Congenital heart defects are the most common birth defects and together account for the highest resource utilization among all hospitalized children. These defects encompass numerous structural heart lesions, both isolated and in combination, and their resulting unique physiologies and treatments. This chapter will focus on the lesions that most commonly require surgery or critical care during infancy. A brief discussion of other lesions that may be incidentally found on neonatal echocardiograms concludes the chapter. Patent ductus arteriosus and pulmonary hypertension are discussed in Chapters 9 and 30, respectively.
Definition
A ventricular septal defect (VSD) is a defect in the ventricular septum between the left and right ventricles. VSDs may be solitary, multiple, or occur as a part of many additional forms of congenital heart disease. VSDs are classified by size and location within the septum.
Incidence
VSDs occur in 1.5-3.5/1000 live births, and isolated VSDs make up approximately 20% of all congenital heart disease. In premature or low-birthweight infants, VSD may occur in as many as 7/1000 births.
Pathophysiology
The pathophysiology of VSD depends on the magnitude of left-to-right shunt across the defect. This is primarily influenced by the defect’s size.
Blood will flow from an area of high pressure (or resistance) to an area of lower pressure (or resistance), so typically blood flows from the left ventricle (LV) through the VSD to the right ventricle (RV) and out to the pulmonary arteries during systole. Relatively little flow across the defect occurs during diastole as both ventricles are at relatively low pressures.
Small defects restrict significant left-to-right shunting, and no significant pathophysiology occurs. Large or multiple defects allow significant left-to-right shunt, causing the pulmonary circuit to have supranormal blood flow.
At 6 to 8 weeks of age, symptoms of congestive heart failure (CHF) may begin to be evident as pulmonary vascular resistance has fallen since birth and hemoglobin has reached its physiologic nadir; both of these events may result in increased left-to-right shunt. Pulmonary venous return to the left atrium is increased. Initially, the neonatal heart compensates for this volume overload by increasing the resting heart rate. Over time, the volume overload causes the left atrium and LV to become dilated. When the heart can no longer compensate for the increased venous return, pulmonary venous congestion occurs. Following these changes, CHF will eventually result in systemic venous congestion and hepatomegaly.
If a VSD is left uncorrected, pulmonary vascular obstructive disease has been shown to develop as early as 6 to 12 months of age; however, Eisenmenger physiology with right-to-left shunt at the VSD typically does not occur until adolescence.
Risk factors
Multiple genes have been implicated. The risk of VSD is increased with a parent who has a VSD. Patients with chromosomal abnormalities, particularly trisomy 13, 18, and 21, are at increased risk of VSD.
Clinical presentation
Signs and symptoms
Isolated VSDs are rarely noted at birth, and murmurs typically do not become prominent until after pulmonary vascular resistance has fallen to subsystemic levels.
As CHF evolves, the infant will typically develop the following signs and symptoms in this order: (1) tachycardia; (2) cardiomegaly; (3) pulmonary venous congestion; (4) systemic venous congestion as evidenced by hepatomegaly; (5) failure to thrive.
Clinical variability
The degree of CHF correlates closely with the degree of left-to-right shunt across the defect. If the defect is small, the infant may remain asymptomatic. If the defect is large, symptoms of CHF may be pronounced.
Diagnosis
Auscultation of a murmur is the most common initial sign of a VSD. It is typically not prominent until after pulmonary vascular resistance has fallen. In smaller defects, a holosystolic murmur due to turbulent blood flow across a pressure-restrictive defect is heard. In large, nonpressure restrictive defects, the blood flow across the defect is not turbulent and may not result in a murmur; however, excess blood flow across the pulmonary valve can cause a systolic ejection murmur.
The electrocardiogram (ECG) is typically nonspecific but may show LV or biventricular hypertrophy.
The chest x-ray may show cardiomegaly and increased pulmonary vascular markings.
Echo is diagnostic and should be obtained in all infants in which VSD is suspected.
Management
Medical
Treatment is directed toward relief of symptoms. Diuretics are typically used to help decrease venous congestion and symptoms of heart failure. Adequate caloric intake and growth should be closely monitored. Many defects, particularly muscular defects or perimembranous defects, may close or become increasingly restrictive with age. Defects at other locations do not typically close with age.
Catheter-based intervention
VSD closure devices implanted in the cardiac catheterization lab are available but are infrequently used in the United States currently.
Surgical intervention
Surgical closure of the VSD is the standard of care for VSDs with significant left-to-right shunt.
Timing of the surgical procedure depends on the severity of heart failure symptoms.
Primary VSD closure in the neonatal period is uncommon.
If an infant has symptomatic heart failure that is not adequately controlled with medication, then surgery is indicated.
Most centers currently electively close VSDs with a significant left-to-right shunt by 1 year of age even without CHF symptoms to avoid the development of pulmonary vascular disease.
Early developmental/therapeutic interventions
Routine developmental interventions should be initiated from birth. Adequate growth requires particular attention given the possibility of CHF.
Prognosis
Surgical mortality is less than 1%. Long-term survival appears equivalent to healthy patients following isolated repair of a VSD.
Postoperative care
Care in the postoperative recovery period is supportive.
Surgical site bleeding in the postoperative period should be monitored and blood products replaced as appropriate until adequate hemostasis is achieved.
Continuous blood pressure monitoring via arterial line is standard. Blood pressure may be inadequate and should be supported with vasoactive infusions as necessary.
After ensuring hemodynamic stability, the ventilator can be immediately weaned as tolerated to extubation. Saturations should be normal following repair.
Urine output may be low following surgery resulting in a positive fluid balance and edema. In an infant who has required diuretics prior to surgery, diuretics are usually required to improve urine output and achieve a negative fluid balance.
Arrhythmias are uncommon, although surgical complete heart block may occur in 1% to 2% of cases.
Residual VSDs, either small additional defects that were unrecognized pre- or intraoperatively or those resulting from incomplete closure of the defect, can cause postoperative CHF and prevent weaning from mechanical ventilation if the residual shunt is large. Other intracardiac structures, most notably the atrioventricular valves and the aortic valve, can be damaged during VSD closure and residual lesions should always be suspected if a patient is not following a typical postoperative course.
Reoperation
Reoperation is uncommon. The rate of early reoperation is 1% and primarily results from VSD patch dehiscence or incomplete closure of the defect.
Complete heart block requiring pacemaker implantation occurs in approximately 1%.
Ongoing developmental/therapeutic interventions
Typical neonatal developmental care should resume as possible following surgical recovery.
Cardiac
After the initial postoperative period, visits following surgery occur every 1 to 2 years initially, but often space to 3 to 5 years by adulthood in uncomplicated cases. Rare (<1%) late abnormalities include complete heart block and double-chambered RV.
Developmental
Neurodevelopmental outcome at 1 year of age has been noted to be within the normal limits for most patients following VSD closure.
However, if surgical closure of the VSD is performed in early infancy, most often associated with failure to thrive, the risk of developmental disabilities or delays is increased.
Developmental screening is recommended and referral for formal developmental evaluation may be useful and beneficial.
Definition
Tetralogy of Fallot (TOF) is a congenital heart defect that consists of the following four abnormalities: a VSD, pulmonary stenosis, overriding aorta, and RV hypertrophy. In actuality, anterior malalignment of the conal septum is the single underlying factor that leads to these four abnormalities. Pulmonary stenosis is always present, but its severity can vary widely, ranging from very mild in some cases to severe with multiple levels of RV outflow tract (RVOT) obstruction or atresia.
The most common form of TOF involves a stenotic but patent RVOT. TOF with pulmonary atresia and TOF with absent pulmonary valve can also occur and present with different pathophysiologic concerns.
Associated cardiovascular abnormalities: Atrial septal defects (ASD) are common. Right-sided aortic arch is reported in 25% of TOF. Coronary artery anomalies, particularly the left anterior descending artery arising from the right coronary artery, are common and are important to surgical planning. Persistent left superior vena cava is reported in 11% of patients. Complete atrioventricular septal defect (AVSD) may occur, particularly in children with trisomy 21. Aortopulmonary collateral vessels may be present, particularly in patients with pulmonary atresia.
Incidence
TOF occurs in 3-5/10,000 live births and makes up approximately 7% of all congenital heart disease. It is the most common form of cyanotic heart disease.
Pathophysiology
Pathophysiology and the resulting clinical presentations of TOF are determined by the degree of RVOT stenosis.
If the stenosis is mild, the neonate may have adequate, or even excess, pulmonary blood flow and have physiology similar to that of a large VSD. The patient may be acyanotic, often referred to as a “pink tet.” With increasing RVOT obstruction, more deoxygenated blood in the right ventricle will shunt right to left across the VSD resulting in cyanosis. The degree of cyanosis is related to magnitude of right-to-left shunt and resulting decrease in pulmonary blood flow.
Risk factors
The genetic mechanisms underlying TOF are unknown, but a genetic component is clearly present with a 2% to 3% recurrence rate with an affected sibling, and a 1.5% to 2.5% recurrence rate with an affected parent.
TOF is also associated with recognized genetic syndromes including DiGeorge, Alagille, Holt-Oram, VACTERL, CHARGE, Kabuki, and the chromosomal defects trisomy 13, 18, and 21.
Environmental associations include maternal diabetes, mothers with PKU and uncontrolled dietary phenylalanine, maternal retinoic acid or trimethadione usage.
Clinical presentation
Signs and symptoms
Infants with typical TOF present with cyanosis in varying degrees as described above.
Infants may or may not be tachypneic or have respiratory distress depending on the degree of pulmonary stenosis and pulmonary blood flow.
A systolic ejection murmur is typically present.
Clinical variability
As discussed above, signs range widely depending on the degree of RVOT obstruction.
Diagnosis
Diagnosis should be considered in any neonate with cyanosis.
Pulse oximetry most often demonstrates decreased saturations in both the upper and lower extremities.
ECG is typically nonspecific but may show prominent right-sided forces and/or right axis deviation.
The classic chest x-ray finding associated with TOF is the “boot-shaped heart” with left heart border concavity and an upturned apex resulting from infundibular and pulmonary artery hypoplasia.This is often not apparent on neonatal x-rays. Pulmonary vascular markings vary with the degree of RVOT obstruction, and are typically decreased in the cyanotic TOF patient.
Echo is diagnostic and should be obtained in all infants in which TOF is suspected.
Management
Medical
Treatment in the neonatal period depends on the degree of cyanosis.
If arterial oxygen saturation is normal, no intervention in the neonatal period may be needed. Mild or moderate cyanosis with arterial oxygen saturation >75% can typically be observed without intervention as well. More profound cyanosis may require intervention.
Arterial blood gas analysis should be obtained, and inadequate partial pressure of oxygen (PaO2) should prompt further treatment. In these cases, prostaglandin infusion should be started to maintain ductal patency and provide an additional source of pulmonary blood flow.
Supplemental oxygen should be provided. If necessary, the patient can be intubated and mechanically ventilated with a high percentage of inspired oxygen.
Transfusion with packed red blood cells may increase systemic oxygen delivery by increasing hematocrit.
Catheter-based intervention historically has little role in the current treatment of TOF. Catheterization with angiography is sometimes necessary to characterize the blood supply of different pulmonary segments. Recently, catheter-placed RVOT stents have begun being used as an early alternative to surgical shunt.
Hypercyanotic spells
Hypercyanotic spells (often called “tet spells”) are a unique aspect of TOF. Hypercyanotic spells are periods of severe, prolonged hypoxemia that may occur in TOF. Although they are uncommon in the neonatal period, they can occur.
The exact, underlying pathophysiology for hypercyanotic spells remains unclear, but they involve an acute increase in right-to-left shunting across the VSD. Abrupt decrease in systemic vascular resistance or increase in RVOT obstruction may contribute. Increasing right-to-left shunting can lead to hypoxia and metabolic acidosis, secondary hyperpnea and increased systemic venous return. Greater systemic venous return leads to greater right-to-left shunt across the VSD, which potentiates a worsening cycle of cyanosis.
Hypercyanotic spells typically present with severe cyanosis. The systolic ejection murmur is typically decreased or absent. This is because the murmur is due to flow across the RVOT, and in a hypercyanotic spell, this flow is decreased, with increased right-to-left shunt across the VSD. If untreated, the infant’s status may deteriorate to obtundation or death.
Management of hypercyanotic spells requires unique interventions aimed at promoting forward flow across the RVOT, in part through increasing systemic vascular resistance to encourage decreased right-to-left shunt. Standard therapy includes administration of oxygen, volume infusion, and sedation with morphine to decrease metabolic demand and decrease hyperpnea. Sodium bicarbonate corrects acidosis and decreases hyperpnea. Placing the infant’s knees to chest can increase systemic vascular resistance. Systemic vasoconstricting agents, such as phenylephrine or vasopressin, may also be used to raise systemic vascular resistance. Ketamine can both increase systemic vascular resistance and sedate the patient. Propranolol or esmolol infusion has also been used effectively to terminate hypercyanotic spells, although the mechanism is slightly unclear. In rare cases of medically refractory hypercyanotic spells, general anesthesia, extra-corporeal membrane oxygenation, or emergent surgical intervention is needed.
Surgical intervention for TOF, like medical therapy, depends on the clinical presentation.
In acyanotic infants or those with mild cyanosis, surgery is typically not necessary in the neonatal period and is performed electively at 3 to 6 months of age.
Complete repair of TOF results in normal physiologic circulation and consists of closure of the VSD, relief of subpulmonary obstruction via division of muscle bundles, and relief of valvar pulmonary stenosis as needed via pulmonary valvotomy, transannular patch, or placement of a RV-to-pulmonary artery conduit.
In patients with severe cyanosis at birth or progressive cyanosis in the neonatal period, earlier surgical intervention is required and may consist of either placement of an aortopulmonary shunt followed by subsequent complete repair when the infant is older or primary complete repair depending on center and surgeon preference.
Early developmental/therapeutic interventions
Maximal oxygenation should be a focus of early therapy to avoid cerebral hypoxemia.
Prognosis
Survival following repair of TOF is excellent with early mortality <3% and similar survival into adulthood in otherwise uncomplicated cases.
Postop care
Care in the postoperative recovery period is supportive.
Surgical site bleeding in the postoperative period should be monitored and blood products replaced as appropriate until adequate hemostasis is achieved.
Continuous blood pressure monitoring via arterial line is standard. Blood pressure may be inadequate and should be supported with vasoactive infusions as necessary.
The RV may be noncompliant and require supranormal central venous pressure to facilitate adequate ventricular filling. This is typically achieved with liberal early fluid administration.
After ensuring hemodynamic stability, the ventilator can be immediately weaned as tolerated to extubation. Oxygenation and systemic saturations should be normal following repair with one specific exception—the presence of a residual ASD. RV noncompliance can result in increased right atrial pressures. This causes blood to shunt right to left across the atrial septum with subsequent cyanosis, but this shunting helps preserve cardiac output. Thus, surgeons may often electively leave a small residual ASD when RV diastolic dysfunction is anticipated.
Neonates undergoing TOF repair are even more prone to this restrictive RV physiology with subsequent third spacing and edema. Urine output may be low following surgery, resulting in a positive fluid balance and edema; this often requires diuretic therapy to improve urine output and achieve a negative fluid balance.
A rare, but important downstream effect of RV diastolic dysfunction is abdominal compartment syndrome. The buildup of ascitic fluid and high intra-abdominal pressure can compromise systemic venous return, renal blood flow, and ventilation, and in the most extreme cases abdominal decompression may be necessary.
Arrhythmias occur frequently in the postoperative period. Junctional ectopic tachycardia (JET) is most commonly associated with TOF. JET results in a narrow complex tachycardia that may be profound and cause hemodynamic instability. Amiodarone infusion, systemic cooling, minimizing catecholamines, and sedation all may be effective in slowing JET. A right bundle branch block is very common following repair of TOF. Surgical heart block may also rarely occur.
Pulmonary valve regurgitation, particularly following transannular patch repair, is often present but is typically well tolerated.
Residual RVOT obstruction can occur to various degrees, and if severe, may cause difficulty weaning from postoperative support and require reintervention.
Reoperation
Early reoperation following TOF repair is rarely required.
Reoperation within the first few years following surgery occurs in 3% to 7% of patients, typically due to residual RVOT obstruction, conduit failure, or residual VSD.
Replacement of the pulmonary valve is increasingly recognized as a necessity in adulthood to prevent progressive RV dilation and is becoming a common procedure in adults repaired using a transannular patch technique as an infant.
Recently reported reoperation rates are approximately 30% to 40% by adulthood.
The advent of catheter-based placement of pulmonary valves may decrease the need for surgery in the future.
Ongoing developmental/therapeutic interventions
Typical neonatal developmental care should resume as possible following surgical recovery. Patients undergoing complete repair as a neonate should be referred for early intervention, and early intervention referral should be considered in all infants.
Cardiac
After the immediate postoperative period follow-up visits most often occur twice yearly or annually. Several specific late cardiac complications may arise.
Pulmonary regurgitation can lead to right ventricular dilation and decreased function. Progressive ventricular dilation, RV dysfunction, or the emergence of new symptoms should prompt consideration for a pulmonary valve replacement. RV volumes are often serially followed by cardiac MRI in patients with significant pulmonary regurgitation.
Residual RVOT obstruction may occur, including subvalvar, valvar, supravalvar, or branch pulmonary artery stenosis. Progression of the stenosis, the development of RV hypertrophy or dysfunction, or symptomatology should prompt consideration of intervention to relieve the obstruction via either surgery or interventional cardiac catheterization.
Arrhythmias, particularly ventricular arrhythmias, have been associated with sudden death in TOF. Any new complaints of palpitations or syncope should be investigated and routine screening with a 24-hour Holter monitor is recommended.
Developmental
Neurodevelopmental evaluation of patients with TOF who have undergone surgical repair has shown decreases in gross motor function, expressive and receptive language, intelligence, and academic achievement, and reduced oral and speech motor control functions.
Referral to early intervention services in infancy can be useful and beneficial.
In addition, at age 5 to 11 years after TOF corrective surgery in infancy, these children have been found to be at significantly increased risk for attentional dysfunction in the area of executive control.
Following TOF repair in infancy, children should be referred for formal developmental evaluation and remain under neurodevelopmental surveillance into adolescence to permit early identification of emerging difficulties.
Definition
D-transposition of the great arteries (d-TGA) is a congenital heart defect in which the aorta arises from the morphologic and physiologic RV and the pulmonary artery arises from the morphologic and physiologic LV.
Venous blood return is normal with systemic veins draining to the right atrium and pulmonary veins draining to the left atrium.
This anatomy results in cardiopulmonary circulations in parallel rather than in series; the pulmonary circuit is oxygen rich, and the systemic circuit is oxygen poor.
In 50% of neonates with d-TGA, there are no other associated heart lesions, 40% to 45% have a VSD, 20% to 25% have obstruction to pulmonary outflow, and 5% have an abnormality of the aortic arch (typically coarctation of the aorta). Coronary artery abnormalities and tricuspid valve abnormalities may also be present.
Incidence
d-TGA occurs in 10-30/100,000 live births and makes up 5% to 7% of all congenital heart disease. It occurs more often in males than females (approximately 3:1).
Pathophysiology
The parallel, separate, pulmonary, and systemic circulations result in cyanosis in all neonates with d-TGA. The degree of cyanosis is dependent on the degree of communication or mixing between the parallel circulations.
Mixing can occur at multiple locations. The patent ductus arteriosus (PDA) allows mixing between the aorta and pulmonary artery; however, this mixing alone is typically inadequate to maintain adequate systemic oxygenation. Mixing of oxygenated and deoxygenated blood can also occur through an ASD or VSD. Atrial level mixing is typically the most effective source of blood exchange between circulations via a patent foramen ovale (PFO) or ASD. If the size of the PFO or ASD is too small and restrictive to blood flow across it, cyanosis may be profound.
Maintaining a PDA via prostaglandin infusion increases blood flow to the left atrium, thus stretching the PFO and providing greater opportunity for adequate mixing.
Mixing between the parallel circulations can also occur at a VSD. However, in the absence of an adequate atrial level defect marked cyanosis may occur despite the presence of a VSD.
Risk factors
No genetic abnormalities have been identified as causative for d-TGA, and it does not have familial associations.
Diabetic mothers, maternal estrogen, or testosterone therapy during pregnancy, male gender, and advanced maternal age have all been associated with d-TGA.
Clinical presentation
Signs and symptoms
Infants with d-TGA present with cyanosis immediately after birth. Tachypnea may be present, although significant respiratory distress typically is absent. Hypotension and shock are less common but can occur.
Clinical variability
The degree of cyanosis may vary greatly depending on the degree of mixing between the parallel circulations.
Diagnosis
Diagnosis should be considered in any neonate with cyanosis.
Pulse oximetry should be documented in all four extremities.
ECG is typically nonspecific.
The classic chest x-ray finding associated with d-TGA is the “egg on a string,” resulting from absence of the main pulmonary artery segment due to the great arteries being oriented in an anterior-posterior manner. However, thymic tissue may make this finding nonapparent in neonatal chest x-rays. Pulmonary vascular markings may be prominent.
Echo is diagnostic and should be obtained in all infants in which d-TGA is suspected.
Management
Medical
Treatment is aimed at improving systemic oxygenation.
Prostaglandin infusion should be started immediately upon diagnosis to maintain PDA patency, although those with adequate mixing at the atrial level may not require continued prostaglandin therapy.
Arterial blood gas analysis should be obtained, and inadequate partial pressure of oxygen (PaO2 <30 mm Hg) should prompt further treatment.
Although the parallel circulations cause supplemental oxygen to have marginal efficacy in improving cyanosis, supplemental oxygen should be provided to optimize pulmonary venous saturation. If necessary, the patient can be intubated and mechanically ventilated with a high percentage of inspired oxygen.
A fluid bolus with crystalloid may temporarily improve mixing at shunts, and significant fluid administration may be necessary.
Transfusion with packed red blood cells may increase systemic oxygen delivery by increasing hematocrit.
Sedation and neuromuscular blockade may decrease metabolic demand and improve oxygen balance.
Catheter-based intervention
Despite medical therapy, cyanosis and inadequate oxygen delivery may persist. In these cases, balloon atrial septostomy (BAS) is generally performed to create a larger ASD and increase mixing at the atrial level.
In BAS, a balloon-tipped catheter is advanced from the right atrium into the left atrium. The balloon is inflated, and the catheter is pulled rapidly back across the atrial septum. This enlarges the atrial communication by disrupting atrial septal tissues.
BAS should be performed urgently in any neonate with prohibitive cyanosis and a restrictive atrial septum.
Surgical intervention
The arterial switch operation (ASO) in the neonatal period is standard of care. The ASO involves transection of both great arteries above the level of the semilunar valves, translocation of the arteries, and reanastomosis in the physiologically correct position, thus establishing normal pulmonary and systemic circulation in series.
The pulmonary artery is typically repositioned anterior to the aorta with the branch pulmonary arteries draping anteriorly over the aorta; this is termed the Lecompte procedure.
In addition, the coronary arteries must be translocated and reanastomosed to the aorta.
Additional defects, such as an ASD, VSD, or coarctation of the aorta (CoA) are typically also repaired during the surgery.
Regarding timing of the operation, if preoperative cyanosis is prohibitive despite BAS, surgery should be urgently performed. If the patient is hemodynamically unstable or acidotic along with the cyanosis, preoperative stabilization with ECMO may be necessary. If the degree of systemic oxygenation is adequate, the optimal timing of the ASO remains controversial.
Some authors have demonstrated a decreased incidence of periventricular leukomalacia in infants who are operated on within the first 4 days of life. Most surgeons agree that for d-TGA with an intact ventricular septum, repair should preferably occur within 7 days.
Early developmental/therapeutic interventions
Maximal oxygenation should be a focus of early therapy to avoid cerebral hypoxemia.
Prognosis
Prognosis of expeditiously diagnosed, uncomplicated d-TGA is very good with an average survival into adulthood following the arterial switch procedure of >95%. A higher mortality risk is associated with d-TGA along with VSD or coarctation.
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