Tricuspid atresia is the third most common form of cyanotic congenital heart disease, with a prevalence of 0.3-3.7% in patients with congenital heart disease. 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.
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.1, 2
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. 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.
The frequency of tricuspid atresia is 2.9% in autopsy series.
Depending on the degree of obstruction and associated anomalies, tricuspid atresia may be lethal at birth. Without repair, the patient rarely survives to adulthood.
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.
Tricuspid atresia is usually detected in infancy because of presenting cyanosis, congestive heart failure, and growth retardation. Parents provide a history of poor skin coloration (ranging from pallor to frank cyanosis), inability to complete a feeding session, frequent pauses during feeding, and/or frank anorexia. As a result, the infant demonstrates poor growth patterns. Respiratory difficulties are often reported as nasal flaring or muscle retractions. (See eMedicine’s Pediatric article Tricuspid Atresia.)
Bacterial endocarditis and brain abscess are common findings in patients with tricuspid atresia and should be considered in children with headaches, seizures, or neurologic deficits.
On inspection, cyanosis is the most common clinical feature of this lesion. The degree of cyanosis depends on the degree of pulmonary blood flow. Infants with associated diminished pulmonary blood flow or infants who depend on a patent ductus arteriosus manifest pronounced cyanosis that worsens as the ductus begins to close. Patients with relatively normal or increased pulmonary blood flow manifest little cyanosis but more pronounced congestive heart failure. For related information, see Medscape’s Heart Failure Resource Center.
Digital clubbing is common in infants older than 3 months. Jugular venous pulsations and distention are common.
The peripheral pulses and pulse volume may be decreased, normal, or increased. The left ventricular impulse is prominent because of volume overload. The apical impulse is hyperdynamic, with displacement to the left of the midclavicular line. A thrill may be felt at the left sternal border in patients with a restrictive ventricular septal defect or pulmonary valve stenosis. The liver may be large and pulsatile.
A single first heart sound that may be increased in intensity is usually present. The second heart sound may be single or normally split. The intensity of this sound varies, depending on associated transposition of the great vessels. In normally related great vessels, the second heart sound may be of normal intensity. In transposed great vessels, the second sound is diminished. Cardiac murmurs are present in 80% of patients with tricuspid atresia. A holosystolic murmur that may have a crescendo and decrescendo quality is present, signifying blood flow through the ventricular septal defect. A continuous murmur may be present. Systemic-to-pulmonary arterial collaterals or arterial-to-pulmonary arterial anastomoses surgically created to improve pulmonary blood flow may cause this finding. A murmur of mitral insufficiency may also be present.
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.