What is Fontan circulation?

From the Guidelines

Fontan circulation is a surgically created blood flow pattern used to treat patients with complex congenital heart defects where only one functional ventricle exists, characterized by passive flow of systemic venous blood into the pulmonary arteries without passing through a ventricle, resulting in chronic venous congestion and reduced cardiac output.

Key Characteristics of Fontan Circulation

• Involves connecting the superior and inferior vena cavae directly to the pulmonary arteries, bypassing the right ventricle
• Creates a series circulation where blood returns from the body, flows directly to the lungs without ventricular pumping, then returns to the heart's single ventricle which pumps it to the body
• Patients with Fontan circulation typically require lifelong medical management including anticoagulation therapy (often aspirin or warfarin), careful fluid management, and monitoring for complications such as protein-losing enteropathy, plastic bronchitis, arrhythmias, and heart failure 1

Complications and Long-term Outcomes

• Fontan patients often have exercise limitations, fluid restrictions, and may eventually need heart transplantation as this circulation typically deteriorates over time
• The prognosis of patients with Fontan circulation is guarded, with a high probability of developing complications such as Fontan circulatory failure, which can result from multiple potential etiologies including ventricular dysfunction, atrioventricular valve failure, increased pulmonary vascular resistance, recurrent arrhythmia, and Fontan pathway dysfunction 1
• The mortality ratio of any congenital heart disease is high, with a more than 20-fold increased risk of death compared to an age-matched population 1

Management and Monitoring

• Patients with Fontan circulation require regular monitoring for complications and adjustment of medical management as needed
• The role of antithrombotic therapy in preventing thrombosis in Fontan patients is still being studied, with some evidence suggesting that antiplatelet therapy or warfarin may be beneficial in reducing the risk of thrombotic events 1

From the Research

Definition of Fontan Circulation

• Fontan circulation refers to the circulatory state resulting from an operation in congenital heart disease where systemic venous return is directed to the lungs without an intervening active pumping chamber 2.
• It is a palliative procedure performed to treat several complex congenital heart abnormalities, including tricuspid atresia, pulmonary atresia with intact ventricular septum, hypoplastic left heart syndrome, and double-inlet ventricle 3.

Characteristics of Fontan Circulation

• Fontan circulation is characterized by chronically elevated systemic venous pressures and decreased cardiac output 4.
• It has three main characteristics: systemic venous hypertension, nonpulsatile low-shear pulmonary blood flow, and low cardiac output 5.
• The creation of Fontan circulation is palliative in nature, with good results in patients with ideal hemodynamics and substantial morbidity and mortality in those with poor hemodynamics 3.

Complications of Fontan Circulation

• Complications of Fontan circulation include exercise intolerance, ventricular failure, right atrium dilatation and arrhythmia, systemic and hepatic venous hypertension, portal hypertension, coagulopathy, pulmonary arteriovenous malformation, venovenous shunts, and lymphatic dysfunction 3.
• Other potential complications include circulatory failure, ventricular dysfunction, atrioventricular valve regurgitation, arrhythmia, protein-losing enteropathy, and plastic bronchitis 4.
• Abnormalities in body composition, bone structure, and growth have been detected, as well as liver fibrosis and renal dysfunction 4.

Management and Treatment

• The treatment of Fontan circulation is still challenging and may include multiple options and tools, such as interventional catheterization, transcatheter cavopulmonary connections, and percutaneous valvular treatments 6.
• Pharmacologic management aims at preserving patency of the circuit, adequate systolic and diastolic ventricular function, atrioventricular valve function, an unobstructed ventricular outflow tract, and pulmonary vascular integrity in order to maintain an acceptable cardiac output 5.
• Heart transplantation remains the only definitive treatment for those with failing Fontan circulation 3.