Key Points
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Current evidence suggests that prenatal diagnosis of congenital heart disease (CHD) reduces morbidity and mortality, gives expectant parents time to prepare and allows planning for delivery in a tertiary care centre.
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About 85% of babies born with CHD are born to mothers that are ‘low risk’, suggesting that screening of the entire pregnant population is essential to optimise detection.
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A comprehensive fetal heart examination protocol, such as the standardised five transverse views, should be incorporated into routine second trimester anatomy screening.
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Suspicion of a cardiac defect should result in referral to a specialist in fetal cardiology
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Management of CHD requires a multidisciplinary team including paediatric cardiology, fetal medicine, obstetrics, neonatology and nursing. Delivery in a tertiary care centre is required for fetuses with duct dependent cardiac lesions or multiple anomalies to coordinate delivery and postnatal interventions
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In almost all pregnancies with CHD, vaginal delivery can be attempted unless there are maternal/obstetric indications for caesarean section. Contraindications to vaginal delivery include congenital heart block and poor cardiac function. Induction of labour may be required if the mother does not live near the tertiary centre or to coordinate perinatal services such as equipment or surgical expertise.
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In selected cases of aortic or pulmonary valve stenosis or intact atrial septum, fetal cardiac intervention may be considered.
Overview
Introduction
Congenital heart disease (CHD) affects about 6 to 9 per 1000 live-born infants; however, the prenatal prevalence is higher because some affected pregnancies result in spontaneous fetal demise, and others will be terminated. About half have major CHD defined as requiring intervention within the first year of life, and just under half of these have important right or left ventricular outlet or arch obstruction and are duct dependent (often called critical CHD ), requiring early intervention soon after birth as the arterial duct closes. The unique features of the prenatal circulation (placenta, ductus venosus (DV), foramen ovale (FO), arterial duct) allow compensation for structural malformations of the heart in utero , and most fetuses with isolated CHD survive to delivery without hydrops. It is estimated that 85% of babies born today with CHD will survive to adult life. The population of adults with CHD is larger than children and is growing rapidly. However, approximately one third of fetuses diagnosed with CHD also have either additional malformations or aneuploidy. Therefore a combined prenatal approach is essential to appreciate the extent of the problems that will require treatment in the perinatal period. Caution should be exercised in perinatal planning because the full extent of a fetus’ malformations, particularly those affecting the upper airways or oesophagus, may not always be recognised prenatally.
Screening for Congenital Heart Disease
Most national screening programs now offer routine population screening, and this is a significant improvement on previous years where CHD screening was only offered to the 15% of pregnancies that were identified through patient history as ‘high risk’.
When there is a history of major CHD, fetal echocardiography at 11 to 14 weeks’ gestation may be diagnostic or reassuring, but interpretation of first trimester heart scans requires special expertise and caution. Some types of major CHD will not be detected at 11 to 14 weeks, particularly semilunar valvar abnormalities, atrioventricular septal defect (AVSD) (because the atrioventricular (AV) septum is still developing) and anomalies of pulmonary venous connection. The increased demand for early fetal echo arising from the nuchal translucency programme (see Chapter 19 ) is likely to recur from the newer tests such as cell-free DNA testing with expanded panels (see Chapter 22 ). The appropriate management of screen-positive results requires careful planning. The optimum time to perform fetal echocardiography will remain during the second trimester anatomy scan. We recommend all women undergo competent cardiac screening as part of their anatomy scan, and if the findings suggest a structural or functional abnormality, referral should be made to a specialist who can perform a full fetal echocardiogram (defined later). The individual may have a fetal medicine or cardiology background. Although specific counselling for cardiac disease is best done by a cardiologist, a team approach is encouraged to provide optimal advice and streamline pregnancy and perinatal management.
In countries where the five transverse view protocol has been supplemented with practical teaching support, there has been an encouraging increase in the prenatal diagnosis of CHD over the past decade. Many series now report an overall 60% prenatal detection rate, but it still tends to be lower for lesions identified predominantly by outflow tract abnormalities such as complete transposition of the great arteries (TGA). It remains higher (∼85%) in centres co-located with fetal medicine facilities where confirmation of suspected abnormality and practical teaching are more readily available to the screening team. The majority of important cardiac defects are detectable during pregnancy, but not all are obvious in the mid-second trimester. Valvular abnormalities such as aortic and pulmonary stenosis may be progressive during pregnancy and manifest during the third trimester, so it is wise to examine the heart at follow-up scans for fetal growth and placental lie. Isolated anomalous pulmonary venous connection is notoriously difficult to detect.
Effects of Prenatal Congenital Heart Disease Screening
An effective screening program should provide evidence of benefit. Prenatal detection of CHD confers several advantages:
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Prenatal diagnosis allows parents to understand the nature of the cardiac lesion and to discuss available treatment options and the prognosis to ultimately come to an informed decision.
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The options include expectant management, transfer of care to a specialised centre, invasive diagnostic procedures or termination of pregnancy. It has been shown that parents prefer comprehensive information to make an informed choice, particularly including information about the quality of life.
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The identification of extracardiac anomalies or a chromosomal or genetic abnormality may significantly alter the prognosis. In selected patients, fetal cardiac intervention may alter the natural history and improve surgical options.
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The most important reason to optimise prenatal screening is its direct impact on postnatal outcome. A reduction in mortality, morbidity and preoperative brain injury has been observed in TGA, outflow tract obstruction and coarctation of the aorta (CoA).
Examination of the Fetal Heart
In 2001, Yagel and colleagues proposed a standardised sonographic approach to simplify routine prenatal cardiac screening based on five transverse planes: abdominal situs, four-chamber, left ventricular outflow tract (LVOT), right ventricular outflow tract (RVOT) and three-vessel and tracheal (3VT) views. ( Fig. 29.1 ). This approach has been broadly accepted by the boards of international societies providing ultrasound guidelines. A checklist is provided in Table 29.1 . Incorporation of colour Doppler in the four-chamber and 3VT views provides important additional information at routine screening.
| Transverse view | Items |
|---|---|
| Situs |
|
| Four-chamber |
|
| LVOT |
|
| RVOT |
|
| 3VT |
|
When an abnormality is suspected in these views, the pregnancy should be referred to a team that can perform a comprehensive fetal echocardiogram, which is intended to be diagnostic. It builds on the five transverse views and includes additional imaging planes: short-axis views of the ventricles and great arteries will demonstrate the morphology and arrangement of the four cardiac valves; coronal views will profile the atrial appendages, atrial septum and systemic venous connections and sagittal planes to clarify suspected abnormality of the aortic arch, such as coarctation or interruption detected in the 3VT. The addition of colour and pulse-wave Doppler evaluation of cardiac flows and interrogation of the systemic and pulmonary venous systems complete the comprehensive diagnostic fetal echocardiogram. Most fetal medicine specialists also routinely incorporate umbilical cord and middle cerebral Doppler studies.
Management of Pregnancies with Congenital Heart Disease
After a cardiac defect and the presence of additional defects or chromosomal abnormalities are confirmed, the family will be offered counselling with a multidisciplinary team. Evaluation in a fetal medicine centre provides the optimal setting for pregnancy management (of the pregnant woman and her fetus) and perinatal planning.
The discussion should cover the need for additional tests to help confirm the diagnosis or diagnose suspected chromosomal associations, pregnancy options such as termination of pregnancy or comfort care after delivery, within local and national laws. For ongoing pregnancies, serial sonographic evaluation, every 4 to 6 weeks, is usually arranged, with complementary imaging such as magnetic resonance imaging (MRI) and consultation with the postnatal surgical teams (cardiovascular and paediatric surgery) as appropriate. At each visit, it is wise to reevaluate the anatomy, the presence of extracardiac malformations, fetal growth and well-being and to check for haemodynamic instability. The majority of fetuses with congenital heart disease can be delivered vaginally at term.
Fetuses with critical CHD or who have additional malformations (or uncertain findings) should be delivered in a facility where the appropriate specialists are co-located to provide the expertise required to evaluate and treat the baby in the first hours after delivery and to avoid separation of the mother and baby.
Neurodevelopmental Delay
An increased risk for neurodevelopmental delay has been recognised for many years in children with CHD. The initial perception that this was entirely postnatal in origin, associated with perinatal events and cardiac surgery is changing. Neurocognitive deficits are seen commonly in children with hypoplastic left heart syndrome (HLHS) but are also reported in those with TGA. Prenatal diagnosis was rare in these series, and neurocognitive deficits appear to be less prevalent and less severe in children with a prenatal diagnosis of TGA. Studies are ongoing, and brain abnormalities described on prenatal and presurgical imaging such as functional MRI may not necessarily correlate with postnatal functional abnormality.
Further information is required to provide guidance for counselling families about the likelihood of important neurodevelopmental deficit in their fetuses with CHD.
Important lesion-specific issues are outlined in the section on perinatal management.
Prenatal Therapy
Certain CHD lesions will promote discussion with families whether prenatal therapy is indicated. Aortic stenosis (AoS) and pulmonary stenosis (PS) and a restrictive FO have been treated prenatally with mixed results. The rationale of fetal therapy is to restore near-normal circulation and thus prevent ventricular involution and maintain a two-ventricle circulation postnatally (for AoS and PS) and to protect the pulmonary bed in HLHS and enable a more successful Fontan procedure. Experience suggests there is a more limited role for fetal aortic or pulmonary valvuloplasty than was originally anticipated, in part because case selection and timing are difficult to assess. Single-centre selection criteria have been developed and subsequently modified but have not been independently verified in other populations. In countries with established fetal valvuloplasty programs, a new diagnosis of AoS of PS could be discussed with the family and, if agreed, evaluated with the experienced interventional team to decide whether a procedure is likely to make a lasting difference. At present, there is no evidence from a trial to inform the discussion further.
Specific Lesions
Lesion with Abnormal Four-Chamber View
Hypoplastic left heart syndrome
Overview
Hypoplastic left heart syndrome is not a specific malformation but rather describes a spectrum of left heart hypoplasia occurring in about 3.5% of all babies born with CHD. The classical definition is aortic atresia or stenosis with mitral atresia or stenosis; usually there is an intact ventricular septum or small ventricular septal defect (VSD).
Pathophysiology
In almost all cases, the mitral valve is either stenotic or imperforate. Thus flow through the FO is reversed, being predominantly left to right. The ascending aorta is usually hypoplastic, and the arterial duct supplies blood to the upper half of the body. Appreciation of the atrial communication is critical in the presence of left heart obstruction because an intact or restrictive atrial septum causes abnormally high pressures in the pulmonary vasculature and results in ‘arterialisation’ of the pulmonary veins and lymphatic dilation (lymphangiectasia).
Associated anomalies
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HLHS includes the spectrum of features of left heart hypoplasia.
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Extracardiac malformations occur in about 30%. Growth restriction is overrepresented in HLHS and affects about 20% of all fetuses.
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Chromosomes are abnormal in 10% to 15%, including Turner syndrome (which is common in the early first trimester, when pregnancy loss occurs), trisomies 18 and 13; and Holt-Oram, Noonan, Jacobsen and 22q11 syndromes.
Ultrasound findings
The four-chamber view is abnormal showing a hypoplastic left ventricle (LV). The mitral valve appears atretic or is absent with a thick band of fibrous tissue separating the left atrium (LA) from the LV. In the LVOT view, the aortic valve is thickened. The ascending aorta is hypoplastic, and reversal of flow in the transverse aortic arch can be seen using colour Doppler in the 3VT. The size of the FO and flow across it can be assessed from the four-chamber view with the septum perpendicular to the ultrasound beam ( Fig. 29.2 and 
) or from a short-axis view of the heart in the coronal plane. Pulsed-wave Doppler of the pulmonary veins may demonstrate reversal of the A wave with restrictive atrial septum. Severe tricuspid valve (TV) regurgitation may indicate right ventricular dysfunction and indicates a poor prognosis.
Specific features to check at follow-up and perinatal management
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Check for flow across mitral and aortic valves.
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Measure left heart dimensions (mitral valve, LV, aortic valve, ascending aorta, transverse aortic arch) and obtain gestational age–adjusted z-scores.
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Check appearance and mobility of the atrial septum.
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Check flow across the FO.
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Check the TV for regurgitation
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Check the direction of flow in the transverse arch.
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Offer invasive diagnosis.
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Consider referral for prenatal atrial stenting in cases with restrictive FO.
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Plan delivery in a tertiary care centre to maintain ductal patency with prostaglandin E (PGE); prepare for urgent balloon atrial septoplasty or surgery in cases with restrictive or closed FO.
Treatment and outcome
Hypoplastic left heart syndrome is a duct-dependent lesion; PGE is given after birth to maintain ductal patency, and the three-staged ‘Norwoods’ procedure or a hybrid is performed ( Fig. 29.3 ). Stage 1 consists of LVOT reconstruction and systemic-to-pulmonary shunt placement between the subclavian and the branch pulmonary artery (Blalock-Taussig shunt) or the right ventricle and the pulmonary artery (Sano shunt) during the first days of life. Stage 2 (Glenn operation) includes redirection of venous return from the superior vena cava (SVC) into the pulmonary artery. Stage 3 (Fontan completion) is redirection of blood from the inferior vena cava (IVC) to the pulmonary artery. The early survival rate for the Norwood stage 1 operation may be 90% in fetuses without risk factors, but the overall survival rate to school age is about 50% to 60%. The mortality rate is higher with restrictive FO or poor right ventricular function. Prenatal diagnosis significantly improves neonatal survival. HLHS has been related to an increased risk for neurodevelopmental delay, and parents should be counselled accordingly. Although this was formerly mainly attributed to cardiac surgery, recent studies suggest that brain abnormalities are developmental.
Critical aortic stenosis
Overview
The severity of AoS varies with a range of outcome from biventricular to functionally univentricular. The early signs of AoS may be subtle and are easily missed at second trimester screening. Valvular aortic stenosis is the most common type. The LV may continue to have relatively normal growth, become dilated or involute, progressing to HLHS.
Pathophysiology
The initial response to AoS may be left ventricular dilatation followed by its involution and secondary damage caused by reduced coronary perfusion and subsequent fibrosis (endocardial fibroelastosis), resulting in poor function.
Associated Anomalies
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AoS may be associated with VSD, bicuspid aortic valve and CoA. Extracardiac anomalies are rare.
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Chromosomal abnormalities are rare with valvular AoS, but supravalvular AOS is associated with William syndrome.
Ultrasound findings
A dilated LV with a hyperechogenic endocardium is seen in the four-chamber view; the contractility is often noticeably reduced. The LA may be dilated if there is severe mitral regurgitation (MR). The FO flow is predominantly left to right. In the LVOT view, the aortic valve appears thickened and does not ‘disappear’ during systole. Pulsed-wave Doppler reveals increased velocities through the aortic valve; however, with poor LV function, the velocities may be normal or low. In severe cases, mitral valve inflow becomes monophasic, and severe regurgitation may be seen. The ascending aorta may show poststenotic dilation beyond the aortic valve or become hypoplastic. Aortic arch flow is often reversed.
Specific features to check at follow-up and perinatal management
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Check left heart dimensions (mitral valve, LV, aortic valve, ascending aorta, transverse aortic arch, isthmus) and obtain gestational age–adjusted z-scores.
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Check the direction and velocity of flow at the FO.
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Check mitral valve Doppler and its duration in the cardiac cycle.
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Check the velocity of flow across the aortic valve.
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Check the direction of flow in the transverse arch and ascending aorta.
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Check diastolic flow velocities in the isthmus (associated CoA).
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Consider referral for prenatal balloon valvuloplasty in selected patients.
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Arrange for interventional cardiology and cardiovascular surgical consultations prenatally.
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Plan delivery in a tertiary care centre. Severe cases will require PGE.
Treatment and outcome
About 45% of fetuses with aortic stenosis will progress to a functionally univentricular circulation, requiring palliative surgery after birth. In selected fetuses, prenatal balloon valvuloplasty may be considered. The postnatal management pathway depends on left heart morphology and function: In mild cases, postnatal balloon valvuloplasty may suffice. However, many children will need more complex surgery after birth, placing the pulmonary valve in the aortic position and inserting a right ventricle (RV) to pulmonary artery conduit, and some will require aortic or mitral valve replacement later in childhood to maintain a biventricular outcome. Univentricular palliation is performed in cases with significant LV hypoplasia or with a thin-walled poorly functioning LV, provided the right heart continues to function well.
Tricuspid atresia
Overview
Tricuspid atresia is characterised by the absence of a connection between the right atrium (RA) and the RV. It is typically associated with right ventricular hypoplasia and varying degrees of PS or pulmonary atresia.
Pathophysiology
In tricuspid atresia, all the systemic venous return is shunted right to left across the (usually) large FO. Both pulmonary and systemic venous return enter the dominant LV through an enlarged mitral valve. A perimembranous VSD may connect the rudimentary RV to the LV and supply the pulmonary artery (80%) or aorta (20%). In the absence of a VSD the right sided structures are miniature.
Associated anomalies
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Pulmonary hypoplasia and atresia are common, and CoA is present in most fetuses with ventriculoarterial discordance (20%).
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Chromosomal abnormalities are rare with tricuspid atresia.
Ultrasound findings
The four-chamber view has one dominant and one rudimentary chamber. Only one inlet valve is identified, and the other AV junction is represented by a band of echo-bright tissue ( Fig. 29.4 ). Colour Doppler confirms ventricular inflow into the dominant chamber. Outflow tract hypoplasia and obstruction are confirmed with colour and pulsed-wave Doppler. Correct identification of the dominant ventricle is essential for counselling. Whereas a dominant LV will show a fish-mouthed mitral valve in the posterior position, a dominant RV will show a trileaflet valve with septal attachments lying anterior, in the short axis-view.
Specific features to check at follow-up and perinatal management
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Identify chamber morphology.
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Check ventriculoarterial connection.
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Check for outflow tract obstruction and coarctation.
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Check for reversal of flow in the arterial duct, confirming duct dependency.
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Plan delivery in a tertiary care centre because PGE will be required.
Treatment and outcome
The initial management of tricuspid atresia depends on the degree of outflow tract obstruction and associated anomalies. A systemic-to-pulmonary artery shunt is required in case of severe PS or atresia. If the great arteries are discordant, coarctation or extended arch repair may be necessary. Ultimately, infants undergo a single-ventricle palliation. Survival of tricuspid atresia was 83% at 1 year with no late deaths in a large multicentre study. Long-term survival favours those with a dominant LV.
Pulmonary atresia with intact septum and pulmonary stenosis
Overview
Pulmonary stenosis is characterised by a narrowing of the RVOT. Valvular obstruction is most common in the fetus, but mild PS is rarely diagnosed prenatally. Pulmonary atresia may be membranous (80%) or a long segment and muscular obstruction (20%). This section discusses severe PS and pulmonary atresia with intact ventricular septum (PAIVS).
Pathophysiology
The RV is often characterised as tripartite (with developed inlet, trabecular and outlet portions), bipartite (where one of these is underdeveloped), or unipartite (where only one ventricular portion is well grown). With moderate to severe PS or pulmonary atresia, the RV is exposed to significant pressure-overload resulting in important fibrosis and subsequent RV dysfunction. The TV is usually small, and the RV involutes secondary to reduced filling. In hearts with severe tricuspid regurgitation (TR) through a dysplastic TV, growth of the TV and RV are usually better, and there is a better chance of following a biventricular surgical pathway after birth. As in tricuspid atresia, all the systemic venous return is shunted right to left through the large FO. The pulmonary vasculature is supplied by reversed flow (left-to-right shunting) through the arterial duct. Ventriculocoronary fistulae are seen in the smallest, unipartite RVs and associated with a poorer outcome.
Associated anomalies
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PS is a component of many other structural heart malformations. PAIVS is associated with ventriculocoronary fistulas in up to one third of cases.
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Extracardiac malformations may occasionally be found, but there is no specific organ involvement.
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Chromosomal abnormalities are rare with PAIVS. PS may be associated with syndromes such as Williams-Beuren, Alagille or Noonan.
Ultrasound findings
The four-chamber view is abnormal in severe PS and PAIVS ( Fig. 29.5A ). The TV is often small and dysplastic with bright chordae secondary to pressure overload and may show moderate to severe TR. In severe PS or pulmonary atresia, trabecular overgrowth leads to a bipartite ventricle. In the severest case, the RV is hypoplastic with tricuspid and pulmonary stenosis or atresia, known as the unipartite ventricle. This may be associated with ventriculocoronary fistulas, confirmed by colour Doppler and bidirectional high velocity flow on pulsed-wave Doppler. The branch pulmonary arteries are usually small and confluent ( Fig. 29.5B ). Colour Doppler confirms flow across the pulmonary valve, and the peak velocity can be estimated by pulsed-wave or continuous-wave Doppler. In the 3VT, reversed flow is seen in the arterial duct. Flow in the DV often shows absent or reversed flow secondary to high right atrial pressure. This does not indicate fetal hypoxemia and may be recorded throughout pregnancy.
Specific features to check at follow-up and perinatal management
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Check right heart dimensions (TV, RV, pulmonary valve, branch pulmonary arteries) and obtain gestational age–adjusted z-scores.
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Check for significant TR and quantify it.
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Check direction of flow in the arterial duct.
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Check for ventriculocoronary fistulas.
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Consider referral for prenatal valvuloplasty in selected patients.
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Plan delivery in tertiary care centre to maintain ductal patency with PGE.
Treatment and outcome
As in most CHD, usually no haemodynamic compromise is seen before delivery unless hydrops develops because of severe TR. There are theoretical reasons why prenatal pulmonary valvuloplasty might lead to improved RV function in childhood, but this is usually reserved for cases with hydrops. A biventricular outcome may be feasible in early childhood, but right heart failure may necessitate conversion to a later Fontan circulation. Severe PS or PAIVS is a duct-dependent lesion associated with a guarded prognosis, particularly in the presence of ventriculocoronary fistulas, which can lead to coronary artery occlusion and death. Cardiac catheterisation is important when fistulas are detected to exclude a right ventricular coronary-dependent circulation and determine the best postnatal approach. The pulmonary valve is not opened in such cases because this will result in coronary steal and myocardial infarction.
Double-inlet left ventricle
Overview
In double-inlet left ventricle (DILV), both atria are connected to a dominant ventricle. The dominant ventricle is usually of left morphology (DILV).
Pathophysiology
Any atrial arrangement is possible, but both AV valves open into a single ventricle. These are usually balanced, but one inlet valve may be dysplastic and become atretic during fetal life, or there may be a common valve. The rudimentary ventricle is supplied by a VSD and may give rise to one or both great arteries as in double outlet right ventricle (DORV).
Associated anomalies
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DILV is associated with a wide variety of great arterial connections and LVOT or RVOT obstruction is common.
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Heterotaxy syndrome should be excluded.
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Chromosomal abnormalities are rare.
Ultrasound findings
Abdominal situs should be carefully assessed because right or left atrial isomerism may occur. The four-chamber view shows one dominant and one rudimentary chamber. Correct identity of the dominant ventricle is essential for counselling.
Specific features to check at follow-up and perinatal management
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Identify situs and chamber morphology.
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Check AV and ventriculoarterial connections.
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Check for progressive outflow tract obstruction.
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Check for reversal of flow in the arterial duct or aortic arch, suggesting duct-dependent pulmonary or systemic circulations respectively.
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Plan for delivery in a tertiary care centre because this is a duct-dependent circulation.
Treatment and outcome
The initial management of DILV depends on the presence of outflow tract obstruction and associated anomalies. A systemic-to-pulmonary arterial shunt is required in case of insufficient forward flow through the pulmonary valve, or aortic arch repair for CoA. Ultimately, infants will undergo single ventricle palliation. Generally, postnatal intermediate-term survival favours those with a dominant LV.
Ebstein Anomaly
Overview
Ebstein anomaly is characterised by a displacement of the TV annulus towards the cardiac apex. This results in ‘atrialisation’ of the RV inlet. The presentation varies depending on the degree of atrialisation and TR. Some may present with fetal tachycardia or hydrops.
Pathophysiology
The functional impairment of the RV and severity of TR cause right heart dilation, often resulting in a wall-to-wall heart. Reduced forward flow contributes to hypoplasia of the pulmonary vasculature and pulmonary atresia often develops prenatally. A pathophysiological ‘circle of death’ occurs when there is reversal of flow through the arterial duct, severe pulmonary regurgitation and severe TR. The high right atrial pressure wave results in reverse A waves in the DV and pulsations in the umbilical vein, and may result in fetal hydrops and demise.
Associated anomalies
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Ebstein anomaly is commonly associated with RVOT obstruction. Atrial septal defects (ASDs) are usual. Tachycardia may occur.
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Severe Ebstein anomaly may result in hydrops from high right atrial pressure and pulmonary hypoplasia.
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In a large multicentre study, genetic abnormalities have been found in 20% of those fetuses that had an amniocentesis, most commonly trisomy 21, CHARGE syndrome and chromosome 1p36 deletion. Therefore invasive testing should be offered.
Ultrasound findings
In the four-chamber view, the heart is large and may be ‘wall to wall’. The RA is markedly enlarged and the FO generous ( Fig. 29.6 ). The hinge point (functional insertion) of the TV is displaced apically, and the valve leaflets do not coapt, resulting in severe regurgitation that typically arises from below the valve and reaches to the back of the atrial wall, demonstrated by colour Doppler. The pulmonary vasculature is underperfused and small, and the 3VT may show reversed ductal flow and pulmonary regurgitation.
Specific features to check at follow-up and perinatal management
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Check for prognostic indicators at diagnosis because they will guide surveillance.
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Fetuses with severe TR should be monitored weekly for signs of hydrops or supraventricular tachycardia by the local team. These require urgent referral to a fetal centre for management of arrhythmia and monitoring for maternal mirror syndrome.
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Invasive genetic testing should be offered.
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Multidisciplinary team discussion should take place during the third trimester to decide whether a path of active treatment is to be initiated after delivery. If so, plan for delivery in a tertiary care centre to provide the appropriate postnatal support or make arrangements for palliative care.
Treatment and outcome
The prognosis of Ebstein anomaly diagnosed prenatally is dismal. In a large retrospective multicentre series, the fetal mortality rate was 17%, and the overall perinatal mortality rate 45%. Tricuspid annular dilation, pulmonary regurgitation, RVOT obstruction, pericardial effusion and diagnosis before 32 weeks of gestation indicate a poor outcome.
Only a minority of children will have surgery, and it is important to offer expectant parents the option of palliative care.
The surgical approach depends on the severity of the malformation. A biventricular approach attempts to repair the TV and reduce right atrial size. Univentricular surgery comprises patch closure of the TV, atrial septectomy and systemic-to-pulmonary arterial shunting followed by Glenn operation at 3 to 6 months and Fontan completion at around 3 years.
Atrioventricular septal defect
Overview
Atrioventricular septal defect accounts for about 4% of all CHDs. It is strongly associated with chromosomal abnormalities, most commonly trisomy 21. AVSD is characterised by a common AV junction. There is usually a common AV valve but more rarely separate valves are identified. The septal defects are of variable size and may even be absent, which makes prenatal detection of this condition more difficult. Depending on the relative sizes of the RV and LV, AVSD may be considered balanced or unbalanced.
Pathophysiology
Usually no haemodynamic effects are seen before birth in isolated AVSD. When it occurs with tetralogy of Fallot (ToF), varying degrees of RVOT obstruction may develop, leading to ductal dependency. It is commonly seen in cases of heterotaxy, and in right atrial isomerism (RAI), obstructed total anomalous pulmonary venous connection (TAPVC) may occur below the diaphragm and require early surgery. In uncomplicated cases, the size of the atrial and ventricular component of the defect will determine the potential for left-to-right shunting and for cardiac failure in infancy.
Associated anomalies
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Unbalanced AVSD is usually associated with hypoplasia of the LV and aorta or pulmonary atresia and TAPVC. About 5% of AVSDs are associated with ToF, increasing the risk for trisomy 21.
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Extracardiac malformations are commonly seen with no specific organ involvement with balanced AVSD. Unbalanced AVSD is typically associated with ‘heterotaxy’ syndrome, usually RAI with asplenia.
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In 40% to 60%, a second trimester prenatal diagnosis of a balanced AVSD is associated with trisomy 21 or less commonly with trisomies 18 and 13. The prevalence is higher in the first trimester.
Ultrasound findings
The abdominal situs may be abnormal. The heart may appear ‘rounded’ as the inlet septum is shorter than the outlet septum. The atrial and ventricular component of the septal defect vary in size ( Fig. 29.7 ). During diastole, colour Doppler shows the characteristic ‘butterfly’ H-shaped appearance, and no offsetting of the inlet valves can be seen. Sometimes a dilated coronary sinus (from a persistent left superior vena) can be mistaken for the atrial component of an AVSD. The visualisation of a septum primum more anteriorly allows their differentiation. A short-axis view at the level of the AV valve should be obtained to confirm the diagnosis of AVSD ( 
). There is no fish-mouth mitral valve because even if separate valves are identified, the left valve opens to the ventricular septum. The outflow tract and 3VT are usually normal in balanced AVSD.
