Groupe d’études et de recherche en analyse des décisions

# A $$Y$$-graft design for the Fontan procedure using computational fluid dynamics and derivative-free optimization

## Weiguang Yang – University of California, San Diego, États-Unis

The Fontan procedure is a palliative surgery to treat patients born with single ventricle heart defects. These patients typically undergo a series of three surgeries (Norwood, Glenn and Fontan procedures), the last of which connects the inferior vena cava (IVC) to the pulmonary arteries (PA) via a tube-shaped Gore-tex graft. Although early survival rates following the Fontan procedure are greater than 90%, significant long term morbidity remains, including diminished exercise capacity, thromboembolic complications, protein-losing enteropathy, arteriovenous malformations, arrhythmias. In recent years there has been increasing interest in using computational fluid dynamics (CFD) to study Fontan hemodynamics. Previous studies show that the geometry plays an important role in Fontan patients' hemodynamic performance. A new Y-shaped graft has been proposed to replace the tube-shaped graft. Preliminary results on a patient-specific model have shown that the $$Y$$-graft is a promising design that improves patients' energy efficiency, Fontan pressure and hepatic flow distribution. However it has not yet been confirmed that the superiority of the $$Y$$-graft is universal. In addition, the use of optimal design is still new to cardiovascular problems though it has been the norm in many engineering applications.

In this talk, some studies on the Fontan surgical design in our lab will be introduced. First I will present a patient-specific study in which multiple virtual patient models were constructed to compare the $$Y$$-graft and traditional designs, with particular attention paid to the hepatic flow distribution. Lagrangian particle tracking was used to quantify the hepatic flow distribution. Then, shape optimization is applied to the Fontan design. A surrogate management framework together with MADS was coupled to a 3-D finite element flow solver to evaluate a Y-graft with unequal branch size, investigate the influence of pulmonary flow split on choice of optimal $$Y$$-graft and improve underperforming $$Y$$-grafts.