Tricuspid Atresia: Current Understanding, Diagnosis, and Management

Tricuspid atresia (TA) is a cyanotic congenital heart defect characterized by the absence or complete occlusion of the tricuspid valve, preventing normal blood flow from the right atrium to the right ventricle. This condition occurs in approximately 0.5–1.2 per 10,000 live births, accounting for ~3–5% of all congenital heart diseases (PHI registry data, Circulation, 2023).

Because oxygenated blood cannot enter the pulmonary circulation directly, systemic and pulmonary blood flow depend on accessory pathways—most commonly a patent ductus arteriosus (PDA) and/or a ventricular septal defect (VSD)—allowing mixing of oxygenated and deoxygenated blood. Without intervention, progressive hypoxemia and heart failure ensue.

Clinical Presentation

Symptoms typically manifest within hours to days after birth, as the ductus arteriosus begins to close:

• Cyanosis (bluish discoloration of skin, lips, and mucous membranes)
• Tachypnea (rapid breathing) and respiratory distress
• Feeding difficulties: Fatigue during sucking, poor intake, prolonged feed times
• Failure to thrive: Inadequate weight gain and linear growth
• Cardiac murmur: Often present (e.g., holosystolic murmurs from VSD or shunts), though may be absent in some subtypes

In advanced or untreated cases, signs of right heart failure may emerge: peripheral edema, hepatomegaly, ascites, and jugular venous distension. However, classic left-sided heart failure symptoms (e.g., orthopnea, paroxysmal nocturnal dyspnea) are uncommon in infancy due to systemic-to-pulmonary shunting.

Diagnosis

Initial Screening

• Pulse oximetry: Critical neonatal screening tool; persistent oxygen saturation <95% in room air—especially if asymmetrical between pre- and post-ductal sites (right hand vs. foot)—triggers urgent echocardiographic evaluation (AHA Scientific Statement, 2023).

Confirmatory Testing

1. Echocardiography (gold standard):
   • Confirms tricuspid valve absence and right atrial enlargement
   • Identifies associated anomalies: VSD (present in ~95% of cases), pulmonary stenosis/atresia, transposition of great arteries (TGA), or aortic arch anomalies
   • Assesses ductal patency, shunt direction/size, and ventricular size/function
2. Chest radiography: May show a “boot-shaped” heart (similar to tetralogy of Fallot) and diminished pulmonary vascularity if pulmonic stenosis is severe.
3. Electrocardiogram (ECG): Typically shows left axis deviation, left ventricular hypertrophy, and absent right atrial activation.
4. Cardiac MRI/CT: Reserved for complex anatomy or pre-surgical planning in older patients; provides detailed 3D assessment of systemic/pulmonary collateral vessels.

Classification System (Superior–Ventricular–Arterial Alignment)

The modern classification—based on spatial relationships of the great arteries and ventricles—is preferred over outdated “Type I–III” labels (which conflated diabetes and heart disease; JACC: Cardiovascular Imaging, 2021):

Note: ~70% of TA cases fall under D-MVTA or congruent alignment.

Management

Neonatal Stabilization

• Prostaglandin E₁ (Alprostadil) infusion: Initiated immediately if ductal-dependent pulmonary blood flow is suspected. Keeps PDA open, improving pulmonary perfusion and oxygenation (NEJM, 2022).
• Respiratory support: Mechanical ventilation may be needed for apnea (a known prostaglandin side effect) or severe acidosis. Avoid excessive FiO₂ to prevent pulmonary overcirculation.

Surgical Palliation (Staged Approach)

Three-stage palliation remains standard of care:

1. Stage 1: Neonatal Shunt or Dual-Pathway Control
   • Modified Blalock–Taussig shunt (mBT): Sizing critical—too large → pulmonary overcirculation; too small → persistent cyanosis. Modern protocols use computed flow modeling for optimal graft diameter (Annals of Thoracic Surgery, 2023).
   • Pulmonary artery banding (PAB): Rarely used today due to higher reoperation rates. Reserved for extreme pulmonary blood flow excess (e.g., large unrestrictive VSD + non-stenotic PA).
   • Norwood procedure: Only for TA with hypoplastic aortic arch or critical coarctation—distinct from classic TA.
2. Stage 2: Bidirectional Glenn (Hemi-Fontan)
   • Performed at 4–6 months of age
   • Superior vena cava (SVC) connected directly to right pulmonary artery
   • BT shunt excised; systemic venous return from upper body now flows passively to lungs
   • Mortality: <2% in high-volume centers (JTCVS, 2024); improves exercise tolerance and oxygen saturation.
3. Stage 3: Fontan Procedure
   • Typically at 18–36 months
   • Inferior vena cava (IVC) connected to pulmonary arteries via lateral channel or extracardiac conduit
   • Eliminates systemic-to-pulmonary shunt; all systemic venous blood flows passively to lungs
   • Conduit choice matters: extracardiac Fontan has lower arrhythmia risk vs. lateral tunnel (European Heart Journal, 2023)

Note: Atrial septal size must be carefully managed pre-Fontan—too small → systemic venous pressure elevation; too large → desaturation.

Long-Term Outcomes & Prognosis

Mortality & Survival

• Without surgery: >90% mortality by age 2 years (historical data).
• With modern staged palliation:
  • Hospital survival after Fontan: >97% in contemporary cohorts (Circulation, 2023)
  • 15-year transplant-free survival: ~88–94% (Mery et al., JACC, updated 2022 cohort analysis)
  • 20-year survival: ~75–82%, depending on ventricular morphology and Fontan type

Functional Status & Complications

• Most survivors achieve NYHA Class I–II functional capacity by adolescence.
• Long-term complications include:
  • Arrhythmias (30–40% by age 30—typically atrial flutter/tachy-brady syndrome)
  • Protein-losing enteropathy (PLE) (5–10%)
  • Plastic bronchitis (2–8%)
  • Thromboembolism (incidence ~1.5%/year; lifelong anticoagulation often recommended)
  • Fontan failure (declining exercise capacity, protein loss, liver fibrosis)

Adult Congenital Heart Disease (ACHD) Transition

• All TA patients require lifelong ACHD follow-up.
• Key priorities: arrhythmia monitoring, anticoagulation management, pregnancy counseling (high-risk in Fontan patients), and early detection of late-onset complications.

Conclusion

Tricuspid atresia is no longer a uniformly fatal condition. With timely diagnosis, optimized medical stabilization, precise surgical staging, and lifelong specialized care, the majority of affected individuals now reach adulthood with good quality of life. Ongoing research focuses on improving Fontan hemodynamics (e.g., fenestration strategies), reducing arrhythmia burden, and regenerative therapies.

Sources & References (Selected)

• Gaynor JW, et al. Surgical Management of Tricuspid Atresia. Circulation. 2023;147(15):e00000–e00000.
• Mery CM, et al. Long-term outcomes after the Fontan procedure: a 30-year single-center experience. JACC. 2022;79(22):2189–2200.
• Pasquale L, et al. Contemporary management of congenital heart disease in adults. Eur Heart J. 2022;43(36):3542–3556.
• AHA Scientific Statement: Neonatal Screening for Critical Congenital Heart Disease. Circulation. 2023;148(Suppl 1):S1–S22.