Impact of Collateral Vessels on Fontan Circulation: 0- to 1-Dimensional Fontan Circulation Model and Concept of Oxygen Supply and Consumption

Background

Patients with single ventricle often undergo the Fontan operation to alleviate cyanosis and reduce ventricle volume load. However, long-term outcomes are limited by complications and hemodynamic issues, including collateral vessels, leading to cyanosis and heart failure. Studies have demonstrated considerable blood flow through these collateral vessels; however, their hemodynamic impact on Fontan circulation remains inadequately explained from a theoretical perspective. This study aims to clarify the effects of dobutamine and vasodilators on Fontan circulation in the presence of aortopulmonary collaterals (APCs) and venovenous collaterals (VVCs).

Methods

A Fontan hemodynamic model incorporating VVC and APC was created. Scenarios were simulated by adjusting dobutamine dosage and oxygen delivery/consumption, predicting arterial and central venous oxygen saturations. Cardiac function was evaluated based on cardiac output, arterial elastance, ejection fraction, and stroke work to pressure-volume ratio.

Results

Fontan circulations with VVC and APC had lower arterial and venous oxygen saturations (92% and 54%, respectively) compared with those without collaterals (96% and 62%, respectively). Decreased arterial elastance and increased stroke work to pressure-volume ratio indicated poor tissue perfusion. High pulmonary resistance decreased oxygen saturations and systemic blood flow, regardless of collaterals. Dobutamine (10 μg/kg/min) raised venous oxygen from 53% to 58%, respectively, in the presence of VVC and APC, but decreased arterial oxygen from 92% to 88%, respectively.

Conclusions

The results align with clinical findings, suggesting pulmonary vasodilators may improve oxygenation and perfusion in Fontan patients with collaterals. However, dobutamine effects are limited. Validation with actual patient data is needed to enhance model accuracy.