Abstract:

Background: Fontan procedure is a palliative surgery for patients with single ventricle circulation. Fenestration Fontan has an advantage for maintaining cardiac output and reducing central venous pressure in the early stage after surgeries. However, its effect on hemodynamics in the long term is still unclear. It is also difficult to evaluate the simple effect of fenestration on hemodynamics in vivo since it is usually applied to the patients with deteriorated circulation.

Methods and results: We constructed a computational model for Fontan circulation. Effects of change in the cardiovascular parameters on Fontan hemodynamics were compared with and without the fenestration. When the baseline ventricular contractility (Ees) was enhanced from 1mmHg/ml to 3mmHg/ml, cardiac index (CI), O₂ delivery and central venous pressure (CVP) improved further with fenestration. Deteriorated baseline diastolic function assessed by ventricular relaxation (τ) and diastolic stiffness (B) reduced the beneficial effect of fenestration on CI, CVP and oxygen delivery. Although fenestration ameliorated CVP rise and CI reduction in patients with high pulmonary vascular resistance (Rp), SaO₂ was markedly reduced and it resulted in the reduction of systemic O₂ delivery. The simulation also shows that fenestration works well within the heart rates (HR) ranges from about 75beats/min (bpm) to 100bpm.

Conclusions: Fenestration improves Fontan hemodynamics. The effects of fenestration vary and depend on the baseline cardiovascular functions. Although fenestration is usually applied in patients with high Rp in clinical situation, this study shows that it works best in the patients with good cardiac function and low Rp.