What is the Fontan procedure and when is it recommended for children with single ventricle heart defects?

Fontan Procedure

What is the Fontan Procedure?

The Fontan procedure is a palliative cardiac operation that directs systemic venous blood directly to the pulmonary arteries without passing through a ventricle, creating a unique circulation where the systemic and pulmonary vascular beds are connected in series downstream of the single functional ventricle. 1

Physiologic Mechanism

• The procedure eliminates the subpulmonary ventricle, resulting in elevated systemic venous pressure that drives passive, non-pulsatile blood flow through the pulmonary circulation 2
• This creates chronically elevated central venous pressure, decreased preload to the systemic ventricle, and impaired cardiac output augmentation during exercise or stress 2
• The circulation relies on elevated, nonpulsatile venous pressure to passively propel blood through the pulmonary vascular bed, fundamentally departing from normal circulatory dynamics 2

Surgical Variations

Current preferred techniques include extracardiac conduit, intra-atrial conduit (lateral tunnel), and intracardiac lateral tunnel with or without bidirectional cavopulmonary anastomosis (BDCPA). 1

• Total cavopulmonary connection (TCPC) with either intracardiac or extracardiac conduit is preferred over older atriopulmonary connections to prevent Fontan pathway obstruction 3
• The lateral tunnel technique directs inferior vena cava blood via a baffle (usually Gore-Tex) within the right atrium into the divided superior vena cava or right atrial appendage, which connects to the pulmonary artery 2
• A fenestration (intentional small opening) may be created to improve early postoperative outcomes by serving as a "pop-off" that maintains cardiac output at the cost of mild systemic desaturation 2, 1

When is the Fontan Procedure Recommended?

Primary Indications

The Fontan procedure is indicated for children with single-ventricle heart defects when the rudimentary pulmonary ventricle is less than 30% of its normal volume, making biventricular repair impossible. 1

Specific anatomic conditions include:

• Tricuspid atresia 2, 4
• Hypoplastic left heart syndrome 2, 4
• Pulmonary atresia with intact ventricular septum 4
• Double-inlet ventricle 4
• Other functional or anatomic single ventricle conditions unsuitable for biventricular repair 1

Critical Preoperative Requirements

Cardiac catheterization must be performed before initial Fontan surgery to assess hemodynamic suitability. 1, 5

The two factors that consistently predict both early and late outcomes are:

• Preserved ventricular function (assessed by qualitative evaluation, echocardiography, or cardiac MRI) 1, 3
• Low pulmonary artery pressures and resistance 1, 3

Additional favorable preoperative factors include:

• Absence of pulmonary artery distortion 6
• Favorable atrioventricular valve anatomy (non-left atrioventricular valve stenosis/atresia or common atrioventricular valve) 6
• Age considerations: while historically performed in older children, the procedure can now be successfully performed in children as young as 3 years with proper selection 6

Staged Surgical Approach

The Fontan procedure represents the final stage of a series of palliative surgical procedures for single ventricle physiology. 5, 7

• Initial palliation (Norwood procedure for hypoplastic left heart syndrome) establishes unobstructed systemic outflow, unrestrictive inter-atrial communication, controlled pulmonary blood flow, and reliable coronary blood flow 5
• Intermediate stage typically involves bidirectional Glenn shunt (bidirectional cavopulmonary anastomosis) connecting the superior vena cava to both pulmonary arteries 2
• Final Fontan completion connects the inferior vena cava to the pulmonary circulation 2

Expected Outcomes and Prognosis

Short-Term Outcomes

• Ten-year survival after Fontan operation is approximately 90%, depending on risk factors present at the time of surgery 1
• Mortality between first and second stages of surgical palliation for hypoplastic left heart syndrome has decreased from 40-50% to now between 2-12% 2
• Survival to Fontan palliation is now the expectation for even the most anatomically complex children with single ventricle heart disease 2

Long-Term Prognosis and Complications

Despite excellent early survival, nearly one-third of patients will either die or require transplant within 35 years post-Fontan, with many patients experiencing a major adverse event by 20 years following the operation. 2

Common long-term complications include:

• Atrial arrhythmias (intra-atrial reentrant tachycardia, focal atrial tachycardia) requiring prompt thromboembolic prevention and electrophysiology consultation 1, 5
• Ventricular dysfunction requiring advanced heart failure consultation when severely depressed 1, 3
• Hepatic congestion and Fontan-associated liver disease (FALD) from chronic systemic venous hypertension 1, 8
• Protein-losing enteropathy with less than 50% 5-year survival once developed 3, 8
• Thrombosis requiring antithrombotic prophylaxis (aspirin 5 mg/kg/day or warfarin with target INR 2-3) 2
• Exercise intolerance from impaired cardiac output augmentation 8, 4
• Lymphatic dysfunction manifesting as ascites, edema, pleural effusions, or plastic bronchitis 2, 8

Thrombosis Management

For primary thrombosis prophylaxis in the first 2 years post-Fontan, aspirin (5 mg/kg/day) and warfarin (INR 2-3) show similar efficacy, though both have suboptimal thrombosis rates requiring alternative therapies to be investigated. 2

• Patients should undergo clinical assessment for anatomic and hemodynamic risk factors for thrombus (arrhythmias, ventricular dysfunction, prolonged immobilization) 2
• Serial monitoring for changes in thrombotic risk factors is indicated because risk factors may change over time 2
• Routine transthoracic echocardiography should monitor for thrombosis as part of routine follow-up, with transesophageal echocardiography every 2 years or if arrhythmia is present 2, 3

Mandatory Lifelong Surveillance

All patients after Fontan palliation require lifelong follow-up with at least yearly evaluation by a cardiologist with expertise in adult congenital heart disease (ACHD). 1, 5, 3

Required Annual Surveillance Components

• Echocardiography or cardiac MRI (cardiac MRI required at least once in adult age and further on indication) 1, 3
• ECG and Holter monitoring to detect arrhythmias 1, 3
• Exercise testing to monitor functional capacity 1, 3
• Biochemical and hematological testing 1
• Liver imaging to assess for hepatic complications 1

Imaging Modalities

Magnetic resonance imaging is best for postoperative evaluation of patients who underwent the Fontan procedure. 4

• Cardiovascular MRI allows comprehensive assessment of Fontan cavo-pulmonary connections, branch pulmonary arteries, pulmonary veins, ventricle(s), atrioventricular valve(s), ventricular outflow tract, and residual leaks or collateral vessels 2
• Velocity mapping can assess flow through suspected cavo-pulmonary narrowing (peak jet velocity exceeding 1 m/s likely represents significant stenosis) 2
• Late gadolinium enhancement (LGE) imaging can evaluate myocardial fibrosis in patients with impaired ventricular function 2

Frequency of Follow-Up Based on Clinical Status

For stable patients:

• ACHD cardiologist visits every 12 months 5
• Echocardiography, ECG, and CMR/CCT every 12-36 months 5

For symptomatic or declining function:

• ACHD cardiologist visits every 3-6 months 5
• Echocardiography or CMR annually 5

Advanced Heart Failure Referral Thresholds

The Advanced Cardiac Therapies Improving Outcomes Network (ACTION) has developed specific thresholds for advanced heart failure referral, divided into 4 categories of clinical Fontan circulatory dysfunction. 2

Categories Requiring Advanced Heart Failure Consultation

1. Cardiac/systemic ventricular dysfunction - severely depressed systolic function on qualitative evaluation, echocardiography, or cardiac MRI 3
2. Fontan pathway dysfunction - obstruction requiring intervention 2
3. Lymphatic dysfunction - protein-losing enteropathy or plastic bronchitis 2
4. Extracardiac dysfunction - symptomatic chronic fluid overload persisting despite new or increasing diuretic therapy 3

Cardiac transplantation remains the only definitive treatment for those with failing Fontan circulation. 4

Special Considerations

Physical Activity

• Physical activity should be limited to recreational sports only on a symptom-limited level, with monitoring of exercise capacity using routine exercise testing 3
• Regular exercise programs appropriate to patient abilities are reasonable to improve aerobic capacity 5

Endocarditis Prophylaxis

Endocarditis prophylaxis is recommended in all Fontan patients, regardless of Fontan type or clinical status. 3

Surgical Expertise Requirement

Surgeons with training and expertise in congenital heart disease must perform operations for single ventricle anatomy to improve outcomes and reduce morbidity. 5