% and 19%. The presence of maternal
hypothyroidism or vitamin D deficiency further increases the risk
141. • AV conduction can be assessed by measuring the mechanical PR
interval in at-risk fetuses.
• However, it has not been possible to demonstrate a progression
from first-degree AV block to second-degree AV block and then
complete AV Block in all fetuses.
• Serial fetal echocardiographic screening is recommended in
expectant mothers with known +SSA/SSB autoantibodies beginning
at 16 weeks, then weekly or every other week to 28 weeks in a first
child .
• For mothers with a prior child with AVB or neonatal lupus,
screening at least weekly from 16 to 28 weeks is recommended
142. • In addition to screening for AVB, serial fetal echocardiograms
should include observation for tachyarrhythmia, including atrial
flutter (AFL), VT, or junctional ectopic tachycardia, all of which
have been reported in fetuses with isoimmunization .
• Mitral or tricuspid valvitis, pericarditis, myocardial dysfunction, or
endocardial fibroelastosis (EFE) may coexist
• Concern for myocardial involvement may justify additional fetal
echocardiographic assessment in the third trimester even if the
rhythm has remained sinus throughout gestation .
• Untreated, fetal mortality ranges from 9% to 34%, with risk of
death increased in those diagnosed before 20 weeks, or with a
ventricular rate
