AUTHOR AND EDITOR INFORMATION

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• Authors and Editors
• Introduction
• Clinical
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• Follow-up
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INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Tricuspid atresia may be defined as congenital absence or agenesis of the tricuspid valve. It is the third most common cyanotic congenital heart defect; the other 2 frequently observed cyanotic congenital cardiac anomalies are transposition of the great arteries and tetralogy of Fallot. Tricuspid atresia is the most common cause of cyanosis with left ventricular hypertrophy.

Although some authors state that Holmes (1824) or Kuhne (1906) first described tricuspid atresia, Rashkind's methodical and thorough historical review indicates that Kreysig reported the first case in 1817. An 1812 report by the editors of the London Medical Review appears to fit the description of tricuspid atresia, but they did not use this specific term.

Terminology

Little more than 2 decades ago, the terminology for this defect (eg, tricuspid atresia, univentricular heart, univentricular atrioventricular connection) was intensely debated. This debate was summarized in a 1990 issue of The American Journal of Cardiology, in which Rao offered strong evidence and argued on the basis of data that Bharati, Wenink and Ottenkamp, Gessner, and Rao collected to support tricuspid atresia as the correct and logical term to describe this well-characterized pathologic and clinical condition.

Embryology

The atrioventricular valves develop shortly after the atrioventricular canal divides. The tricuspid valve leaflets have several origins. The septal leaflet of the tricuspid valve develops mostly from the inferior endocardial cushion with a small contribution from the superior cushion. The anterior and posterior tricuspid valve leaflets develop by undermining of a skirt of ventricular muscle tissue. The process of undermining extends until the atrioventricular valve junction is reached. Resorption of the muscle tissue produces normal-appearing valve leaflets and chordae tendineae. Fusion of developing valve leaflet components results in stenosis (partial fusion) or atresia (complete fusion) of the valve.

Whether a muscular type of tricuspid atresia develops or whether well-formed but fused tricuspid-valve leaflets develop depends on the stage of development when the embryologic aberration takes place. The classic muscular form of tricuspid atresia develops if the embryologic insult occurs early in gestation, and fused valve leaflets with improved formation occur if the embryologic abnormality occurs slightly later than this in gestation. If the valve fusion is incomplete, stenosis of the tricuspid valve develops.

The pathologic, clinical, and electrocardiographic features of tricuspid stenosis and atresia are similar. Therefore, the fact that isolated congenital tricuspid stenosis belongs to the group of tricuspid atresia defects and that their embryologic developments are similar is no surprise. Thus, the tricuspid valve stenosis, tricuspid atresia with well formed but fused valve leaflets, and the muscular type of tricuspid atresia represent a spectrum of morphologic abnormalities.

Anatomy

The pathologic anatomy of tricuspid atresia is best understood by reviewing variations in valvar morphology, as follows:

• The most common type of tricuspid atresia is muscular (see Image 1). It is characterized by a dimple or a localized fibrous thickening in the floor of the right atrium at the expected site of the tricuspid valve. The muscular variety accounts for 89% of cases.
• In the membranous type (6.6%), the atrioventricular portion of the membranous septum forms the floor of the right atrium at the expected location of the tricuspid valve. This particular type appears to be associated with absent pulmonary valve leaflets.
• Minute valvar cusps are fused together in the valvar type (1%).
• In the Ebstein type (2.6%), fusion of the tricuspid valve leaflets occurs; attachment is displaced downward, and plastering of the leaflets to the right ventricular wall occurs. This variant is rare but well documented.
• The atrioventricular canal type is extremely rare (0.2%). In this type, a leaflet of the common atrioventricular valve seals off the only entrance into the right ventricle.
• In the final type, unguarded with a muscular shelf (0.6%), the atrioventricular junction is unguarded, but the inlet component of the morphologic right ventricle is separated from its outlet by a muscular shelf.

The right atrium is enlarged and hypertrophied. An interatrial communication is necessary for survival. This communication most commonly is a stretched patent foramen ovale. Sometimes, an ostium secundum or an ostium primum atrial septal defect (ASD) is present. In rare cases, the patent foramen ovale is obstructive and may form an aneurysm of the fossa ovalis, which is sometimes large enough to produce mitral inflow obstruction. The left atrium may be enlarged, especially when the pulmonary blood flow is increased. The mitral valve is morphologically normal; it is rarely incompetent and has a large orifice. The left ventricle is enlarged and hypertrophied but often morphologically normal.

The ventricular septal defect (VSD) is usually small; however, it can be large, or several VSDs may be present. The ventricular septum is rarely intact. When present, the VSD may be conoventricular or perimembranous in type (inferior to the septal band), it may be of conal septal malalignment type (between the limbs of the septal band), or it may be of the muscular or atrioventricular canal type. Muscular VSDs are the most common defects and are usually restrictive; they produce subpulmonary stenosis in patients with normally related great arteries and simulate subaortic obstruction in patients with transposition of the great arteries.

The right ventricle is small and hypoplastic, and its size largely depends on the anatomic type. In patients with a large VSD or transposition of the great arteries, the size of the right ventricle may be larger, but, even in these patients, the right ventricle is smaller than normal. In patients with pulmonary atresia and normally related great arteries, the right ventricle is small and may escape detection. However, it is a true right ventricle in most patients; it is composed of a sharply demarcated infundibulum with septal and parietal bands and a sinus with trabeculae, which may communicate with the left ventricle by means of a VSD. By definition, the inflow region is absent, though papillary muscles may occasionally be present.

The great artery relationship is variable and forms the basis of a major classification (see Subtypes). Obstruction to the pulmonary outflow tract is present in most cases of tricuspid atresia and is used in the scheme of classification. The aorta is either normal or slightly larger than normal. In 30% of patients, a variety of associated cardiac defects are present (see the list below); notable among these defects are aortic coarctation and persistent left superior vena cava.

Associated cardiac defects in tricuspid atresia are as follows (adapted from Rao, 1992, page 297):

• Defects that form the basis for classification are as follows:
• • D-Transposition of the great arteries
  • L-Transposition of the great arteries
  • Double-outlet right ventricle
  • Double-outlet left ventricle
  • Other malpositions of the great arteries
  • Truncus arteriosus
• Defects that may need attention before or during palliative or total surgical correction are as follows:
• • Absent pulmonary valve
  • Aneurysm of the atrial septum
  • Anomalous origin of the coronary arteries from the pulmonary artery
  • Anomalous origin of the left subclavian artery
  • Anomalous origin of the right subclavian artery
  • Aortopulmonary fistula
  • Coarctation of the aorta
  • Common atrium
  • Cor triatriatum dexter
  • Coronary sinus septal defect
  • Double aortic arch
  • Double-outlet left atrium
  • Hemitruncus
  • Hypoplastic ascending aorta and/or aortic atresia
  • Ostium primum ASD
  • Parchment right ventricle
  • Patent ductus arteriosus
  • Persistent left superior vena cava
  • Right aortic arch
  • Subaortic stenosis
  • Total anomalous pulmonary venous connection
  • Tubular hypoplasia of the aortic arch
  • Valvar aortic stenosis
• Other associated defects are as follows:
• • Juxtaposition of the atrial appendages
  • Anomalous entry of coronary sinus into the left atrium

Subtypes

Tricuspid atresia is classified according to the morphology of the valve, the radiographic appearance of pulmonary vascular markings, and the associated cardiac defects.

Van Praagh and associates (1971) initially proposed a classification based on the morphology of the atretic tricuspid valve. He and others later modified and expanded the classification, as described in Tricuspid Atresia, (Rao, 1992). All other morphologic types are described in Anatomy. For pathologic, echocardiographic, and angiographic examples, particularly the rare anatomic types, the interested reader is referred to Tricuspid Atresia, (Rao, 1992), and the Atlas of Heart Disease: Congenital Heart Disease (Braunwald, 1997).

Astley and associates (1953) proposed the following classification based on pulmonary vascular markings on a chest radiograph: Group A are cases with decreased pulmonary vascular markings, and group B are those with increased pulmonary vascular markings. Dick et al (1975) added a third group, group C, to describe cases with a transition from increased to decreased pulmonary vascular markings. This type of classification has some clinical value, though a more precise definition than these can often be made by using noninvasive 2-dimensional (2D) and Doppler echocardiography.

In 1906, Kuhne first proposed a classification based on great-artery relationships, which Edwards and Burchell expanded in 1949. Keith, Rowe, and Vlad popularized this classification in 1967. Other investigators have offered a variety of other classifications. These are reviewed in detail in the American Heart Journal and Tricuspid Atresia, (Rao, 1992). Although these classifications are generally good, their exclusion of some variations in great-artery relationships and the lack of consistency in subgroups are problematic. Therefore, we propose the following new, comprehensive-yet-unified classification (adapted from Rao, 1980):

• The principle grouping continues to be based on the following interrelationships of the great arteries:
• • Type I - Normally related great arteries
  • Type II - D-Transposition of the great arteries
  • Type III - Great artery positional abnormalities other than D-transposition of the great arteries
  • • Subtype 1 - L-Transposition of the great arteries
    • Subtype 2 - Double outlet right ventricle
    • Subtype 3 - Double outlet left ventricle
    • Subtype 4 - D-Malposition of the great arteries (anatomically corrected malposition)
    • Subtype 5 - L-Malposition of the great arteries (anatomically corrected malposition)
  • Type IV - Persistent truncus arteriosus
• All types and subtypes are subdivided into the following subgroups:
• • Subgroup a - Pulmonary atresia
  • Subgroup b - Pulmonary stenosis or hypoplasia
  • Subgroup c - No pulmonary stenosis (normal pulmonary arteries)

After the above categorization, the status of the ventricular septum (intact or VSD) and the presence of other associated malformations are described (see Associated cardiac defects in tricuspid atresia).

This unified classification includes all the previously described abnormalities in the positions of the great arteries and can be further expanded if new variations are revealed. This classification maintains uniformity of the subgroups and preserves the basic principles of classification that Kuhne, Edwards and Burchell, and Keith, Rowe, and Vlad devised.

Pathophysiology

Prenatal circulation

Despite the clinically significant alterations in fetal circulation in tricuspid atresia, such changes are not detrimental to normal fetal development. In the fetus with a normally developed heart, a substantial portion of the highly saturated blood in the inferior vena cava, which carries umbilical venous return from the placenta, is diverted into the left atrium through the patent foramen ovale. From there, it travels into the left ventricle and aorta. Thus, the brain and heart receive blood with a high partial pressure of oxygen (PO₂).

The desaturated blood in the superior vena caval passes through the tricuspid valve, right ventricle, and pulmonary artery. Because of high pulmonary vascular resistance (PVR), the desaturated blood is then diverted through the ductus arteriosus into the descending aorta and umbilical arteries. The blood then returns to the placenta for oxygenation.

In tricuspid atresia, blood from both venae cavae is forced across the patent foramen ovale into the left heart. As a consequence, the PO₂ differential present in a normally developed fetus is not present in the fetus with tricuspid atresia. The lowered PO₂ to the brain and heart and elevated PO₂ to the lungs do not seem to produce clinically discernible postnatal abnormalities.

In patients with tricuspid atresia and associated pulmonary atresia (types Ia and IIa), the pulmonary blood flow is supplied entirely through the ductus arteriosus. Therefore, the ductus carries only 8-10% of combined ventricular output compared with 66% of combined ventricular output in a normally developed fetus. Also, acute angulation of the ductus arteriosus occurs at its origin because of reversed direction of ductal flow. These 2 factors may make the ductus arteriosus less responsive to postnatal stimuli than it usually is.

In a fetus with tricuspid atresia type I anatomy and a small or absent VSD (types Ia and Ib), almost all the left ventricular output is ejected into the aorta and transported down to the placenta. As a consequence, the isthmus of the aorta carries a larger-than-normal proportion of cardiac output; this is thought to be the reason for rarity of aortic coarctation in this subset of patients with tricuspid atresia.

In contrast, in patients with tricuspid atresia type II (transposition of the great arteries), an increased portion of the blood goes through the ductus arteriosus into the descending aorta. Therefore, the flow across the aortic isthmus is minimal, which accounts for the relatively high incidence of aortic coarctation in this subset of patients.

Postnatal circulation

Because of the atretic tricuspid valve, all systemic venous blood must be shunted across the interatrial septal communication into the left atrium. This obligatory shunting causes admixture of all systemic venous and pulmonary venous returns. This blood then passes onto the left ventricle across the mitral valve. This flow pattern occurs in all types but type III subtypes 1 and 5. In these exceptions, the atretic morphologic tricuspid valve is left sided because of ventricular inversion; therefore, the pathophysiology is that of mitral atresia with consequent left-to-right shunting of pulmonary venous return.

In patients with normally related great arteries (type I) and a VSD, shunting across the VSD permits perfusion of the lungs. In the absence of VSD, pulmonary blood flow is derived through a patent ductus arteriosus or aortopulmonary collateral vessels. Some means of lung perfusion is crucial for patient survival. The systemic blood flow is derived directly from the left ventricle.

In patients with D-transposition of the great arteries (type II), the lungs receive the blood flow from the left ventricle. The aorta receives blood from the left ventricle via the VSD and right ventricle. In other types of tricuspid atresia, the routes of aortic and pulmonary artery flow depend on the size of the VSD and associated cardiac defects.

Other physiologic principles

Arterial desaturation

Systemic arterial desaturation is present in all patients with tricuspid atresia because of obligatory admixture of the systemic, coronary, and pulmonary venous returns in the left atrium. The degree of arterial desaturation depends on the amount of pulmonary blood-flow. The arterial oxygen saturation has a curvilinear relationship (see Image 2), with a pulmonary-to-systemic blood flow ratio (Qp:Qs) that reflects the pulmonary blood flow. A Qp:Qs ratio of 1.5-2.5 seems to result in adequate oxygen saturation. Higher pulmonary flow does not significantly increase oxygen saturation but instead produces left ventricular volume overloading.

Pulmonary blood flow

The clinical features of tricuspid atresia largely depend on the quantity of pulmonary blood flow. A neonate with markedly decreased pulmonary flow is likely to present early in the neonatal period with signs of severe cyanosis, hypoxemia, and acidosis. On the contrary, if the pulmonary blood flow is increased, the neonate may not appear cyanotic but may present with signs of heart failure. Patients with pulmonary oligemia generally have type I (normally related great arteries); those with pulmonary plethora usually have type II (transposition of the great arteries) and, rarely, type Ic.

The magnitude of pulmonary blood flow without previous surgery largely depends on the degree of pulmonary outflow tract obstruction and patency of the ductus arteriosus. In patients with a type I defect, the obstruction is valvar, subvalvar, or, most frequently, at the VSD level. In patients with a type II defect, the obstruction is either valvar or subvalvar. In patients with a type I defect, if the VSD is large and nonrestrictive without pulmonary stenosis, the pulmonary flow is inversely proportional to the pulmonary-to-systemic vascular resistance ratio. If the ductus is patent or if a surgical systemic-to-pulmonary artery shunt was performed, the pulmonary blood flow is proportional to the size of the natural or surgical aortopulmonary connection.

Left ventricular volume overloading

The left ventricle ejects the entire systemic, coronary, and pulmonary outputs. Therefore, left ventricular volume overloading is present in all patients with tricuspid atresia. The degree of volume overloading increases further if mild or no pulmonary outflow obstruction is present or if systemic-to-pulmonary artery shunting was performed. Because normal left ventricular function is critical to a successful Fontan operation, maintenance of normal left ventricular function is essential. Left ventricular function tends to decrease with increasing age, increasing Qp:Qs, and arterial desaturation.

Obstruction of the interatrial communication

Patency of the interatrial communication, usually a patent foramen ovale, is essential for survival. Because the entire systemic venous blood must egress through the interatrial communication, development of interatrial obstruction is not unexpected, but it is rarely clinically significant. Right-to-left shunting occurs in late atrial diastole, with augmentation of flow during atrial systole.

In patients with obstruction, patent foramen ovale obstruction is presumed to be present if the mean pressure difference between the atria is more than 5 mm Hg and a tall a wave is present in the right atrial pressure trace. Clinical evaluation may reveal prominent a waves in the jugular venous pulse, presystolic hepatic pulsations, and hepatomegaly.

Changing hemodynamics

Several changes in hemodynamics occur as infants with tricuspid atresia grow. These involved the ductus arteriosus, ASD, and VSD.

Closure of the ductus arteriosus in a neonate with severe pulmonary outflow tract obstruction or atresia results in severe hypoxemia, and the administration of prostaglandin E1 (PGE1) or surgical creation of systemic-to-pulmonary artery shunt is required.

Regarding ASD, restrictive interatrial communication may develop, causing systemic venous congestion. Transcatheter or surgical atrial septostomy may be needed.

Patency of the VSD is essential to maintain intracardiac shunting necessary for patient survival; these VSDs have been named physiologically advantageous VSDs. Functional and partial or complete anatomic closures have been documented. Intermittent functional closure of the VSD results in cyanotic spells in tricuspid atresia. The etiology of such closures has not been identified but is likely similar to that postulated for tetralogy of Fallot.

Closure of a VSD in type I may result in progressive cyanosis, increasing polycythemia, and diminution or disappearance of the murmur of VSD. Both partial and complete closures are reported and require surgical intervention earlier than otherwise anticipated.

Closure of a VSD in type II (transposition) produces subaortic, ie, systemic, outflow obstruction. Partial closures have been reported; however, to the author's knowledge, complete closures have not been documented. Partial closures result in increased left ventricular mass, complicating late Fontan operations.

From the author's studies and those of Sauer and Hall (1980), the estimated prevalence of spontaneous VSD closures is 38-48%. This prevalence is similar to that of isolated VSDs. VSD closures are documented in patients younger than 1 year to those aged 20 years, with a median of age 1.3 years. These statistics are also similar to those observed in isolated defects. The most common mechanism of closure is progressive muscular encroachment of margins of the defect with subsequent fibrosis and covering by endocardial proliferation, though other mechanisms of closure in isolated VSDs have been observed. How such closures are initiated is not known.

Frequency

United States

Although the true incidence of tricuspid atresia is not well defined, the prevalence of tricuspid atresia among congenital heart defects was estimated to be 2.9% in autopsy series and 1.4% in clinical series after extensive review. Given the prevalence of congenital heart defects in 0.8% of live births, tricuspid atresia may be estimated to occur in approximately 1 per 10,000 live births.

International

Extensive review of the literature indicated no differences in prevalence in tricuspid atresia between the United States and countries on other continents (see Image 3), though geographic differences in prevalence for aortic stenosis and coarctation have been documented.

Mortality/Morbidity

Poor prognosis of untreated tricuspid atresia patients is well known; only 10-20% of infants may live through the first year of life.

• Image 4 shows actuarial survival rates from 3 medical centers that Dick et al (1982) compiled. Considerable early mortality occurs and may be related to hypoxemia, cardiac failure, surgical intervention, or their combination. Surgical palliation to normalize pulmonary blood flow by means of systemic-to-pulmonary artery shunting in neonates with pulmonary oligemia and banding of the pulmonary artery in infants with markedly increased pulmonary flow improves survival rates.
• The availability of PGE1 to keep the ductus open and advances in neonatal care (eg, early identification, safe transport to a tertiary care institution, noninvasive diagnosis by means of echocardiography), anesthesia, and surgical techniques should further decrease the initial mortality rate.
• After the early high mortality rate, survival curves become stable and reach a plateau (see Image 4). In patients aged approximately 15 years, a second fall in survival begins and continues through the remaining observation period. Physiologically corrective Fontan procedures may reverse this late mortality. Whether the benefits of Fontan procedure (ie, improving hypoxemia and eliminating left ventricular volume overloading) improve survival rates is not clear. Preliminary data suggest that they do, even after the immediate and late mortality of the surgery itself are accounted for (see Image 5). This potential for improved prognosis means that each patient with tricuspid atresia undergoes aggressive medical and surgical treatment.
• Mortality and morbidity are best depicted in Image 4. The natural history after a Fontan operation is shown in Image 5.
• Adult patients who had classic a Fontan operation have high initial mortality (28%) and high morbidity rates. The latter is related to reoperation (58%) to revise Fontan connections, arrhythmia (56%) and thromboembolic events (25%). Patients with a total cavopulmonary connection appear to have improved survival and decreased morbidity rates, though follow-up of these patients has been relatively short.
• The natural history of the component defects (ie, patent ductus arteriosus, ASD and/or patent foramen ovale, and VSD) is described in Changing hemodynamics.

Race

• Although data in the 1950s and early 1960s indicated that the prevalence of congenital heart disease was higher in Caucasians than in African Americans, a thorough and appropriate statistical analysis by Mitchell et al suggests that the prevalences of congenital heart disease are similar in Caucasians and in African Americans (8.3 vs 8.1 per 1000).
• According to Schriere (1963), the incidences of tricuspid atresia among congenital heart defects are 1.2% in Caucasians and 1.4% in African Americans, indicating no racial predilection.
• Furthermore, extensive review and tabulation of the prevalences of tricuspid atresia in populations on several continents revealed no difference in prevalences despite different racial compositions on these continents (see Image 3). Therefore, no specific racial predilection exists for tricuspid atresia.

Sex

• Researchers found a slight male preponderance for tricuspid atresia. An extensive review of 1857 cases revealed that 53% of cases occurred in male individuals and 47% occurred in female individuals. However, these findings were not statistically significant (P >.1), indicating no evidence for sex predilection.
• Dick et al suggested that a male preponderance exists only in patients with tricuspid atresia and associated transposition. To test this hypothesis, they evaluated data of patients in whom sex and great-artery relationships were known. In patients without transposition of the great arteries, the prevalences were 54% in male patients and 46% in female patients (P >.1). In patients with transposition of the great arteries, the prevalence was higher in male patients than in female patients (66% vs 34%, P <.05). Therefore, a male preponderance for tricuspid atresia was observed in patients with transposition of the great arteries.

Age

Patients with tricuspid atresia present early in life.

• One half of patients present on the first day of life, two thirds present by the end of the first week, and 80% present by the first month of life. No more than 15% of patients present with symptoms for the first time after 2 months of life.
• The magnitude of pulmonary blood flow determines the timing and mode of presentation.
• Neonates with pulmonary oligemia present early in life with cyanosis, whereas those with pulmonary plethora present slightly later with signs of congestive heart failure, cyanosis, or both, depending on the magnitude of pulmonary flow.

CLINICAL

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History

Symptoms of tricuspid atresia manifest early in life. Nearly one half of patients have symptoms on first day of life, and 80% are symptomatic by the first month of life. The clinical features largely depend on the magnitude of pulmonary blood flow. The 2 known presentations are decreased pulmonary blood flow and increased pulmonary blood flow.

• Cyanosis occurs in the first few days of life in infants with pulmonary oligemia.
• • The lower the pulmonary flow, the earlier the infant becomes cyanotic.
  • Hyperpnea and acidosis are also present if the pulmonary blood flow is markedly decreased.
  • Most infants have the type Ib defect. If pulmonary atresia is present (subgroup a), early cyanosis appears as the ductus begins to close.
  • Hypercyanotic episodes are not common in the neonate but can be present later in infancy.
• Patients with pulmonary plethora present with symptoms of dyspnea, fatigue, difficulty feeding, and perspiration, which are suggestive of congestive heart failure.
• • Cyanosis is minimal if present.
  • Other presenting symptoms include failure to thrive and recurrent respiratory tract infection.
  • Most symptoms develop within several weeks of life, though patients occasionally present in the first week of life.
  • Most patients have type IIc (ie, transposition without pulmonary stenosis, but with VSD); some have type Ic (ie, normally related great arteries and no pulmonary stenosis and a VSD).
  • Coarctation of the aorta may be present in patients with a type II defect; in these patients, the onset of cardiac failure is early.
• Patients with rare, late-appearing cyanosis may present with exercise intolerance and a cardiac murmur.

Physical

The physical findings for pulmonary oligemia and pulmonary plethora are discussed separately.

• Patients with pulmonary oligemia may have central cyanosis, tachypnea or hyperpnea, normal pulses, and prominent a waves in the jugular venous pulse (in the presence of clinically significant interatrial obstruction). No hepatomegaly is observed.
• • A quiet precordium and no thrills are found on palpation.
  • On auscultation, the second heart sound is single, and a holosystolic type of murmur at the lower sternal border, suggestive of VSD, is heard. Diastolic murmurs are usually not heard. In patients with pulmonary atresia, the holosystolic murmur is not present, and a continuous murmur of patent ductus arteriosus is occasionally heard.
  • Clinical signs of heart failure are not observed.
• Patients with pulmonary plethora usually have tachypnea, tachycardia, minimal cyanosis (if any), decreased femoral pulse (if aortic coarctation is present), prominent neck venous pulsations, and hepatomegaly.
• • Prominent a waves in the jugular veins and/or presystolic hepatic pulsations may be observed if interatrial obstruction is severe.
  • Increased and hyperdynamic precordial impulses may be palpated.
  • The second heart sound may be single or split, and a third heart sound at the apex may be heard.
  • Additional auscultatory findings include holosystolic murmur of VSD at the left lower sternal border and middiastolic rumble at the apex.
  • Clinical signs of congestive heart failure are usually evident.
• Problems related to chronic cyanosis, such as clubbing, polycythemia, relative anemia, stroke, brain abscess, coagulation abnormalities, and hyperuricemia, are similar to those observed in other cyanotic congenital heart defects.
• • The risk for bacterial endocarditis is similar to that for other cardiac defects.
  • Atrial arrhythmias (flutter and/or fibrillation) may be observed in older children and adolescents with long-standing cyanosis, a systemic-to-pulmonary artery shunt, or left ventricular volume overloading or in those who previously underwent a classic Fontan operation.
• Tricuspid atresia may be associated with cat's-eye syndrome, Christmas disease, and asplenia syndrome.
• Extracardiac anomalies often involving gastrointestinal or musculoskeletal systems may be present in as many as 20% of patients, as observed in the New England Regional Infant Cardiac Program.

Causes

The etiology of tricuspid atresia is unknown.

• A multifactorial inheritance hypothesis is offered to explain all congenital heart defects, including tricuspid atresia.
• • This hypothesis states that disease results if a predisposed fetus is exposed to a given environmental trigger (to which the fetus is sensitive) during a critical period of cardiac morphogenesis.
  • This genetic and environmental interaction is most likely the pathogenic mechanism for congenital heart defects in general and for tricuspid atresia in particular.
• A variety of risk factors are statistically associated with certain heart defects. However, no specific factors are clearly identified for tricuspid atresia.

DIFFERENTIALS

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Other Problems to be Considered

Differential diagnostic considerations depend on the type of presentation, including moderate-to-severe cyanosis with decreased pulmonary flow on a chest radiograph and mild cyanosis with increased pulmonary vascular marking on a chest radiograph with or without congestive heart failure.

Decreased pulmonary blood flow

The differential diagnosis of cyanotic infants with pulmonary oligemia is included in Special Concerns. Electrocardiography is useful for arriving at a diagnosis (see Image 6). Echocardiography and/or selective cineangiography may be needed to confirm the diagnosis.

Increased pulmonary blood flow

The differential diagnosis of mild cyanosis with pulmonary plethora is listed in Special Concerns. Although the characteristic abnormal superior vector (left axis deviation) of tricuspid atresia is helpful, it is not present in all cases of tricuspid atresia with transposition of the great arteries. In addition, some of the defects listed in Special Concerns have similar electrocardiographic features. Often, echocardiography and, occasionally, angiocardiography are necessary to confirm the diagnosis.

WORKUP

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Lab Studies

• Pulse oximetry and arterial blood gas determination
• • Estimation of systemic arterial oxygen saturation by means of pulse oximetry, which is readily available in most outpatient and inpatient settings, is a useful adjunct in the clinical assessment. Arterial oxygen saturations less than 70-80% are of concern and lead one to expedite intervention to relieve pulmonary oligemia.
  • Arterial blood gas determinations provide accurate information regarding PO₂, the partial pressure of carbon dioxide (PCO₂), and base deficit. This test provides data about blood oxygen values (ie, PO₂), ventilatory status (ie, PCO₂), and metabolic status (ie, base deficit). However, this is an invasive test and not reliable if the child is agitated or crying during blood sampling. If an arterial line is already in place, blood gas analysis is of value.
• Hemoglobin and hematocrit measurements
• • Whereas the oxygen saturation measurement gives the value at one point in time, the level of hemoglobin indicates the degree and duration of hypoxemia. A rapid increase in hemoglobin suggests severe or long-standing hypoxemia.
  • The author routinely obtains red blood cell indices to ensure that no relative iron-deficiency anemia is present. Microcytosis and hypochromia suggest iron deficiency and warrant treatment with iron supplements.

Imaging Studies

• Chest radiography
• • Chest radiography is a useful adjunct in the evaluation of any congenital heart defect, including tricuspid atresia. The radiographic features are also dependent on the pulmonary blood flow and categorized into pulmonary oligemia and pulmonary plethora groups.
  • If the pulmonary blood flow is decreased, the heart is normal is size or only mildly enlarged. If pulmonary blood flow is excessive, moderate-to-severe cardiac enlargement is observed. The cardiac silhouette has been characterized in the literature as egg, bell, square, or boot shaped (coeur en sabot). However, in the experience of the author and of others, no consistent pattern is diagnostic of tricuspid atresia. Concavity in the region of the pulmonary artery segment is observed in patients with pulmonary oligemia and a small pulmonary artery or pulmonary atresia. The right atrial border may be prominent, especially if interatrial obstruction is present. With a restrictive ASD, the right atrial shadow may be prominent.
  • A right aortic arch, which is frequently observed in patients with tetralogy of Fallot (25%) or truncus arteriosus (40%), is present in only 8% of patients with tricuspid atresia. In rare types of tricuspid atresia (type III, subtypes 1 and 5), an unusual contour of the left border of the heart secondary to leftward and anterior displacement of the ascending aorta is present.
  • Chest radiography is useful in depicting the position of the heart; visceroatrial situs; and abnormalities of lungs, diaphragm, or vertebrae.
  • The most useful aspect of chest radiography is that it allows for the differentiation of decreased and increased pulmonary vascular markings. This distinction is often all that is necessary to establish a diagnosis after history taking, physical examination, and electrocardiography are performed.
• Echocardiography
• • 2D echocardiography reveals a small right ventricle and an enlarged right atrium, left atrium, and left ventricle. In the most common muscular type of tricuspid atresia, a dense band of echoes is observed where the tricuspid valve is usually located (see Image 8). The anterior leaflet of the detectable atrioventricular valve is attached to the left side of the interatrial septum. These echocardiographic features are best demonstrated in the apical and subcostal 4-chamber views. The size of the left atrium and the size and function of the left ventricle can be assessed with M-mode echocardiography. Repeated measurements during follow-up are useful in evaluating left ventricular function.
  • Demonstration of ASDs and VSDs by means of 2D echocardiography is essential, and shunting across the defects can be documented by using Doppler echocardiography. Semilunar valves can be similarly identified as pulmonic or aortic by following the great vessels until the bifurcation of the pulmonary artery or the arch of the aorta is seen. Coarctation of the aorta, which is more frequent in patients with tricuspid atresia type II, may be demonstrated in the suprasternal notch view.
  • Doppler echocardiography is useful for demonstrating the degree of obstruction across the ASD or VSD, for detecting stenosis of the right ventricular outflow tract and pulmonary valve, and for showing aortic coarctation.
  • Contrast echocardiography with an injection of agitated sodium chloride solution or other contrast material demonstrates sequential opacification of the right atrium, left atrium, left ventricle, and, subsequently, the right ventricle, though the study is not required for diagnosis.
• Radionuclide scanning
• • Radioisotopic scanning studies may be used to identify and quantitate a right-to-left shunt, to demonstrate cardiac anatomy by means of nuclear angiography, and to quantitate relative perfusions to both lungs.
  • However, pulse oximetry, blood gas analysis, and echocardiography are preferred because they are more simple and less cumbersome than nuclear scanning for demonstrating a right-to-left shunt and cardiac anatomy.
  • Quantitative pulmonary perfusion scans are useful if stenosis of a branch pulmonary artery is suspected, especially after a Fontan operation.

Other Tests

• Electrocardiography
• • In an infant with cyanosis, electrocardiographic findings are virtually diagnostic of tricuspid atresia. The electrocardiogram demonstrates right atrial hypertrophy, an abnormal and superiorly oriented major QRS vector, the so-called left axis deviation in the frontal plane, left ventricular hypertrophy, and decreased right ventricular forces.
  • Right atrial hypertrophy, manifested by tall and peaked P waves (>2.5 mm) in lead II and right chest leads may be present in 75% of patients with tricuspid atresia. The so-called P-tricuspidale with a double peak, spike, and dome configuration may be present. The initial tall peak is related to right atrial depolarization, and the second small peak is presumed to be secondary to left atrial depolarization. Regardless of the P wave configuration, its duration is prolonged, which may be caused by right atrial enlargement.
  • An abnormal superior vector (left axis deviation 0° to -90° in the frontal plane) is present in most patients with tricuspid atresia (see Image 7). This abnormal vector is present in 80% of patients with tricuspid atresia type I (normally related great arteries) but only 50% of patients with tricuspid atresia type II or III. Normal (0° to +90°) or right axis deviation (+90° to ± 180°) is present in a minority of patients, mainly those with tricuspid atresia type II or III.
  • A number of mechanisms have been postulated to explain the abnormal superior vector, including destructive lesions on the left anterior bundle, fibrosis of the left bundle branch, a long right bundle branch along with an early origin of left bundle branch, a small right ventricle, and a large left ventricle. Data from recent ventricular activation studies suggest that the superior vector is likely due to the interaction of several factors. The most crucial findings are right-to-left phase asynchrony of ventricular activation, right-to-left ventricular disproportion, and asymmetric distribution of the left ventricular mass favoring the superior wall.
  • Regardless of the abnormality in the frontal-plane vector, left ventricular hypertrophy is observed in most patients. This usually manifests as increased amplitude of S waves in leads V₁ and V₂ and R waves in V₅ and V₆. ST–T-wave changes indicative of left ventricular strain are present in 50% of patients. The pattern of left ventricular hypertrophy is related to the anatomic nature of the lesion and left ventricular overload, and it is secondary to a lack of opposition to the left ventricular electrical forces by the small right ventricle. Biventricular hypertrophy is occasionally observed; when such a pattern is present, it is usually tricuspid atresia type II or III with a good-sized right ventricle. Decreased R waves in leads V₁ and V₂ and S waves in leads V₅ and V₆ are secondary to a hypoplastic right ventricle.

Procedures

• Cardiac catheterization
• • Indications
  • • Perform cardiac catheterization if noninvasive evaluation provides insufficient data to address the management issues. Catheterization may be indicated before planned surgical correction is performed to provide the surgeon with important anatomic detail. Accurate data about the pulmonary-artery anatomy, size, and pressures and about left ventricular end-diastolic pressure (LVEDP), size, and function are needed before a Fontan procedure can be performed.
    • Perform a methodic evaluation of Choussat criteria: ie, normal vena caval drainage, normal right atrial volume, mean pulmonary artery pressure <15 mm Hg, PVR <4 U/m², pulmonary artery–to–aortic root diameter ratio >0.75, normal left ventricular function (ejection fraction >0.60), no mitral insufficiency, and undistorted pulmonary arteries. However, exceptions to most of these criteria have been made. Introduction of the bidirectional Glenn procedure before the Fontan procedure has changed the rigid adherence to some of these criteria.
    • Also, cardiac catheterization is indicated as an integral part of transcatheter therapeutic intervention, which may be necessary in some patients (see Catheter intervention).
  • Catheter insertion: The percutaneous femoral venous route is preferred because it facilitates access into the left side of the heart. The percutaneous jugular venous route may be used when a bidirectional Glenn procedure was already performed or if infrahepatic interruption of the inferior vena cava with azygos or hemiazygos continuation is present. Percutaneous femoral arterial access is also used to define aortic coarctation and subaortic stenosis, to visualize collateral vessels to the lungs, or to aid in contemplation of balloon coarctation angioplasty or coil occlusion of aortopulmonary collateral vessels.
  • Catheter course
  • • The course of the catheter in the right side of the heart is abnormal. The right ventricle cannot be directly entered from the right atrium because of the atretic tricuspid valve. Instead, the catheter can be easily advanced into the left atrium through the interatrial defect, especially when femoral venous access is used. From the left atrium, the left ventricle can be entered across the mitral valve. In neonates, further catheter manipulation to enter a great vessel or the right ventricle is usually unnecessary; hemodynamic and angiographic information is usually adequate. Cardiac catheterization in neonates is rarely needed for diagnostic purposes.
    • With the availability of balloon-tipped catheters and a variety of catheters and guide wires, the right ventricle may be catheterized through the VSD. In patients with normally related great vessels (type I), the aorta and pulmonary artery may also be catheterized from the left and right ventricles, respectively. In patients with transposed great vessels (type II), the aorta and pulmonary artery may also be catheterized from the right and left ventricles, respectively.
    • The course of a retrograde arterial catheter is normal in patients with tricuspid atresia type I, whereas it traverses anteriorly as it enters the right ventricle from the aorta in patients with tricuspid atresia type II. In patients with corrected transposition (type III, subtypes 1 and 5), the catheter courses anteriorly and to the left. (See Tricuspid Atresia, [Rao, 1992], for typical catheter positions in tricuspid atresia.)
  • Oxygen saturations
  • • Oxygen saturation in the vena cavae is decreased. The extent of this reduction is proportional to the systemic arterial desaturation and the degree of congestive heart failure. A step up in right atrial oxygen saturation is not ordinarily observed because of the obligatory right-to-left shunt. In some patients, a step up in oxygen saturation may be observed and explained on the basis of instantaneous pressure differences between the atria.
    • The oxygen saturation in the pulmonary veins is usually normal, with a step down in saturations in the left atrium secondary to obligatory right-to-left shunt at the atrial level. Oxygen saturation in the left ventricle is also decreased and may reflect a better admixture of the pulmonary venous and systemic venous returns. The left atrial, left ventricular, right ventricular, pulmonary arterial, and aortic saturations are similar, reflecting complete admixture of systemic and pulmonary venous returns in the left atrium. The aortic oxygen saturation is always lower than normal and proportional to the Qp:Qs.
    • The oxygen saturations are generally lower in patients with a type I defect than those in patients with a type II defect. This difference appears to be related to the relatively high prevalence of pulmonary oligemia in patients with a type I defect.
  • Pressures
  • • Right atrial pressure is normal or slightly elevated and depends on the LVEDP. The a waves are usually prominent. Interatrial obstruction results in giant a waves in the right atrial pressure recording. A mean atrial pressure difference >5 mm Hg indicates interatrial obstruction. If the LVEDP is markedly elevated, the interatrial pressure difference may be eliminated, even in the presence of considerable interatrial obstruction.
    • The left ventricular end-diastolic and left atrial pressures are usually normal. They increase with increasing Qp:Qs and diminishing left ventricular function. Prominent left atrial v waves may be observed with a high Qp:Qs and mitral insufficiency.
    • The peak systolic pressure in the left ventricle is usually normal, but it may be elevated in subaortic obstruction and aortic coarctation. Aortic systolic pressure is normal unless aortic coarctation is present. Aortic diastolic pressure may be decreased because of diastolic runoff secondary to a patent ductus arteriosus or a surgical aortopulmonary shunt. In patients with type II (transposition) defects, perform careful pressure pullback recordings across the aortic valve and across the VSD. A pressure gradient between the ventricles (across the VSD) indicates subaortic obstruction due to spontaneous shrinkage of the VSD.
    • In patients with normally related great arteries (type I), the systolic pressure in the right ventricle is proportional to the size of the VSD; the larger the VSD, the higher the pressure. Of course, pulmonary stenosis influences the right ventricular pressure. In patients with transposition of the great arteries (type II), the right ventricular pressure is at a systemic level.
    • Pulmonary artery pressure is usually normal in patients with tricuspid atresia type I; however, in those with tricuspid atresia type I with a large VSD, it may be elevated depending on the size of the VSD. In tricuspid atresia type II, the pulmonary pressures are high unless a clinically significant subvalvar or valvar pulmonary stenosis is present.
    • Because of the importance of pulmonary artery pressure in the overall treatment of patients with tricuspid atresia, every attempt should be made to measure pulmonary artery pressure. Pulmonary venous wedge pressure should be measured to estimate pulmonary artery pressure if all methods of catheterizing the pulmonary artery fail.
  • Calculated variables
  • • Calculation of systemic and pulmonary blood flows and shunts are made using the Fick principle, either by measuring oxygen consumption (preferred) or by assuming it from the tables of normal values. Detailed methods and formulas for calculation may be found in Tricuspid Atresia (Rao, 1992). The Qp:Qs and PVR are particularly critical calculations.
    • The reliability of Qp:Qs is not adversely influenced by not measuring the oxygen consumption.
    • A PVR >4 U/m² is a contraindication for Fontan operation.
    • Mair et al (1990) suggested that the preoperative catheterization index (PI) is useful for predicting poor results after Fontan surgery. The index is calculated as PVR + [LVEDP/(PI + SI)], where LVEDP is in millimeters of mercury, PI = the pulmonary flow index in liters per minute per meters squared, PVR is in units per meters squared, and SI is the systemic flow index in liters per minute per meters squared.
    • An index <4 U/m² is associated with an overall lower mortality rate. Although it has some limitations, this index reflects the importance of PVR and left ventricular function in the preoperative selection of patients for Fontan surgery.
  • Summary: Characteristic findings in tricuspid atresia are nonentry of the right ventricle directly from the right atrium and complete admixture of systemic, pulmonary, and coronary venous returns in the left atrium with similar oxygen saturations in the left atrium, left ventricle, right ventricle, aorta, and pulmonary artery. Systemic arterial oxygen saturation, Qp:Qs, pulmonary artery pressure and resistance, and LVEDP are useful in evaluating patients with tricuspid atresia. Routinely evaluate for interatrial obstruction in all patients and for subaortic obstruction at the VSD level in patients with type II (transposition).
• Cineangiography: Lack of direct anatomic continuity between the right atrium and right ventricle is the hallmark angiographic finding of tricuspid atresia. After tricuspid atresia is demonstrated, the ventricular anatomy, type and size of inter-VSDs, ventriculoarterial connections, pulmonary artery anatomy, sources of pulmonary blood flow, and associated defects should be defined.
• • Right atrial angiography
  • • Selective cineangiography from the superior vena cava or right atrium demonstrates successive opacification of the left atrium and left ventricle without opacification of the right ventricle (see Image 9). The negative shadow between the right atrium and left ventricle, called the right ventricular window, corresponds to the unfilled right ventricle. These features are best illustrated on a posteroanterior view. Although initially thought to be pathognomonic for tricuspid atresia, these signs may be present in a number of other conditions, including pulmonary atresia or severe pulmonary stenosis with intact ventricular septum, tetralogy of Fallot with ASD (pentalogy), total anomalous venous return to coronary sinus, and cor triatriatum dexter.
    • The size and location of the interatrial communication is optimally visualized on hepatoclavicular or lateral views. Opacification of the left atrium through an obstructed patent foramen ovale may produce the onionskin or waterfall appearance.
    • During right atrial angiography, contrast material refluxes normally into the vena cavae and hepatic veins and does not indicate interatrial obstruction. However, dense opacification of the coronary sinus (see Image 10) suggests interatrial obstruction. Aneurysmal formation of the atrial septum may also suggest a restrictive atrial defect.
    • Right atrial angiography is useful in demonstrating the size and position of the right atrial appendage and morphologic variants of the atretic tricuspid valve.
  • Left ventricular angiography
  • • Selective left ventricular angiography demonstrates a finely trabeculated, morphologically left ventricle, which is typical in most cases of tricuspid atresia. The left ventricle is slightly enlarged, and its size is proportional to pulmonary blood flow. The size and position of the VSDs, the presence of mitral insufficiency, and the origin and relative positions of the great vessels should also be evaluated.
    • Left ventriculography is initially performed in posteroanterior and lateral views. Left anterior oblique, hepatoclavicular, or long axial oblique views may also be used, depending on the structure that needs greater definition. Particular attention is needed to define the size of the VSD in type II (transposition) because of the potential for development of subaortic obstruction.
  • Right ventriculography: In cases of type II (transposition), right ventricular cineangiography can be accomplished by passing a catheter antegrade from the left ventricle or retrograde from the aorta. Right ventriculography may improve assessment of the size of the right ventricle compared with left ventriculography. This information was of considerable importance in the past, when incorporation of the right ventricle into the Fontan circuit and its potential for growth were serious considerations. However, this issue is not longer as important since the advent of total cavopulmonary connection.
  • Aortography: Aortography should be performed in patients with tricuspid atresia type II because of a high incidence of aortic arch anomalies, particularly aortic coarctation. An anterograde or retrograde approach via the femoral artery may be used. In addition, aortography is used to define sources of pulmonary blood flow and the origin and distribution of the coronary arteries.
  • Sources of pulmonary blood flow and pulmonary arterial anatomy
  • • These sources should be defined by means of anterograde for retrograde aortography. Selective angiography with a catheter positioned proximal to the ductus or a surgically created shunt clearly demonstrates the pulmonary arterial anatomy. Likewise, injections close to suspected aortopulmonary collateral vessels may help depict the pulmonary arteries. Angiography in the ventricle giving origin to pulmonary artery may demonstrate pulmonary artery anatomy. Finally, if the pulmonary artery can be entered with an angiographic catheter, direct pulmonary arteriograms should be obtained.
    • Hepatoclavicular and lateral views are preferred to demonstrate the main pulmonary artery and the confluence of branch pulmonary arteries. Right and left anterior oblique views are preferred to demonstrate the right and left pulmonary arteries.
    • The size of the pulmonary arteries can be directly measured and compared with the size of the aorta, and the Nakata index or McGoon ratio can be calculated, according to the cardiologist or surgeon's preference. If the pulmonary artery cannot be catheterized, pulmonary venous wedge angiography may be attempted to demonstrate the pulmonary artery.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Medical Care

The prognosis for patients with tricuspid atresia and other complex congenital cardiac defects with 1 functioning ventricle has improved because of the advent of physiologically corrective surgery for tricuspid atresia and its modifications. However, such procedures are usually restricted to patients older than 1 year, though patients with tricuspid atresia are symptomatic in the neonatal period or early infancy. Palliation should be performed to allow infants to reach the age and weight requirements for correction. As a consequence, the objective of any management plan is not only to provide symptomatic relief but also to preserve, protect, and restore the anatomy (with good-sized and undistorted pulmonary arteries) and physiology (normal pulmonary artery pressure and preserved left ventricular function) to normal so that a corrective procedure can be safely performed when the patient reaches an optimal age and weight.

• Management at presentation
• • Medical management during the process of identification, transfer to a pediatric cardiology center, initial workup, and cardiac catheterization (if needed) and during and after palliative surgery or procedures includes maintenance of a neutral thermal environment, normal acid-base balance, normoglycemia, and normocalcemia with appropriate monitoring and correction, if necessary. Unless associated pulmonary parenchymal pathology is present, the fraction of inspired oxygen (FIO₂) administered should be no more than 0.4.
  • Neonates who have low arterial PO₂ and O₂ saturation and ductal-dependent pulmonary blood flow should receive an intravenous infusion of PGE1 0.03-0.1 mcg/kg/min to open the ductus arteriosus or to maintain its patency. This is followed by an aortopulmonary shunt (see Palliative surgery).
  • In the infant who presents with signs of congestive heart failure (type Ic or IIc), anticongestive therapy with digoxin, diuretics, and afterload reduction should be promptly given. Considerations pertaining to pulmonary artery banding are reviewed in Surgical Care.
  • With ductal dilation, an infusion of PGE1 may improve systemic perfusion in patients with severe aortic coarctation, which is particularly observed in those with type II disease. Surgical repair of the coarctation should follow. Some cardiologists use balloon angioplasty to relieve the aortic obstruction.
  • If interatrial obstruction is present, it should be relieved by means of balloon atrial septostomy. On occasion, blade or surgical septostomy is necessary.
  • For patients presenting after infancy, the treatment approach is similar to that described above except that PGE1 is not effective in opening the ductus.
• Medical management after palliation
• • The management issues in tricuspid atresia are similar to those in other cyanotic congenital heart defects and are discussed in Tricuspid Atresia (Rao, 1992).
  • Hemoglobin should be periodically measured, and anemia and polycythemia, when present, should be treated.
  • Patients should receive antibiotic prophylaxis before undergoing any bacteremia-producing surgery or procedures.
  • The risks of stroke and brain abscess are similar to those in other cyanotic heart defects. When such a problem develops, appropriate neurologic or neurosurgical consultation and treatment is indicated.
  • Routine well-child care, including immunizations, by the primary care physician is suggested. Administration of polyvalent pneumococcal vaccine and influenza vaccine and immunization against respiratory syncytial virus should be considered.
  • Issues such as physical and emotional development, genetic counseling, vocational training and rehabilitation, pregnancy, and contraception are addressed similarly to those in other cyanotic heart defects.
  • The development of hyperuricemia, gout, and uric acid nephropathy in adolescents and adults with long-standing cyanosis and polycythemia is similar to that in other cyanotic heart defects. Timely palliative and corrective surgery may prevent such complications. 
• Catheter intervention
• • In the neonate, obstruction at the level of the atrial septum may be treated with conventional Rashkind balloon atrial septostomy. In infants and children, the interatrial septum may be too thick to be torn with balloon septostomy; therefore, Park blade septostomy should precede the Rashkind procedure.
  • In most patients, obstruction to pulmonary blood flow is at the VSD level or in the subpulmonary region. In some patients, the obstruction is at the pulmonary valve. In such patients, balloon pulmonary valvuloplasty may be useful in improving pulmonary blood flow and oxygen saturation.
  • If progressive cyanosis develops after a previous Blalock-Taussig shunt and if the hypoxemia is due to a stenotic shunt, balloon dilatation may be used to improve oxygen saturation. However, if the patient is of sufficient size and age to undergo a bidirectional Glenn procedure, this procedure should be performed instead of balloon angioplasty of a narrowed Blalock-Taussig shunt.
  • If severe aortic coarctation is present, particularly in patients with tricuspid atresia type II, balloon angioplasty may be useful in relieving aortic obstruction and may help achieve better control of congestive heart failure.
  • If clinically significant branch pulmonary artery stenosis is present before bidirectional Glenn or Fontan conversion or after a Fontan procedure is performed, balloon angioplasty or placement of intravascular stents is recommended.
  • Development of aortopulmonary collateral vessels has been increasingly observed in recent studies. Before the final Fontan conversion, occlusion of these vessels in the catheterization laboratory, usually by means of coil embolization, is recommended to reduce left ventricular volume overloading and, probably, the duration of chest-tube drainage.
  • After a Fontan procedure, some patients may have recurrent pleural effusion, liver dysfunction, plastic bronchitis or protein-losing enteropathy. In these patients, rule out obstructive lesions in the Fontan circuit, then puncture of the atrial septum by using a Brockenbrough technique followed by static balloon atrial septal dilatation or stent implantation may be beneficial.
  • Patients who undergo a fenestrated Fontan operation or who have a residual atrial defect despite correction may have clinically significant right-to-left shunting that causes severe hypoxemia. These residual atrial defects may be closed by using transcatheter techniques.

Surgical Care

Surgical management may be broadly grouped into palliative and corrective therapies.  

• Palliative surgery: Palliative therapy depends on the hemodynamic disturbance the associated cardiac anomalies produce and may be discussed in terms of decreased pulmonary flow, increased pulmonary flow, or intracardiac obstruction.
• • Decreased pulmonary blood flow
  • • Pulmonary blood flow may be increased by surgical creation of an aortopulmonary shunt. After Blalock and Taussig initially described subclavian artery–to–ipsilateral pulmonary artery anastomosis in 1945, other procedures have been described, including Potts shunting (descending aorta–to–left pulmonary artery anastomosis), Waterston-Cooley shunting (ascending aorta–to–right pulmonary artery anastomosis), central aortopulmonary fenestration or expanded polytetrafluoroethylene (Gore-Tex; W. L. Gore & Associates, Inc, Newark, DE) shunting, modified Blalock-Taussig shunt (Gore-Tex interposition graft between the subclavian artery and the ipsilateral pulmonary artery), Glenn shunt (superior vena cava–to–right pulmonary artery anastomosis, end-to-end), formalin infiltration of the wall of ductus arteriosus, enlargement of the VSDs, and stent implantation into the ductus.
    • The classic Blalock-Taussig shunt and its modification with an interposition Gore-Tex tube graft between the subclavian artery and the ipsilateral pulmonary artery, which de Leval et al (1981) described, have stood the test of time and are currently the procedures of choice for palliation in pulmonary oligemia.
    • Because the site of obstruction to pulmonary flow in most patients with tricuspid atresia is at the VSD, resection of the septal muscle to enlarge the VSD, which Annechino et al (1980) advocate, appears to be a logical choice because it addresses rather than bypasses the site of obstruction. However, this resection is an open-heart surgical procedure and more cumbersome than the modified Blalock-Taussig shunt in augmenting the pulmonary blood flow; it has not been used routinely. In the rare patient with predominant obstruction at the pulmonary valve, balloon pulmonary valvuloplasty may be used to increase the pulmonary blood flow. Stenting the arterial duct is an attractive nonsurgical option, but because of limited experience, it is not currently a first-line therapeutic option.
    • In summary, a number of palliative procedures are available to augment pulmonary blood flow, but the modified Blalock-Taussig shunt is the recommended procedure of choice in most, if not in all, patients with tricuspid atresia with pulmonary oligemia.
  • Increased pulmonary blood flow
  • • Patients with increased pulmonary blood flow are likely to have type Ic or type IIc defects without associated pulmonary stenosis. Congestive heart failure is likely to occur in these patients.
    • In patients with tricuspid atresia type II (transposition of the great arteries), pulmonary artery banding should be performed after stabilization with anticongestive measures. Banding not only improves congestive heart failure but also helps achieve normal pulmonary artery pressure so that bidirectional Glenn and Fontan procedures can safely be performed later. If associated aortic coarctation is present, it must be relieved. Pulmonary artery banding stimulates more ventricular hypertrophy, which may further reduce the size of the VSD, thus increasing subaortic obstruction.
    • In patients with tricuspid atresia type I (normally related great arteries), aggressive anticongestive measures should promptly be undertaken. Because natural history studies suggest that the VSD spontaneously closes or becomes smaller with time and the patients with pulmonary plethora develop pulmonary oligemia, banding of the pulmonary artery is generally not recommended in this group of patients. However, if symptoms are not relieved after optimal anticongestive therapy and some delay, pulmonary-artery banding should be performed. Patients with no pulmonary-artery banding should receive careful follow-up and monitoring of pulmonary artery pressure.
    • Absorbable pulmonary artery bands have been used (Bonnet, 2001) for palliation in such infants. By restricting the pulmonary blood flow, the absorbable polydioxanone band decreases pulmonary artery pressure and initially helps abate symptoms of heart failure. As the VSD spontaneously closes, the pulmonary artery band is resorbed and does not produce the severe pulmonary oligemia that might have been associated with a conventional nonabsorbable band. This is an ingenious approach, though it is likely to be helpful in a limited number of patients (Rao, 2001).
  • Intracardiac obstruction, which may occur at the level of patent foramen ovale and VSD
  • • Interatrial obstruction
    • • Because the entire systemic venous return must pass through the patent foramen ovale, it should be large enough to allow unimpeded egress of systemic venous blood. Because of the compliant right atrium and proximal systemic veins, evaluating interatrial obstruction is difficult. Clinical signs of systemic venous congestion and presystolic hepatic and jugular venous pulsations suggest obstructed atrial septum. A mean atrial pressure difference of more than 5 mm Hg and prominent a waves in the right atrial pressure wave are generally considered diagnostic of clinically significant obstruction.
      • Balloon atrial septostomy usually promptly improves presystolic hepatic and jugular pulsations and decreases interatrial pressure difference. Blade atrial septostomy is occasionally necessary, especially in older infants and children. Surgical atrial septostomy is needed even less frequently than this. However, surgical septostomy to allow unrestricted flow across the atrial system may be performed concurrently with bidirectional Glenn procedure.
    • Interventricular obstruction
    • • Spontaneous closure of the VSD can occur, causing interventricular obstruction.
      • Functional VSD closure in tricuspid atresia type I results in cyanotic spells, similar to those in tetralogy of Fallot. Initial management is similar to that of tetralogy of Fallot and includes knee-chest positioning, humidified oxygenation, and the administration of morphine sulfate 0.1 mg/kg. If the patient's condition is unresponsive, beta-blockers (propranolol, esmolol) or intravenous pressors (methoxamine, phenylephrine) are administered to increase systolic blood pressure by 10-20%. Concurrent correction of anemia or metabolic acidosis should also be undertaken. If no improvement occurs, emergency surgical palliation with a Blalock-Taussig type of shunt may be necessary. If the infant's condition improves clinically, elective surgery, Blalock-Taussig shunting, or a bidirectional Glenn or Fontan procedure may be performed, depending on the patient's age and weight and the status of pulmonary arteries and left ventricle.
      • Partial or complete anatomic closure of the VSD can also occur in patients with type I, causing pulmonary oligemia. The management is as described in the decreased pulmonary blood flow section above.
      • In patients with tricuspid atresia type II, spontaneous closure of the VSD produces subaortic obstruction. This obstruction should be relieved or bypassed as soon as it is detected because it produces left ventricular hypertrophy, which in turn increases the risk at the time of Fontan operation. The VSD, right ventricle, and aortic valve may be bypassed with an anastomosis of the proximal stump of the divided pulmonary artery to the ascending aorta (Damus-Kaye-Stansel procedure) directly or by means of a prosthetic conduct at the time of bidirectional Glenn or Fontan conversion. As an alternative, the conal septal muscle may be resected to enlarge the VSD; this is a direct approach in relieving the subaortic obstruction. However, development of heart block, inadequate relief of obstruction, and spontaneous closure of the surgically enlarged or created VSD remain major concerns.
• Corrective surgery
• • After Fontan and Kreutzer's initial description of the physiologically corrective operation for tricuspid atresia, corrective surgery was widely adapted by most workers in the field. The concept was even extended to treat other cardiac defects with a functionally single ventricle. The originally described Fontan operation consisted of the following:
  • • Superior vena cava–to–right pulmonary artery end-to-end anastomosis (Glenn procedure)
    • Anastomosis of the proximal end of the divided right pulmonary artery to the right atrium directly or by means of an aortic homograft
    • Closure of the ASD
    • Insertion of a pulmonary valve homograft into the inferior vena caval orifice
    • Ligation of the main pulmonary artery to completely bypass the right ventricle
  • Kreutzer performed anastomosis of the right atrial appendage and pulmonary artery directly or by using a pulmonary homograft and closed the ASD. A Glenn procedure was not performed, and a prosthetic valve was not inserted into the inferior vena cava.
  • Fontan's concept was to use the right atrium as a pumping chamber; therefore, he inserted a prosthetic valve into the inferior vena cava and right atrial–pulmonary artery junction. Kreutzer's view was that the right atrium may not function as a pump and that the left ventricle functions as a suction pump in the system.
  • A number of modifications to the aforementioned procedures were done by these and other workers in the field, as Chopra and Rao reviewed in the American Heart Journal (1992). When their review was published, the 4 major types of Fontan-Kreutzer procedures used were right atrium–to–pulmonary artery anastomosis with or without a valved conduit and right atrium–to–right ventricular connection with and without a valved conduit.
  • On the basis of immediate- and intermediate-term results, direct atriopulmonary anastomoses (ie, without a conduit) appears to be the best procedure for patients with type I defects who have a small ( <30% of normal) right ventricle and for all patients with type II (transposition) defects. Right atrial–to–right ventricular valved conduit (preferably homograft) anastomosis appears to be most suitable for patients with type I defects who have good-sized (>30% of normal) right ventricles and a trabecular component. During the time of Chopra and Rao's review, several other emerging concepts were noted, including bidirectional cavopulmonary anastomosis, fenestrated Fontan, and total cavopulmonary connection.
  • Bidirectional cavopulmonary anastomosis
  • • This is a modified Glenn procedure in which the upper end of the divided superior vena cava is anastomosed end-to-side to the right pulmonary artery without disconnecting the latter from the main pulmonary artery. Thus, the superior vena caval blood is diverted into both the right and left pulmonary arteries. Haller et al (1996) studied experimental bidirectional cavopulmonary connection in animal models, and Azzolina et al (1972) first described its clinical use. Others later applied this technique to palliate complex heart defects with decreased pulmonary blood flow. Hemodynamic advantages of the bidirectional Glenn procedure are improved effective pulmonary blood flow, decreased total pulmonary blood flow, and reduced left ventricular volume overloading. Preserved continuity of the pulmonary artery is another advantage and may help enable a low-risk Fontan procedure.
    • When right and left superior vena cavae are present, bilateral bidirectional Glenn shunting should beperformed, especially if the bridging innominate vein is absent or small.
  • Fenestrated Fontan operation
  • • Many cardiologists and surgeons have modified the criteria Choussat et al (1978) outlined. Patients not meeting these criteria are at higher risk for a poor prognosis after a Fontan operation than patients who do. For the high-risk group, several workers have advanced the concept of leaving a small ASD open to facilitate decompression of the right atrium. Laks et al (1991) advocated closure of the atrial defect by constricting the preplaced suture in the postoperative period, whereas Bridges used a transcatheter closure technique.
    • Clinically significant decreases in the postoperative pleural effusions and systemic venous congestion and higher cardiac output have been noted after a fenestrated Fontan procedure. The duration of hospitalization appears to be decreased. However, these beneficial effects are at the expense of mild arterial hypoxemia.
    • Although the fenestrated Fontan procedure was initially conceived for patients at high risk, it has since been used in patients with modest or even low risk. Although rare, reports of cerebrovascular or other systemic arterial embolic events occurring after a fenestrated Fontan operation tend to contraindicate the use of fenestrations in patients with low or usual risk. Some data indicate that routine fenestration is not necessary (Thompson, 1999).
  • Total cavopulmonary connection
  • • On the basis of their hemodynamic studies, de Leval et al (1988) concluded that the right atrium is not an efficient pump. Flow in nonvalved circulation generates turbulence with consequent net decrease in flow, and energy losses are significant in the nonpulsatile chambers, corners, and obstructions. Using these principles, they designed and performed total cavopulmonary diversion in which the upper end of the divided superior vena cava is anastomosed end-to-side to the top of the undivided right pulmonary artery, and the inferior vena caval blood is routed via an intra-atrial tunnel into the cardiac end of the superior vena cava, which, in turn, is connected end-to-side to the undersurface of the right pulmonary artery.
    • Technical simplicity, maintenance of low right atrial and coronary sinus pressures, and reduction in right atrial thrombi are advantages of the procedure. Subsequent experimental work by Sharma et al (1996) indicated that complete or minimal offset between the orifices of the superior and inferior vena cavae into the right pulmonary artery decreases energy losses.
    • Although the total cavopulmonary connection was initially devised for patients with complex atrial anatomy and/or systemic venous anomalies, it has since been used extensively for all types of cardiac anatomy with one functioning ventricle and irrespective of venous anomalies.
  • Recent developments
  • • Since the author's review more than a decade ago, several observations have been made that tended to support that total cavopulmonary connection is the Fontan procedure of choice, staged Fontan (ie, a bidirectional Glenn followed later by final conversion to Fontan) is preferred, and extracardiac conduit is preferable to lateral tunnel for diversion of inferior vena caval blood into the pulmonary artery.
    • However, some studies indicated equal efficacy with these 2 methods of Fontan conversion.
    • The author prefers lateral tunnel Fontan conversion because creation of fenestration, if necessary, will be easier to perform and the lack growth potential for the extracardiac conduit.
  • Current surgical approaches
  • • The patient's age, weight, and anatomic and physiologic status determine the types of surgery recommended. The overall objective is to achieve a total cavopulmonary connection.
    • In the neonates and young infants with pulmonary oligemia, classic or modified Blalock-Taussig shunting is undertaken to improve the pulmonary oligemia.
    • In patients aged 6 months to 1 year, Blalock-Taussig shunting and bidirectional Glenn procedure are the choices. The author prefers the bidirectional Glenn operation at this age. Some clinicians perform bidirectional Glenn procedures in patients as young as 3 months; however, the probability of failure is increased at this young age presumably because of pulmonary vascular reactivity.
    • For children aged 1-2 years, the bidirectional Glenn procedure is preferable.
    • For patients older than 2 years, total cavopulmonary connection may be performed, but most authorities suggest staging by using an initial bidirectional Glenn operation followed by Fontan conversion in 6-12 months.
    • At the time of bidirectional Glenn surgery, any narrowing of the pulmonary artery should be repaired. Issues related to subaortic obstruction and mitral valve regurgitation should also be addressed.
    • Before Fontan conversion, cardiac catheterization should be undertaken to ensure normal anatomy and pressure of the pulmonary artery as well as normal LVEDP. At the same time, aortopulmonary collaterals should be evaluated by means of selective subclavian artery and descending thoracic aortic angiography. If collateral vessels are present, they should be occluded with coils. Some authors question routine use of pre-Fontan catheterization and suggest prospective evaluation of this issue.
    • At the time of Fontan conversion, most surgeons currently prefer extracardiac conduit diversion of inferior vena caval blood into the right pulmonary artery. The author prefers a lateral tunnel Fontan procedure. (Reasons for it are addressed above.) To address the growth issue related to extracardiac Fontan surgery, some surgeons use autologous pericardial roll grafts.
    • In patients with associated transposition of the great arteries, early banding of the pulmonary artery, relief of aortic coarctation (if present), and bypassing (by means of a Damus-Kaye-Stansel procedure) or resecting the subaortic obstruction should be incorporated into the management plan.
  • Emerging therapies
  • • Two-stage cavopulmonary connection is currently recommended for achieving Fontan circulation. Konertz et al (1995) proposed a staged surgical-catheter approach. They initially perform a modified hemi-Fontan that is later completed by transcatheter method. This approach reduces the total number of operations required.
    • The modified hemi-Fontan operation involves the usual bidirectional Glenn technique. The lower end of the divided superior vena cava is anastomosed to the undersurface of the right pulmonary artery. The superior vena cava is then banded around a 16-gauge catheter with 6-0 Prolene suture slightly above the cavoatrial junction. A lateral tunnel with a Gore-Tex baffle is created to divert the inferior vena caval blood toward the superior vena cava. The baffle is then fenestrated with 3-5 holes 5 mm wide. Thus, the first stage achieves a physiologic bidirectional Glenn condition.
    • At the time of the second stage, the transcatheter stage, the superior vena caval constriction is dilated with a balloon, and fenestrations are closed with devices or by placement of covered stent.
    • The original and other workers have performed these procedures in a limited number of patients, and preliminary data suggest that the usual post-Fontan complications, such as pleural effusion and ascites, have not occurred with this approach. Scrutiny of results of larger experience and longer-term follow-up and ready availability of covered stents are necessary for routine application of this innovative approach.

Consultations

• When neurologic complications such as strokes or brain abscesses develop, consultation with neurologist or neurosurgeon is advisable for appropriate guidance of therapy.
• At some time, patients may require catheter-directed therapy.
• • Examples include balloon and/or blade atrial septostomy, static dilation of the atrial septum, balloon pulmonary valvuloplasty, balloon angioplasty of aortic coarctation, implantation of stents, coil occlusion of collateral vessels, transcatheter closure of ASDs and/or fenestrations and creation of fenestration.
  • Consultation with an interventional pediatric cardiologist is needed to determine the feasibility and timing of the procedures and to perform them.

Diet

In most patients with tricuspid atresia, no dietary restrictions are necessary.

• In patients with heart failure, fluid and salt restriction may be appropriate. When fluid is administered by means of an intravenous and/or nasogastric route, only maintenance quantities of 100 mL/kg/day should be given. When the infant feeds independently, ad lib feedings are suggested; thirst and hunger mechanisms control intake, and the infant is unlikely to become overloaded.
• Salt restriction is advised for patients with heart failure. Because food without salt is unpalatable, patients may be allowed a diet with regular salt but with a slight increase in diuretic therapy. This approach is taken in the interest of encouraging adequate caloric intake; however, adding salt to foods with a high salt content is not advised.
• In infants with heart failure and failure to thrive, a high-calorie formula (24, 27, or even 30 cal/oz.) may be needed to ensure adequate weight gain. Lowered amounts of diluent (water) combined with glucose polymers (Polycose) and medium-chain triglycerides may be used.
• A diet rich in medium-chain triglycerides may be useful in postoperative patients with chylothorax.

Activity

• Exercise
• • No specific exercise restrictions are recommended.
  • Allow patients to set their own pace of activity. Participation in scholastic physical education is not discouraged, but patients may set their limits of tolerance.
  • Patients with tricuspid atresia, with or without corrective surgery, are not able to participate in competitive sports.
• Lifestyle implications
  • Even after effective palliation or successful Fontan surgery, patients are left with single-ventricle physiology, ie, 1 functioning ventricle.
  • These patients tolerate normal activity, but they may not be able to participate in highly exertional activities. Changes in lifestyle are necessary to avoid highly exertional activities, such as professional sports or work that requires substantial physical activity.
  • Traveling or living at altitudes higher than 5000 feet should be undertaken carefully and with consultation and approval from the cardiologist.
• Pregnancy
  • Significant hemodynamic and hematologic changes occur during normal pregnancy. Cardiac output increases, initially due to an increase in stroke volume and later due to an increase in heart rate. Most of the increase takes place in the first 30 weeks of gestation, and t