Tricuspid Atresia

Absence of the tricuspid valve with no direct connection from the right atrium to the right ventricle; right atrial blood crosses an atrial septal defect or patent foramen ovale to the left atrium. The right ventricle is hypoplastic. About 1 to 3% of congenital heart disease, about 1 per 10,000 live births.

• Types by great artery relationship: type I with normally related great arteries (about 70 to 80%), type II with transposition (about 12 to 25%), type III other (rare). Subtypes by pulmonary flow: a atresia, b stenosis, c no obstruction.
• Mechanism: mixing of systemic and pulmonary venous blood in the left heart. Pulmonary blood flow is supplied by a ventricular septal defect or the ductus; reduced flow causes cyanosis, increased flow causes heart failure.
• Untreated, about 90% die in infancy or childhood.

• Cyanosis in the neonatal period (reduced pulmonary flow), or heart failure over the first weeks (increased pulmonary flow, usually with transposition or a large ventricular septal defect).
• Single second heart sound; ventricular septal defect murmur; prominent jugular a waves.
• Clubbing and hypoxic spells later; hepatomegaly with heart failure.
• Differential diagnosis: pulmonary atresia, tetralogy of Fallot, Ebstein anomaly, transposition of the great arteries, single ventricle, critical pulmonary stenosis.
• Complications: hypoxaemic spells, polycythaemia, stroke and brain abscess, infective endocarditis, atrial arrhythmia, heart failure from excess pulmonary blood flow, and after the Fontan operation protein losing enteropathy, plastic bronchitis, thrombosis and liver disease.

• ECG: left axis deviation (superior axis, a key finding), right atrial enlargement, left ventricular hypertrophy, reduced right ventricular forces.
• Chest X-ray: normal or small heart with decreased pulmonary flow (type I with stenosis), or enlarged heart with plethora.
• Echocardiography: absent tricuspid valve (echo dense plate), hypoplastic right ventricle, size of atrial and ventricular septal defects, pulmonary valve and arteries, great artery relationship, ventricular function, arch anatomy.
• Cardiac catheterisation or MR angiography before the Fontan operation: pulmonary artery pressure and size, pulmonary vascular resistance, ventricular function.

• Neonatal ductal dependent circulation: alprostadil 0.05 to 0.1 micrograms/kg/min then 0.01 to 0.05 micrograms/kg/min; target SpO2 75 to 85%; avoid excessive oxygen.
• Palliation in the first weeks of life:
  • Reduced pulmonary flow: modified Blalock-Taussig shunt or ductal stent; aspirin 3 to 5 mg/kg/day afterwards.
  • Excess pulmonary flow: pulmonary artery banding or, with systemic outflow obstruction, a Norwood type operation; furosemide 1 mg/kg per dose orally 2 to 3 times daily and captopril 0.1 to 0.5 mg/kg per dose 8-hourly while waiting.
  • Balanced circulation with SpO2 80 to 85%: observe.
  • Enlarge the atrial communication by balloon or surgical septectomy if the atrial defect is restrictive (right atrial to left atrial gradient 5 mmHg or more).
• Bidirectional Glenn (superior vena cava to pulmonary artery) at 3 to 6 months. Fontan completion (inferior vena cava to pulmonary artery, usually extracardiac conduit) at 2 to 5 years.
• Fontan candidacy: mean pulmonary artery pressure less than 15 mmHg, pulmonary vascular resistance less than 2 Wood units m2, ejection fraction greater than 50%, sinus rhythm, little atrioventricular valve regurgitation, good pulmonary artery size (Nakata index about 200 mm2/m2 or more).
• After the Fontan: aspirin 3 to 5 mg/kg/day, or warfarin with INR 2.0 to 3.0 if there is thrombus, arrhythmia or a fenestration; diuretics (furosemide 20 to 40 mg daily, spironolactone 25 to 50 mg daily) for effusions or ascites; avoid dehydration and long immobility.
• Fontan failure: protein losing enteropathy (albumin less than 30 g/L, raised stool alpha-1-antitrypsin), plastic bronchitis, arrhythmia, ventricular failure, hepatic fibrosis, thrombosis. Treatment: diuretics, budesonide 9 mg daily orally for enteropathy (evidence is limited), high protein low fat diet with medium chain triglycerides, albumin infusions for severe losses, catheter or surgical relief of obstruction, creation of a fenestration, and heart transplantation (the definitive option).
• Atrial tachyarrhythmia: cardioversion and anticoagulation (warfarin INR 2.0 to 3.0); amiodarone 400 to 600 mg daily for a loading period then 200 mg daily for rhythm control, with thyroid, liver and pulmonary monitoring; catheter ablation in specialist centres; pacing for sinus node dysfunction.
• Endocarditis prophylaxis: amoxicillin 2 g orally (50 mg/kg in children) 30 to 60 minutes before dental procedures after palliation with prosthetic material, with azithromycin or clarithromycin 500 mg for penicillin allergy (clindamycin is no longer recommended).
• Special groups: pregnancy (high risk after Fontan; preconception counselling is essential; maternal heart failure, arrhythmia, miscarriage and fetal growth restriction are common); older children and adults (annual surveillance, liver imaging every 1 to 2 years after Fontan).
• Survival: 10-year survival after Fontan about 85 to 90%, 25-year survival about 70 to 75%.
• Red flags: new oedema, ascites, diarrhoea with hypoalbuminaemia, palpitations, cough producing casts, cyanosis after a Fontan.
• Follow up: every 3 to 6 months in infancy, yearly thereafter, with echocardiography, ECG, Holter monitoring, liver function and albumin.