Using CFD Simulation to Analyze the Repaired Coarctation of the Aorta

Coarctation of the aorta (CoA) is defined as a stenosis of the descending thoracic aorta (DAo) ¹ which results in narrowing of the aortic arch. Current clinical guidelines recommend intervention when there is significant aortic narrowing, ² and when a significant pressure gradient is measured during cardiac catheterization. The arch contains four outlets, three of which distribute oxygenated blood to the upper half of the body, while the fourth delivers to the lower body. If left untreated, serious heart conditions can arise later in life due to the hindrance in blood flow to both the upper and lower extremities. Patients with untreated CoA remain at high risk due to complications including increased mortality, hypertension, stroke, and decreased exercise capacity. ³ This condition affects approximately 6-8% of the population. ⁴ Today, surgical techniques to repair arches include extended end-to-end anastomosis which involves removing the constricted part of the aorta. Depending on the size of the constricted area, the ends of the artery can be reconnected simply by stitches or inserting a graft. Earlier techniques involve aortoplasty, which uses synthetic materials such as balloons or stents to reinforce the artery wall.

This project aims to model the flow through the aortic arch using computational fluid dynamics (CFD) to analyze the complex flow patterns and pressure gradients in patients pre and post CoA repair with the goal of providing insight to the flow patterns to better understand the effect of the repair, as well as contribute to future repair strategies. CFD is a branch of mechanics that creates simulations for a variety of applications. Under an IRB (Internal Review Board) approved study, clinical data was supplied by the University of Rochester Medical Center. This data included aortic arch anatomy in MRI and CT scan format, along with flow data and heart rates from cardiac MRI studies, and blood pressures from outpatient visits. These scans were then mapped onto a 3D model and imported into ANSYS, the CFD program used to conduct all flow modeling. Once an unrepaired arch was modeled, a virtual surgery was performed on the arch at two common cutting points in end-to-end anastomosis. The blood flow was then modeled again through the newly repaired arch to assess the change and quality of the flow. This will allow surgeons to be better informed on the quality of the surgery they are performing, and how to better assess the optimal snipping points in the arch. All simulations were conducted with normal blood parameters for density and viscosity, and governed using the Continuity and Navier-Stokes equations for turbulent flow under the SST k-omega flow model.

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