Fontan Procedure
Fontan Procedure
🫀 Fontan Procedure — 20 Clinical MCQs
1. The Fontan procedure is primarily indicated for which of the following conditions?
Indicated in single-ventricle physiology such as tricuspid atresia or hypoplastic left heart syndrome.
2. The Fontan procedure directs systemic venous blood to the pulmonary arteries without using which chamber?
The procedure bypasses the right ventricle; pulmonary blood flow becomes passive.
3. The driving force for pulmonary blood flow in the Fontan circulation is:
Flow is passive; systemic venous pressure propels blood into pulmonary arteries.
4. The mean pulmonary artery pressure suitable for Fontan circulation should be:
Pulmonary vascular resistance and mean PA pressure must be low (~10–15 mmHg) for Fontan success.
5. The bidirectional Glenn shunt connects which vessels?
The Glenn shunt (stage II) connects the SVC to the RPA to divert upper body venous return to the lungs.
6. Which of the following is NOT a suitable condition for Fontan completion?
High PVR (>3 Wood units·m²) contraindicates Fontan due to inadequate pulmonary flow.
7. What is the typical central venous pressure in a successful Fontan circulation?
Systemic venous pressure is elevated (12–18 mmHg) to drive pulmonary flow.
8. The Fontan circulation is characterized by:
Fontan creates passive, non-pulsatile flow to the pulmonary arteries.
9. Protein-losing enteropathy is a late complication due to:
Chronic systemic venous hypertension leads to intestinal lymphatic congestion and protein loss.
10. The standard modern modification of the Fontan operation is:
TCPC avoids atrial dilation and arrhythmias, providing direct SVC/IVC connection to PA.
Fontan Procedure — Summary for Medical Exams
📘 Definition
The Fontan procedure is a palliative surgical operation that directs systemic venous blood directly to the pulmonary arteries without passing through a subpulmonary ventricle.
It is the final stage of single-ventricle palliation for congenital heart defects where only one ventricle is functionally adequate.
⚙️ Purpose
To separate the systemic and pulmonary circulations in patients with univentricular physiology, improving oxygenation and reducing cyanosis.
🧩 Indications
Used in congenital heart diseases with:
- Only one functional ventricle
- Examples:
- Tricuspid atresia
- Hypoplastic left heart syndrome (HLHS)
- Double-inlet left ventricle
- Pulmonary atresia with intact ventricular septum
- Unbalanced atrioventricular septal defect
🩺 Physiological Principle
- Systemic venous blood (deoxygenated) → directed to pulmonary arteries passively (no right ventricular pump).
- Pulmonary blood flow depends on low pulmonary vascular resistance (PVR) and adequate systemic venous pressure.
🧠 Historical Evolution
| Stage | Modification | Key Feature |
|---|---|---|
| 1971 (Fontan & Baudet) | Original Fontan | Right atrium connected to pulmonary artery |
| 1980s | Modified Fontan (Kreutzer, Björk)** | Atrial appendage / conduit to PA |
| 1990s onward | Total Cavopulmonary Connection (TCPC) | IVC and SVC connected to PA (no atrial component) |
| Current Standard | Extracardiac Conduit Fontan | Synthetic tube from IVC to PA + bidirectional Glenn |
🔬 Steps / Components
- Stage I — Neonatal Palliation: e.g., Norwood or systemic-to-pulmonary shunt
- Stage II — Bidirectional Glenn (Hemi-Fontan): SVC → Right pulmonary artery
- Stage III — Fontan Completion: IVC → Pulmonary artery via extracardiac conduit
🫧 Hemodynamics
- No right ventricular output to pulmonary artery
- Central venous pressure (CVP): 12–18 mmHg
- Mean pulmonary artery pressure: 10–15 mmHg
- Cardiac output limited by venous return
⚠️ Contraindications
- High pulmonary vascular resistance (>2–3 Wood units·m²)
- Ventricular dysfunction
- Atrioventricular valve regurgitation
- Pulmonary artery hypoplasia
- Elevated left atrial pressure
💊 Complications
Early:
- Pleural effusion
- Low cardiac output
- Arrhythmias
Late (Fontan Failure):
- Protein-losing enteropathy (PLE)
- Plastic bronchitis
- Cyanosis (due to collaterals or shunts)
- Hepatic congestion → Fontan-associated liver disease (FALD)
- Thrombosis
- Exercise intolerance
🧪 Investigations / Follow-up
- Echocardiography: assess flow, valve function, conduit patency
- MRI/CT: to visualize Fontan pathway
- Liver elastography for FALD
- BNP for ventricular strain
| Aspect | Details |
|---|---|
| Purpose | Palliation for single-ventricle physiology — separates systemic and pulmonary circulations |
| Typical Indications | Tricuspid atresia, Hypoplastic left heart syndrome (HLHS), Double-inlet ventricle, Unbalanced AV canal |
| Key Principle | Systemic venous blood → Pulmonary arteries without passing through right ventricle |
| Pulmonary Flow Type | Passive / Non-pulsatile |
| Driving Force | Systemic venous pressure (not ventricular contraction) |
| Mean Pulmonary Artery Pressure Required | ≤ 15 mmHg (low PVR ≤ 2–3 Wood units·m²) |
| Central Venous Pressure (CVP) | 12 – 18 mmHg |
| Standard Current Technique | Extracardiac Total Cavopulmonary Connection (TCPC) using a Gore-Tex conduit |
| Stage I (Neonatal) | Systemic-to-pulmonary shunt (e.g., Norwood) |
| Stage II | Bidirectional Glenn / Hemi-Fontan — SVC → RPA |
| Stage III (Completion) | IVC → PA conduit → full Fontan circulation |
| Advantages of Extracardiac TCPC | Lower atrial pressure, fewer arrhythmias, laminar flow |
| Contraindications | High PVR > 3 WU·m², Ventricular dysfunction, AV valve regurgitation, Pulmonary artery hypoplasia |
| Early Complications | Pleural effusion, Low cardiac output, Arrhythmia |
| Late Complications | Protein-losing enteropathy, Plastic bronchitis, Fontan-associated liver disease (FALD), Thrombosis, Cyanosis due to collaterals |
| Hemodynamic Hallmark | Elevated systemic venous pressure with reduced preload and limited cardiac output |
| Follow-up Investigations | Echocardiography, MRI/CT for conduit patency, Liver elastography, BNP monitoring |
| Post-Op Management | Anticoagulation / antiplatelet therapy, Surveillance for arrhythmia & liver dysfunction |
| Key Mnemonic – “FONTAN” | F Flow passive, O One ventricle, N Non-pulsatile, T Transcatheter follow-up, A Avoid high PVR, N Nutritional & hepatic monitoring |
💉 Management After Fontan
- Anticoagulation/antiplatelet therapy
- Regular surveillance for arrhythmia, liver, renal function
- Exercise & oxygen optimization
📊 Fontan Circulation Summary Table
| Parameter | Fontan Circulation |
|---|---|
| Pulmonary flow | Passive (non-pulsatile) |
| Driving force | Systemic venous pressure |
| Ventricle | Single |
| Pulmonary resistance | Must be low |
| Systemic venous pressure | High |
| Common long-term issue | Protein-losing enteropathy, liver fibrosis |
🧩 Mnemonic — “FONTAN”
F – Flow passive to lungs
O – Only one ventricle
N – Non-pulsatile pulmonary flow
T – Transcatheter follow-up often needed
A – Avoid high PVR
N – Nutritional, hepatic monitoring lifelong
🩻 Diagram (Conceptual)
SVC → PA (via Glenn) IVC → PA (via conduit) → Lungs → LA → LV → Aorta📚 References
- Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971.
- Mavroudis C, Backer CL. Atlas of Pediatric Cardiac Surgery.
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