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A rare congenital heart malformation characterized by absence of the tricuspid valuvar annulus (absent right atrioventricular connection/junction) or an imperforate tricuspid valve leading to severe hypoplasia of right ventricle (functionally univentricular heart). The malformation is associated with normally related great arteries (70 to 80% of cases) or transposed great vessels, an obligatory interatrial connection that is crucial for survival (patent oval foramen or atrial septal defect ostium secundum type), ventricular septal defect (VSD), pulmonary outflow obstruction (pulmonary atresia, stenosis or hypoplasia), aortic coarctation and/or aortic arch interruption.
ORPHA:1209Classification level: Disorder
In Europe, the prevalence at birth ranges between 1/11,000-50,000 worldwide. Tricuspid atresia accounts for around 1% of all congenital heart defects. Both sexes are equally affected.
At least 80% of children born with tricuspid atresia are symptomatic during the first month of life. Two main clinical presentations are observed, depending on the anatomy: patients with high pulmonary blood flow, and patients with reduced pulmonary blood flow. Subpulmonary obstruction is due to a restrictive VSD when ventriculo-arterial connections are concordant. Patients with high pulmonary blood flow can have either concordant or discordant ventriculo-arterial connections. In the latter case, coarctation of the aorta can occur if the VSD is restrictive. These patients develop cardiac failure, failure to thrive and recurrent upper respiratory tract infections. Patients with reduced pulmonary blood flow exhibit cyanosis and tachypnea without signs of heart failure.
Etiology is still largely unknown. Tricuspid atresia results from an arrest in cardiac development at an early stage, when the atrioventricular canal is supported only by the primary (left) ventricle and there is no connection between the right atrium and the developing right ventricle. Tricuspid atresia is found in chromosomal anomalies such as 22q11, 4q31, 8p23 and 3p microdeletions. Some genes have been recognized as potentially involved: ZFPM2, HEY2, NFATC1, NKX2.5, and MYH6. Tricuspid atresia has also been reported in association with Alagille and Ellis Van Creveld syndromes.
Diagnosis is suspected on clinical examination of cyanosis and heart murmur, and is confirmed on cross-sectional echocardiography. Echocardiography will assess the position of the great vessels, transposed or not, the magnitude of the shunt between the ventricles and the atria, and the presence of subpulmonary stenosis or coarctation, allowing to plan surgical management.
Differential diagnosis includes all cyanotic congenital heart defects and non-cardiac causes of neonatal cyanosis in forms with reduced pulmonary blood flow, and other causes of high pulmonary blood flow. It also includes other univentricular hearts.
Like all other types of univentricular hearts, the prenatal detection rate of tricuspid atresia is high (between 70 and 90%) in countries with antenatal screening policies implemented.
Most cases of tricuspid atresia occur sporadically as a result of spontaneous genetic mutations. The recurrence risk for tricuspid atresia is low, 1%.
Management and treatment
The management of neonates with tricuspid atresia depends on the pulmonary blood flow. If pulmonary blood flow is high, pulmonary banding will be indicated to protect the pulmonary vascular bed. If it is reduced, prostaglandin E1 may be needed to maintain the permeability of the arterial duct before a surgical Blalock-Taussig-Thomas systemic-to-pulmonary anastomosis is performed. Rashkind maneuver may be needed if the interatrial shunt is restrictive. The second surgical stage will consist of a partial cavopulmonary connection (superior caval vein to pulmonary artery anastomosis) between 4 and 6 months of age, followed by the Fontan procedure (total cavopulmonary connection, fenestrated or not) between 2 and 4 years of age.
Fontan procedure is a palliative surgery which does not restore a biventricular circulation. Current pooled survival estimates at 5, 10 and 15 years are 88.4%, 85.7% and 84.1% respectively. Long-term complications include left ventricular dysfunction, atrial arrhythmias, cardiac conduction disorders, thromboembolism, cirrhosis and hepatocellular carcinoma, and protein-losing enteropathy. Many of these patients will ultimately require cardiac transplantation.