Effect of Fontan geometry on exercise haemodynamics and its potential implications

Area of Science:

• Cardiovascular Physiology
• Medical Imaging
• Computational Fluid Dynamics

Background:

• Exercise intolerance is a significant limitation for patients with Fontan-associated total cavopulmonary connections (TCPCs).
• Optimizing the design of TCPCs is hypothesized to improve exercise capacity in these patients.

Purpose of the Study:

• To investigate the relationship between total cavopulmonary connection (TCPC) geometries and exercise hemodynamics and performance in Fontan patients.
• To quantify the impact of TCPC indexed power loss (iPL) at the ventilatory anaerobic threshold (VAT) on exercise capacity.

Main Methods:

• 47 Fontan patients underwent metabolic exercise stress testing with simultaneous cardiac magnetic resonance (CMR) imaging.
• Phase-contrast CMR quantified vessel flow rates, and vascular modeling toolkits analyzed TCPC geometries.
• Computational simulations determined TCPC indexed power loss (iPL) at the ventilatory anaerobic threshold (VAT).

Main Results:

• A significant inverse correlation was found between TCPC diameter index and iPL at VAT (r=-0.723, p<0.001).
• Positive correlations were observed between TCPC diameter index and exercise performance metrics (VO2 at VAT and peak, work at VAT/weight).
• Elevated iPL at VAT was negatively correlated with exercise performance variables.

Conclusions:

• Reducing vessel narrowing and indexed power loss (iPL) in total cavopulmonary connections (TCPCs) at the ventilatory anaerobic threshold (VAT) can enhance exercise tolerance.
• These findings support the development of surgical or catheter-based strategies to improve exercise capacity in Fontan patients.