Tricuspid atresia (TA) is a congenital defect of the heart valve between the right atrium (RA) and the right ventricle (RV) preventing the normal flow of blood from the right ventricle to the lungs and from the lungs to the rest of the body. Solid tissue is formed instead of a functional tricuspid valve between the two chambers. TA is one of the manifestations of the so-called blue baby syndrome.
The infant is born cyanotic, which becomes more intense in the next few months, because of impaired pulmonary blood flow. By the 4th to 6th weeks of life, signs of heart failure (e.g., tachypnea, dyspnea with feeding, poor weight gain, and diaphoresis) may be present in infants with increased pulmonary blood flow, which will need emergency control measures.
Auscultation will reveal a single second heart sound and a grade 2 to 3 holosystolic or early systolic murmur of a ventricular septal defect at the lower left sternal border. A systolic ejection murmur of pulmonary stenosis or a continuous murmur of patent ductus arteriosus is audible in the upper left sternal border. An apical diastolic rumble indicates increased pulmonary blood flow. Cyanosis may persist for more than 6 months resulting in clubbing of the fingers or toes on account of the reduced amount of oxygen in the blood.
Successful management of congenital heart disease requires close coordination of a panel of experts in pediatric cardiology, neonatology and reconstructive surgery, for optimum care of the patient. Antenatal and postnatal evaluations are important for early diagnosis and treatment. Precision diagnostic tools are available and the choice of treatment modality depends on the child's status and institutional capability.
Cyanosis is the prominent sign that there is a problem with the newborn. A heart murmur heard during physical examination indicates turbulence of blood crossing an obstructed pulmonary valve or flowing through the openings where arterial and venous blood mix.
Confirmatory tests that are recommended:
There are three major areas of concern in the treatment of infants with TA. These are:
Most infants have decreased pulmonary blood flow, characterized by marked cyanosis and hypoxemia, the latter if severe may lead to acidemia and death. Prostaglandin E infusion is administered to keep the ductus arteriosus open and to increase pulmonary blood flow.
Increased pulmonary blood flow is associated with an unrestrictive ventricular septal defect (VSD) and transposed great vessels. Infants with these defects are likely to succumb to severe congestive heart failure and should be placed on digitalis and diuretics to restrict pulmonary blood flow until surgery can be performed.
Standard palliative procedures are at the discretion of the physician to improve the chances of survival of the patient. With reconstructive surgery, 50% may live up to adolescence. However, there is always the risk for developing complications such as polycythemia, arrhythmia, ventricular dysfunction, paradoxical emboli, stroke, brain abscess, progressive cardiac dilatation, and mitral valve insufficiency.
Most infants with TA undergo reconstructive surgery on their first year of life. Depending upon the severity of the disorder, the infant is admitted to the neonatal intensive unit (NICU) and administered prostaglandin E1 for blood to circulate to the lungs via a patent ductus arteriosus.
A series of surgical procedures may be needed. If the heart is unable to pump sufficient blood into the lungs, surgery is initiated via an artificial shunt. Otherwise, the infant is sent home to prepare for the Glenn shunt or Hemifontan procedure at 4 to 6 months of age. The procedure connects veins carrying blood from the upper half of the body directly to the pulmonary artery. At this stage, the child may still be cyanotic.
In infants with decreased pulmonary blood flow, the shunt procedure connects the systemic circulation and the pulmonary circulation, via a cavopulmonary anastomosis (Glenn shunt) or from the subclavian artery to the pulmonary artery (Blalock-Taussig shunt). In patients with increased pulmonary blood flow and severe congestive heart failure, pulmonary artery binding is undertaken to decrease blood flow to the lungs and to facilitate treatment of congestive heart failure  .
Shunt failure, persistence of cyanosis, progression of the disease and increasing pulmonary obstruction will necessitate a third and final operation, the Fontan procedure. Otherwise, palliative treatment to alleviate symptoms should be initiated.
The Fontan operation bypasses the right ventricle by connecting the right atrium to the pulmonary artery or by creating an extracardiac cavopulmonary anastomosis with a synthetic graft. The procedure requires the following specifications: minimum age of the patient (4 years or older), normal capacity of right atrium and caval drainage, sinus rhythm, mean pulmonary artery pressure less than 15 mm Hg, mean pulmonary arteriolar resistance low, pulmonary artery-to-aorta diameter ratio more than 0.75 and previous shunt procedures should not impair the current operation.
A 3-stage Fontan pathway without cardiopulmonary bypass can been achieved in patients with a single functional ventricle and cardiac abnormalities (tricuspid atresia, pulmonary atresia with intact ventricular septum, double outlet right ventricle)  . The procedure connects the right atrium to the systemic pulmonary artery at its point of exit or at the bifurcation of the main trunk, and closes the atrial septal defect        .
The goal of treatment is the survival of the atretic child. To achieve this, consultations among the attending physicians and with the parents of the affected child should include counselling and monitoring of the patient's progress in time. Certain prescriptions must be observed such as the use of diuretics, low sodium diet, electrolyte replacements, proper nutrition for growth and development, and limiting activities to prevent dyspnea and possible congestive heart failure.
Prognosis is good with early recognition of the disorder, possibly of the fetus in utero and with immediate surgical intervention postnatally to repair the congenital heart defects. A series of reconstructive surgical procedures are performed at birth and later when the infant is older. With Fontan operation, the survival rate is 85% after one year and 78% after five years. The procedure eliminates cyanosis and polycythemia. Left ventricular volume overload is relieved. Patients can be expected to live longer.
The etiology of tricupid atresia remains to be elucidated. Animal experimentation has shown that mice with aberration in FOG2 gene are born with tricuspid atresia indicating possible involvement of genetic factors in humans. Further studies are needed to validate this hypothesis.
The incidence of TA in the United States is 2.9%, based on post-mortem data. Depending on the extent of impairment of cardiac function and concomitant anomalies, TA is potentially fatal if left untreated. Survivors of treatment with corrective surgery may live well into adolescence or adulthood. There is no predilection for age, ethnic origin, and gender, although more males are found with transposed great vessel defect than females.
Tricuspid atresia is classified into three types according to the relative positions of the great vessels.These are:
Under each of these types, blood flow from the heart to the lungs is determined by the presence or absence of ventricular septal defect (VSD) and/or pulmonary valve pathology  . Fifteen to twenty percent of TA patients may have other cardiovascular defects which are linked to the transposition of the great vessels. For example, a persistent left superior vena cava anomaly has been observed in 15% of patients.
In patients with type I great arteries with a VSD, perfusion may take place in the lungs. Without a VSD, pulmonary blood flow is diverted through a patent ductus arteriosus, and systemic blood flow proceeds directly from the left ventricle. With type II (d-transposed great arteries), blood flows from the left ventricle to the lungs. Likewise, blood flows to the aorta from the left ventricle via the VSD and right ventricle. As for the other types of TA, the pathway of the aortic and pulmonary blood flow is determined by the size of the VSD and presence of other cardiac abnormalities.
The presence or absence of defects of the pulmonary artery affects the flow of blood in the heart in tricuspid atresia . In patients without pulmonary atresia or pulmonary valve stenosis, the volume of blood flow to the lungs may still be normal with adequate oxygenation. Cyanosis is not too severe. In the presence of pulmonary pathology, pulmonary blood flow is greatly reduced and cyanosis is increased. Obstruction of pulmonary blood flow often occurs in type I TA patients whereas type II TA patients generally have unobstructed pulmonary blood flow.
In the absence of a right atrioventricular connection, venous blood from the right atrium is diverted to the left atrium via an intra-atrial route or atrial septal defect (ASD), where venous and arterial blood mix. This obligatory right-to-left shunt diminishes the saturation of oxygen in the left atrial blood, and eventually, the supply of oxygen-rich blood to the rest of the body. Systemic arterial desaturation is present in all tricuspid atresia patients because of the pooling of systemic, coronary and pulmonary venous blood in the left atrium.
Whereas the right ventricle is degenerate, the left ventricle compensates by making up most of the ventricular mass in TA. It ejects all the venous blood (systemic, coronary and pulmonary) output and its pumping capacity is strained. Left ventricular overloading is present in all TA cases. A number of sequelae have been reported, namely: fibrosis, persistent hypoxemia, ventricular dysfunction, decreased ejection fraction, mitral annular dilatation, and mitral insufficiency.
Congenital heart defects may be averted or minimized by conscientious antenatal care of mother and fetus in terms of proper nutrition, good hygienic practices, avoidance of exposure to infections, abstinence from unhealthy habits, and unprescribed drugs. Regular consultation with specialists is the best option.
Tricuspid atresia (TA) is one of congenital heart defects characterized by the absence or underdevelopment of the connection between the right atrium (RA) and the right ventricle (RV). This results in decreased ventricular function, thus the impairment of the passage of blood to the right ventricle and from there, to the lungs where venous blood is oxygenated. The defect is acquired in utero during the first 8 weeks of fetal development.
The right ventricle is usually hypoplastic or underdeveloped. To compensate for the absence of an atrioventricular connection, other congenital defects may occur, like an atrial septal defect (ASD) or a ventricular septal defect (VSD). These allow mixing of oxygenated and non-oxygenated blood.
Diagnosis is based on the results of antenatal and postnatal imaging studies and presentation at birth. The newborn with TA is cyanotic, has low birth weight, shows abnormal heart sounds, has feeding and respiratory problems, and is prone to aspiration pneumonia. Early diagnosis and prompt treatment are essential. Treatment may require a series of operations to correct the defect. Those who survive these procedures may live long and be able to cope with normal daily activities.
Risks coming from complications due to highly vulnerable status of the newborn should be taken into consideration. A multidisciplinary panel of experts (in neonatology, pediatrics, cardiology, internal medicine, and surgery) is required to ensure optimum care for the mother and the child. Prevention can best be achieved following regular consultations with the aforementioned specialists.
Tricuspid atresia (TA) is an inborn defect of the heart in which the connection between the right atrium and the right ventricle is replaced by a solid mass of tissue instead of the tricuspid valve. The right ventricle degenerates and is unable to pump blood into the lungs via the pulmonary artery for the vital process of oxygenation. To compensate for this loss of atrioventricular connection, two other congenital anomalies develop, a passageway connecting the right and left atria called atrial septal defect (ASD) and one connecting the two ventricles, where venous (deoxygenated) and arterial (oxygenated) blood mix, called ventricular septal defect (VSD). Thus, blood that is delivered to the rest of the body is deficient in oxygen. The lungs likewise receives blood through a fetal vessel called ductus arteriosius which normally closes after birth.
The end result of these aberrations is a cyanotic newborn (blue baby syndrome) with oxygen-poor blood. The patient might have feeding, breathing and other co-existing pathological conditions, and needs immediate remedial measures to survive.
Tricuspid atresia affects 5 in every 100,000 live births; 20% of these patients are with other congenital defects which are likely to be the source of complications with fatal outcomes. The TA baby has bluish skin, tires easily, is underweight, has respiratory problems (tachypnea, dyspnea), drools a lot, and is at risk for aspiration pneumonia.
TA can be detected prenatally and postnatally by routine and high precision diagnostic tools. A heart murmur may present at birth indicating an abnormal heart condition. Confirmatory tests include: ECG, echocardiogram, chest x-ray, cardiac catheterization, and MRI of the heart.
If the heart has difficulty pumping blood into the lungs and to the rest of the body, the baby may be admitted in the intensive care unit for an artificial shunt procedure within the first few days of life. This first surgery may or may not be needed, if the baby can cope with palliative treatment (oral medication) under the supervision of a pediatric cardiologist. If cyanosis and other symptoms persist, a series of reconstructive surgery may be needed. In more advanced cases, a second (Glenn procedure) and third (Fontan) operative procedure may be required a few months later and within 3 years of life, respectively. The baby should no longer be cyanotic after Fontan surgery.
Some possible complications may occur in the course of treatment. These include:
The best strategy for care and prevention of tricuspid atresia is compliance with early prenatal and postnatal interventions and good maternal health practices.