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Tetralogy of Fallot Pulmonary Stenosis Pulmonary Atresia Tricuspid Atresia Ebstein's Anomaly

Tricuspid Atresia

  • Tricuspid atresia refers to a defect where the tricuspid valve is absent and right ventricle is variably hypoplastic. It can be classified into three types which have implications for clinical manifestations and surgical correction (St. Louis).
    • Type I includes those without transposition of the great arteries.
    • Type II includes those with transposition of the great arteries.
    • Type III refers to those with congenitally corrected transposition of the great vessels.
    • Each of these types can be subdivided based on the degree of obstruction to pulmonary blood flow. "Subtype a" consists of pulmonary arteries that are atretic, "subtype b" includes either pulmonary stenosis or hypoplasia, those with "subtype c" have no obstruction to pulmonary flow.
  • When the tricuspid valve is absent, blood from the right atrium usually passes through a patent foramen ovale to the left atrium and left ventricle. In more rare cases, it may also pass through an arterial septal defect.
  • Atresia of the tricuspid valve results in both the pulmonary and systemic venous returns passing through the foramen ovale and into the left atrium and left ventricle which functions as a single ventricle.
    • When the great vessels are normally related (type I), blood passes from the left ventricle out the aorta and through a ventricular septal defect to the right ventricle and pulmonary artery. Closure of the septal defect combined with restriction by the pulmonary valve and limited right ventricular outflow due to hypoplasia results in a progressive decrease in pulmonary blood flow. The patent ductus arteriosus provides a time-limited source of blood to the pulmonary artery, as it typically closes on schedule a few days after birth.
    • When the great vessels are transposed (type II), blood from the left ventricle passes out the pulmonary artery and through a ventricular septal defect into the aorta. Closure of the septal defect leads to subaortic stenosis and decrease in cardiac output. To compensate, pressure in the left ventricle increases which in turn, increases pulmonary outflow leading to congestive heart failure.
  • Most patients with tricuspid atresia present with cyanosis that increases in severity over a period of months as ventricular septal defects and the ductus arteriosus constrict. As the degree of cyanosis worsens, infants may also begin to have cyanotic spells.
  • Management of tricuspid atresia typically involves a Fontan operation around 2 years of age. This procedure involves creating a connection between the lateral aspect of the right atrium to reach the left atrium to produce a right-to-left shunt and allow blood to reach the systemic circuit, albeit with some reduction in arterial oxygen saturation.