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Impact of the Fenestration Size at Fontan Procedure: A Theoretical Analysis Based on CFD Modeling of Fontan Circulation
Koichi Sughimoto1, Fuyou Liang2, Hideaki Senzaki3, Shu Takagi2, Hao Liu4.
1Tokyo Women's Medical University, Tokyo, Japan, 2RIKEN, Wako, Japan, 3Saitama Medical Center, Kawagoe, Japan, 4Chiba University, Chiba, Japan.
OBJECTIVE:
Placing a fenestration at Fontan procedure is still controversial. Although decision making for the placement of fenestration is often based on surgeon’s experiences, judgment and planning should be made with
theoretical understandings. Fontan whole circulation computational fluid dynamic simulation model will give answers for this problem.
METHODS:
Three sizes of diameter for fenestration (0.4, 3.2, 6.4 mm) were created as
a Fontan circulation model, compared with no fenestration. Various parameters such as heart rate (HR), Pulmonary resistance (Rp), systemic resistance (Rs), and active (for systole) / passive (for diastole) elastance of the ventricle (Elva/Elvb) were varied to examine influences on cardiac output (CO), pulmonary flow (Qp), pulmonary to systemic flow ratio (Qp/Qs), mean PA pressure (mPAP) by various sizes of fenestration.
RESULTS:
A) Placing fenestrations increased CO from 3.35 l/min (no fenestration) to 3.48 l/min (104 %) in 3.2 mm, 3.95 l/min(118 %) in 6.4 mm; while 6.4 mm of fenestration even decreased the CVP by 0.5 mmHg. B) 6.4 mm of fenestration had a better response to HR in increasing CO with a peak
increase of 0.46 l/min at HR of 150 than with smaller or no fenestration. C) An increase in Rp decreased CO, Qp/Qs, and Qp; larger fenestration demonstrated smaller reduction of CO, dramatic decrease of Qp/Qs, and Qp; and smaller increase in mPAP. D) As Rs increases, larger fenestration showed more dramatic fall in CO, Qp/Qs, Qp and mPAP. E) Elevation of Elva increased CO, higher in larger fenestration. F) Increasing Elvb decreased CO, CO decreased more markedly in larger fenestration.
CONCLUSIONS:
By using a novel developed fenestrated Fontan CFD simulation model, the mechanical characteristics of Fontan circulation were successfully demonstrated. Patients with higher HR and well preserved ventricular systolic function may benefit more from fenestration. A larger fenestration slightly reduces CVP while better preserving CO as Rp increases. A fenestration may however lead to a negative impact in patients with an elevated Rs or a stiffer ventricle in diastole.
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