184. VIRTUAL SURGICAL DESIGN AND SHAPE OPTIMIZATION OF A NEW Y-GRAFT DESIGN FOR THE FONTAN PROCEDURE

Department: Mechanical & Aerospace Engineering
Faculty Advisor(s): Alison Marsden

Primary Student
Name: Weiguang Yang
Email: w1yang@ucsd.edu
Phone: 858-775-8263
Grad Year: 2012

Abstract
It has been shown that the geometry of the Fontan surgery plays an important role in hemodynamics. In order to improve Fontan hemodynamics, a novel Y-graft design\cite{soerensen07,marsden08b}, in which the inferior vena cava is connected to the left and right pulmonary arteries by two branches, has been proposed to replace current designs (T-junction and offset). Recent advances in blood flow simulations and optimization techniques make it possible to perform the computer-aided surgical design and optimization in an automated and systematic framework. The optimization method used in this work couples a time-dependent 3D Navier-Stokes solver with an optimization algorithm called the surrogate management framework (SMF). In the first part of this study, the optimization framework is applied to an idealized Y-graft model with six design parameters. Energy efficiency is chosen as the objective function and a function of wall shear stress (WSS) is imposed as a constraint in the optimization. Results demonstrate that the optimal graft size decreases with increasing exercise level in order to maximize energy efficiency but that a large Y-graft results in significant low wall shear stress (WSS) regions near the outer wall of the bifurcation under rest conditions. The impact of the WSS constraint is suppressed under exercise conditions. Based on these findings, we virtually implant two graft designs into multiple patient specific Glenn patient models: first, a customized Y-graft with a 20mm trunk and 15mm branches, and second an offset design with 20 mm diameter graft. We present results showing energy efficiency, SVC pressure, particle residence time and WSS to compare the performance of the Y-graft and traditional offset designs.

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