Understanding Fontan Circulation

Fontan Operation Overview

• First performed in 1968; significantly improves outcomes for many patients.
• Patient outcomes vary widely; some lead normal lives, while others face severe complications.

Patient Outcomes and Complications

• Best case: a medical practitioner actively cycling in the Alps.
• Complications from Fontan failure include:
  • Early and late mortality.
  • Limited exercise capacity.
  • Ventricular dysfunction (systolic and diastolic).
  • Dysrhythmias and cyanosis.
  • Hepatic issues, such as hepatomegaly, cirrhosis, and hepatic carcinoma.
  • Lymphatic failure resulting in protein-losing enteropathy and plastic bronchitis.
  • Venous thrombosis, ascites, and peripheral edema.

Mortality and Survival Rates

• Hospital survival rates have improved; current mortality is down to 1%-2%.
• Recent improvements in clinical outcomes have been minimal despite costly treatments.
• Patients need an improvement of 50%-200% for substantial benefits, but current advancements only yield a 1%-8% improvement.

Need for Better Understanding

• A deeper grasp of Fontan circulation pathophysiology is crucial to identify critical factors affecting outcomes.
• Understanding the circulatory circuit can facilitate better treatment for complications and prevent Fontan failure.

Fontan Circulation Mechanics

• Normal cardiovascular system comprises two circuits—pulmonary and systemic—working together via two synchronized pumps.
• In the Fontan circulation, the systemic veins connect directly to the pulmonary arteries without a pump.
• Remaining postcapillary energy drives blood through the lungs, but pulmonary impedance can hinder venous return.
• Upstream congestion leads to clinical and physiological issues, while downstream output becomes restricted, likened to a dam or bottleneck effect.