FCPS Paediatrics TOACS · Tricuspid Atresia

✅ Candidate's answer:
• ECG findings in tricuspid atresia:
  - Left axis deviation (superior QRS axis) – the hallmark feature. The axis is typically between -30° and -90° (superior/leftward).
  - Left ventricular hypertrophy (LVH) – tall R waves in V5-V6 (since LV is the systemic ventricle).
  - Right atrial enlargement – tall, peaked P waves (P pulmonale) due to the ASD and increased RA pressure.
  - Q waves may be present in leads I, aVL, V5-V6 (septal Q waves).
• Pathognomonic feature: Left axis deviation (superior QRS axis) in a cyanotic neonate is highly suggestive of tricuspid atresia. This is seen in Type I (normally related great arteries).
• If the ECG shows a normal or right axis deviation, consider tricuspid atresia with transposed great arteries (Type II).
• Differential diagnosis: Tricuspid atresia, truncus arteriosus, and single ventricle variants can also have left axis deviation, but tricuspid atresia is the most common cause.

✅ Candidate's answer:
• Anatomical abnormalities:
  - Absent tricuspid valve – no connection between the right atrium and right ventricle.
  - Hypoplastic right ventricle – RV is small and underdeveloped.
  - Atrial septal defect (ASD) – required for survival to allow mixing of systemic and pulmonary venous return (all blood crosses from RA to LA).
  - Ventricular septal defect (VSD) – usually present; size determines pulmonary blood flow.
  - Left ventricle – is the systemic ventricle (normal or enlarged).
  - Great arteries: Normally related (Type I, 70%) or transposed (Type II, 30%).
• Hemodynamics:
  - All systemic venous return (RA) and pulmonary venous return (LA) mix in the LA/RA via the ASD.
  - Pulmonary blood flow depends on the size of the VSD and the presence of pulmonary stenosis.
  - If the VSD is large and there is no pulmonary stenosis → increased pulmonary blood flow (heart failure).
  - If the VSD is small or there is pulmonary stenosis → decreased pulmonary blood flow (cyanosis) → ductal-dependent.

✅ Candidate's answer:
• Ductal-dependent pulmonary flow in tricuspid atresia:
  - In tricuspid atresia with pulmonary stenosis or pulmonary atresia, the pulmonary blood flow is dependent on the patent ductus arteriosus (PDA).
  - Without a PDA, there is no source of pulmonary blood flow → severe hypoxia and death.
• Acute management:
  1️⃣ PGE1 (Prostaglandin E1): 0.05-0.1 mcg/kg/min IV to maintain ductal patency.
  2️⃣ Supplemental oxygen – may be given but can cause pulmonary vasodilation and increase flow (caution).
  3️⃣ Correct acidosis, hypoglycemia, and hypocalcemia.
  4️⃣ Echocardiogram – to confirm anatomy, assess ASD, VSD, pulmonary stenosis, and PDA.
  5️⃣ BT shunt (Blalock-Taussig) – performed in the neonatal period to provide a reliable source of pulmonary blood flow.

✅ Candidate's answer:
• Staged Fontan palliation (Single Ventricle Pathway):
  1️⃣ Stage 1 (Neonatal period): BT shunt (Blalock-Taussig) – a systemic-to-pulmonary artery shunt (subclavian artery to PA) to provide pulmonary blood flow. OR Pulmonary artery banding if there is increased pulmonary flow (large VSD, no PS) to prevent heart failure and pulmonary vascular disease.
  2️⃣ Stage 2 (4-6 months): Bidirectional Glenn shunt – SVC is anastomosed to the right pulmonary artery (end-to-side). This provides passive pulmonary flow from the SVC. The BT shunt is taken down. This reduces the volume load on the single ventricle.
  3️⃣ Stage 3 (2-3 years): Fontan procedure – the IVC is connected to the pulmonary artery (via lateral tunnel or extracardiac conduit). The Glenn is left intact (total cavopulmonary connection – TCPC). This completes the separation of pulmonary and systemic circulations.
• Purpose: The staged approach allows the single ventricle (LV) to adapt to the volume load, reduces the risk of failure, and achieves separation of pulmonary and systemic circulation.
• Fontan criteria: Normal pulmonary artery pressure (<15 mmHg), normal ventricular function (EF >50%), no AV valve regurgitation, normal sinus rhythm, normal pulmonary vascular resistance (<2 Wood units).

✅ Candidate's answer:
• Classification of tricuspid atresia (based on great artery relationship and pulmonary flow):
  Type I (70%): Normally related great arteries (aorta from LV, PA from RV). Subtypes:
    - Type Ia: No pulmonary stenosis (large VSD, increased pulmonary flow).
    - Type Ib: Mild pulmonary stenosis (VSD present, variable flow).
    - Type Ic: Severe pulmonary stenosis or pulmonary atresia (decreased flow, ductal-dependent).
  Type II (30%): Transposition of the great arteries (aorta from RV, PA from LV). Subtypes:
    - Type IIa: No pulmonary stenosis (increased flow).
    - Type IIb: Pulmonary stenosis (decreased flow).
  Type III (rare): Other anomalies (e.g., truncus arteriosus).
• Clinical relevance: Type Ia and IIa present with heart failure and mild cyanosis; Type Ic and IIb present with severe cyanosis (ductal-dependent). Type II with TGA has a higher risk of pulmonary vascular disease.

✅ Candidate's answer:
• BT shunt (Blalock-Taussig): A systemic-to-pulmonary artery shunt that provides pulmonary blood flow in cyanotic congenital heart disease with decreased pulmonary flow.
  - Classic BT: Subclavian artery (end-to-side) anastomosed to the pulmonary artery.
  - Modified BT: A Gore-Tex graft is placed from the subclavian artery or innominate artery to the pulmonary artery – now preferred (controls flow better).
• Indications in tricuspid atresia:
  - Type I with severe PS or pulmonary atresia (ductal-dependent).
  - Type II with decreased pulmonary flow.
• Complications:
  - Shunt thrombosis – early (aspirin prophylaxis).
  - Shunt occlusion – may require revision.
  - Pulmonary artery distortion – can affect future Fontan.
  - Heart failure – if the shunt is too large (pulmonary overflow).
  - Paradoxical embolism – due to right-to-left shunting.
  - Chylothorax – from surgical injury.

✅ Candidate's answer:
• Bidirectional Glenn shunt: The superior vena cava (SVC) is anastomosed end-to-side to the right pulmonary artery. This provides passive pulmonary blood flow from the upper body (SVC) to the lungs.
• Timing: Typically performed at 4-6 months of age.
• Purpose:
  - Reduces volume load on the single ventricle (LV).
  - Improves oxygenation – saturations typically rise to 75-85%.
  - Removes the BT shunt (taken down) – reduces the risk of shunt complications.
• Prerequisites: Normal pulmonary artery pressure, good ventricular function, and no significant AV valve regurgitation.
• Hemodynamics: SVC blood flows passively to the lungs; the IVC blood still returns to the heart and mixes in the atria.
• Complications: SVC syndrome, pulmonary artery stenosis, chylothorax, arrhythmias.

✅ Candidate's answer:
• Fontan procedure: A cavopulmonary connection where the inferior vena cava (IVC) is connected to the pulmonary artery (via a lateral tunnel or extracardiac conduit). The Glenn shunt (SVC to PA) remains intact. This completes the total cavopulmonary connection (TCPC).
• Timing: Typically performed at 2-3 years of age.
• Purpose: Achieves complete separation of pulmonary and systemic circulations – all systemic venous return (SVC + IVC) flows passively to the lungs.
• Fontan criteria (must be met for successful Fontan):
  - Normal pulmonary artery pressure (<15 mmHg).
  - Normal ventricular function (EF >50%).
  - No or mild AV valve regurgitation.
  - Normal pulmonary vascular resistance (<2 Wood units).
  - Normal sinus rhythm.
  - No significant ventricular outflow obstruction.
• Complications of Fontan: Protein-losing enteropathy (PLE), plastic bronchitis, thromboembolism, atrial arrhythmias, Fontan-associated liver disease (FALD), heart failure, renal dysfunction.

✅ Candidate's answer:
• Diagnosis: Protein-losing enteropathy (PLE) – a known complication of the Fontan circulation.
• Pathophysiology: Elevated central venous pressure (CVP) → intestinal lymphangiectasia → loss of protein into the gut. Leads to hypoalbuminemia, edema, ascites, and immunodeficiency.
• Management:
  1️⃣ Diuretics: To reduce volume overload.
  2️⃣ Albumin infusion: For symptomatic hypoalbuminemia.
  3️⃣ Heparin or low-molecular-weight heparin: May reduce protein loss.
  4️⃣ Corticosteroids: Some benefit in PLE.
  5️⃣ Interventional: Consider Fontan revision (fenestration, revision of the Fontan pathway) to reduce CVP.
  6️⃣ Heart transplantation: For refractory PLE.
• Prognosis: Poor without intervention; PLE is a major cause of morbidity and mortality after Fontan.

✅ Candidate's answer:
• Diagnosis: Plastic bronchitis – a rare but serious complication of Fontan circulation.
• Pathophysiology: Lymphatic abnormalities (elevated CVP) lead to the formation of fibrin-rich bronchial casts (plastic bronchitis) that obstruct the airways.
• Presentation: Recurrent coughing, wheezing, expectoration of "plastic" (hard, branch-like) casts.
• Management:
  1️⃣ Inhaled tissue plasminogen activator (tPA): To dissolve casts.
  2️⃣ Chest physiotherapy: To help expel casts.
  3️⃣ Bronchoscopy: To remove airway casts.
  4️⃣ Fontan revision: To reduce CVP.
  5️⃣ Heart transplantation: For refractory cases.

✅ Candidate's answer:
• Risk of thromboembolism in Fontan:
  - Stagnant flow – passive pulmonary flow leads to reduced shear stress and stasis.
  - Prothrombotic state – due to venous stasis, endothelial dysfunction, and liver dysfunction.
  - Fontan conduit thrombosis – risk of both pulmonary embolism and systemic embolism.
• Prophylaxis:
  - Anticoagulation: Warfarin (INR 2-3) or low-molecular-weight heparin (LMWH) – especially in patients with fenestrated Fontan or prior thromboembolism.
  - Aspirin: Antiplatelet therapy for patients with lower-risk Fontan (non-fenestrated).
  - Lifelong surveillance: Regular echocardiograms to assess for thrombus in the Fontan pathway.
  - MRI: For assessment of Fontan flow and thrombus detection.
• Risk factors for thromboembolism: Atrial arrhythmias, fenestrated Fontan, ventricular dysfunction, hepatic dysfunction.

✅ Candidate's answer:
• Fontan-associated liver disease (FALD): Chronic liver injury due to elevated central venous pressure and hepatic congestion. Can progress to cirrhosis and hepatocellular carcinoma (HCC).
• Monitoring:
  1️⃣ Liver function tests (LFTs): ALT, AST, GGT, bilirubin, albumin (monitor annually).
  2️⃣ Platelet count: Low platelet count suggests portal hypertension.
  3️⃣ Liver ultrasound with elastography: To assess for fibrosis and HCC (annually).
  4️⃣ Fibroscan: Non-invasive assessment of liver stiffness.
  5️⃣ Liver biopsy: For unclear fibrosis or if HCC is suspected.
  6️⃣ MELD score: To assess liver failure risk.
• Management: Optimize Fontan hemodynamics, avoid hepatotoxic drugs, screen for HCC (AFP). Heart-liver transplantation may be needed.

✅ Candidate's answer:
• Long-term prognosis:
  - Survival: 90% survival at 20 years post-Fontan. However, survival declines with age (70-80% at 30 years).
  - Complications: Increase with time – PLE, plastic bronchitis, thromboembolism, arrhythmias, liver disease, heart failure.
  - Quality of life: Most patients lead active lives but have exercise limitations and require lifelong follow-up.
  - Heart transplantation: For failed Fontan (refractory PLE, plastic bronchitis, severe ventricular dysfunction).
• Factors affecting prognosis:
  - Ventricular function (LV function).
  - AV valve regurgitation.
  - Fontan hemodynamics (pressure, fenestration).
  - Rhythm (sinus rhythm vs atrial arrhythmias).
  - Age at Fontan completion.
• Transition to adult care: Lifelong follow-up with adult congenital cardiology is essential.

✅ Candidate's structured answer:
• “Your baby has a condition called Tricuspid Atresia – the valve between the right upper and lower chambers of the heart did not form properly. This means your baby's heart cannot pump blood to the lungs normally.”
• “The good news is that we have a very effective treatment plan. Your baby will need to be on a medication called PGE1 to keep the blood vessel open so that blood can reach the lungs. Your baby will then have the first of three planned surgeries – a BT shunt – which will provide a reliable way for blood to get to the lungs.”
• “There will be two more surgeries as your baby grows – at 4-6 months and at 2-3 years. These surgeries will allow the heart to function with only one pumping chamber, and many children go on to lead active lives.”
• “We have a team of specialists who will guide you through each step. Most children with this condition survive to adulthood with good quality of life.”
• “You are not alone – we will support you and your baby every step of the way.”