Fontan Completion

Anatomy and Physiology

The Fontan completion procedure is a palliative surgical solution for patients with functionally single-ventricle congenital heart defects, conditions where only 1 ventricle supports both systemic and pulmonary circulation. Normally, the heart consists of 4 chambers—2 atria and 2 ventricles—but in these patients, a single ventricle must fulfill the workload, leading to significant physiological challenges.[7] The Fontan circulation achieves total cavopulmonary connection by rerouting systemic venous blood directly to the pulmonary arteries, bypassing the heart, and allowing the single ventricle to focus on systemic arterial flow. The ventricle must be efficient, pulmonary vascular resistance low, and the rerouted pathways unobstructed for this system to function.[8]

Initially described for tricuspid atresia, the Fontan procedure now addresses a variety of univentricular congenital heart defects, including hypoplastic left heart syndrome, which accounts for 25% to 67% of cases.[2] Modern treatment strategies employ a staged surgical approach, often beginning with procedures like the Norwood or Glenn (superior cavopulmonary connection), to optimize hemodynamics before Fontan completion.[3] These staged interventions improve early survival in cases with suboptimal physiology, such as high pulmonary vascular resistance.

Successful Fontan circulation relies on low pulmonary vascular resistance and preserved ventricular function.[9] Despite advancements, Fontan circulation inherently leads to long-term challenges, including reduced preload, systemic venous hypertension, and low cardiac output.[4][9] Prolonged Fontan circulation can ultimately result in "Fontan failure," underscoring the need for careful management and monitoring of these patients over their lifetimes.

Indications

Common Indications

The Fontan procedure is indicated for patients with congenital heart defects that result in a functionally single ventricle, where the heart cannot sustain both systemic and pulmonary circulation effectively. These conditions necessitate rerouting systemic venous blood to the pulmonary circulation without passing through the heart, allowing the single ventricle to handle systemic circulation exclusively. Cardiac defects for which the Fontan completion procedure may be considered include:

• Tricuspid atresia
• Hypoplastic left heart syndrome (most common)
• Hypoplastic right heart syndrome
• Pulmonary atresia with intact ventricular septum
• Double-inlet left ventricle
• Double-outlet right ventricle
• Unbalanced atrioventricular canal defects
• Ebstein anomalies that are adequate for Fontan correction
• Congenitally corrected transposition of the great arteries [2]

Patient Selection Criteria

Specific criteria must be met to ensure successful outcomes. These include:

• Low pulmonary vascular resistance
• Well-functioning single ventricle
• Absence of significant atrioventricular valve regurgitation
• Normal sinus rhythm or controlled arrhythmias
• Absence of pulmonary artery obstruction
• Adequately sized pulmonary arteries [10]

Timing

The Fontan procedure is typically performed after staged interventions, such as the Norwood or Glenn procedure, to prepare the cardiovascular system and minimize complications associated with the Fontan physiology. Generally, the procedure is considered in patients aged between 2 and 5 when the pulmonary vascular resistance is sufficiently low. By carefully selecting patients and staging surgical interventions, the Fontan procedure provides a viable long-term solution for many children with single-ventricle physiology.

Contraindications

While lifesaving for many patients with single-ventricle physiology, the Fontan procedure is unsuitable for all cases. The procedure's success depends on strict patient selection, with contraindications centered on factors that compromise the hemodynamic feasibility of the Fontan circulation or pose a significant procedural risk.[11]

Absolute Contraindications

• High pulmonary vascular resistance 
  • Elevated pulmonary vascular resistance prevents the passive flow of systemic venous blood into the pulmonary circulation, a cornerstone of Fontan physiology. Pulmonary vascular resistance greater than 3 Wood units/m² is generally considered a contraindication. 
  • Elevated pulmonary artery pressures have been identified as leading to less favorable surgical outcomes after Fontan.[12]
• Severe ventricular dysfunction
  • A poorly functioning single ventricle cannot effectively sustain systemic circulation, leading to inadequate cardiac output and poor outcomes.
• Severe atrioventricular valve regurgitation
  • Significant regurgitation increases ventricular volume overload, compromising the efficiency of the Fontan circulation.
• Pulmonary artery hypoplasia or obstruction
  • Narrow or underdeveloped pulmonary arteries impair blood flow and increase resistance, making Fontan physiology unworkable.
• Severe cyanosis or hypoxemia
  • These conditions suggest poor systemic and pulmonary oxygenation, which may worsen with Fontan physiology.
• End-stage liver or renal disease
  • Chronic organ dysfunction, often secondary to prior surgeries or cyanotic heart disease, increases surgical risk and impacts long-term survival.

Relative Contraindications

• Significant collateral vessels
  • Systemic-to-pulmonary collaterals can lead to volume overload of the pulmonary circulation and must be addressed preoperatively.
• Persistent arrhythmias
  • Uncontrolled arrhythmias may lead to hemodynamic instability in Fontan physiology.
• Severe scoliosis or thoracic deformities
  • These anatomical abnormalities can impair pulmonary blood flow dynamics and reduce procedural success.
• Poor ventricular compliance
  • A stiff single ventricle may not adequately adapt to Fontan physiology, leading to diastolic dysfunction.
• Chronic thromboembolic disease
  • A history of thrombosis increases the risk of Fontan failure due to clot formation in the passive venous circuit.

Equipment

The Fontan procedure requires a congenital cardiac surgery operating room equipped with specialized instruments and staffed by a skilled surgical team familiar with complex congenital heart repairs. Ensuring the availability and functionality of all necessary equipment is paramount to the procedure's success. For an extracardiac Fontan, it is critical to have the appropriate conduit or graft material readily available, as this plays a central role in creating the systemic-to-pulmonary connection. Thorough preparation, including double-checking supplies and confirming the availability of all essential tools and materials, reduces procedural delays and leads to better outcomes.

Personnel

Personnel needed to perform the Fontan includes but is not limited to the following:

• Trained congenital cardiac surgeon
• Pediatric cardiac anesthesiologist
• First surgical assistant
• Surgical technician
• Surgical nurse
• Perfusionist
• Pediatric cardiologist with or without an echocardiogram sonographer

Postoperative care should ideally be in a specialized congenital cardiac intensive care unit where pediatric intensivists and nurses are familiar with the specialized care for single ventricles and patients undergoing the Fontan procedure. 

Preparation

Preparing the Fontan procedure is critical to ensure optimal surgical outcomes and minimize perioperative risks. The primary goal is to confirm that the patient meets the established criteria for surgery while addressing any modifiable risk factors.[1] Successful Fontan physiology relies on low pulmonary vascular resistance and preserved ventricular function, making preoperative evaluation and optimization essential.[4]

Eligibility Criteria

To proceed with the Fontan procedure, patients must meet specific historical and clinical criteria, including:

• Patient age between 4 and 15 
• No arrhythmia (only sinus rhythm present)
• Normal drainage of the vena cava
• Normal right atrial volume
• Low pulmonary artery pressure, less than 15 mm Hg
• Low pulmonary resistance (less than 4 Wood units/m²)
• Adequate pulmonary artery size (pulmonary artery to aorta ratio greater than 0.75)
• Normal ventricular function, greater than 55%
• Absent atrioventricular valve regurgitation
• Normal pulmonary artery anatomy 

Preoperative Evaluation

Patients undergo a comprehensive series of assessments to confirm eligibility and optimize their condition:

• Electrocardiography 
  • To document sinus rhythm and exclude arrhythmias
• Transthoracic echocardiogram
  • To evaluate ventricular function, valve integrity, and pulmonary artery size
• Pulmonary assessment
  • Includes imaging and functional studies to ensure adequate pulmonary circulation
• Cardiac catheterization
  • Measures pulmonary artery pressure and pulmonary vascular resistance and evaluates pulmonary artery anatomy and ventricular function

Optimization Strategies

• Pulmonary vascular resistance 
  • If borderline elevations are present, interventions such as supplemental oxygen, sildenafil, or nitric oxide reduce pulmonary vascular resistance.
  • Pulmonary artery interventions, including balloon angioplasty, may be performed to address stenosis.
• Nutritional status
  • Nutritional supplementation addresses failure to thrive, which is common in children with congenital heart disease.
• Arrhythmia management
  • Preoperative arrhythmias are treated with medical therapy or ablation to prevent postoperative complications.
• Hematological optimization
  • Anemia and thrombocytopenia are corrected to enhance oxygen delivery and minimize bleeding risks.
• Infection prophylaxis
  • Active infections are treated preoperatively to reduce the risk of complications.
• Family education
  • Families are counseled on the procedure, potential risks, and long-term care expectations.

Surgical Planning

The surgical team reviews the patient's prior palliative procedures (eg, Norwood or Glenn) and anatomical variations to select the most appropriate Fontan technique. By adhering to these preparation protocols, clinicians can ensure that patients undergoing the Fontan procedure have the best opportunity for a successful outcome and improved long-term survival.

Technique or Treatment

The Fontan procedure represents the culmination of staged surgical interventions in patients with single-ventricle congenital heart defects. This procedure reroutes systemic venous blood into the pulmonary vasculature, bypassing the heart. These patients typically undergo general anesthesia, endotracheal intubation, and invasive monitoring, including arterial and central venous lines. The surgery is performed via median sternotomy, often in a reoperative setting, with preparation for cardiopulmonary bypass. Results from recent studies reported a new open "clamp-and-sew" surgical technique that does not require a cardiopulmonary bypass, but a peer review of this method has not been completed yet.[13]

Historically, the original atriopulmonary connection described by Francis Fontan involved routing the right atrium directly to the pulmonary artery.[1] This step followed the Glenn procedure, where the superior vena cava was anastomosed to the pulmonary artery. A pulmonary homograft was utilized for the inferior vena cava, enabling the systemic venous blood to bypass the heart and flow directly into the pulmonary circulation. The success of this approach was largely reliant on the adequate size of both the pulmonary arteries and the right atrium to ensure efficient blood flow and minimize resistance.

Modern modifications have refined this approach into 2 primary techniques: the extracardiac conduit (EC) and the lateral tunnel (LT).[14] The LT Fontan procedure is an intracardiac approach where a baffle is constructed within the atrium to connect the inferior vena cava directly to the pulmonary artery.[2] This technique and the EC method are typically performed under cardiopulmonary bypass, although the EC method can sometimes be accomplished with minimal or no bypass.[15]

Research by Azakie and colleagues at a Toronto institution compared the 2 techniques in a cohort of 600 patients, finding similar operative mortality rates and overall outcomes. However, the EC method demonstrated advantages in reducing the early and intermediate risk of atrial arrhythmias. Similarly, results from a retrospective study involving 341 patients treated over more than 2 decades showed low operative mortality of the nonfenestrated EC technique.[14][16] The EC approach can also include creating a "fenestration," a small opening between the EC and the right atrium, to manage pressure dynamics and improve hemodynamics. Some centers favor the EC method due to its shorter bypass times, a critical factor in reducing morbidity, and its potential for better preservation of ventricular and pulmonary vascular function.[17] 

Surgical Classification

The Fontan procedure is categorized based on the method and fenestration use, as per the Society for Thoracic Surgeons National Congenital Heart Surgery Database:

• LT, fenestrated or nonfenestrated
• External conduit, fenestrated or nonfenestrated
• Intra/extracardiac conduit, fenestrated or nonfenestrated
• External conduit with hepatic veins connected to the pulmonary artery, fenestrated or nonfenestrated
• One-and-a-half ventricular repair
  • This type entails both ventricles directing blood into their respective great vessels, supplemented by an extracardiac systemic-to-pulmonary artery connection (typically a Glenn shunt) to enhance pulmonary blood flow. Patient selection is critical for the success of this technique, as it seems that the most effective use of this strategy is for patients with small yet functional right ventricles that possess well-defined inlet, body, and outlet segments.[18][19][20]
• Transcatheter completion of the EC method
  • Dual venous entry into the right jugular and femoral veins is used to reach the superior and inferior vena cava, respectively. The pericardial membrane separating the 2 circulations is punctured and dilated, then a covered stent is deployed, bypassing the right ventricle and establishing a total cavopulmonary connection. This method is currently preserved for patients with contraindications to open Fontan completion.[21][22]

Historical and Technical Considerations

The Fontan procedure has evolved significantly since its inception, particularly in staged surgeries like the Norwood and Glenn procedures, which optimize conditions for Fontan circulation by lowering pulmonary resistance and enhancing systemic output. Both EC and LT techniques require careful patient selection to maximize success. Key criteria include low pulmonary vascular resistance, preserved ventricular function, and absence of significant atrioventricular valve regurgitation. The ultimate success of the Fontan circuit relies on precise surgical execution and management of postoperative complications, such as arrhythmias, pleural effusions, and thromboembolic events. Lifelong monitoring is critical, as prolonged Fontan circulation may lead to complications, including "Fontan failure," characterized by reduced preload, increased systemic venous pressure, and chronic low cardiac output.

Complications

The Society of Thoracic Surgeons Congenital Heart Surgery Database published in 2017 reported an estimated operative mortality of 1.2% and an average length of stay of 13 days for the Fontan procedure nationally.[18] The risk of death for univentricular patients is highest in the first 5 years but eventually levels off at 15 years. One single-institution study, whose results were published by d'Ukedem et al in 2012, followed 499 patients and finally had 229 patients reach the third stage palliation Fontan procedure at an average age of 5 years old for operation. Survival rates were 82% for the first year, 74% for the 5-year, and 71% for 10-year survival. Results from a recent study demonstrated absent 1- and 2-year mortality and morbidity in patients undergoing Fontan completion at the early adult phase (18 to 21 years). However, a long-term assessment is still missing.[23][24]

The postoperative period is an important part of the Fontan procedure. Complications include but are not limited to the following:

• Hemorrhage
• Arrhythmias
• Pleural effusions
• Hepatic fibrosis
• Heart failure
• Chylothorax
• Cyanosis of the body 
• Exercise intolerance
• Aortic root dysfunction
• Ventricular dysfunction
• Pulmonary vascular dysfunction
• Protein-losing enteropathy 
• Thromboembolism
• Kidney disease
• Liver disease
• Venous insufficiency
• Death [2][8][25][26]

Although life-saving, physiologic disturbances affect the rest of the body and result in short- and long-term complications.[8] Multiple risk factors have been identified that may contribute to increased mortality, takedown, or transplantation rates.[27] This is a large area of research since complications are consistently related to ultimate mortality.[25] There are mixed results for whether the ventricular side of dominance predisposes patients to a worse outcome; however, some data suggest that patients with right ventricular dominance may predict higher mortality than those with left-sided ventricular dominance.[23][28]

Systemic complications become challenging to quantify since they occur outside of the heart and affect other organ systems. Research is ongoing to determine lymphatic drainage's role in failed Fontan circulation, which results in multiple comorbidities.[26] Systemic complications such as protein-losing enteropathy (PLE) and plastic bronchitis can occur in up to 5% of all Fontan patients and result in a notably increased risk of mortality of up to 50% after 5 years of diagnosis.[8] Plastic bronchitis is a rare and ominous complication for patients with Fontan circulation, marked by the formation of casts within the tracheobronchial tree. These casts may be cellular, containing inflammatory debris, or acellular, consisting of mucin and fibrin—the latter more commonly linked to congenital heart disease. The proposed mechanism mirrors PLEs, involving protein and lymphatic leakage within the airways. Associations have been noted with diaphragm plication, chylothorax, and seasonal allergies.[29][30] 

These casts can obstruct the airway and may prove acutely fatal. The condition carries substantial morbidity, as highlighted in the results from a study where, among 671 Fontan respondents, 53 reported plastic bronchitis. Of these, only 9% had no hospitalizations, while 17% experienced more than 10 admissions related to the condition. Treatment focuses on optimizing Fontan hemodynamics and managing the disease’s effects.[31][32]

Crupi first documented PLE in a patient with Fontan with single-ventricle physiology.[33] PLE has been observed not only in Fontan circulation but also in connection with various cardiovascular conditions, including constrictive pericarditis, tricuspid regurgitation, and congenital heart disease. Notably, Moodie et al reported PLE in a patient with transposition of the great arteries and systemic venous obstruction postatrial switch.[34] The unifying feature among these cardiovascular conditions is elevated systemic venous pressure, leading to a hypothesis: heightened venous pressure may cause lymphatic dilation (lymphangiectasis) and protein loss into the gut lumen.[35]

However, this theory is insufficient, as systemic venous pressures alone do not consistently correlate with PLE presence or severity. For example, PLE is uncommon following the Glenn procedure, which raises superior vena cava and thoracic duct pressure, and lymphangiectasis is not consistently seen in PLE patients post Fontan procedure. Despite elevated systemic venous pressures across all Fontan patients, not all develop PLE, suggesting additional contributory factors.

Results from an international multi-center study conducted by Mertens et al in 1998 revealed a common feature in PLE individuals post Fontan procedure: significantly reduced cardiac output, averaging 2.4 L/min/m², compared to the typical range of 3 to 3.5 L/min/m² in patients with Fontan but without PLE.[36] Those with PLE demonstrated even lower cardiac output indices, around 1.5 to 2.0 L/min/m². This finding implies that PLE may result not solely from elevated venous pressures but from slightly raised venous pressure and markedly reduced cardiac output, which limits intestinal perfusion pressure and end-organ blood flow. Thus, a connection between reduced cardiac output and the development of PLE in patients with Fontan may exist.

Another etiology discovered by Rychik and colleagues in 1991 was the association of PLE with excessively elevated mesenteric arterial pressures.[37] Through Doppler echocardiography, blood flow was assessed at the origin of the superior mesenteric artery. The resistance index—a marker of vascular resistance— was calculated in control subjects with normal circulation, those with Fontan without PLE, and Fontan individuals with active PLE. Distinct variations in resistance indices emerged, with Fontan individuals exhibiting elevated resistance compared to controls, and further increased resistance was observed in those with PLE.

Qualitative inspection of Doppler flow patterns revealed a clear trend: as mesenteric vascular resistance rose, diastolic flow velocities fell. Patients with active PLE showed nearly absent diastolic flow, indicating high mesenteric vascular resistance. These findings point to a fundamental connection between the unique physiology of Fontan circulation and altered mesenteric blood flow, offering valuable insight into the pathophysiology of PLE post-Fontan operation.

In addition, increased central venous pressure can contribute to liver disease, hepatocellular carcinoma, liver fibrosis, and cirrhosis.[38] Anticoagulants such as warfarin or antiplatelet therapy such as aspirin are used for thromboembolic complications.[39] There is currently no consensus for optimal antithrombotics regimen or duration after the Fontan procedure, but up to 25% of thromboembolic events can result in death.[10]

Ultimately, patients with Fontan circulation will have lower-than-expected exercise tolerance when they reach adolescence. Usually, there is some type of ventricular dysfunction. Long-term results are still being studied since more patients survive into adolescence and early adulthood. Whether there are modifiable risk factors that will prevent this clinical deterioration or not is still uncertain. Still, if a patient is in heart failure after Fontan, they will need to be considered for heart transplantation.[8]  Mechanical circulatory devices have also been described as being used to bridge failing Fontan individuals to transplant.[40]

Atz et al, as part of the Pediatric Heart Network, followed about 373 adult patients from an initial cohort of 546 subjects to study the transplant-free survival rates into adulthood. Their results found cardiac reoperation (32%), arrhythmia treatment (32%), thrombosis (12%), and PLE (9%) as the most common complications. About 10% received transplants or succumbed without transplantation.[41]

Clinical Significance

The Fontan procedure represents a transformative milestone in managing congenital single-ventricle heart disease. Before the 1940s, such conditions were universally fatal. Today, the staged palliative approach culminating in the Fontan procedure has dramatically extended survival and improved the quality of life for these patients.[8] Currently, there are an estimated 50,000 to 70,000 Fontan individuals worldwide, a number expected to double in the next 2 decades, according to Yves d'Udekem, founder of the Australian and New Zealand Fontan Registry.[5][42] This underscores the growing population of individuals living with Fontan physiology and the necessity of optimizing their long-term care.

Research results from a study conducted by Atz et al, published in The Journal of the American College of Cardiology in 2017, demonstrated favorable transplant-free survival for 90% of Fontan individuals over 12 years, reflecting the success of this surgical strategy.[41] However, poor functional status and reduced exercise tolerance were associated with an increased risk of death or transplantation. As survival continues to improve for pediatric individuals with single-ventricle conditions, the focus has shifted to addressing systemic complications related to Fontan failure. Continued research into potential therapies and strategies to enhance transplant-free survival is essential to ensure optimal outcomes for this growing patient population.[8][40][43]

Enhancing Healthcare Team Outcomes

The successful treatment of patients undergoing the Fontan completion procedure relies on a multidisciplinary team approach that prioritizes patient-centered care, safety, and optimal outcomes. Clinicians and surgeons must coordinate preoperative assessment, surgical planning, and postoperative care, ensuring patients meet the stringent criteria for Fontan completion. Advanced clinicians and nurses play a vital role in preoperative education, facilitating communication between the patient and the healthcare team and providing postoperative monitoring for complications like arrhythmias or thromboembolism. Pharmacists contribute by optimizing anticoagulation protocols and managing medication regimens tailored to individual needs, particularly for patients with complex histories or comorbidities.

Interprofessional communication is essential to streamline decision-making and maintain cohesive care throughout the perioperative period. Regular team meetings and standardized protocols can help align goals across disciplines, fostering collaboration. Coordinated care includes meticulous monitoring of hemodynamic parameters, effective management of extracardiac manifestations such as liver dysfunction, and integration of long-term follow-up plans for managing Fontan-associated complications. By leveraging the expertise of each team member and maintaining open communication, healthcare professionals can enhance patient safety, improve outcomes, and support the growing population of Fontan individuals with comprehensive, high-quality care.

Nursing, Allied Health, and Interprofessional Team Interventions

Regionalizing databases and interventions is a promising approach to addressing the unique challenges of studying and managing congenital heart disease, particularly for complex procedures like the Fontan. The Southwest Congenital Cardiac Consortium exemplifies this strategy by fostering interprofessional collaboration across institutions to identify and mitigate healthcare disparities. This initiative highlights the potential for regional efforts to improve outcomes and equity for high-risk populations, such as those in the southwest United States.[5] By leveraging shared data and collaborative practices, such consortiums aim to standardize care and address systemic barriers contributing to health inequities.

Efforts to enhance post Fontan recovery and long-term health outcomes have also explored targeted rehabilitation interventions. For example, results from a study assessing muscle training in Fontan individuals demonstrated promising improvements in exercise capacity over 12 weeks. While the study showed encouraging results, it was limited by its small sample size, underscoring the need for further research. These findings suggest that structured rehabilitation programs could become integral to post Fontan care, potentially improving functional status and quality of life in this growing patient population.[7]