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This chapter focuses on noncyanotic congenital heart disease with a basic description of the epidemiology, embryology, clinical manifestation, diagnostic testing, management, treatment, and prognosis of each lesion. The intent is to provide a framework for the major types of noncyanotic congenital heart disease, ranging from septal defects, left ventricular outflow tract (LVOT) obstruction disease, and right ventricular outflow tract obstruction disease. The chapter forms a guide for managing neonates with these common heart conditions.
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The atrial septal defect (ASD) is one of the first forms of congenital heart disease that was corrected surgically. It represents a communication between the left and right atria and does not usually manifest in the neonatal period unless there is associated congenital heart disease, which usually makes it difficult to diagnose. There are 3 major types: secundum ASD, primum ASD, and sinus venosus ASD. The primum ASD is discussed as a part of the atrioventricular canal (AVC) defect (Figure 19-1).
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The ASD represents the second-most-common form of congenital heart disease behind the ventricular septal defect (VSD). The occurrence is between 3% and 4.1% of 1000 live births1,2 and 7% and 15% of all congenital heart disease cases.3,4 For defects that are larger and measure over 5 mm in diameter, there tends to be a female predominance.5,6 The secundum ASD is by far the most common type (Table 19-1). Nearly 1 of every neonates will have an atrial communication that is difficult to distinguish from a patent foramen ovale.7 Approximately 15% of trisomy 21 patients will have a secundum ASD, and 1% of ASD patients will have Holt-Oram syndrome.8 Of note, patients with Holt-Oram tend to have very large ASDs and can have a common atrium with no wall separating the atria.
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Patients with ASDs that are hemodynamically significant tend to have problems later in life and do not present in the neonatal period. Specifically, there is a chronic left-to-right atrial shunt that enlarges the right atrium and right ventricle. This shunt increases blood flow to the pulmonary arteries, which chronically can change the pulmonary vascular bed, leading to pulmonary hypertension. Approximately 22% of ASD patients will develop pulmonary hypertension in adulthood if the ASD is left unrepaired, and 15% will have elevated pulmonary vascular resistance.9 Eisenmenger syndrome develops if a chronic left-to-right shunt lesion causes severe pulmonary vascular changes such that there is significant elevation in the pulmonary vascular resistance and a reversal of the shunt. Thus, blood would flow from the right atrium to the left atrium, resulting in arterial hypoxemia. Eisenmenger syndrome occurs 14% of the time in patients with an ASD.9 Again, if left untreated another complication is right heart failure from the chronic volume overload as well as atrial arrhythmias from right atrial distension.9 Fewer than 1% of infants with an isolated secundum ASD will develop significant symptoms that may lead to death.10
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Infants can develop early right heart failure, which is presumably from a rapid drop in the pulmonary vascular resistance.11 The degree of shunting is related to the relative compliance of the left ventricle in comparison to the right ventricle. As the resistance in the pulmonary bed drops, the right ventricular “stiffness” decreases, leading to the left-to-right shunt. Thus, ASD should be considered in the differential diagnosis of any infant with congestive heart failure or failure to thrive.12
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The secundum ASD represents a defect in the flap of the foramen ovale where it is incompetent, leading to left-right shunting. The sinus venosus ASD, however, is quite separate and high, where the right pulmonary veins and superior vena cava drain; frequently, there is no associated shunting across the foramen ovale. Thus, anomalous drainage of the right pulmonary veins into the superior vena cava is associated with the sinus venosus ASD.
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Regardless of the type of ASD, most patients are asymptomatic in early childhood; however, congestive heart failure symptoms begin before the age of 6 years in 84% of patients and, as mentioned, symptoms can develop during infancy if there is a rapid drop in the pulmonary vascular resistance.9,11,13 The symptoms in the infant would include failure to thrive, tachypnea, feeding difficulties, and diaphoresis with feeds. Cyanosis would be unlikely because this defect does not produce Eisenmenger syndrome until adulthood. In the older patient, easy fatigability, syncope, and hemoptysis may also be present along with frequent pulmonary infections from the chronic left-to-right shunt. Unfortunately, 30% of children have only 1 or no typical physical sign from an ASD, which makes the diagnosis in the young child difficult.14
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As a result of the extra volume of blood traversing the pulmonary valve, there is a relative pulmonary valve stenosis murmur. The systolic ejection-type murmur is present in 87% to 100% of the time.14,15 In addition, extra volume across the tricuspid valve may lead to diastolic murmur from relative tricuspid stenosis in some cases. As a result of this volume-loaded right ventricle, the pulmonary valve closes later than the aortic valve throughout the cardiac cycle, resulting in the “fixed” split in S2, which is present 57% of the time.14 Again, the neonate presents a challenge because in most patients the right ventricle is not volume loaded since the pulmonary vascular resistance remains relatively high and the right ventricle is “stiff.” Thus, the physical examination findings may not be present during infancy.12
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A few etiologies have been discovered for the ASD. The only reported maternal exposure associated with ASD is maternal alcohol consumption, which appears to double the risk of ASD.16 Mutations in the fetus NKX2.5 gene have been identified in patients with many forms of congenital heart malformations, and ASD is common among them.17,18
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Differential Diagnosis
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Because the child with an ASD can have signs of congestive heart failure, other disease processes that cause congestive heart failure should be included in the differential diagnosis. Specifically, congenital heart disease that leads to a chronic left-to-right shunt should be considered, such as a VSD, patent ductus arteriosus, or an AVC defect. Infants with cardiomyopathy may also have the same symptoms noted for ASD. Finally, other noncardiac conditions that can cause congestive heart failure should also be considered, such as sepsis, severe anemia, or pulmonary infection.
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Prior to the advent of echocardiography, the cardiac catheterization was used in patients with a clinical suspicion of ASD for diagnostic purposes, and repair was considered if the relative pulmonary blood was 50% greater than the flow across the aorta.3 The electrocardiogram (ECG) in the neonate and infant may not demonstrate the classic RSR′ pattern because this is a marker for volume load, and right ventricular hypertrophy is a common finding in normal neonates (Figure 19-2). Also, ECG findings are often missing in children with ASD.14
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Currently, the echocardiogram remains the gold standard for the diagnosis of all types of ASD. In addition to identifying the type of ASD, this technique is used to guide transcatheter closure and evaluate the surgical repair of an ASD.
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The decision to close a secundum ASD depends on the size of the defect, the degree of shunting, and the evidence of right ventricular enlargement. Traditionally, if the relative flow across the pulmonary artery is 50% more than the flow across the aorta because of the ASD, then an intervention is recommended.3 Surgical closure or modern-day device closure with interventional cardiology of secundum ASDs is generally low risk and curative. The sinus venosus ASD is surgically repaired because there is no intervention available for this defect at this time.
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In general, the closure of an ASD should be done in early childhood; however, as mentioned, there are cases where an infant would have evidence of congestive heart failure and secondary failure to thrive, which would warrant an earlier intervention.19 Infants can also safely undergo ASD device closure in the catheterization laboratory, which would avoid a sternotomy and cardiopulmonary bypass.20
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Spontaneous closure occurs in 26% of patients before the age of 2 years, and in general an ASD is unlikely to close after this age, which supports the idea of repair in early childhood.21 Ninety-eight percent of ASDs less than 3 mm in diameter in neonates close by 18 months of age, and defects greater than 3 mm take longer to close.6,22 Thus, size of the defect at initial presentation has an impact on the spontaneous closure rate. The ASDs in premature infants take longer to close; however, an associated patent ductus arteriosus tends to close the ASD sooner, presumably because of elevated left atrial pressure, which causes the septum primum flap to abut against the septum, resulting in closure of the defect.6
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Outcome and Follow-up
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Death is rare in patients with unrepaired ASD; however, atrial arrhythmias in adult patients with chronic atrial distension from the left-to-right shunt is much more common.3 Cerebrovascular accidents are even rarer than mortality but still may occur.3 Most patients are not symptomatic until the third decade of life; however, intervention is recommended in early childhood.3,9
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With the advent of echocardiography and color Doppler, ASDs are recognized more readily at an earlier age. Over 70% to 80% of all secundum ASDs close spontaneously by 18 months of age.1,5 A defect less than 3 mm in diameter has a nearly 100% spontaneous closure rate, while a defect greater than 8 mm is unlikely to close,8,23 confirmed by later studies.24, 25, and 26
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Ventricular Septal Defect
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The VSD represents a communication between the right and left ventricles and varies significantly in presentation. For the most part, the neonate may not have symptoms from a VSD even when it is large because flow across it relies on a drop in the pulmonary vascular resistance. The defect is classified by its location within the ventricular wall, the size, and the number of defects. Essentially, there are 3 major types: perimembranous, doubly committed subarterial (supracristal), inlet, and muscular (Figure 19-3). The perimembranous VSD lies superior and anterior within the region of the membranous septum, which is bordered by the tricuspid valve and aortic valve. The supracristal VSD is also anterior but represents a defect below the pulmonary and aortic valves. Both of these defects are outlet VSDs. The inlet VSD is a defect that is near the atrioventricular valves and located quite posteriorly. This defect is most commonly discovered with a complete atrioventricular canal (CAVC) defect, which is discussed further in this chapter. The muscular VSD represents a defect in the trabecular end of the ventricular septum and is bordered completely by muscle. Any combination of these defects may coexist; thus, the clinician should always be suspicious of multiple defects.
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The VSDs occur approximately in 0.95 of 1000 live births and represent the most common form of congenital heart disease other than bicuspid aortic valve. The majority of defects are perimembranous, ranging between 62% and 83%, followed by muscular defects, which vary between 9% and 12%.27, 28, 29, and 30 Supracristal defects are much less common and occur between 2% and 3% of the time.27,29 Muscular defects are less likely to be associated with a syndrome or a karyotype anomaly.1
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The primary issue with the VSD is related to the degree of shunting from the left to the right ventricle. Multiple variables influence the degree of shunting and resultant symptoms from this type of defect. Specifically, the size and location of the defect are important in that small defects tend to protect against congestive heart failure. However, multiple small defects, known as a “Swiss cheese” VSD, may cause significant heart failure because of the collective size of all of the defects. Swiss cheese–type defects account for 0.5% of VSDs.28 The other variable of importance is the relative resistance of the systemic and pulmonary vascular bed. In the neonatal period, the pulmonary vascular resistance is high; therefore, there is minimal shunting. As the pulmonary vascular resistance falls dramatically in the first few weeks of life, more left-to-right systolic shunting occurs across the defect. Because the relative pressures in diastole are similar between the ventricles, there is minimal diastolic shunting. Blood that shunts in systole enters directly into the main pulmonary artery; therefore, there is no nidus for right ventricular enlargement. The main pulmonary artery, left atrium, and left ventricle dilate with VSD physiology but not the right heart structures.
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As the pulmonary vascular resistance drops, infants develop symptoms, which include tachypnea, feeding intolerance, failure to thrive, and diaphoresis.27,31 However, 50% of infants may have no symptoms despite having a large defect. If the pulmonary vascular resistance fails to drop significantly, then the shunting and congestive heart failure symptoms would be minimal. Of note, premature infants tend to go into congestive heart failure much quicker than term infants; however, the proportion of patients in either group with these symptoms is the same.31 The pulmonary vascular resistance drops with age, as expected in the setting of a VSD, but the resistance is generally higher for larger VSDs.31
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The VSD murmur is usually not heard in the first few days of life unless it is a small defect. In fact, the murmur typically occurs within the first week to month of life in most cases.31 Classically, the VSD’s murmur is holosystolic in that it blends with the first heart sound, which generally cannot be auscultated. In addition, there may be excessive flow across the pulmonary and mitral valves, which would lead to a relative stenosis murmur in systole and diastole, respectively. In the case of a large VSD, the murmur may be difficult to hear.
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Spontaneous closure of the VSD has been noted for the perimembranous and muscular VSD through various mechanisms. Tricuspid valve tissue may adhere to the perimembranous defect, resulting in occlusion of the defect over time.32,33 The aortic valve sinus of Valsalva may also occlude the defect over time; however, this may be associated with herniation or rupture of the sinus into the right ventricle or aortic insufficiency. The margins of the muscular defect become relatively small as the child grows and the interventricular septum thickens, which is believed to be the mechanism of spontaneous closure.
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Many associations have been noted with the outlet VSDs. Specifically, there can be a subaortic membrane or ridge associated with the defect that causes stenosis.28,34 As noted, aortic insufficiency is associated with perimembranous defects but is also associated with supracristal defects because of the lack of tissue supporting the subvalvar apparatus.28,35 However, subacute bacterial endocarditis associated with having a high-velocity jet and endothelial damage has also been noted to occur in 6% of all VSDs and can lead to aortic insufficiency secondary to direct damage; this will only exaggerate the congestive heart failure symptoms.36 Subacute bacterial endocarditis and aortic insufficiency tend to be manifestations of a VSD later in life; congestive heart failure begins in infancy. An additional association is double-chamber right ventricle, for which a callous formation develops on the opposing wall of the right ventricle, which causes subpulmonary valve obstruction. Any outlet VSD can have an association with a coarctation of the aorta, which is discussed further in this chapter. VSD has an association with other forms of more complex cyanotic congenital heart disease; discussion of this is beyond the scope of this chapter.
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The associated noncardiac conditions include trisomy 21, the VACTERL (vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities) association of congenital defects, cleft palate, bronchopulmonary dysplasia, chondrodysplasia, Klippel-Feil syndrome plus omphalocele, and polysplenia syndrome.37
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Differential Diagnosis
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Given that the VSD presents with signs of congestive heart failure in the infant after decreases in pulmonary vascular resistance, any other disease process that causes congestive heart failure must be ruled out. As with the ASD differential diagnosis, the left-to-right shunt lesions must be considered, such as AVC, patent ductus arteriosus, and aortopulmonary window. Also, as the pulmonary vascular resistance drops, infants with anomalous origin of the coronary artery from the pulmonary artery would present as well because of coronary ischemia and steal. These patients would present with heart failure symptoms as well. In addition, lesions that cause high-output failure can mimic symptoms of a VSD. These include and are not limited to sepsis, severe anemia, and hepatic and cerebral arteriovenous malformations.
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Ascultatory findings may not be evident on large defects because a VSD murmur may not be present. The ECG will demonstrate left atrial enlargement and left ventricular hypertrophy in the setting of large defects; chest x-ray will show evidence of cardiomegaly with increased pulmonary vascular markings. These findings, however, are nonspecific, and the diagnosis is usually made by echocardiography.38 In fact, detection and closure of a VSD can be determined by fetal echocardiography as well.39,40 In the past, these defects were confirmed by cardiac catheterization, which is no longer necessary.
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Large VSDs need to be repaired during infancy, and the elevated pulmonary vascular resistance as a result of the chronic shunt should improve postoperatively.27 There is no difference in outcome for large VSD closure in children less than 4 kg vs greater than 4 kg; thus, it is recommended to intervene early to prevent recurrent respiratory infection, failure to thrive, and feeding difficulties.37
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In the past, a pulmonary artery band (PAB) was positioned to limit pulmonary blood flow, and the VSD was closed as a separate procedure to minimize morbidity and mortality; however, VSDs are now closed in 1 step with primary closure regardless of the type. The indications for surgery include left heart failure, failure to thrive, feeding problems, and elevated pulmonary artery pressure. VSDs are usually closed through the right atrium41,42 as opposed to a ventriculotomy, which can create a scar on the myocardium. For defects closer to the semilunar valves, repair can also occur through the pulmonary valve.43 Multiple muscular VSDs can be closed primarily instead of with a PAB; however, if the septum is Swiss cheese, a PAB may be necessary because a patch across all of the defects may be difficult and may result in ventricular dysfunction.44 After PAB placement, the defects may close spontaneously. Perventricular device closure of muscular VSDs in the cardiac catheterization lab may be an option in some select patients45,46; however, closure of perimembranous VSDs was not available when this chapter was written. This option is attractive to avoid a sternotomy, PAB, or cardiopulmonary bypass.
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Outcome and Follow-up
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The natural history of a VSD is for spontaneous closure, reduction in size, or development of pulmonary vascular disease. Death in infancy is most probably related to congestive heart failure.47 The overall mortality is approximately 3% in all patients.36 In general, muscular defects tend to have less congestive heart failure, higher closure rate, and less need for operative intervention compared to outlet defects.48
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The natural closure rate for all VSDs is 22% to 36%.31,33,49 The vast majority of defects that close do so before the eighth year of life and tend to be less than 6 mm in diameter.49 Approximately 15% to 29% of perimembranous defects close compared to 57% to 65% of muscular defects.1,28,50 Muscular defects tend to close during the first 6 to 12 months of life.51 The most common complications after cardiac surgery include a residual VSD, right bundle branch block, complete heart block, death, persistent pulmonary hypertension, cerebrovascular accident, or tricuspid valve regurgitation, which may be related to perimembranous patch closure. However, in a recent article, the surgical results for isolated VSD were noted to be good, with 0% reoperation for residual defect, 0.5% mortality, 99.5% of patients asymptomatic, and none had more than mild new-onset tricuspid valve regurgitation.30
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Atrioventricular Septal Defect
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An atrioventricular septal, or canal, defect represents a malformation of the AVC whereby the crux of the heart does not develop, which potentially renders a primum ASD and inlet VSD. Thus, there is a spectrum of disease ranging from an isolated primum ASD with a cleft mitral valve to a CAVC defect with a large inlet VSD and primum ASD (Figure 19-4). As a result of these communications, patients can develop a chronic left-to-right shunt and atrioventricular valve regurgitation. As with other ASDs, a patient with an isolated primum ASD and cleft mitral valve does not usually present with heart failure in infancy; however, a CAVC can cause significant congestive heart failure in the first few months of life.
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The diagnosis of AVC defect often occurs with trisomy 21. In fact, about 50% of patients with trisomy 21 and congenital heart disease have this defect. Specifically, 36% of patients with trisomy 21 have AVC defects.52
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The AVC defect represents the most common form of heart disease in trisomy 21,53 followed by VSD, ASD, and then tetralogy of Fallot. Importantly, about 40% to 50% of patients with Down syndrome have congenital heart disease in general.52,54 For trisomy 21, a CAVC defect is more common than an isolated primum ASD with cleft mitral valve, which only occurs in 3% to 25% of patients with isolated primum ASD and cleft mitral valve series.13,52,55 A CAVC defect can also occur in the setting of tetralogy of Fallot, which is associated with a genetic abnormality about 88% of the time, 67.2% of which is trisomy 21.56
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As with the VSD and ASD, the shunt for a CAVC or isolated primum ASD is related to a drop in pulmonary vascular resistance. Thus, neonates may not have symptoms unless there are associated abnormalities. As the pulmonary vascular resistance falls, the infant can have symptoms of tachypnea, diaphoresis, and feeding difficulties, which can lead to failure to thrive. Of course, the VSD physiology of the AVC has a higher likelihood of causing symptoms than an isolated primum ASD with mitral valve cleft because the pulmonary arterial bed is under a pressure load and not just a volume load.
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In addition to the left-to-right shunt, patients may have significant left atrioventricular, mitral valve, regurgitation, which elevates the left atrial pressure and can lead to worsening pulmonary venous congestion and respiratory symptoms. As with any of the left-to-right shunts, patients are at risk of recurrent respiratory infections if left untreated. Given that a large portion of patients with AVC have trisomy 21, it is important to note that children with trisomy 21 can have persistently elevated pulmonary vascular resistance in the first year of life compared to the normal patient population, which would make them potentially asymptomatic with no significant shunt.57 However, children with trisomy 21 have a higher risk of fixed pulmonary vascular disease compared to children without trisomy 21, making the need for repair even greater.57
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Several important associated anomalies must be accounted for when treating neonates with AVC. If the canal is unbalanced, the atrioventricular valve favors 1 ventricle over the other, making the other somewhat hypoplastic. In some cases, the ventricles are so unbalanced that the hypoplastic chamber is inadequate to serve the needs of the systemic or pulmonary circulation. Most of the time, this is an unbalanced left ventricular AVC, which renders hypoplastic left heart syndrome. Coarctation of the aorta, atrioventricular valve regurgitation, LVOT obstruction, and tetralogy of Fallot (discussed previously) are other conditions associated with AVC defects. Rarer anomalies would include heterotaxy with either right or left atrial isomerism, double-orifice mitral valve,58, 59, 60, and 61 and cor triatriatum, a membrane that obstructs flow into the left ventricle.62,63
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Differential Diagnosis
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The AVC defect usually presents with symptoms of a chronic left-to-right shunt just like the ASD or VSD; however, the patients may present sooner given the multiple levels of shunting and the association with other congenital heart disease noted previously. Thus, these patients can present with congestive heart failure, and other diseases that present in this manner must be excluded. Namely, noncardiac conditions would include sepsis, severe anemia, and hepatic and cerebral arteriovenous malformations, and an additional cardiac condition would be a patent ductus arteriosus or aortopulmonary window.
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The ECG in patients with AVC defect have an unusual counterclockwise direction of the frontal electrical conduction vector, resulting in the classic northwestern QRS axis52 (Figure 19-5). Thus, a patient with this classic ECG finding along with the stigmata of trisomy 21 has an AVC defect until proven otherwise. Nonetheless, the echocardiogram can help determine the diagnosis more specifically. In addition, the associated lesions, such as balancing of the ventricles, valve regurgitation, left or ventricular outflow tract obstruction, and coarctation of the aorta, can be entertained. The typical appearance of the AVC is readily recognized from the 4-chamber view (Figure 19-4). The cardiac catheterization is reserved for those cases where the pulmonary vascular resistance is called into question if a child does not receive a repair early in infancy.
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Initial management in the past was PAB placement in infancy because of the poor results in infancy from CAVC defect repair.64 Now, with improved techniques, surgery occurs predominantly in infancy without the need for a PAB. In the setting of a CAVC defect, there is no reason to wait beyond the 3-month age group to repair if there is a large VSD, which will only cause pulmonary vascular disease, especially in the large subgroup of trisomy 21 patients with pulmonary resistance issues from the start.57 A primum ASD with a cleft mitral valve can be corrected later in life, and the timing of surgery is dependent on the institution’s practice. At the time of repair, the primum ASD and inlet VSD are repaired along with an associated lesion, with patching of the defects and repair of a cleft in the mitral valve. In the past, the CAVC defect was repaired late in infancy; however, improved morbidity and mortality associated with earlier repair supports the idea of not delaying surgical intervention.65
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Outcome and Follow-up
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Without surgery, the survival for CAVC defect is 54% at 6 months of age and 35% at 12 months of age, 15% reach 24 months, and 4% reach 5 years of age66; thus, surgery is recommended for the children at risk for florid heart failure as the pulmonary vascular resistance decreases and there are multiple shunts. Heart failure in combination and severe respiratory infections are the modes of death among patients with trisomy 21.52 However, there is no difference in outcomes comparing the patients with trisomy 21 with the nonsyndromic patients for AVC defect, ASD, or VSD lesions, which eventually lead to more children with trisomy 21 having congenital heart disease surgery.53,67 The operative mortality has decreased significantly,68, 69, and 70 from 25% before 1976 to less than 4% after 1987. Complications after repair include death, 1.6%; postpericardiotomy syndrome, 13%; atrial arrhythmia, 3%; transient heart block, 1.6% to 3.5%; sternal wound infection, 0.5%; and left hemiparesis, 0.5%.55,70 The 10-year survival is 98% in patients with AVC repair.55 Some patients will require reintervention for mitral valve regurgitation (4%–7%)70,71 or LVOT obstruction.
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LEFT VENTRICULAR OUTFLOW TRACT ABNORMALITIES
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The aortic valve in patients with aortic stenosis can have a variable morphology, appearing dysplastic, thickened, bicuspid, or hypoplastic. As a result of this aortic valve disease, neonates tend to present with variable degrees of obstruction; however, it is rare for infants to have significant aortic insufficiency without intervention. The presentation of aortic stenosis can be variable and depends on the degree of obstruction. In the most severe examples, the neonate is ductal dependent for systemic blood flow because of inadequate output from the left ventricle, and there is retrograde flow from the ductus arteriosus and aortic arch that feeds the brachiocephalic vessels and descending aorta. This clinical presentation is an example of critical aortic stenosis; however, much milder forms of aortic stenosis render the neonate asymptomatic.
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Aortic stenosis represents approximately 6% of all congenital heart disease and occurs in 6 of 10,000 live births.72 Twenty-five percent of cases will also have a fibrous or muscular subaortic stenosis associated with the aortic stenosis. Rarely, this condition can be associated with pulmonary stenosis, especially in the setting of congenital rubella syndrome.73 Genetic syndromes are also known to be associated with aortic stenosis and include Turner, Goltz, Costello, and Williams syndrome. If these genetic syndromes are suspected, an evaluation for aortic stenosis and other congenital heart disease should be initiated.
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As discussed, the presentation of aortic stenosis will vary depending on the degree of obstruction, which can be mild to severe. The aortic valve leaflets typically are bicuspid and thickened with a decrease in cross-sectional area and can have associated supravalvar or subvalvar narrowing. Because of the obstruction to the aortic valve, the left ventricle can be hypertrophied in accordance with the degree of stenosis. In some cases with severe obstruction, the left ventricle begins to fail, resulting in a dilated ventricle with diminished systolic function. As a result of the high afterload, there can be endocardial fibroelastosis, which can impair both systolic and diastolic function of the left ventricle. With impaired diastolic function, the left ventricle fails to relax, resulting in high end-diastolic pressure and thus high left atrial and pulmonary arterial pressure from the back pressure.
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The other common associated lesions include patent ductus arteriosus, coarctation of the aorta, VSD, ASD, mitral stenosis, and Shone’s complex.73,74 Shone’s complex is a heart condition with multiple left heart obstruction lesions that traditionally include parachute mitral valve (single papillary muscle), supravalvar mitral ring, congenital mitral stenosis, subaortic stenosis (and valvar aortic stenosis), and coarctation of the aorta. Eight percent of patients with aortic stenosis have Shone’s complex.75 Often with Shone’s complex, the left ventricle is deemed inadequate to handle the work of the systemic circulation, and the neonate must undergo a Norwood procedure for hypoplastic left heart syndrome.
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Approximately 63% of the time, however, there is no associated pathology. As a result of the high left atrial pressure from decreased relaxation, there can be associated pulmonary hypertension 7% of the time.75
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Neonates with aortic stenosis will present with the symptoms of congestive heart failure only if there is a significant amount of obstruction across the valve, and they can have tachypnea, diaphoresis, feeding difficulties, and failure to thrive. On physical examination, there should be a systolic ejection murmur that radiates to the neck with or without an associated thrill. A click should accompany the murmur because there is valvar involvement while the apical impulse will be increased.73,76 Patients with even mild aortic stenosis should have the murmur findings but would probably be asymptomatic; however, patients with significant obstruction may also have a narrow pulse pressure.73
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Differential Diagnosis
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Neonates with critical aortic stenosis tend to be very ill and present in shock unless the ductus arteriosus is open and there is retrograde flow from the descending aorta to the ascending aorta. Thus, any lesion in the neonate that can cause symptoms of shock should be present in the differential diagnosis, such as sepsis, severe anemia, or hypovolemic shock from blood loss. In addition, any cardiac condition that is ductal dependent for systemic blood flow can present similarly, such as coarctation of the aorta, hypoplastic left heart syndrome, or aortic arch interruption.
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The neonate with aortic stenosis who is not ductal dependent for systemic blood flow may still have severe aortic stenosis and would present with a heart murmur. The location of the heart murmur should be at the right upper sternal border with radiation to the neck; however, this distinction may be difficult in the neonate with faster heart rates and smaller chests. Thus, pulmonary stenosis may be confused with the diagnosis of aortic stenosis. Also, valvar aortic stenosis would present with the same type of murmur as supravalvar aortic stenosis or subvalvar aortic stenosis given the location of turbulent blood flow. However, valvar aortic stenosis is accompanied by a click, which should be absent in the last 2.
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On ECG, the neonate may have ECG features of left ventricular hypertrophy with a strain pattern. This feature on the ECG would be unusual because most neonates have right-dominant forces. A chest x-ray in a patient with severe aortic stenosis would have a cardiothoracic ratio greater than 50% and would not necessarily have poststenotic dilation of the ascending aorta.72,73 Again, both of these tests would be nonspecific, and the echocardiogram would provide more definitive information, such as aortic valve thickening, bicuspid aortic valve, patent ductus arteriosus, aortic arch issues, or coarctation (Figure 19-6). Some features of the aortic valve, mitral valve, endocardial fibrosis, and left ventricle size help determine if the neonate has merely severe aortic stenosis or features of hypoplastic left heart syndrome.77,78 In addition, Doppler techniques define the aortic valve gradient, which aids in the management of this lesion.
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The mainstay of treatment of either critical or severe aortic stenosis with a normal-size left ventricle and no significant mitral valve disease is balloon aortic valvuloplasty as opposed to surgical valvotomy. Aortic valve stenosis is the most common type of LVOT obstruction, and balloon valvuloplasty only works at the valvar level.79 The efficacy and mortality rate are similar to surgical techniques without the need of cardiopulmonary bypass and sternotomy.80 The aortic valve gradient improves to acceptable levels without severe aortic insufficiency in most cases. Critical aortic stenosis is defined as enough left ventricular outflow obstruction such that the neonate is ductal dependent for systemic blood flow, an indication for balloon valvuloplasty. Severe aortic stenosis presentation and management strategies, however, vary. Nonetheless, the guidelines for valvuloplasty in severe aortic stenosis are a peak systolic gradient by echocardiographic Doppler techniques of 75 mm Hg, presence of strain on ECG, syncope, angina pectoris, fatigue with exercise, or severe left ventricular dysfunction.81 Thus, balloon aortic valvuloplasty has become a widely accepted modality for the initial treatment of severe aortic stenosis; however, more complicated cases may require direct visualization with surgery.82, 83, 84, 85, 86, and 87
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A major complication from balloon valvuloplasty is aortic wall injury, specifically creation of an intimal flap, which is an underrecognized complication of neonatal balloon aortic valvuloplasty, occurring in 15% of cases even in the recent era.88 Repeat balloon dilation may be necessary, especially in the neonatal period with the risk of increasing aortic regurgitation.
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Outcome and Follow-up
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In cases of aortic stenosis for which there is heart failure in patients under the age of 18 months, the natural history is that 72% of these patients die.73 Untreated severe aortic stenosis also has a poor prognosis.76 Mild aortic stenosis still needs follow-up because only 20% of patients with mild aortic valve stenosis remain with mild symptoms into adulthood and may likely need some form of intervention.89 In general, neonatal critical aortic stenosis, which occurs 10% of the time, tends to have a worse prognosis.90
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Other factors also influence prognosis and increase mortality in severe aortic stenosis and include small aortic annulus, depressed systolic function, low aortic valve gradient, and endocardial fibroelastosis.86 In addition, the size of the aortic valve and mitral valve calls into question the possibility of whether the left ventricle is suitable as a systemic pump given the relatively smaller size. Thus, some studies have investigated the use of certain morphologic characteristics of the left heart structures to determine if a single ventricle or biventricular physiology is superior.77,91
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In those patients who are deemed to be amenable to an aortic balloon valvuloplasty, the prognosis is good, with about two-thirds of the patients needing no further surgical intervention 10 years after intervention.81 Mortality is predominantly limited to the neonatal period around the time of aortic valve intervention. Beyond this period, mortality is nearly absent; however, many may require reintervention at some point for either recurrent aortic stenosis or aortic insufficiency from the balloon valvuloplasty.92 The rate of progression of the aortic valve gradient tends to be slow over time.92 Sudden death after balloon aortic valvuloplasty is extremely low, at 18 of 100,000 patient-years in children over 4 years of age.93
+++
Coarctation of the Aorta
++
The coarctation of the aorta represents a narrowing in the aortic arch, typically beyond the left subclavian artery near the ductus arteriosus. Usually, there is a localized, narrow, constrictive lesion that appears as an infolding of the aortic media into the lumen.94 As a result of this obstruction, neonates can present with shock from the lack of blood flow into the descending aorta to just a murmur with some systemic hypertension. Diminished lower-extremity pulses are the hallmark of this lesion and are the best, most reliable method of detecting it. Given that patients with aortic coarctation can present in shock, the clinician managing neonates should always attempt to detect this lesion.
++
Coarctation is 1 of the 4 most common cardiac malformations, representing 14.8% of cardiac lesions.95 As a frame of reference, VSD occurs 18% and transposition occurs 16% of the time in the same series.95 Approximately 50% of deaths from neonatal coarctation occur after 7 days of life, and it is rare the first 2 days of life.95 Noncardiac anomalies associated coarctation which include urinary tract malformations and tracheoesophageal fistula. The natural history of aortic coarctation is that 60% will die during infancy, with only 1 additional cardiac lesion, while 76% die if there are multiple cardiac defects.94
++
Simple coarctation occurs 61% of the time if there is no associated lesion. Complex coarctation with a VSD occurs 33% of the time; the remaining 6% of coarctation lesions are more complicated lesions.96 One of the more common genetic syndromes associated with aortic coarctation is Turner syndrome.97
++
The primary issue in neonates with critical coarctation of the aorta is the ventricular dysfunction and shock that accompany the lack of cardiac output distal to the obstruction, leading to metabolic acidosis. Neonates do not present with symptoms usually until after 48 hours of life because the ductus arteriosus is protective and allows for distal perfusion.95 The ductus arteriosus, with the blood flow from the right ventricle, usually supplies the descending aorta distal to the obstruction, and when the ductus arteriosus closes, the obstruction to the aortic arch is unmasked. Another mechanism of obstruction is where the aortic arch has an associated sling of ductal tissue that forms a ring around the aorta.98 When the ductus arteriosus closes, the aortic arch becomes obstructed.
++
In 1 series, all infants with coarctation develop signs of congestive heart failure by 6 months of age; however, there are other series in which patients do not present until later with systemic hypertension.94 Usually, in addition to the aortic isthmus obstruction, there is tubular hypoplasia of the distal transverse arch in a majority of neonatal coarctation.94,98 Rarer forms of coarctation can occur between the left common carotid and left subclavian artery as well as the abdominal aorta.99 The former will give rise to discrepant arm blood pressures, while an abdominal aorta coarctation will appear similar to the standard isthmus coarctation on physical examination.
++
Complex coarctation can occur with a VSD, ASD, or aortic stenosis.94 Often, the aortic valve will be malformed, with a dysplastic or bicuspid aortic valve.99 The VSD with aortic coarctation is often a posterior malalignment type, which can lead to subaortic obstruction and a somewhat smaller aortic valve. Coarctation can also occur with AVC defects, as previously described in this chapter.99 Other reported associations include double-outlet right ventricle and complete transposition.100
++
Bicuspid aortic valve with fusion of the left and right coronary cusps is associated with coarctation, while those with right noncoronary fusion are associated with severe aortic stenosis and valve dysfunction.101 Both forms of bicuspid aortic valve are associated with aortic root dilation, but this is more common in the latter form.101 Bicuspid aortic valve with coarctation tends to have less aortic root dilation over time compared to isolated bicuspid aortic valve.102
++
Neonates who present with coarctation of the aorta tend to have symptoms of tachypnea, respiratory distress, and feeding intolerance.103, 104, and 105 As mentioned, coarctation of the aorta symptoms develop usually after the ductus arteriosus begins to close. With the development of symptoms, the pulses will be diminished or absent on physical examination. There will be radial-to-femoral delay in pulses. In critical coarctation of the aorta, the lower-extremity pulses will have lower oxygen saturations compared to upper-extremity pulses because the less-oxygenated blood of the right ventricle supplies the descending aorta. However, this may not be appreciable in the setting of a VSD because there can be left-to-right shunting that increases the ductal oxygen saturations. Upper- and lower-extremity blood pressure should be obtained whenever coarctation of the aorta is suspected to confirm a decrease in the lower-extremity blood pressure.
++
For neonates with coarctation that is not severe or critical, the presenting sign may be merely diminished pulses and upper-extremity hypertension. Upper- and lower-extremity blood pressure would also be discrepant in milder forms of coarctation.
+++
Differential Diagnosis
++
Because shock and metabolic acidosis may be the presenting symptoms of coarctation, any disease process that can give those types of symptoms ought to be ruled out, such as sepsis, severe anemia, hypovolemic shock from blood loss, or other metabolic processes. Again, neonates with hypoplastic left heart syndrome and critical coarctation will also present in shock as a result of ductal closure and should be included in the differential diagnosis as well.
++
The physical examination is the single most important diagnostic test for coarctation with the presentation of absent or weak pulses. An ECG may demonstrate right axis deviation with right ventricular hypertrophy in 63% to 73% of cases94; however, this test is nonspecific. Echocardiography accurately detects coarctation of the aorta using suprasternal notch imaging99; however, the presence of a bicuspid aortic valve or VSD should provide some clues for coarctation as well. Computed tomographic (CT) angiography can provide excellent visualization of the aortic arch and coarctation when ultrasound imaging is deficient or the arch anatomy is complicated (Figure 19-7). With modern fetal echocardiography, the prenatal diagnosis of coarctation is feasible; however, the normal presence of the ductus arteriosus makes the diagnosis difficult.96
++
++
The initial management strategy in the most severe forms of coarctation is to reverse the congestive heart failure and reverse metabolic acidosis, especially when neonates present in shock. Mechanical ventilation aids with removing the work of breathing. Most important, prostaglandin El (PGE1) should be used to dilate the ductus arteriosus, improve systemic output, and increase renal blood flow and urine output. Thus, as the ductus arteriosus opens, the ductal sling around the aorta opens, and the right ventricle can help with supplying descending aorta flow with right-to-left ductal shunting. Surgery is used in the neonatal period to avoid systemic hypertension even with milder forms of coarctation. Unrepaired, there can also be left ventricular failure, myocardial fibrosis, or death. If the ductus arteriosus does not open in critical coarctation despite high-dose PGE1 therapy, urgent surgery will become necessary because there is a failure in medical management. In neonates who present with shock and the ductus opens, time should be provided to allow for end-organ recovery from the shock.
++
The surgical treatment of coarctation has evolved from the subclavian flap to the end-to-end anastomosis and synthetic graft to fix coarctation.106,107 Most centers elect to perform an extended end-end or an end-to-side anastomosis.108,109 With modern techniques, the recoarctation rate is much less at less than 6% (Figure 19-8).108, 109, and 110
++
++
Balloon angioplasty of native coarctation is not a great option because of the residual coarctation, greater than 20 mm Hg in 38% of patients.111 In addition, this technique does not address distal hypoplasia of the arch, and there can be an intimal tear in 2.5%, resulting in aneurysm formation.111, 112, and 113 After surgical repair, echocardiogram Doppler techniques along with 4-limb blood pressure measurements can be used to assess the surgical repair.
+++
Outcome and Follow-up
++
Medical management alone is inadequate, and there is no survival for critical coarctation with additional defects.94 However, even with critically ill patients treated with PGE1, mechanical ventilation, and catecholamines, at least 84% survive to at least 24 months.114
++
After surgical repair, many complications may arise and include spinal cord injury, left hemidiaphragm paralysis, left vocal cord paralysis, weak left radial pulse (subclavian flap-type repair), scoliosis about 3 years after surgery,115 and residual systemic hypertension.103,116,117 Persistent residual systemic hypertension is highly unlikely for neonates.103,116 The mortality rate is low even when the neonate presents with shock and severe metabolic acidosis and is typically less than 5% in more recent series.109,118,119
+++
Aortic Arch Interruption
++
The aortic arch interruption lesion, like the double-outlet right ventricle, tetralogy of Fallot, or transposition of the great vessels, is thought of as a conotruncal abnormality. The aortic arch can be completely interrupted in 3 primary locations between the left subclavian artery and the descending aorta (type A), the left common carotid artery and the left subclavian artery (type B), and the right innominate artery and the left common carotid artery (Figure 19-9). Type A interruption could represent the most severe form of aortic coarctation given its location. In coarctation, there is some prograde flow across the narrowing, and in interruption, there is no communication between the vessels. Because there is no communication between the proximal and distal arch, a patent ductus arteriosus must be present to supply the distal perfusion. If the ductus arteriosus were to close in neonates with aortic arch interruption, profound shock and metabolic acidosis would ensue. The lower-extremity oxygen saturation tends to be decreased when compared to the right upper extremity because deoxygenated blood arises from the right ventricle, which pumps to the ductus arteriosus and feeds the distal arch.
++
++
Type B aortic arch interruption between the left common carotid and left subclavian artery is the most common form of arch interruption at 67%.120 Type A is less common at 25%, and type C is rare at 8%.120 The advent of PGE1 has increased survival because lower-extremity perfusion is dependent on patency of the ductus arteriosus121; otherwise, surgery to repair the arch must take place before the ductus arteriosus closes. Like all conotruncal abnormalities, 22q11 microdeletion should always be considered and is present in 82% of type B but is less common in type A interruption.122,123
++
Embryologically, involution of the fourth arch in utero, which represents the communication between the common carotid and subclavian artery on either the left or the right depending on the arch sidedness, is the mechanism of type B interruption.124 Failure of the left or right dorsal aorta beyond the fourth arch creates a type A interruption, while type C is caused by failure of the third and fourth arches.
++
Neonates with arch interruption, regardless of the type, will present with early heart failure, weak lower-extremity pulses, strong carotid pulses, and differential cyanosis from the desaturated blood exiting the right ventricle and supplying the lower extremities via a ductus arteriosus. Often with arch interruption, the right subclavian artery can arise anomalously and also be the ductus arteriosus, resulting in lower oxygen saturation in all limbs compared to the cerebral saturation.
++
There is almost always a ductus arteriosus to supply the lower-extremity perfusion; however, there are case reports of collateral flow from the vertebral arteries and thyrocervical trunk.125 In 94% of cases, there is a large, posterior malalignment-type VSD126; there are also case reports of direct connections between the aorta and pulmonary artery, also known as an aortopulmonary window, and no VSD.127, 128, and 129 Most important, as a result of a narrow LVOT, the aortic valve can be malformed, bicuspid, and hypoplastic.130 This outflow tract pathology may lead to severe subaortic or aortic stenosis, which can alter the management of these patients significantly. An interrupted aortic arch is also associated with mitral stenosis/atresia, persistent truncus arteriosus, or double-outlet right ventricle. The mortality rate for arch interruption increases significantly when associated with persistent truncus arteriosus.131
+++
Differential Diagnosis
++
Patients with arch interruption, if left alone, will present with shock, metabolic acidosis, and diminished pulses. As mentioned regarding aortic stenosis or coarctation of the aorta, other lesions that can cause shock in the neonate must be excluded. Interrupted aortic arch has an interesting diagnostic feature of differential cyanosis as well; however, this is not necessarily unique because severe coarctation that is nearly interrupted and severe pulmonary hypertension may also show decreased lower-extremity saturation. As mentioned, the differential cyanosis may not be appreciable if the right subclavian artery also arises below the interruption and all extremities are fed by the ductus arteriosus. In addition, because there is a VSD, the left-to-right shunt as the pulmonary vascular resistance drops in the neonate may cause the lower-extremity saturation to increase, minimizing any differential cyanosis.
++
An ECG may show left or right ventricular hypertrophy; the chest x-ray may demonstrate cardiomegaly with increased pulmonary vascular markings. Both findings would be nonspecific and not diagnostic. Echocardiography is the mainstay of diagnosis even in fetal life.132 The arch interruption level can be defined as well as the location of the VSD. The LVOT can be visualized to ascertain any obstruction or hypoplasia.
++
Once the diagnosis of aortic arch obstruction has been identified, PGE1 can be initiated to ensure adequate systemic perfusion. PGE1 therapy can be accompanied by fever, irritability, hypotension, or apnea. Thus, the clinician should search for these side effects. Given the presence of a VSD and runoff diastolic flow into the branch pulmonary arteries from the ductus arteriosus, neonates can quickly develop pulmonary edema. Therefore, surgical intervention should not be delayed too long because of this complication.
++
The surgical procedure involves an aortic arch reconstruction and repairing any VSD or subaortic obstruction.133,134 If the LVOT is deemed to be too small, the left ventricle can often be baffled to the pulmonary valve to relieve obstruction, and a conduit from the right ventricle to pulmonary arteries would function as the right ventricular outflow. This procedure with the arch reconstruction is not as ideal as repairing the arch and closing the VSD because the conduit will not grow with the neonate and would need to be replaced in the future.
+++
Outcome and Follow-up
++
Untreated, 80% of infants with aortic arch interruption will die in the first month of life.135 If a child survives the infancy period because of a ductus arteriosus, uncorrected Eisenmenger syndrome is the natural outcome because of unrestrictive shunting through a VSD and ductus arteriosus.136 Interrupted aortic arch with subaortic obstruction is a more complicated lesion because of residual subaortic obstruction or the complex baffling the left ventricular flow to the pulmonary valve. In fact, this combination of defects is met with 13% mortality and risk for need of reoperation.134,137 However, with modern techniques and the advent of PGE1, the operative mortality of all aortic arch interruption has decreased dramatically from 65% to less than 5%.138, 139, and 140 Most heart centers now advocate for a single-stage repair approach.140,141
+++
RIGHT VENTRICULAR OUTFLOW TRACT ABNORMALITY
++
As with aortic stenosis, pulmonary stenosis is a result of a malformed, dysplastic, thickened, or bicuspid pulmonary valve. The clinical manifestations vary significantly from just a heart murmur to critical pulmonary stenosis by which the neonate is dependent on a patent ductus arteriosus for pulmonary blood flow. Management strategies will depend mostly on the degree of obstruction across the right ventricular outflow tract.
++
The frequency of pulmonary stenosis is similar to that of aortic stenosis, occurring in 6 of 10,000 live births and 6 of 100 live births with congenital heart disease.72 In the past, there was a high association with congenital rubella syndrome, for which there can be multiple levels of obstruction at the pulmonary valve, main pulmonary artery, or the branches.142 Genetic syndromes are also heavily implicated with pulmonary stenosis, especially Williams and Noonan syndromes.143 The valve is highly dysplastic when there is an associated genetic condition.
++
When there is severe obstruction as a result of pulmonary stenosis, the majority of neonates will have some degree of cyanosis, and some will have right ventricular failure as a result of the high afterload on the myocardium.144 Because of severely elevated right ventricular end-diastolic pressure from the pulmonary stenosis and sometimes somewhat hypoplastic tricuspid valves, neonates will frequently shunt right to left across a patent foramen ovale, which (although it causes cyanosis) also allows the left ventricle to fill. Some neonates will have a true secundum ASD in association with pulmonary valve stenosis. As a result of pulmonary stenosis, older children may have dilation of the main pulmonary artery; however, this is unlikely in a neonate or infant.144
++
The pulmonary valve is supposed to have 3 thin mobile leaflets with excellent excursion; however, with pulmonary stenosis, the leaflets may dome in systole with fusion of the cusps or have a pinhole orifice, resulting in right ventricular hypertrophy and near obliteration of the cavity.145 As a result of the pulmonary stenosis, the infundibulum will also hypertrophy, which can lead to subpulmonary valve obstruction as well. In fact, the most severe form of pulmonary stenosis would be atresia of the pulmonary valve with an intact ventricular septum. This particular lesion can have a similar presentation to critical pulmonary stenosis with a pinhole orifice. Despite all of the pathology associated with the pulmonary valve, it is rare to have significant pulmonary insufficiency in the neonatal period.72
++
Neonates will present quickly with dyspnea, feeding difficulties, hepatomegaly, and a harsh systolic ejection-type murmur with a thrill if there is severe pulmonary stenosis.145 In fact, the right ventricular pressure can be above systemic levels as a result of pulmonary stenosis. Despite the high afterload on the right ventricle, rarely do newborns or infants present with edema.145 Neonates with mild-to-moderate pulmonary stenosis will in all likelihood be relatively asymptomatic.72
+++
Differential Diagnosis
++
The murmur of aortic stenosis may sound similar to that of pulmonary stenosis; however, in the latter there is radiation of the murmur to the back. If there is significant obstruction, the clinician must differentiate this lesion from cyanotic congenital heart disease, which is discussed in another chapter. If there is significant obstruction, the tricuspid valve regurgitation may also be audible and would be holosystolic. Given that there can be a paucity of pulmonary vascular markings and an increase in right ventricular forces in neonates with severe pulmonary stenosis, this lesion must be differentiated from pulmonary hypertension.
++
The classic ECG findings in neonates with severe pulmonary stenosis would include right atrial enlargement and right ventricular hypertrophy with voltages exceeding 20 mm; however, the ECG can be normal in milder forms of the disease.144,145 As discussed previously, the chest x-ray can demonstrate cardiomegaly with decreased pulmonary vascular markings; however, the enlargement of the main pulmonary artery from poststenotic dilation may not be apparent until after infancy.144
++
The echocardiogram is the mainstay for the diagnosis, can provide accurate Doppler-derived pulmonary stenosis gradients, and can provide an anatomic view of the pulmonary valve.146 The gradient by echo correlates well with the cardiac catheterization-derived pressure gradient146 (r = 0.98). Of note, careful attention should be placed on the pulmonary and tricuspid valve annulus size to see if surgical or cardiac catheterization interventions would be successful.
++
Even in the early surgical era, the mortality rate for pulmonary valve repair was low at 4%.144 Management has been altered, however, with the advent of advanced interventional cardiac techniques (Figure 19-10). Pulmonary valvuloplasty has become the standard of care for patients with critical pulmonary stenosis, with great short- and long-term results. Surgery should be reserved for those patients with a hypoplastic tricuspid valve and right ventricle.147, 148, 149, 150, 151, 152, and 153 In these cases with hypoplastic right ventricle associated with severe pulmonary stenosis, an aortopulmonary shunt may be necessary with a single- or “1.5-ventricle” repair strategy in the future.154
++
++
The advantage of balloon intervention is that there is no need for cardiopulmonary bypass, blood products, and sternotomy. Results are variable when the pulmonary valve is very dysplastic and thickened, however.148,149 The mechanism by which balloon valvuloplasty works is by splitting the commissural fusion of the pulmonary valve and thereby relieving the stenosis.149
+++
Outcome and Follow-up
++
Survival has improved with the advent of PGE1 as a part of therapy to augment pulmonary blood flow in cases of critical pulmonary stenosis. Patients with critical pulmonary stenosis have not done well in the past prior to the use of PGE1 therapy.155 Severe pulmonary stenosis is a grave condition, leading to death if no intervention is conducted early in life.144,145
++
In 1 large series of 68 patients with pulmonary stenosis but no congestive heart failure or cyanosis, pulmonary stenosis was unlikely to progress, and the patient generally had a good prognosis.156 If pulmonary stenosis remains mild after 1 year of life, it is unlikely to progress, while moderate-to-severe pulmonary stenosis can worsen in severity.156, 157, and 158 At older ages, it is unlikely for mild pulmonary stenosis to progress. In fact, there are cases of a natural cure for mild pulmonary stenosis by which the gradient across the valve goes away.159
++
After pulmonary valvuloplasty, there might still be right-to-left shunting across an atrial communication despite adequate relief of the pulmonary outflow obstruction because the right ventricular end-diastolic pressure might be high from impaired right ventricular compliance.155 However, as the obstruction is most often relieved with adequate balloon dilation, the right ventricle relaxes over time, and the cyanosis improves.
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