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Tricuspid Atresia

  
Tricuspid atresia is absence of the tricuspid valve accompanied by a hypoplastic right ventricle. Associated anomalies are common and include atrial septal defect, ventricular septal defect, patent ductus arteriosus, and transposition of the great arteries. Symptoms include cyanosis and those of heart failure. S2 is single, and murmurs depend on the presence of the associated anomalies. Diagnosis is by echocardiography or cardiac catheterization. Definitive treatment is surgical repair. Endocarditis prophylaxis is recommended.

Tricuspid atresia accounts for 1 to 3% of congenital heart anomalies. In the most common type (about 50%), a ventricular septal defect (VSD) and pulmonary stenosis are present, and pulmonary blood flow is decreased. A right-to-left shunt occurs at the atrial level, causing cyanosis. In another 30%, the great arteries are transposed, with a normal pulmonary valve, and pulmonary blood flow comes directly from the left ventricle, typically resulting in heart failure (HF).

Symptoms and Signs
Infants usually have severe cyanosis at birth. Signs of HF (tachypnea, dyspnea with feeding, poor weight gain, diaphoresis) may appear by age 4 to 6 wk.
Physical examination usually detects a single S2 and a grade 2 to 3/6 holosystolic or early systolic murmur of a VSD at the lower left sternal border. A systolic murmur of pulmonary stenosis or a continuous murmur of patent ductus arteriosus may be present in the upper left sternal border. A systolic thrill is rarely palpable if pulmonary stenosis is present. An apical diastolic rumble is rarely audible if pulmonary blood flow is increased. Long-standing cyanosis may result in clubbing.

Diagnosis
Diagnosis is suspected clinically, supported by chest x-ray and ECG, and established by 2-dimensional echocardiography with color flow and Doppler studies.
In the most common form, chest x-rays show normal or slightly increased heart size, right atrial enlargement, and decreased pulmonary vascular markings. Occasionally, the cardiac silhouette resembles that of tetralogy of Fallot (with a boot-shaped heart and concave pulmonary artery segment). Pulmonary vascular markings may be increased and cardiomegaly present in infants with transposition of the great arteries. ECG characteristically shows left superior QRS axis (between 0° and −90°) and left ventricular hypertrophy. Right atrial hypertrophy or combined atrial hypertrophy is also common.
Cardiac catheterization is usually necessary to further characterize the anatomy before surgical repair.

Treatment
In severely cyanotic neonates, prostaglandin E1 (beginning at 0.05 to 0.1 μg/kg/min IV) is infused to prevent closure of the ductus arteriosus or to reopen the constricted ductus before planned cardiac catheterization or surgical repair.
Balloon atrial septostomy (Rashkind's procedure) may be done as part of the initial catheterization to improve the right-to-left atrial shunt when the interatrial communication is inadequate. Some infants with transposition of the great arteries and signs of HF require medical treatment (eg, diuretics, digoxin)

Definitive repair requires staged operations: soon after birth, a Blalock-Taussig shunt (connection of a systemic and a pulmonary artery by a Gore-Tex tube); at age 4 to 8 mo, a bidirectional Glenn shunt (anastomosis between the superior vena cava and right pulmonary artery) or the hemi-Fontan procedure (diversion of blood from the superior vena cava to the central portion of the pulmonary artery through an anastomosis between the right atrial appendage and pulmonary artery and a patch sewed in the upper part of the right atrium); and by age 2 yr, a modified Fontan procedure. This approach has increased early survival rates to > 90%; survival rates are 85% at 1 mo, 80% at 5 yr, and 70% at 10 yr.



http://www.merck.com/mmpe/sec19/ch287/ch287i.html
 

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