Influence of age (body size) on the Fontan circulation--analysis by a theoretical model

Area of Science:

• Pediatric Cardiology
• Cardiovascular Physiology
• Surgical Innovation

Background:

• The Fontan operation, a complex surgical procedure for single-ventricle congenital heart defects, traditionally has an age criterion of 4 years or older.
• Recent clinical observations suggest that younger patients may also be candidates for the Fontan procedure.
• Age-related changes in systemic vascular properties could impact the Fontan circulation's hemodynamics.

Purpose of the Study:

• To quantify changes in systemic vascular resistance (Rs) and systemic vascular compliance (Cs) with physical development in pediatric patients.
• To analyze the effects of age and body size on Fontan circulation using a cardiovascular model.
• To determine the feasibility of earlier Fontan operations based on hemodynamic factors.

Main Methods:

• Quantified systemic vascular resistance and compliance in 86 pediatric patients without systemic circulation abnormalities.
• Utilized an analytical model of the cardiovascular system to simulate Fontan circulation.
• Analyzed the relationship between body surface area (BSA), vascular compliance, and circulatory impedance.

Main Results:

• Systemic vascular compliance (Cs) significantly decreased as body surface area (BSA) decreased (r=0.81, p<0.001).
• The analytical model demonstrated that decreased BSA led to increased impedance (ventricular afterload) in the Fontan circulation.
• The impact of BSA on impedance was most significant for BSA values below 0.3 m2.

Conclusions:

• Fontan circulation hemodynamics are minimally affected by small BSA (younger age) until BSA approaches infant values.
• The Fontan operation may be feasible at an earlier age than previously recommended, provided hemodynamics are acceptable.
• Understanding age-related changes in vascular properties is crucial for optimizing Fontan procedure timing.