A computational fluid study on hemodynamics in visceral arteries in a complicated type B aortic dissection after thoracic endovascular repair

Patient-Specific Haemodynamic Analysis of Virtual Grafting Strategies in Type-B Aortic Dissection: Impact of Compliance Mismatch

INTRODUCTION

Compliance mismatch between the aortic wall and Dacron Grafts is a clinical problem concerning aortic haemodynamics and morphological degeneration. The aortic stiffness introduced by grafts can lead to an increased left ventricular (LV) afterload. This study quantifies the impact of compliance mismatch by virtually testing different Type-B aortic dissection (TBAD) surgical grafting strategies in patient-specific, compliant computational fluid dynamics (CFD) simulations.

MATERIALS AND METHODS

A post-operative case of TBAD was segmented from computed tomography angiography data. Three virtual surgeries were generated using different grafts; two additional cases with compliant grafts were assessed. Compliant CFD simulations were performed using a patient-specific inlet flow rate and three-element Windkessel outlet boundary conditions informed by 2D-Flow MRI data. The wall compliance was calibrated using Cine-MRI images. Pressure, wall shear stress (WSS) indices and energy loss (EL) were computed.

RESULTS

Increased aortic stiffness and longer grafts increased aortic pressure and EL. Implementing a compliant graft matching the aortic compliance of the patient reduced the pulse pressure by 11% and EL by 4%. The endothelial cell activation potential (ECAP) differed the most within the aneurysm, where the maximum percentage difference between the reference case and the mid (MDA) and complete (CDA) descending aorta replacements increased by 16% and 20%, respectively.

CONCLUSION

This study suggests that by minimising graft length and matching its compliance to the native aorta whilst aligning with surgical requirements, the risk of LV hypertrophy may be reduced. This provides evidence that compliance-matching grafts may enhance patient outcomes.

GUIDANCE ON AREA OF CREATED TEARS FOR AORTIC FENESTRATION TREATMENT BASED ON COMPUTATIONAL FLUID DYNAMICS

Aortic fenestration (AF) uses puncture and a dilation balloon to create a tear in the intimal flap, which can directly relieve ischemia syndrome and reduce hypertension in the false lumen. The selection of a dilation balloon as well as the area of the created tear applied in reality depend on clinical experience, so we aim to provide a quantitative guidance and reference for doctors to better plan the treatment of aortic fenestration. In this study, the area of the created tear was virtually enlarged to at least 10 different values for four cases including one ideal case, and a computational fluid dynamic approach was applied to simulate blood flows in the aorta. The area ratio (AR) between the created tear and entry tear was introduced to express the enlargement of the created tear. The quantitative hemodynamic results indicate that the AR should be controlled to be larger than 7.0, but not too big to obtain the best treatment for acute aortic dissection (AD) case. Additionally, we assessed that AR might also be a risk factor for the prediction of dissection propagation.