The Fontan circulation after 45 years: update in physiology

Area of Science:

• Cardiology
• Pediatric Cardiac Surgery
• Congenital Heart Disease

Background:

• The Fontan operation, developed in 1968, is a palliative surgical procedure for complex single-ventricle congenital heart defects.
• While it has saved many lives, outcomes vary widely, with a significant incidence of complications and mortality.
• Understanding the unique physiology is crucial for improving long-term results.

Observation:

• The Fontan connection creates an obligatory physiological bottleneck, causing upstream venous congestion and downstream hypoperfusion.
• The single ventricle, unable to generate sufficient suction, cannot adequately compensate for this flow restriction.
• Pulmonary artery growth and low impedance are critical for Fontan circulation success.

Findings:

• The Fontan ventricle experiences initial volume overload followed by chronic preload deprivation and increasing filling pressures.
• A progressive functional decline is observed as pulmonary vascular resistance and ventricular filling pressures rise over time.
• The heart's ability to control cardiac output and systemic venous congestion is significantly impaired.

Implications:

• Future treatment strategies must focus on alleviating the Fontan bottleneck or improving ventricular performance.
• Interventions targeting pulmonary vascular impedance, fenestration, or ventricular suction are essential.
• Optimizing the Fontan circuit requires a comprehensive approach to manage its inherent physiological limitations.