Comparison of Blood Flow in Branched and Fenestrated Stent-Grafts for Endovascular Repair of Abdominal Aortic Aneurysms

Abstract

Reliability of antegrade and retrograde stent-grafts, collectively known as branched stent-3 grafts (BSG), has not been appropriately analysed. This computational study assesses the 4 haemodynamic outcomes of BSG for different anatomical variations. 5Methods 6 Ideal models of BSG and fenestrated stent-grafts (FSG) were constructed with different 7 visceral take-off angles (TOA) and lateral aortic neck angle. TOA was defined as the angle 8 between the centrelines of the main stent-graft and side branch, with 90° representing normal 9 alignment while 30° and 120° representing angulated side branches. Computational 10 simulations were performed by solving the conservation equations governing the blood flow 11 under physiologically realistic conditions. 12 Results 13Largest renal flow recirculation zones (FRZ) were observed in FSG (at TOA of 30°) and the 14 smallest FRZ was also found in FSG (at TOA of 120°).

Haemodynamic Variations of Flow to Renal Arteries in Custom-Made and Pivot Branch Fenestrated Endografting

“…14 The model design played a pivotal role in the computational simulation. Two previous studies analysed the haemodynamic variation resulting from fenestration misalignment, 15,16 with RSGs rising vertically from the fenestration then facing towards different directions. In the present study custom-made fenestrated models were designed with RSGs protruding into the stent graft body, which may constitute a more accurate description in terms of conforming to clinical reality.…”

Computational Fluid Dynamics Simulations of Flow in the Renal Arteries after Stent Graft Implantation

“…Based on monitoring the Courant number in pulsatile flow simulations, a uniform 0.02 s time-step was adopted. As suggested by Kandail et al [7], simulations for all geometries were performed for four cardiac cycles to achieve periodic results.…”

“…As a first step towards understanding post-surgical complications of FEVAR, including AKI and renal artery thrombosis, this study aims to use computational fluid dynamics (CFD) to determine how fenestration misalignment impacts renal artery hemodynamics. Two factors, renal artery flow rate and renal artery time-averaged wall shear stress (TAWSS) were adopted as hemodynamics indices [6][7][8][9][10] to indicate the risks of AKI and renal thrombosis.…”

Commentary: Computational Modeling of Contemporary Stent-Grafts

“…Intuitively, antegrade seems like the better option if one is concerned with increasing flow through the conduit; however, a previous report that used CFD to investigate antegrade and retrograde configurations 6 showed this is not the case, as a retrograde configuration provided an equal flow rate, especially in lengths applicable to branched AAA stent-grafts. Kandail et al 5 have built on this foundation, however, in their geometries, demonstrating that retrograde BSGs underperform in terms of flow to the renal arteries compared to antegrade BSGs and FSGs in all ToAs investigated. The retrograde BSGs also supplied less blood to the kidneys when the neck angle was increased to 60°.…”

“…Also, a recent investigation into the number of cardiac cycles required to achieve robust convergence of CFD simulations has identified that more than three cycles may be needed. 8 In Kandail et al, 5 as is common in many previous reports, [9][10][11][12] data were deemed repeatable from the third or fourth cycle onward.…”