Atrial Septal Defect

Atrial septal defects (ASDs) constitute 5% to 10% of all congenital heart defects and occur in approximately one in 1500 live births. There are five types of ASDs (Figure 43-1). The most common type is the ostium secundum ASD, which results from a deficiency in septum primum, the thin membrane-like septum that normally closes the foramen ovale. The second most common type is the ostium primum ASD, which is a defect in the canal septum. This septum normally divides the common atrioventricular (AV) canal and in so doing completes the anterior portion of the atrial septum and the posterior portion of the ventricular septum while dividing the common AV valve into the tricuspid and mitral valve. Defects in this septum result in AV canal defects, which are discussed later in this chapter. The third type is the sinus venosus defect, which is not a defect in atrial septum per se but rather a communication between the two atria by way of a “straddling” venous structure, either a pulmonary vein or a vena cava. It is frequently associated with partial anomalous drainage of the right-sided pulmonary veins connected to the superior vena cava (SVC). Coronary sinus ASDs are the fourth type and again are not true defects in the atrial septum but rather the physiologic consequence of a partially or completely unroofed coronary sinus with left atrial to right atrial drainage through the coronary sinus ostium. The fifth type of ASD is that seen with juxtaposition of the atrial appendages. This is extremely rare and results from an absence or misplacement of septum secundum, which normally closes the foramen ovale.

Figure 43-1 Defects of the atrial septum.

Children with ASDs are usually asymptomatic unless the defect is very large. Cardiac auscultation reveals a systolic ejection murmur at the left upper sternal border from increased blood flow across the pulmonary valve and a fixed, widely split S2 because of increased venous return to the right heart with both inspiration, when there is normally increased return to the right heart, and expiration when there is increased pulmonary venous return to the left atrium and from there to the right atrium through the ASD. Electrocardiography (ECG) may show right axis deviation and right ventricular hypertrophy because of volume overload (typically an rSR′ pattern, or possibly right bundle branch block. With a significant defect, cardiomegaly may be apparent on chest radiography. Echocardiography is used to confirm the diagnosis.

Ostium secundum defects may spontaneously close within the first 4 years of life, but the other types of ASDs usually do not. Options for repair include surgical closure or transcatheter device closure (Figure 43-2). Secundum defects with well-defined margins are the only type amenable to device closure. If left untreated into adulthood, ASDs can lead to pulmonary hypertension; exercise intolerance; atrial arrhythmias; increased risk of paradoxical embolus or stroke; and, late in life, to heart failure. Even when successfully closed in childhood, atrial arrhythmias may still occur decades later.

Figure 43-2 Amplatzer septal occluder.

Ventricular Septal Defect

Ventricular septal defects (VSDs) account for about 20% of all congenital heart disease and occur in 2-10 of /1000 live births. The ventricular septum consists of the inlet (canal septum) posteriorly and inferiorly, running the full superoinferior length of the septal leaflet of the tricuspid valve; the infundibular, conal, or outlet septum superiorly, the muscular or trabecular septum; and the small, membranous septum at the junction of the other three (Figure 43-3). There are five types of VSDs that result from defects in or between these various components of the ventricular septum.

Figure 43-3 Ventricular septal defect.

The most common type of VSDs are the conoventricular VSDs, which are defects between the conal or infundibular septum and the rest of the ventricular septum (see Figure 43-3). They may include the membranous septum, in which case they are a type of perimembranous VSD. These VSDs can be partially closed by tissue from the tricuspid valve, and many defects become smaller with time. Rarely, aortic regurgitation may occur because of prolapse of the right or noncoronary cusp into the VSD. Canal-type or inlet defects are usually seen in common AV canal defects (described more fully below) and occur from absence of the inlet septum; they extend along the full length of the AV valve. They may also be seen in straddling tricuspid valve and in some cases of transposition or double outlet right ventricle without AV valve abnormality. Malalignment and conal septal hypoplasia defects occur as a result of malalignment or absence of the conal or infundibular septum, respectively. Malalignment defects are seen in patients with tetralogy of Fallot (discussed in Chapter 44) and interrupted aortic arch along with other complex congenital lesions. Conal septal hypoplasia defects (see Figure 43-3) are sometimes referred to as subpulmonary or supracristal VSDs. They occur within the Y-shaped septal band beneath both semilunar valves and may be associated with prolapse of an aortic cusp resulting in aortic regurgitation. The second most common type of VSDs are called muscular VSDs, which are defects located anywhere other than those described above. These defects often spontaneously close if they are small to moderate in size (see Figure 43-3).

At 4 to 6 weeks of age, the pulmonary vascular resistance (PVR) decreases, and left-to-right shunting at the ventricular level increases. If the defect is large enough to cause a significant shunt, infants may also show signs of congestive heart failure (CHF) such as sweating with feeds, poor weight gain, tachypnea, tachycardia, and hepatomegaly. On cardiac auscultation, moderate to large defects may not produce a murmur early in the newborn period. As the PVR decreases, a harsh, holosystolic murmur can be heard at the left lower sternal border, and large defects can cause a mid-diastolic rumble from an increase in flow across the mitral valve. Children with significant VSDs may also have a hyperactive precordium and a right ventricular heave. If left untreated, larger defects can eventually cause irreversible pulmonary hypertension (Eisenmenger reaction). Eventually, cyanosis results from Eisenmenger’s physiology (right-to-left shunting across the defect) when PVR exceeds systemic. At that point, closure of the VSD would not result in a decrease in pulmonary resistance or pressure.

ECG can be normal with small defects or show biventricular hypertrophy in larger defects. Chest radiography can show cardiomegaly and increased pulmonary vascular markings in symptomatic patients. Echocardiography is used to confirm the diagnosis and characterize the type of VSD.

Both small conoventricular and muscular defects often decrease in size and have a high rate of spontaneous closure within the first several years of life. Canal-type, malalignment, and conal septal hypoplasia defects do not spontaneously close and usually require surgical correction. In the absence of symptoms, smaller defects often do not require closure or medical treatment. Treatment is guided by the size of the defect. Large defects (equal to or greater than the size of the aortic valve) require repair, even in the absence of symptoms, to prevent pulmonary vascular disease. With smaller defects, treatment may depend on the child’s symptoms. Medical management includes diuretics, digoxin, higher caloric formula to meet metabolic demands, and iron supplementation if anemia is present. In hemodynamically significant lesions, surgical correction is usually performed before 1 year of age but can be done sooner if the child is symptomatic. Several centers are starting to use a transcatheter approach with an occlusion device for certain muscular VSDs.

Common Atrioventricular Canal

Common AV canal (otherwise known as endocardial cushion defect or AV septal defect) accounts for about 4% to 5% of all congenital heart disease and 40% of heart disease in children with trisomy 21. This results from the failure of the endocardial cushions to fuse (forming the canal septum), preventing separation of the common AV valve into the tricuspid and mitral valves. All cases of common AV canal with two ventricles have deficiency of the anterior portion of the atrial septum and the posterior portion of the ventricular septum. However, there are two frequent combinations of AV valve morphology and attachment to the ventricular septum.

A complete common AV canal consists of the above-mentioned septal deficiency, with the common AV valve suspended within the septal defect such that there is space proximal to the valve between the two atria (ostium primum ASD) and space distal to the valve between the two ventricles (canal-type VSD) (see Figure 43-3). An incomplete (or partial) AV canal has the same septal deficiency but has leaflet tissue dividing the valve orifice into two orifices and adhering to the crest of the ventricular septum such that there is no direct communication between ventricles. Thus, the entire septal defect, being proximal to the AV valve, is called an ostium primum ASD, and the morphology of the left side of the common AV valve is described as a cleft “mitral” because the two components of what should have formed the anterior leaflet of a mitral valve, remain separate or cleft. A transitional AV canal, similar to an incomplete canal, occurs when the AV valve attachments to the ventricular septum result in a restrictive VSD. The AV valve in this case also has two orifices. The primary defect in the canal septum remains the same, but the defects vary by degree of VSD closure by valve tissue.

Infants with a complete AV canal have symptoms consistent with large VSDs, as outlined above. Incomplete AV canals develop symptoms more consistent with ASDs but can be compounded by symptomatology from left AV valve regurgitation. Transitional AV canal defects can vary in their presentation and symptoms depending on the size and level of restriction at the VSD and the amount of AV valve regurgitation. The cardiac examination varies with each defect and can reveal a hyperactive precordium, a holosystolic murmur at the lower left sternal border (VSD), a systolic murmur at the apex (left AV valve regurgitation), and a diastolic rumble at the lower left sternal border or the apex (because of increased flow across the AV valves in diastole). An ECG with a “superior QRS axis” (−4- to −150 degrees) is a hallmark of this defect. A chest radiogram can show cardiomegaly with increased pulmonary vascular markings. An echocardiogram will readily identify and characterize the defect.

Medical and surgical management of complete AV canals is similar to that of large VSDs. Surgical repair is usually performed by 4 to 6 months of life with a concern for developing pulmonary vascular disease with delayed closure. Medical management and timing of surgical repair of incomplete AV canals depend largely on the degree of left-sided AV valve regurgitation. Long-term complications of these defects include AV valve regurgitation or stenosis, heart block, and left ventricular outflow tract obstruction. Even with early surgical repair, a subset of patients (especially those with Down syndrome) can still develop pulmonary vascular disease.

Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) accounts for 5% to 10% of all congenital heart disease in term infants. In premature infants weighing less than 1750 g, the incidence is much higher at about 40%.

Failure of the ductus to close after birth results in a left-to-right shunt between the aorta and the pulmonary artery (Figure 43-4). The magnitude and direction of the shunt depend on the size of the open ductus and pulmonary versus systemic vascular resistance. For example, neonates with severe pulmonary hypertension will have a right-to-left shunt (pulmonary artery to aorta).

Figure 43-4 Patent ductus arteriosus.

Infants with small PDAs are asymptomatic; however, those with larger PDAs can present with CHF symptoms. Physical examination reveals bounding pulses, widened pulse pressures, and a continuous murmur on cardiac auscultation. ECG and chest radiography findings are similar to those of a VSD; normal if the ductus is small; and with evidence of cardiomegaly, biventricular hypertrophy, and increased pulmonary markings if the defect is large.

Patients with a suspected PDA should be evaluated with chest radiography and ECG, as well as echocardiography. In premature infants, indomethacin can be used to induce PDA closure. In term infants and children, closure is achieved either through catheter closure with a coil or other ductus occluder or with surgical ligation. If a large ductus is left unrepaired, patients may develop pulmonary vascular disease over time.

Aortic Valve Disease

Valvar aortic stenosis (AS) comprises about 3% to 8% of congenital heart defects or four in 100,000 live births. There is a strong male predominance (80%). Whereas critical AS (unicuspid aortic valve) presents shortly after birth with symptoms of CHF or shock, noncritical AS (bicuspid aortic valve) is often detected through physical examination findings of a systolic murmur. Bicuspid aortic valve is the most common congenital heart defect and occurs in 1% to 2% of the population. Not all bicuspid aortic valves become stenotic or regurgitant, but patients should continue to be screened periodically throughout life because patients with bicuspid aortic valves can develop aortic regurgitation in later childhood or adulthood and calcific AS or aortic root dilatation and dissection in adulthood.

Supravalvar AS occurs above the level of the aortic valve and is seen in Williams syndrome. It is the least common type of AS and often involves abnormalities in the elastin gene. Subaortic stenosis accounts for 10% to 20% of AS in children. It can result from a subaortic membrane (fibrous tissue in the aortic outflow tract), tunnel-like narrowing of the outflow tract or from dynamic obstruction as seen in hypertrophic cardiomyopathy. Subaortic stenosis may be seen with other cardiac defects such as VSDs, common AV canal, and coarctation of the aorta.

AS tends to progress rapidly during the first 2 years of life and during puberty. Most children with AS presenting after infancy are asymptomatic. With severe obstruction, children might present with chest pain on exercise, syncope, heart failure, or sudden death. Exercise restriction to lower intensity sports is extremely important in AS.

Cardiac examination can reveal a thrill at the suprasternal notch and the carotids. In severe cases, the second heart sound can be narrowly or even paradoxically split (rare in children because severe stenosis usually causes an inaudible aortic valve closure). Auscultation reveals a systolic ejection click followed by a crescendo-decrescendo systolic ejection murmur at the right upper sternal border radiating to the carotids. An ECG can show left ventricular hypertrophy (LVH) and, when accompanied by ST changes and T inversion, suggest severe obstruction. ECGs in newborns can be normal. Chest radiography results are usually normal. Echocardiography is important in the differentiation of valvar, supravalvar, and subvalvar AS and in assessing the gradient across the area of stenosis.

Intervention in the form of surgical valvotomy or balloon valvuloplasty is done for all infants with critical AS regardless of the gradient and in children with noncritical AS with a gradient greater than 50 to 60 mm Hg as measured by cardiac catheterization (Figure 43-5). The gradient upon which intervention is undertaken also depends on the presence of symptoms, changes on rest or exercise ECG, and the desire to play competitive sports. After intervention, the gradient is usually reduced, but resultant aortic regurgitation is not uncommon.

Figure 43-5 Balloon aortic valvotomy.

Aortic insufficiency (AI) very infrequently occurs as an isolated lesion. Instead, it can be seen in association with conoventricular VSDs with a prolapsed aortic leaflet, subaortic stenosis, bicuspid aortic valve, connective tissue disorders such as Marfan’s disease, or as a result of endocarditis. Rheumatic fever should always be considered in a patient with new-onset AI. The presentation and treatment of AI are discussed in Chapter 49.

Coarctation of the Aorta

Coarctation of the aorta is a discrete narrowing of the distal aortic arch opposite the entrance of the ductus arteriosus or the ligamentum (after ductal closure) (Figure 43-6). In some rare instances, it can be a narrowing of the abdominal aorta. It constitutes about 8% of all congenital heart defects. Boys are affected about four times more frequently than girls. Turner’s syndrome should be suspected in any girl with aortic coarctation. Coarctation is also frequently associated with left-sided lesions such as bicuspid aortic valve, AS, mitral valve abnormalities, and VSDs. It can also be associated with noncardiac abnormalities such as intracranial aneurysms.

Figure 43-6 Coarctation of the aorta.

In neonates with critical or severe coarctation, the presentation is usually shock. Although they too sometimes have discrete juxtaductal coarctation, infants usually have arch hypoplasia proximal to the entrance of the ductus arteriosus (see Figure 43-6) along with intracardiac abnormalities. With slightly less severe coarctation, infants can present with symptoms of CHF, notably feeding intolerance. Children who have adapted to the gradual development of discrete coarctation are often asymptomatic despite upper extremity hypertension but may experience claudication; cold extremities; and rarely, chest pain with exercise.

The typical findings in patients with coarctation are elevated systolic pressures in the upper extremities and lower systolic blood pressures in the lower extremities. However, infants may not have upper extremity hypertension but only a lower extremity hypotension. Therefore, blood pressures in all four extremities should be measured because the blood pressure differential can vary in location based on the area of coarctation and the arch anatomy. Absent or diminished femoral pulses and a delay between the radial pulse and the femoral pulse may be noted. Continuous murmurs from collateral vessels can be auscultated in the back in older children. Children with significant collaterals may not have a significant blood pressure differential. ECG may show right ventricular hypertrophy (RVH) (infants) or LVH (older infants and children) depending on the severity. The chest radiography usually shows increased pulmonary markings and cardiomegaly. In older children, rib notching can be seen in the third through eighth ribs secondary to the erosion by dilated tortuous intercostal arteries connected to collaterals. In younger children, echocardiography may be sufficient for the diagnosis. In older children and adults, further imaging of the distal arch by magnetic resonance imaging (MRI) or computed tomography scan may be required.

Primary surgical repair is recommended in infants and young children because of the high incidence of recoarctation with balloon angioplasty. Older adolescents and adults are candidates for covered stent placement and balloon angioplasty in the cardiac catheterization laboratory. Patients are still at risk for developing hypertension even after repair. The older the patient is at the time of diagnosis, the more likely he or she is to develop chronic hypertension.

Pulmonary Valve Disease

Pulmonary stenosis (PS) occurs in about 8% of children with congenital heart disease or seven in 100,000 live births. PS can be valvular, subvalvular, or supravalvular. Valvular PS is the most common (90%) and is usually seen with varying degrees of leaflet fusion of all three commissures (Figure 43-7). Dysplastic pulmonary valve abnormalities can be seen in association with Noonan’s syndrome. Supravalvular stenosis is very rarely an isolated finding and is associated with Williams syndrome, Alagille syndrome, or LEOPARD (lentigines, ECG conduction abnormalities, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retarded growth, and sensorineural deafness) syndrome. Subvalvar PS is rare in isolation and is typically part of tetralogy of Fallot or is caused by an anomalous muscle bundle of the right ventricle (so-called double-chambered RV) associated with a conoventricular VSD.

Figure 43-7 Pulmonary stenosis.

Infants and children with noncritical PS are rarely symptomatic. In more severe cases, children can have dyspnea with exertion and right-sided heart failure. Newborns with critical or severe PS present with cyanosis from right-to-left shunting through a patent foramen ovale, tachypnea, and poor feeding. On cardiac examination, one should hear a decreased P2 and a harsh systolic ejection murmur radiating to the back. On chest radiography, a dilated pulmonary artery may be evident. RVH is usually present on ECG with moderate to severe cases of PS. Echocardiography will characterize the type of PS and allows for measurement of the gradient across the area of stenosis. Gradients of less than 40 mm Hg are mild, 40 to 70 mm Hg are moderate, and greater than 70 mm Hg is considered severe PS.

No restriction of activity is necessary unless PS is severe. For children with mild degrees of stenosis, periodic echocardiograms are recommended to follow for worsening stenosis. For children with valvar PS with a gradient greater than 50 mm Hg as measured by cardiac catheterization, a balloon valvuloplasty is performed. Newborns with severe or critical PS need balloon valvuloplasty regardless of the gradients because severe PS may result in decrease output across the valve and therefore a lower gradient. (If unsuccessful, a surgical valvotomy can be performed.) Subvalvar PS is corrected by a surgical approach.

Mitral Valve Disease

Mitral stenosis (MS) is an uncommon isolated congenital heart defect but appears more commonly as a complication of rheumatic heart disease. Structural abnormalities that can cause MS include parachute mitral valve (a defect in the mitral valve in which there is only one papillary muscle present), mitral valve arcade (direct attachment of leaflets to the papillary muscles without intervening chordae and therefore absence of interchordal spaces), or a supramitral ring. Any left-sided obstructive lesion warrants evaluation of the mitral valve.

Mitral regurgitation (MR) is also commonly found as a complication of rheumatic heart disease but can occur with structural abnormalities as well. Isolated cleft mitral valve is a rare form of congenital MR. Mitral valve prolapse (MVP) may also result in MR caused by posterior movement of one leaflet into the left atrium during systole (Figure 43-8). Although unusual in infants, MVP can be seen in patients with connective tissue disorders such as Marfan and Ehlers-Danlos syndromes. Bacterial endocarditis of the mitral valve may also result in MR.

Figure 43-8 Mitral valve prolapse.

Mitral valve disease caused by rheumatic heart disease is discussed in further detail in Chapter 49.

Vascular Ring

Vascular rings are anomalies of the aortic arch that can cause compression of the trachea, esophagus, or both. Infants may present with “noisy breathing” or with stridor. Respiratory distress associated concomitant upper respiratory infections is common. Older children and toddlers might present with swallowing difficulties, although asthma without family history and unresponsive to medical management warrants consideration of a vascular ring. Double aortic arch and right aortic arch with a retroesophageal diverticulum of Kommerell are the two most common types of vascular rings (Figure 43-9). If a vascular ring is suspected, chest radiography can determine arch sidedness and sometimes indentation of the trachea (double aortic arch). In addition, a barium esophagram can reveal a large posterior indentation on the esophagus (virtually all rings). Definitive diagnosis can be made by MRI. Surgical repair is indicated in any symptomatic patient. Symptoms do not always improve immediately and may persist for up to 1 year after repair.

Figure 43-9 Vascular rings.