3.1 AORTIC COARCTATION
Definition Aortic coarctation (AC) is a narrowing of the aorta; greater than 90% occur between the left subclavian artery and the ductus arteriosus (aortic isthmus). The most severe form of AC is complete interruption of the aortic arch, with most interruptions occurring between the left carotid artery and the left subclavian artery.
Epidemiology The prevalence is 0.6 per 1000 live births and has a M2:F1 ratio. AC accounts for 7% of all congenital cardiac disease. Of AC, 32% are isolated, while the remaining 68% have additional anomalies, including cardiovascular (24%), genitourinary (20%), central nervous system (12%), and skeletal (6%) anomalies.
Embryology There are two theories to explain the different types of AC. A preductal AC is theorized to result from decreased blood flow through the left ventricle and aorta leading to impaired growth of the isthmus. A ductal, or postductal, AC is suspected to result from ductal tissue present around the posterior aspect of the proximal descending aorta. This tissue constricts along with the ductus, causing aortic constriction.
Inheritance Pattern The inheritance pattern is thought to be polygenic. There is a strong association with monosomy X (Turner syndrome). At least 5% of girls with coarctation may be found to have monosomy X; thus, the prevalence may be higher prenatally. The recurrence risk for isolated coarctation is 2% when one sibling is affected and 6% when two siblings are affected. The recurrence risk for congenital heart defects in offspring given one affected parent is 4% when the mother is affected and 2% when the father is affected. Coarctation also occurs in mosaic trisomy 16, DiGeorge syndrome (deletion 22q), Noonan syndrome, and many other syndromes.
Teratogens Maternal diabetes mellitus.
Prognosis With isolated coarctation of the aorta, surgical management generally results in a good long-term outcome. When coarctation occurs along with other, more complex intracardiac disease, it is often the associated disease that more strongly influences the prognosis. If the AC goes undetected in the newborn, severe heart failure and acidosis can occur.
Ultrasound identification of a discrete narrowing of the aortic arch is limited due to compensation from the ductus arteriosus.
Indirect signs of AC can lead to a very strong suspicion in the mid-second and early third trimester. These include the following:
Discrepant ventricular size with the right larger than the left. This finding is more useful in the second compared to the third trimester.
The ratio of the diameter of the ascending aorta to the diameter of the main pulmonary artery is a helpful clue to AC, with a normal ratio being 1.25. One study found that AC was associated with a ratio greater than 2.
At 14 to 16 weeks, a significant discrepancy between a large ductus arteriosus and a smaller aorta may be seen.
Left-to-right flow across the atrial septum occurs in AC when the left heart is significantly hypoplastic and may be a marker for a ductal-dependent lesion.
Ventricular septal defects (VSDs) are present in approximately 50% of patients.
When there is a posterior misalignment type of defect, there is often critical arch obstruction or even an interrupted aortic arch.
In a posterior misalignment type of defect, the conal septum is deviated posteriorly under the aortic valve, resulting in a VSD with subaortic stenosis.
Other morphologic abnormalities of the left heart are common in coarctation.
The aortic valve is abnormal in approximately 60% of infants, with a bicuspid valve the most common. Color and pulse Doppler interrogation of the aortic valve may show accelerated flow if there is significant stenosis.
On detailed fetal echocardiography, closely spaced papillary muscles or a single left ventricular papillary muscle (a “parachute” mitral valve) may be detected. This is recognized in short-axis scans of the left ventricle.
A left superior vena cava is present in approximately 18% of patients with AC.
An increased nuchal translucency is frequently identified at 11 to 14 weeks.
Fetal echocardiography can diagnose AC when it is severe, but the test has weak sensitivity, particularly with mild AC.
One needs to realize the inadequacy of prenatal echocardiography in reliably predicting all cases of AC.
The severity of left heart hypoplasia can progress during the second and third trimester. If there is a family history of left-sided disease, such as hypoplastic left heart syndrome (HLHS), valvular aortic stenosis, or AC, it is wise to reexamine the fetus at 28 weeks, even if the initial study results are normal.
AC needs to be distinguished from interrupted aortic arch. Most commonly, interruptions occur between the left carotid and left subclavian arteries.
Investigations and Consultations Required Karyotype analysis (with microarray for the chromosome 22q deletion) should be considered when AC or interrupted aortic arch is suspected because of the association with Turner syndrome and DiGeorge syndrome. With interrupted aortic arch, chromosome 22q deletion may be present in more than 50% of patients. In this situation, the interruption is most often between the left common carotid artery and left subclavian artery. A complete fetal survey is indicated. The family should meet with a pediatric cardiologist to discuss the cardiac findings and to coordinate a prenatal and postnatal management plan.
Pregnancy Course Generally, the pregnancy course is routine.
Fetal Intervention No fetal intervention is available.
Pregnancy Termination Issues If termination is chosen, an intact fetus is necessary to confirm the cardiac findings and to assess for other noncardiac abnormalities.
Monitoring No special fetal monitoring is usually required. Follow-up fetal echocardiography should be performed in the third trimester to confirm the diagnosis and discuss delivery plans.
Delivery Delivery should occur at a tertiary care center where prostaglandin E1 therapy can be administered if the lesion is ductus dependent.
Resuscitation Assistance with respiration is usually not required. However, if there is delay in the spontaneous onset of breathing, oxygen supplementation should be limited to 40% to 60% maximum, and only for the time needed to establish adequate color, to avoid closing the ductus. If a severe coarctation is diagnosed prenatally, therapy with prostaglandin E1 infusion should be started as soon as possible. Coarctation clinically presents after the first few days of life, when the ductus closes. Therefore, infants who are suspected to have AC by antenatal echocardiogram should be closely monitored in the neonatal intensive care unit. If the femoral pulses diminish or there are significant blood pressure changes, then prostaglandin E1 can be started, even before echo confirmation.
Transport Immediate transport to a tertiary center with neonatology and pediatric cardiac diagnostic and surgical capabilities is essential for infants with AC with congestive heart failure (CHF), low cardiac output, or evidence of ductus-dependent systemic perfusion. Consultation with a pediatric cardiologist prior to transport to determine appropriate supportive measures is indicated. Management during transport should be by personnel experienced in neonatal transport with capability for mechanical ventilation and delivery of cardiotonic infusions.
Testing and Confirmation AC should be considered when lower-extremity pulses are decreased or when there is a gradient of more than 10 mm Hg between upper and lower extremity systolic blood pressures. Oxygen saturation of 94% or less in the lower extremity is suggestive of right-to-left shunting at the ductal level, which can occur in severe arch obstruction. Echocardiography should be definitive in making the diagnosis of coarctation.
Nursery Management Babies with a suspicion of AC prenatally should not go home until the echo shows the ductus arteriosus has closed and the arch is normal. In infants with AC, the goal of initial neonatal management is to achieve and sustain a balance between pulmonary and systemic blood flow by maintaining patency of the ductus and a pulmonary-to-systemic shunt across the ductus that can provide adequate perfusion to the lower body, particularly the liver and kidneys. Hyperventilation and supplemental oxygen decrease pulmonary resistance and thereby alter the direction and magnitude of ductal, or intracardiac, shunting through associated lesions. Both should be avoided. Acidosis should be treated aggressively with buffer. Dopamine infusion may be needed to improve cardiac output and renal perfusion. Limiting organ damage from inadequate perfusion prior to surgery enhances recovery from surgical repair.
Developmental follow-up is recommended in infants with critical neonatal coarctation requiring surgery in the first few weeks of life, as they are at risk for developmental delay.
Preoperative Assessment Echocardiography is sufficient for preoperative diagnosis in most cases of AC.
Operative Indications Surgery is indicated during the newborn period when the lesion is ductal dependent or when the AC is severe. In less-severe cases of AC, surgery is usually performed after 2 months of age.
Types of Procedures One of two procedures can be performed. The AC can be resected and an end-to-end anastomosis performed. An alternative approach is the left subclavian flap plasty procedure in which the proximal left subclavian artery is used to augment the area of coarctation.
Surgical Results and Prognosis Operative mortality for AC is less than 5%. Recurrent AC can develop in approximately 10% of patients and is usually successfully treated with balloon angioplasty.
3.2 ATRIOVENTRICULAR SEPTAL DEFECT (ATRIOVENTRICULAR CANAL DEFECTS OR ENDOCARDIAL CUSHION DEFECT)
Definition Atrioventricular septal defects (AVSDs) include a spectrum of lesions ranging from a complete common atrioventricular (AV) canal to an isolated primum type of atrial septal defect. A complete canal defect consists of good-size ventricular and atrial defects associated with a common AV valve. Intermediate AVSDs differ from complete defects in that there are distinct and separate left AV (“mitral”) and right AV (“tricuspid”) valves, and any combination of (1) VSD; (2) cleft anterior mitral defect; and (3) cleft septal tricuspid leaflet. An intermediate AVSD has anterior and posterior septal bridging leaflets between the two AV valves that are fused over the ventricular septum, giving rise to separate mitral and tricuspid valves. Of the two types of AVSDs described, the intermediate type is the most infrequent. AVSDs that are mostly contiguous with one ventricle result in the majority of the blood flow into the ventricle with minimal flow into the opposite ventricle, causing this ventricle to become hypoplastic. This results in an unbalanced defect. When there is a balanced AVSD, an equal amount of blood enters both ventricular cavities.
Epidemiology The prevalence is 0.19 per 1000 live births and accounts for approximately 5% of patients followed with congenital heart disease postnatally. AVSDs are slightly more common in female fetuses (1.3:1), and 60%-70% of these fetuses have a chromosomal abnormality. When complete AVSDs occur as isolated lesions, trisomy 21 is present in 56% to 72% of fetuses. AVSDs also occur, but less commonly, in trisomies 13 and 18, Turner syndrome, and other chromosome abnormalities.
Embryology Abnormalities of the AV canal result from malformation in the development of the endocardial cushions. The endocardial cushions are involved in the closure of both the atrial and the ventricular septa and in the development of both AV valves.
Inheritance Pattern When isolated, the pattern of inheritance generally appears to be multifactorial; however, a single gene pattern has been suggested in some families. The recurrence risk for congenital heart disease is 3% when one sibling is affected with an endocardial cushion defect and 10% when two siblings are affected. When a parent is affected, the recurrence risk is 14% when the mother is affected and only 1% when the father is affected.
Teratogens Maternal diabetes mellitus.
Prognosis AVSDs occurring in isolation generally have a good prognosis in terms of the cardiac disease, but surgery is required. When occurrence is associated with chromosomal abnormalities or as a part of a heterotaxy syndrome, the prognosis is frequently poor.
An evaluation of the heart can distinguish
A complete from an incomplete AVSD
The severity of regurgitation of AV valve/valves
A balanced from an unbalanced AVSD
Valve abnormalities are nearly always present with endocardial cushion defects.
A common AV valve is well demonstrated in short-axis imaging of the ventricles.
In an isolated primum atrial septal defect, the AV valves are separate, but aligned at the same level. Normally, the tricuspid valve is offset slightly toward the apex of the ventricle.
Although a cleft mitral valve can be a feature of an intermediate AVSD, it is rarely identified in the fetal period.
Color Doppler interrogation for AV valve regurgitation is important because the outcome is worse when there is a severely regurgitant AV valve (or valves).
A comparison of the ventricles provides an initial assessment of the balance of the AVSD.
If one ventricle appears hypoplastic, the AVSD is most likely unbalanced.
The orientation of the defect over the interventricular septum and color Doppler mapping of blood flow can confirm the diagnosis.
Increased nuchal translucency is often present at 11 to 14 weeks.
Transabdominal imaging reveals AVSDs at 16 to 18 weeks, and transvaginal imaging can demonstrate a defect as early as 10 to 14 weeks.
False dropout can mimic atrial septal defects and VSDs.
Imaging in a scan plane perpendicular to the suspected defect and identification of the abnormalities of the AV valve (which are nearly always present in true AVSDs) are important.
Cine clips can be used to assess AV valve motion and establish that there is a single large valve.
Because both are located near the level of the AV valve, a dilated coronary sinus may be easily confused for a primum type of atrial septal defect.
The dilated coronary sinus is more posterior (along the posterior AV valve groove) than the primum atrial septal defect, which is located just posterior to the aortic root.
Atrioventricular valve abnormalities are also nearly always present in primum defects and are not present with isolated coronary sinus dilation.
The most common reason for a dilated coronary sinus is a left superior vena cava.
An AVSD can occur in the heterotaxy syndrome. Conotruncal abnormalities, such as double-outlet right ventricle (DORV), are frequent in heterotaxy. Therefore, abnormalities of the outflow tracts and venous return should be excluded.
Investigations and Consultations Required An extended fetal anatomy survey should be completed to assess for additional associated anomalies. A fetal echocardiogram and pediatric cardiology consultation should be obtained to provide prenatal counseling and to help exclude the association of more complex congenital heart disease. Consultation with a geneticist should be obtained. A fetal karyotype and microarray should be performed on amniocytes.
Pregnancy Course Unless there are associated anomalies or other congenital heart defects, fetuses with isolated balanced AVSDs do well, and pregnancy complications are not expected. Delivery should be anticipated at term, with cesarean section reserved for the usual obstetrical indications.
Fetal Intervention Fetal intervention is not indicated.
Pregnancy Termination Issues If termination is chosen, an intact fetus should be delivered for confirming the diagnosis and performing a chromosome analysis with microarray.
Monitoring With significant AV valve regurgitation, hydrops may develop. These fetuses are at increased risk for heart block, so monitoring with interval ultrasound examinations is warranted. A follow-up fetal echocardiogram to assess AV valve function in the third trimester is recommended.
Delivery A defect that is isolated, balanced, and without regurgitation could be considered for delivery in the patient’s community. However, in any fetus with an unbalanced or regurgitant AVSD, delivery should be performed at a center where immediate neonatology and pediatric cardiac consultation is available.
Resuscitation Assistance with the onset of respiration is usually not required for infants with an isolated defect. In the presence of other defects, particularly those involving the central nervous system or the respiratory tract, spontaneous breathing may be affected and assistance required.
Transport Infants with isolated AVSDs do not require referral in the immediate neonatal period.
Testing and Confirmation Postnatal diagnosis is confirmed with echocardiography.
Nursery Management Mild oxygen desaturation is typical while the pulmonary vascular resistance remains elevated. As the pulmonary resistance falls, the oxygen saturation will gradually increase, there is increased blood flow to the right ventricle, and symptoms of CHF may develop. However, with complete AVSD, resistance takes longer to fall than normal, and CHF does not occur in the immediate newborn period, but later. A significant percentage of these newborns will not drop their resistance. Hence, CHF will not develop. AV valve regurgitation will make failure occur sooner. While failure with a partial AVSD is rare, it may occur if there is significant left AV valve regurgitation.
Preoperative Assessment Echocardiography is usually definitive in assessing AVSDs.
Operative Indications Nearly all AVSDs require surgery. Infants with complete AVSDs should undergo elective repair by 4 months of age, earlier if CHF limits growth. Primum atrial septal defects should be closed between 6 and 18 months of age. When there is pulmonary artery hypertension, surgery should take place earlier.
Types of Procedures Canal defects are generally approached through a right atriotomy, and septal defects are closed with either a single- or a double-patch technique. The common AV valve is divided at the time of the repair. A pulmonary artery band is sometimes used as a palliative procedure, instead of performing a complete repair to control pulmonary blood flow, when the repair cannot be performed at acceptable risk (i.e., with other more complex lesions or if the patient is too small).
Surgical Results and Prognosis Repair of isolated complete AVSD carries a good prognosis, with operative survival in excess of 97%. A minority of patients will have significant AV canal regurgitation postoperatively, and some may require mitral valve replacement or reoperation. There is a less than 5% incidence of postoperative complete heart block, which would require a pacemaker.
3.3 DOUBLE-OUTLET RIGHT VENTRICLE
Definition Double-outlet right ventricle (DORV) is commonly defined as a defect in which greater than 50% of both the aorta and the pulmonary arteries are contiguous with a single ventricle that has a right morphological appearance. A VSD is almost always present. DORV is most commonly divided into four types: (1) VSD type, DORV with a subaortic VSD; (2) Fallot type, DORV with subaortic or double committed VSD and pulmonic stenosis; (3) Transposition of the great arteries type (Taussig-Bing), DORV with a subpulmonic VSD; and (4) noncommitted VSD type, DORV with a remote VSD. A double committed VSD consists of two VSDs, one below the aorta and one below the pulmonary artery. A noncommitted VSD is a VSD that is not located near the aorta or pulmonary artery.
Epidemiology The prevalence is 0.033 to 0.09 per 1000 live births. It accounts for 1%-3% of children with congenital heart defects.
Embryology The primitive right ventricle starts out as a DORV with a conotruncus. In the absence of normal migration of the aortic side of the conotruncus toward the mitral valve, the primitive DORV anatomy persists. It is assumed that DORV is a spectrum of complex defects that are the consequence of failure of a normal, expected sequence of developmental events.
Inheritance Pattern The sibling recurrence rate has not been reliably reported but is probably low. Karyotype abnormalities are present in up to 41% of fetuses with DORV. It has been reported in trisomies 13 and 18 and in duplication 3p. Chromosome 22q11 deletion occurs in approximately 5% of patients with DORV. In addition, a variety of genetic syndromes have been reported, including Adams-Oliver, Ellis–van Creveld, Melnick-Needles, Noonan, Opitz, and Robinow syndromes.
Teratogens Maternal diabetes mellitus, alcohol, isotretinoin, thalidomide, and trimethadione.
Prognosis DORV requires surgical treatment. The prognosis varies considerably depending on the complexity of the defect and the presence, or absence, of associated congenital and karyotypic abnormalities. Overall, DORV has a poor prognosis.
The principle feature is demonstration of the connection of the aorta and the pulmonary artery to the right ventricle.
The apical four-chamber view frequently appears normal. The long-axis views of the left and right outflow tracts tend to be the most helpful in determining DORV.
The most common orientation of the great arteries is side to side (64%).
The VSD in DORV tends to be a malalignment defect that is most commonly subaortic (68%).
A common feature is subvalvular or valvular obstruction of either outflow tract.
With aortic stenosis, there is frequently hypoplasia of the ascending aorta and the association of aortic coarctation (AC) or interrupted aortic arch.
With pulmonary stenosis, there may be hypoplasia of the branch pulmonary arteries.
The three-vessel view can be helpful to compare the relative sizes of the aorta and pulmonary artery.
The presence, or absence, of antegrade flow should be evaluated.
Significant valvular stenosis has been associated with nonimmune hydrops.
Polyhydramnios may develop with the onset of hydrops.
The manner by which both vessels connect with the right ventricle is variable and important for definitive counseling regarding prognosis.
The VSD can be subaortic, subpulmonary, doubly committed, or uncommitted, and more than one VSD may be present.
Although the location of the VSD is important for directing surgical consultation, the exact location of the VSD can be difficult to accurately determine on fetal ultrasound.
Color and power Doppler can help identify the VSD; however, equal pressures in the ventricles limit identification of small defects.
DORV sometimes occurs with abnormalities of the AV valves, including atresia, straddling (in which the AV valve attaches into the contralateral ventricles), or overriding (in which the annulus overrides both ventricles but does not necessarily attach to both ventricles).
DORV can occur with complete common AV canal defects, particularly in heterotaxy syndrome.
Heterotaxy syndrome should be considered when DORV is suspected. Clear determination of abdominal and atrial situs, as well as pulmonary and systemic venous return, should be performed.
Chromosomal abnormalities (21%), additional structural abnormalities (40%), and heterotaxy (35%) are associated with DORV.
DORV is detectable at 16 to 18 weeks by transabdominal imaging and potentially at 14 weeks with transvaginal imaging.
DORV should be distinguished from transposition, as they are mutually exclusive.
In transposition, the aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle. It is inaccurate to say that transposition of the great arteries and DORV are present in the same heart.
If more than one and a half great vessels connect with the right ventricle, the convention is to label the heart as double outlet.
Tetralogy of Fallot (TOF) with considerable aortic overriding may appear similar to DORV with a subaortic VSD.
In tetralogy, the aorta arises predominantly from the left ventricle (i.e., is more than 50% above the left ventricle), and the aortic valve is typically in direct continuity with the anterior leaflet of the mitral valve.
In DORV with subaortic VSD, more than one and a half great vessels arise from the right ventricle, and usually there is discontinuity between the aortic and mitral valves due to subaortic conal muscle.
Investigations and Consultations Required An extended fetal anatomy survey should be completed to assess for additional associated anomalies. A fetal echocardiogram and pediatric cardiology consultation should be obtained to provide prenatal counseling and to exclude the association of more complex congenital heart disease. Consultation with a geneticist should be obtained. Amniocentesis for karyotyping and microarray should be done, especially looking for the 22q11 deletion.
Pregnancy Course Pregnancies complicated by isolated DORV tend to do well and have no associated pregnancy complications. However, many cases of DORV are associated with other congenital and karyotypic abnormalities, which may lead to pregnancy complications. Delivery should be anticipated at term, with cesarean section reserved for the usual obstetrical indications. Serial ultrasound assessment is recommended in those subjects with valvular stenosis, given the increased risk for nonimmune hydrops.
Fetal Intervention No fetal intervention is available.
Pregnancy Termination Issues If termination is chosen, an intact fetus should be delivered for confirmation of diagnosis and karyotyping with microarray.
Monitoring With significant valvular regurgitation, hydrops may develop; therefore, serial monitoring with interval ultrasound examinations is warranted. A follow-up fetal echocardiogram to assess valve function in the third trimester may also be helpful.
Delivery There is a significant association of DORV with other anomalies and neonatal cyanosis requiring prostaglandin E1 therapy. Delivery should be performed at a center where immediate neonatology and pediatric cardiac consultation and treatment are available.
Resuscitation Initial resuscitation is generally not required. When there is significant pulmonary outflow tract obstruction, persistent cyanosis may be present from birth, which may be confusing in the immediate transition following delivery. If significant outflow tract obstruction is suspected, venous access should be established to allow administration of prostaglandin E1 as required. Placement of umbilical catheters may be helpful.
Transport Transport to a tertiary center with full pediatric cardiac diagnostic and surgical capability is essential. If the infant presents with cyanosis, consultation with a pediatric cardiologist prior to transport is recommended to determine the need for prostaglandin E1 infusion during the transport.
Testing and Confirmation Echocardiography provides definitive diagnosis, and preoperative catheterization is generally not required.
Nursery Management Management depends on establishing an appropriate balance of systemic and pulmonary blood flow. If there is severe obstruction to pulmonary blood flow, prostaglandin E1 therapy may be indicated to maintain ductal patency and ensure adequate pulmonary blood flow. When there is severe obstruction to systemic blood flow, prostaglandin E1 therapy is necessary to maintain adequate systemic perfusion. When there is no significant obstruction to either outflow tract, CHF may develop with the normal fall in pulmonary vascular resistance. In these cases, anticongestive medications are used to control CHF.
Developmental follow-up is recommended in infants with cyanotic heart disease requiring surgery in the first few weeks of life as they are at risk for developmental delay.
Preoperative Assessment Echocardiography provides definitive diagnosis, and preoperative catheterization is generally not required.
Operative Indications All forms of DORV require surgical treatment. The purpose of all operations is to establish unobstructed blood flow of saturated blood to the aorta (preferably from the left ventricle), closure of the VSD, and establishment of unobstructed effective pulmonary blood flow (preferably from the right ventricle). In some cases, a homograft is required to connect the right ventricle with the branch pulmonary arteries
Types of Procedures Because of the spectrum of DORV, the methods of surgical correction vary considerably. When the VSD is subaortic, the surgical treatment resembles that used for treatment of TOF. When the VSD is subpulmonary and there is no pulmonary stenosis, the treatment is similar to that used in transposition of the great arteries with VSD. In cases with an uncommitted VSD, it may be impossible to connect the left ventricle with either great vessel. In these unusual cases, single-ventricle management may be necessary. Baffling the left ventricle to the aorta is relatively straightforward in DORV with a subaortic VSD. DORV with a subpulmonary VSD may still allow treatment with a relatively low rate of operative mortality, but the surgery often involves an arterial switch operation as with transposition of the great arteries.
Surgical Results and Prognosis The operative mortality rate varies, depending on the complexity of the form of DORV and the presence of associated lesions. In general, the operative mortality rate ranges between 3% and 10%.
Fetal dysrhythmias occur in 2% of pregnancies: 90% are ectopic beats, 8% are tachyarrhythmias, and 2% are bradyarrhythmias (BAs).
Atrial ectopic beats (extrasystoles)
These most frequently occur in the third trimester.
On M-mode, the space between an ectopic beat and the prior normal beat is shortened.
Two percent become a bradycardia or tachycardia.
The majority of tachyarrhythmias are either supraventricular tachycardia (80%) or atrial flutter (17%).
Congenital heart block (CHB) is the most common fetal BA (80%).
Five percent of fetuses exposed to maternal lupus develop CHB, usually between 18 and 38 weeks’ gestation; approximately 50% are identified prior to 24 weeks’ gestation.
In CHB secondary to maternal lupus, anti-SSA-Ro or anti-SSB-La antibodies are causative.
The same antibodies are present in Sjogren syndrome, which can result in CHB.
CHB in the first trimester is due to a structural cardiac defect.
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Rate (beats per minute)
Due to a change in autonomic tone
1-to-1 AV conduction
2 electrical pathways between the atria and ventricles
Reentrant tachycardia is the predominant pathway
2 electrical pathways between the atria and ventricles with 1-to-1 conduction
Single reentry circuit around tricuspid valve
2-to-1 block characteristic
Variable degrees of AV block may occur
Multiple atrial impulses through AV node
Rate: irregularly irregular
Variable block at AV node
Due to reentry mechanism
Rare in the fetus
Underlying conduction abnormality
Associated with maternal Ro antibodies
Complete Heart Block (third-degree block)
Dysfunction at AV node or bundle of His
May be due to a structural cardiac anomaly
Associated with maternal autoimmune disease
High association with hydrops
Second-degree block (Mobitz, type I)
Ventricular: usually normal depending on P-to-QRS ratio
Time to travel through AV node gradually increases until it does not penetrate the AV node
Atrial rate regular; ventricular rate regularly irregular
Does not progress to CHB
Second-degree block (Mobitz, type II)
Ventricular: slower than atria based on number of impulses conducted.
AV conduction time constant
Distal conduction system in ventricle affected
May progress to CHB
Inheritance Pattern Most cases of dysrhythmia are sporadic. There is a small subgroup of patients with familial preexcitation syndromes for which an accessory pathway is found in 1.06% of first-degree relatives, compared to 0.15% in the general population. CHB is unlikely to recur in future pregnancies unless associated with maternal lupus, in which the recurrence risk is 14%-18%.
Teratogens None are known.
Survival and prognosis are most highly correlated with the development of hydrops.
Sustained supraventricular tachycardia (>12 h) and early gestational age at presentation correlate with hydrops.
One-third of fetuses with CHB do not survive.
Risk factors for mortality include a ventricular rate less than 55 beats per minute (bpm), a rapid decrease in ventricular rate, the severity of any associated structural cardiac defect, and the development of hydrops.
Identify relationship between atrial and ventricular rate to assess type of arrhythmia.
M-mode echocardiography of the atrial wall and a ventricular event (free wall motion or semilunar valve motion) are reliable for determining timing.
Supraventricular tachycardia and atrial flutter have an abrupt onset and offset.
AV valvular regurgitation
Poor myometrial contractility
Structural cardiac defects, congenitally corrected transposition (with ventricular inversion)
Polyhydramnios, if hydrops develops
Supraventricular tachycardia is frequently intermittent.
During the echocardiogram, tachycardia may not be present, even though at other times there are periods of sustained tachycardia.
Continuous fetal heart rate monitoring may be useful to confirm, and determine, the frequency and duration of tachycardia episodes.
Intermittent tachycardia does not usually lead to hydrops.
Make sure a bradycardia is not preterminal or related to a central nervous system anomaly.
Detectible by transabdominal imaging at 16 to 18 weeks. With transvaginal imaging, arrhythmias have been determined during the first trimester.
Investigations and Consultations Required
Fetuses with a dysrhythmia are usually best managed in consultation with a perinatalogist, and a pediatric cardiologist skilled in the analysis and treatment of arrhythmias.
In all cases of CHB, autoantibodies to anti-SSA/Ro and/or anti-SSB/La should be measured in the mother.
In cases of maternal lupus, management should be coordinated with a rheumatologist with experience in lupus and a pediatric cardiologist with experience in the management of arrhythmias.
Fetal karyotype and microarray are recommended in cases of structural cardiac anomalies.
Once AV node disease has been recognized, the fetus should be examined weekly for progression of the disease or the development of either hydrops or ventricular dysfunction.
With atrial bigeminy and no evidence of AV node disease, the fetus should be evaluated weekly for evidence of supraventricular tachycardia or sequelae of this arrhythmia that may be intermittent and missed on the weekly fetal evaluation.
Sinus bradycardia requires an evaluation of overall fetal well-being.
Maternal thyroid status should be screened.
Since Romano-Ward syndrome has been recognized prenatally, a family history for long QT syndrome should be sought.
Sinus bradycardia is one feature of the long QT syndrome.
Complete heart block
In the fetus greater than 32-34 weeks’ gestational age with CHB, early delivery and postnatal pacing can be considered.
In fetuses of mothers with lupus, maternal treatment with fluorinated steroids could be considered when the fetus is diagnosed with second- or third-degree block. However, treatment with high-dose steroids, as well as intravenous immunoglobulin (IVIG), is controversial. Caution must be emphasized if steroids are to be considered in treatment, given the maternal and fetal consequences and the lack of any strong evidence that treatment makes a clinically significant impact on the outcome of CHB.
With CHB, β-agonists can increase the fetal heart rate approximately 10%.
If hydrops is present, the addition of β-agonists will not improve hydropic status.
Hydrops is unlikely with a ventricular rate of 55-60 bpm in the absence of a cardiac anomaly.
Hydroxychloroquine may prevent recurrence of autoantibody-related CHB in families with a previously affected child, but there are no controlled studies. The recurrence risk is 18% with no treatment.
Check maternal thyroid function.
Obtain a middle cerebral artery peak systolic velocity to exclude fetal anemia.
First-/second-line therapy: digoxin, flecainide, or sotolol. Third-line therapy: amiodarone.
Intermittent tachycardia, without evidence of hydrops, does not require treatment.
Ventricular tachycardia greater than 200 bpm is the exception due to the potential for rapid progression to hydrops.
If there is hydrops with supraventricular tachycardia that is unresponsive to medical therapy, then intramuscular injection of digoxin into the fetal thigh can be considered.
Pregnancy Termination Issues If the etiology is unclear, an intact fetus should be delivered for a complete examination due to the potential presence of associated abnormalities.
Monitoring Until effective rate control is achieved, the fetus with sustained tachycardia should be reexamined daily. In most cases, the mother should be hospitalized until effective rate control is achieved. Maternal drug levels should be drawn to ensure adequacy of dosing.
Delivery A fetus with CHB or second-degree block should be delivered at a center where pediatric cardiology consultation and ventricular pacing are available. If the fetal size allows epicardial pacing, early delivery should be considered if hydrops develops. Cesarean section is recommended, as the fetal heart rate cannot be monitored in labor to assess fetal well-being.