Description and Special Anatomic Considerations

Acyanotic congenital heart disease (Table 28-4) is characterized by a lack of cyanosis. In further defining these disorders, they are often classified on the basis of the presence or absence of left-to-right shunt.

TABLE 28-4 Acyanotic Congenital Heart Disease with a Left-to-Right Shunt

Ventricular septal defect (VSD), the most common form of congenital heart disease, represents approximately one third of all major congenital cardiac defects. VSDs are generally classified into one of four groups, depending on their location in the interventricular septum (Fig. 28-1). These may be associated with other cardiac defects, such as atrioventricular valve defects, coarctation of the aorta, and other left-to-right shunts. The ventricular septum anatomy is complex, and many associated anatomic structures are key in the consideration of the repair, such as location of the conduction system of the heart.

FIGURE 28-1 The classic anatomic nomenclature assigning VSDs to one of four anatomic types.

(Redrawn from Wells WJ, Lindesmith GG. Ventricular septal defect. In Arciniegas E [ed]. Pediatric Cardiac Surgery. Chicago, Year Book Medical, 1985.)

Atrial septal defects, which usually cause volume overload of the right ventricle and increased pulmonary blood flow, are also categorized on the basis of their location within the atrial septum. These defects can go undiagnosed for decades and can be associated with other defects, such as partial anomalous pulmonary venous return. Unfortunately, when they are undiagnosed for several decades, fixed pulmonary vascular changes may develop that prohibit surgical correction.

Aortopulmonary-level shunts, such as a patent ductus arteriosus, are less common as isolated defects because they typically close spontaneously in the newborn period. However, they are often seen in conjunction with other complex congenital heart disease. If they are undiagnosed during the course of many years, there is some risk for bacterial endocarditis (rare), and if the connection is large, Eisenmenger syndrome or fixed irreversible pulmonary vascular changes may develop. Aortopulmonary windows, which are direct communications between the great vessels, are much more uncommon and can be challenging to diagnose if one is not attentive to subtle echocardiographic findings.

Aortic root–to–right heart shunts, such as a ruptured sinus of Valsalva aneurysm, coronary artery fistula, or anomalous origin of the left coronary artery from the pulmonary artery, are uncommon. However, a high index of suspicion must be present when one evaluates a newborn or older infant with a diagnosis of dilated cardiomyopathy because anomalous origin of the left coronary artery from the pulmonary artery may be difficult to exclude as a source of the dysfunction.

Multiple-level shunts are typified by the complete atrioventricular septal defect (AVSD, previously known as endocardial cushion defect) with a common atrial- and ventricular-level shunt. A variety of any or all of these defects can combine to present with multiple-level shunts. The most challenging aspect for the surgeon in addressing AVSD is often the common valve function and anatomy.

Indications

Surgical intervention for acyanotic heart defects with left-to-right shunt is almost always primarily driven by clinical symptoms and secondarily by risks of not intervening in a timely fashion. Many lesions can be corrected in infancy but do not need to be addressed until the child is older (or larger) to allow better surgical field access or more optimal tissue “durability.” For example, atrioventricular valve tissue is very thin and friable and may be better manipulated at some point later than 1 month of age, if surgery can be safely delayed without resulting in any negative clinical outcomes.

In this broad category of defects, the usual driving indication for early surgical intervention is congestive heart failure and how difficult it is to control with medical management. This is balanced against the surgical risks for the various procedures and the possible comorbidities that may exist as a part of a clinical syndrome or initial clinical presentation. An infant’s weight and gestational age also may play a role in the surgical timing for many of these defects. A typical scenario for surgical intervention based on prematurity and significant lung disease as a result of left-to-right shunt is a patent ductus arteriosus. The advent of indomethacin⁸ as medical management for closure of these defects has significantly reduced the need for surgical intervention.⁹ However, in extreme prematurity, renal disease, and severe diastolic “runoff” through a large patent ductus arteriosus, surgery may be a relative emergency.

For example, surgical timing for closure of a hemodynamically significant VSD may be indicated at a few weeks or as late as a few years. The later closure may be indicated for a late-identified supracristal VSD or a perimembranous VSD with a coexistent subaortic membrane or prolapse of the aortic valve leaflets. Both of these defects have been implicated in progressive aortic valve damage,^10,11 even though they may be quite small and have no risks for long-term pulmonary vascular disease or congestive heart failure.

The diagnosis of anomalous left coronary artery is typically an emergent one; acute surgical intervention is indicated to reestablish appropriate coronary blood flow and to avert continued or permanent myocardial damage or infarction. Less commonly, these anomalies may present after a referral for a murmur in an otherwise normal infant or child. Although they are rare presentations, surgical intervention may be delayed for a few days to allow further diagnostic evaluation, if indicated, or when other medical considerations exist.

With the diagnosis of AVSD, there can be tremendous variability of the surgical timing based on the level of shunting (i.e., atrial vs. ventricular), the complexity of the associated common atrioventricular valve disease, and the associated clinical status (Fig. 28-2).

FIGURE 28-2 Exposure and assessment of anatomy. A, The atrial incision (broken line) is parallel to the right atrioventricular groove. B, The right atrium has been opened after administration of cardioplegia. Note the coronary sinus and the location of the atrioventricular (AV) node. C, Relationship of ventricular septal defect (VSD), atrial septal defect (ASD), and common atrioventricular valve. The valve leaflets are identified as follows: LIL, left inferior leaflet; LLL, left lateral leaflet; LSL, left superior leaflet; RIL, right inferior leaflet; RLL, right lateral leaflet; and RSL, right superior leaflet. IVC, inferior vena cava; LV, left ventricle; PFO, patent foramen ovale; RV, right ventricle; SVC, superior vena cava.

(Redrawn from Backer CL, Mavroudis C, Alboliras ET, Zales VR. Repair of complete atrioventricular canal defects: results with the two-patch technique. Ann Thorac Surg 1995; 60:530-537.)

Finally, the surgical timing and types of surgery that may be employed to correct these defects are biased against the surgical experience of the performing center. This bias will be derived from a variety of issues—a surgeon’s level of expertise, perfusion and anesthesia support, and, in some cases, the presence of advanced support in the postoperative period, such as extracorporeal membrane oxygenation programs.

Contraindications

As discussed, there are many relative contraindications to surgical intervention that are usually related to weight, gestational age, coexistent disease, and surgical center bias. However, there are a few absolute contraindications to surgical interventions for acyanotic cardiac defects with left-to-right shunt. The primary contraindication to cardiac surgery for complete repair of these defects is the presence of fixed pulmonary hypertension. A pulmonary-to-systemic vascular resistance ratio greater than 0.9 : 1 or pulmonary arteriolar resistance greater than 12 Wood units is regarded as an absolute contraindication to surgery. A pulmonary arteriolar resistance of more than 8 Wood units obtained during cardiac catheterization with pulmonary vasodilation is also a contraindication to surgery.

A reactive pulmonary vascular bed noted during provocative testing in the catheterization laboratory may be a relative contraindication and merits further discussion. Small atrial septal defects with systemic-to-pulmonary shunts of less than 0.7 may be a relative contraindication to surgical or device closure, depending on other pathologic processes.

Outcomes and Complications

Overall surgical results for this diverse spectrum of diseases are very good, with disease-specific mortality much less than 5% for the majority of these lesions and morbidity generally in the same range. Surgical center bias and preexistent morbidity or complicating factors will dramatically affect these predicted results.

Imaging Findings

Description and Special Anatomic Considerations

Acyanotic heart defects without a shunt generally have normal oxygen saturations at rest, unless they suffer from an A-a gradient secondary to pulmonary vascular congestion from their cardiac defect. These defects⁵ include left-sided and right-sided heart obstructive lesions and regurgitant valve disease (Table 28-5).

TABLE 28-5 Acyanotic Congenital Heart Disease without a Shunt

Mitral valve disease is a rare entity in children as a primary defect although it is a common sequela in postoperative AVSD patients. As in aortic valve disease, in the younger children and infants with mitral valve disease, there is much effort made to delay surgical interventions for these disease entities. Surgical palliation with surgical repairs of the valves has been the preferred choice because homograft replacements have limited durability. Both repair and homograft replacement may provide early hemodynamic success but often require early reoperation and ultimate mechanical valve replacement. Although it is a durable solution for many decades, the size of the patient often limits the size of the mechanical valve that can be used. Furthermore, the need for long-term anticoagulation can be of significant medical risk for the complications of bleeding in these children while having a negative impact on their quality of life.

Coarctation of the aorta may occur as an isolated defect or in association with various other lesions, most commonly bicuspid aortic valve and VSD.¹³ Surgical repair of coarctation of the aorta has been one of the oldest surgical procedures available. Early limitations revolved around the size or weight of the infant, but these considerations have virtually disappeared. The controversy that continues to smolder is the role of balloon dilation or stent for the native coarctation of the aorta. Additional intracardiac defects, such as a posterior malaligned VSD, may complicate the surgery and the surgical approach. Complete repair has become the generally accepted approach to these complex defects because the prior approach of repair of the coarctation of the aorta and pulmonary artery banding has resulted in complications such as double-outlet obstruction early postoperatively and a more complicated medical and surgical management approach long term.

The extreme forms of obstructive left-sided heart lesions include hypoplastic left heart syndrome and its many variants.¹⁴ These patients can have varying degrees of hypoplasia or atresia of the left ventricle, aorta, and mitral or aortic valves, usually in some combination thereof. They all have coarctation of the aorta. Because these are duct-dependent lesions, they tend to be manifested in the first few days of life, although they may on occasion present late at several weeks of age. It is a lethal condition. Norwood first presented his approach to palliation of this entity in 1979. It essentially created a hemodynamically stable single ventricle, which could proceed down the single ventricle pathway of palliation with a bidirectional caval anastomosis and a subsequent Fontan procedure.

Acyanotic right-sided heart lesions are few in number but tend to be more approachable through interventional cardiac catheterization procedures of balloon pulmonary valvuloplasty, angioplasty, or pulmonary artery stent placement.

Anomalies of the tricuspid valve, such as Ebstein anomaly,¹⁵ tend to be manifested with cyanosis in the newborn period, and the infants can be quite ill. If acyanotic, they are typically diagnosed after an echocardiogram is obtained as part of evaluation of a murmur. The diagnosis of Ebstein anomaly may be a coincident finding made as part of a work-up for Wolff-Parkinson-White syndrome–mediated supraventricular tachycardia. The mean age at diagnosis of the acyanotic forms of this disease is the middle teenage years. These anomalies are almost uniformly associated with atrial septal defects.

Indications and Contraindications

Surgical interventions for both aortic and mitral valve disease share similar indications and contraindications. The primary indications for early intervention in the neonate or young infant are primarily clinically driven. As previously discussed, there are limited options in the smaller patient for operative intervention because mechanical valve replacement is fraught with an extraordinary number of risks and the need for early and repeated surgeries to essentially “up-size” these valves as the patient grows.

Catheter-based intervention for severe aortic valve stenosis in the newborn¹⁶ is typically the preferred option. However, often less than perfect reduction in the stenosis gradient is tolerated such that one minimizes the risks for significant aortic insufficiency.

Aortic insufficiency is a much more difficult disease to treat in infants and children. A variety of clinical parameters have been used to prompt surgical intervention.¹⁷ Decreasing clinical activity level, decreasing left ventricular performance (as measured by echocardiography or MRI), and progressive left ventricular dilation and secondary mitral insufficiency or left atrial hypertension have been considered useful in formulating surgical intervention plans.

The Ross procedure has been an effective surgical procedure to provide good relief of aortic valve disease in children while avoiding many of the long-term medical management concerns of a mechanical aortic valve replacement. However, this has some significant controversy associated with it.¹⁸ More recent surgical approaches have aimed at “reconstruction” of the valve leaflets, although this is controversial as well and appears to be dependent on the surgical center’s abilities.

Mitral valve repair continues to be the optimal goal of most surgeons when possible, secondary to the issues revolving around mitral valve replacement at an early age. Somatic growth and the issues of chronic anticoagulation in the younger and more active patients empower surgeons to continue to develop surgical repair procedures for the mitral valve.

The Norwood procedure for the hypoplastic left heart constellation of defects has significantly altered the approach to these formerly uniformly fatal lesions. Modifications of this procedure have resulted in the Sano shunt and a move toward even more creative attempts at palliation, such as the hybrid procedure, or patent ductus arteriosus stent and bilateral pulmonary artery banding.

Pulmonary valve stenosis has long been a disease that lends itself to interventional catheterization procedures.¹⁹ More recent use of radiofrequency catheters to perforate pulmonary atresia, as a method to pass a wire and then a balloon catheter across such an obstruction to achieve some degree of palliation, is an exciting advancement in the hands of the skilled interventionalist. Surgical open pulmonary valvotomy is still an option, but it is often reserved for unique circumstances at this time.

Postoperative Surveillance

As is repeatedly emphasized in the diagnosis and surveillance of children with cardiac defects, the consideration of noninvasive and radiation-free imaging modalities is mandatory. The role of echocardiography as a standard follow-up imaging modality is typical. Exercise treadmill testing and periodic rhythm monitoring are also common for children and adults with congenital heart disease.

What is important is the growing role of cardiac MR for both functional and routine anatomic surveillance. In combination with newer technologies such as three-dimensional echocardiography to evaluate valve morphology, much can be done to mitigate complications of surgery or the natural history of these defects.

Cardiac CT is an added modality, although it does carry with it some risk of radiation exposure.

Description and Special Anatomic Considerations

These congenital cardiac lesions are characterized by cyanosis or bluish coloration of the skin due to arterial oxygen desaturation resulting from the shunting of systemic venous blood to the arterial circulation. To help understand the basic physiology involved in these lesions, they are typically classified by degree of pulmonary blood flow (Table 28-6).

TABLE 28-6 Cyanotic Congenital Heart Disease with Increased Pulmonary Blood Flow

Complete transposition of the great arteries is the most common cyanotic congenital heart lesion that presents in neonates.²⁰ This entity was first described more than 200 years ago. However, until the development of the surgical atrial septectomy in the 1950s and the balloon atrial septostomy in the 1960s, early death was expected. These palliative interventions allowed the development of physiologic palliative procedures, such as the atrial switch operation (Mustard and Senning),²¹ and later the anatomic correction with the arterial switch procedure. Although survival rates for the arterial switch procedure approach 95%, significant anatomic variations influence the outcome. These include associated cardiac anomalies, relationship of the great arteries to each other, and coronary artery anatomy variants.²² Echocardiography is the mainstay of this diagnosis, which is one that often may be made in utero by fetal echocardiography.

Single-ventricle defects are rare defects and can present with either increased or decreased pulmonary blood flow. To strictly fit this diagnosis, the single ventricle is missing the nontrabeculated inflow region of either ventricle. This differentiates these defects from tricuspid atresia patients, who typically have a smooth inlet of the remaining ventricle. These cardiac defects invariably have other associated cardiac defects, such as complex outflow tract obstruction or interrupted aortic arch. They also may have significant noncardiac congenital defects.²³ Two-dimensional echocardiography is diagnostic for single ventricle and usually provides most detail of the associated cardiac defects.

Indications

The surgical intervention in these defects depends on the age at presentation, the size and weight of the patient, and the presence of associated congenital cardiac and extracardiac defects.

Complete repair of the patient with transposition of the great arteries with the arterial switch operation is the goal of the experienced cardiothoracic surgeon. The age at which to attempt complete repair is generally within the first 1 to 2 weeks of life because the left ventricular function and mass change as pulmonary vascular resistance changes with age. However, many variables have an impact on these decisions.²⁴

There is still the occasional patient for whom the atrial switch or a Rastelli procedure may be the optimal intervention. The surgical approach to the patient with single ventricle remains one in which the preoperative medical management and the skill of the congenital cardiac surgeon dictate much of the operative timing and decision-making.

The single-ventricle pathway,²⁵ as it has become known, requires careful medical and surgical management of pulmonary vascular resistance and single-ventricle systolic function, with an attempt to preserve single-ventricle diastolic function. The staged approach to ultimate palliation with a Fontan variant repair of these defects is now common. These palliative procedures may include pulmonary artery banding, pulmonary artery transection and creation of systemic-to-pulmonary artery shunt, and the Damus-Kaye-Stansel approach for selected defects. Caval anastomoses, hemi-Fontan, and the Fontan variant are the typical considerations for subsequent surgery for these patients. However, when this palliation fails or the poor hemodynamics of the patient preclude consideration of a Fontan intervention, cardiac transplantation remains a viable option.

Contraindications

Pulmonary vascular resistance has a common role for this category of defects, although for different reasons. The ability to perform the arterial switch operation for transposition of the great arteries is influenced by “deconditioning,” changes that occur within the left ventricular myocardium as a result of decreasing pulmonary artery resistance, which typically occurs within the first several days after birth. Although it is not an absolute contraindication to the arterial switch operation, alternative approaches may be needed to “recondition” the left ventricle; extracorporeal membrane oxygenation or left ventricular support may be employed, or in certain cases, the atrial switch operation may be considered. Abnormal coronary artery patterns, an early contraindication, are no longer considered a contraindication to this operation.

Palliative operations for the single ventricle are dependent on preservation of good ventricular systolic and diastolic function as well as a low-resistance pulmonary vascular bed to allow passive return of blood from the pulmonary vascular bed to the receiving atrium of the single ventricle. Problems with either, and often both, may limit the ability to fully palliate these patients.

Outcomes and Complications

Surgical results of the arterial switch operation are influenced by a large number of factors. However, the simple arterial switch procedure in a patient with an intact ventricular septum has survival results that are above 95%. It is the associated congenital cardiac defects that often increase the potential morbidity and increase the need for a diverse approach to monitoring of these patients postoperatively. Clinical follow-up, complemented by echocardiography and cardiac MRI, has become common in the long-term assessment of these patients.

The single-ventricle patients have more issues involving close follow-up of the passive cavopulmonary circuits, which are necessary to provide adequate cardiac output and oxygenation of blood.²⁶ The role of MRI and, for selected patients, CT has become common as a regular method to serially observe them longitudinally and to plan for any necessary interventions.

Description and Special Anatomic Considerations

The typical congenital cardiac lesions considered in this category of defects include tetralogy of Fallot, tricuspid atresia, and Ebstein anomaly (Table 28-7). Acyanotic patients can also present these defects, as noted before, and their manifestations are influenced by the degree of pulmonary blood flow.

TABLE 28-7 Cyanotic Congenital Heart Disease with Decreased Pulmonary Blood Flow

Tetralogy of Fallot represents approximately 7% to 10% of cases of congenital heart disease and is the most common cause of cyanotic congenital heart disease in all ages. This defect is composed of four abnormalities: VSD with anterior malalignment, over-riding aorta, right ventricular outflow tract hypertrophy, and valvular pulmonary stenosis. The degree of valvular pulmonary stenosis and right ventricular hypertrophy or outflow tract obstruction dictates the time of presentation because these patients may be acyanotic at birth and infancy if this is not significant. However, the natural history of this lesion is progression of the cyanosis as the hypertrophy and pulmonary stenosis worsen with age.

Tricuspid atresia is the third most common cyanotic congenital defect. Again, these patients can present with varying amounts of pulmonary blood flow and a variety of associated congenital cardiac defects. Pulmonary obstruction is usually associated with normally related great vessels. This is a cyanotic defect for which electrocardiography can be quite helpful in the diagnosis because right-sided electrical forces are typically diminished or absent.

Ebstein anomaly can be manifested in the neonatal period with intense cyanosis. This presentation is often associated with right ventricular outflow obstruction from the inferiorly displaced septal leaflet of the tricuspid valve, right ventricular hypoplasia, and elevated pulmonary vascular resistance. These are perhaps some of the sickest infants with congenital heart disease because of the associated defects and complicating physiology.

Indications

Definitive surgical repair for the patients with tetralogy of Fallot has become the goal of the pediatric cardiologist and cardiothoracic surgeon.²⁷ However, palliation is still needed for a variety of complicating cardiac and extracardiac issues.

Some adult patients may have undergone initial palliation with either a Potts shunt (descending aorta to pulmonary artery) or a Waterston shunt (ascending aorta to pulmonary artery) as a method to improve pulmonary blood flow. These carried significant risks for pulmonary artery hypertension and distorted pulmonary artery anatomy. For this reason, these procedures have been abandoned and replaced with the modified Blalock-Taussig shunt (typically Gore-Tex) as a palliative procedure to augment pulmonary blood flow. This procedure often provides several months to years of time to allow other medical issues to be addressed as well as adequate growth to permit corrective surgery.

Definitive surgery involves closure of the VSD, resection of the right ventricular outflow tract muscle obstruction, and elimination of the valvular pulmonary stenosis. Because of the long-term chronic right ventricular volume overload from the common pulmonary insufficiency seen after resection of the right ventricular outflow tract or pulmonary stenosis, there have been recent attempts to preserve some pulmonary valve tissue and to tolerate some degree of pulmonary stenosis. The belief is that this may limit the degree of insufficiency and protect the right ventricle from the damage of chronic volume overload and ventricular dilation.

Tricuspid atresia patients are almost always confined to a single-ventricle palliation pathway. This may involve a Blalock-Taussig shunt to augment pulmonary blood flow but limit damage to the pulmonary vascular bed for chronic pressure or volume overload of the pulmonary arteries.²⁸

Contraindications

The contraindications to definitive surgery for correction of tetralogy of Fallot are related to the native pulmonary artery architecture. In more extreme forms of the lesion, the pulmonary arteries may be very small, noncontinuous, or almost exclusively supplied by systemic collaterals. On rare occasion, there may not be a corrective or palliative option. Much work has been done to try to improve pulmonary blood flow through unifocalization procedures with systemic-to-pulmonary artery shunts. However, these patients have varied native pulmonary architecture, so no absolute surgical options may be available.

Patients with tricuspid atresia have contraindications to single-ventricle palliation options similar to those of other single-ventricle patients. Pulmonary vascular resistance and ventricular performance dictate whether these are viable options or if cardiac transplantation is the only endpoint.

Outcomes and Complications

Surgical outcomes for patients with tetralogy of Fallot are very much dependent on the native pulmonary artery anatomy. With proper anatomic substrate, surgical survival for definitive repair approaches 95%. Palliative shunts can be associated with pulmonary artery distortion and stenosis at the anastomosis site between the shunt and pulmonary artery. Although uncommon, acute thrombosis of the shunt can precipitate a life-threatening event from a lack of pulmonary blood flow and severe cyanosis.

Tricuspid atresia patients tend to do quite well with the single-ventricle pathway for palliation. Because these patients have a normally functioning left ventricle, they tend to be the ideal patients for excellent long-term survival after the Fontan procedure, with a good quality of life. Three patients with tricuspid atresia were the first to undergo the Fontan operation, which he published in 1971. It is not uncommon for these patients who have done well to be able to successfully carry a pregnancy to term with little adverse hemodynamic effect. However, this does require close pre-conception planning and cardiac surveillance during the pregnancy.²⁹

KEY POINTS

Repair of left-to-right shunts is primarily driven by clinical symptoms, and many lesions can be corrected in later childhood rather than in infancy.

Coarctation of the aorta is amenable to early surgery. There is some controversy related to the role of angioplasty and stent placement as a primary treatment.

Admixture lesions, such as transposition of the great arteries, are usually treated with a complete repair.

In tetralogy of Fallot, definitive repair is the usual treatment. To reduce the risk of postoperative pulmonary regurgitation that can lead to right ventricular volume overload, some surgeons have recently tolerated a degree of postoperative pulmonary stenosis.

For congenital heart disease, echocardiography is the mainstay of preoperative planning and postoperative monitoring. The role of MRI and CT has grown to replace catheterization in many instances for anatomic and functional information.