Background
Tricuspid atresia is the third most common form of cyanotic congenital heart disease, with a prevalence of 1.03 per 10,000 live births. [1] The deformity consists of a complete lack of formation of the tricuspid valve with absence of direct connection between the right atrium and right ventricle.
Pathophysiology
Three types of tricuspid atresia are described, depending on the associated relationship of the great vessels. In type I, the great arteries are related normally; in type II, the great arteries are d-transposed; and in type III, the great arteries are l-transposed. The types are further subclassified according to the presence or absence of ventricular septal defects and pulmonary valve pathology. [2, 3]
Other cardiovascular anomalies occur in 15-20% of patients with tricuspid atresia. Most of the associated anomalies relate to transposition of the great vessels. A persistent left superior vena cava anomaly is observed in 15% of patients.
With the absence of the tricuspid valve and no continuity between the right atrium and right ventricle, venous blood returning to the right atrium can exit only by an intra-atrial communication. Because of the obligatory right-to-left shunt at the level of the atria, saturation of the left atrial blood is diminished.
The intracardiac blood flow in tricuspid atresia further depends on the presence or absence of pulmonary arterial pathology. [4] In the absence of pulmonary atresia or pulmonary valve stenosis, the volume of blood to the lungs may be normal with normal oxygenation occurring, resulting in reduced cyanosis. In contrast, with accompanying pulmonary artery or valve stenosis, pulmonary blood flow is reduced, resulting in increased cyanosis.
Pulmonary obstruction occurs most often in patients with tricuspid atresia and normally related great arteries. Patients with d-transposed great arteries and tricuspid atresia generally have unobstructed pulmonary blood flow.
The left ventricle comprises most of the ventricular mass in tricuspid atresia. Because of volume overload (the left ventricle receives all the venous return) and persistent hypoxemia, decreased ventricular function may result in fibrosis, decreased ejection fraction, mitral annular dilatation, and mitral insufficiency.
Etiology
The cause is unknown. Although specific genetic causes of the malformation remain to be determined in humans, the FOG2 gene may be involved in the process. Mice in which the FOG2 gene is knocked out are born with tricuspid atresia. The significance of this finding and its applicability in humans requires further investigation.
Epidemiology
United States data
An estimated 404 babies are born with tricuspid atresia each year in the United States. [1]
Race-, sex-, and age-related demographics
No racial predilection is apparent.
Considering all forms of tricuspid atresia, no sexual predilection exists. Males present more frequently with transposed great vessels than females.
The anomaly is congenital and is evident at birth.
Prognosis
The 1-year survival rate after the Fontan operation is 85%; the 5-year survival rate is 78%. Because the procedure eliminates cyanosis, polycythemia and left ventricular volume overload are relieved; therefore, this population can be expected to live longer.
Morbidity/mortality
Depending on the degree of obstruction and associated anomalies, tricuspid atresia may be lethal at birth. Without repair, the patient rarely survives to adulthood.
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Tricuspid Atresia. Fontan procedure: Illustration of the atrial-to-pulmonary artery anastomosis.
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Tricuspid Atresia. Frontal chest radiograph in a child with tricuspid atresia and a nonrestrictive ventricular septal defect. There is pulmonary plethora. Note the prominent right atrium.
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Tricuspid Atresia. Frontal chest radiograph in a child with tricuspid atresia and a nonrestrictive ventricular septal defect, mild pulmonary plethora and, atypically, a right aortic arch (arrow). Note enlarged right atrium and the typical rounded configuration of the left cardiac apex. In the absence of the right ventricle, the left ventricle becomes hypertrophied and dilated, causing the development of a more rounded cardiac apex.
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Tricuspid Atresia. Frontal chest radiograph in an adult with untreated tricuspid atresia. Increased pulmonary blood flow through a nonrestrictive ventricular septal defect has been tolerated for years but has led to the development of pulmonary hypertension, as shown by the large proximal pulmonary arteries (arrows) and pruned distal pulmonary arteries. The development of pulmonary hypertension prevents conventional surgical treatment.
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Tricuspid Atresia. Axial ECG-gated spin-echo MRI in an adult patient with tricuspid atresia shows the high signal from atrioventricular sulcus tissue (black arrow), replacing the tricuspid valve, and an enlarged right atrium. Note how the mitral valve orientation (white arrows) is abnormal. The right ventricular outflow chamber (R) is anterior.
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Tricuspid Atresia. Axial ECG-gated spin-echo MRI (10 mm caudad to previous Image ) shows the high signal intensity from atrioventricular sulcus tissue and the restrictive ventricular septal defect (arrow) between the ventricle and the right ventricular outflow chamber. Note the dilated and rounded left ventricular cavity.
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Tricuspid Atresia. Axial ECG-gated spin-echo MRI in an adolescent patient with tricuspid atresia with modified Fontan repair. The Fontan conduit (white arrow) runs from the right atrium (A) around the front of the heart towards the pulmonary artery. Note that the front of the heart is identified by the anterior atrioventricular sulcus tissue containing the signal void of the right coronary artery (black arrow).
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Tricuspid Atresia. Axial ECG-gated spin-echo MRI in an adolescent patient with tricuspid atresia with modified Fontan repair (10 mm inferior to previous Image ). Thick atrioventricular sulcus tissue (arrow) is noted replacing the tricuspid valve. The ventricular septal defect has been repaired, and the ventricular septum is now intact.
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Tricuspid Atresia. Apical 4-chamber 2-dimensional echocardiogram shows atrioventricular sulcus tissue (solid arrow) replacing the tricuspid valve in a patient with tricuspid atresia. Note the enlarged right atrium posterior to the abnormal atrioventricular sulcus tissue. A moderate-sized ventricular septal defect (open arrow) is noted between the ventricle (V) and outflow chamber (C).
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Tricuspid Atresia. Fluoroscopic image shows a Park blade septostomy catheter with cutting blade extended in a patient with tricuspid atresia. The catheter has been passed through a restrictive atrial septal defect, which was resistant to balloon septostomy. The blade was used to make 2 cuts in the atrial septum, starting a tear, which then was completed using balloon septostomy.
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Tricuspid Atresia. Frontal ventriculogram in a patient with tricuspid atresia shows the pulmonary arteries arising from a small right ventricular type outflow chamber (arrow). A restrictive ventricular septal defect and a large globular ventricle (V) are noted.
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Tricuspid Atresia. Steep left anterior oblique ventriculogram in a patient with tricuspid atresia shows a restrictive ventricular septal defect (between arrows) and a typically large globular ventricle (V).
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Tricuspid Atresia. Steep left anterior oblique ventriculogram in a patient with tricuspid atresia shows a larger nonrestrictive ventricular septal defect (white arrow). A typically large globular ventricle (V) is seen, which is receiving inflow from a single atrioventricular valve (mitral valve, black arrows). Note how the aorta and pulmonary arteries are superimposed, making interpretation of their attachments difficult. Angiography must be performed in multiple projections to fully define complex relationships accurately.
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Tricuspid Atresia. Shallow right anterior oblique view from a ventriculogram in a patient with tricuspid atresia shows mitral regurgitation with contrast filling in both the left atrium (LA) and right atrium (RA), through the atrial septal defect. Contrast outlines the thick band of atrioventricular sulcus tissue (arrow), which is demonstrated well on cross-sectional imaging techniques.
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Tricuspid Atresia. Right anterior oblique ventriculogram in a patient with tricuspid atresia shows simultaneous filling of the aorta (Ao) and pulmonary arteries (PA). Nonrestrictive ventricular septal defect was present, which necessitated pulmonary artery banding (arrow) to reduce pulmonary blood flow and protect against development of pulmonary hypertension before proceeding to a Fontan procedure.
