Flow visualization in arteriovenous fistula and aneurysm using computational fluid dynamics

Abstract

The arteriovenous fistula (AVF) is characterized by enhanced blood flow and is the most widely used vascular access for chronic haemodialysis (Sivanesan et al., 1998). A large proportion of the AVF late failures are related to local haemodynamics (Sivanesan et al., 1999a).As in AVF, blood flow dynamics plays an important role in growth, rupture, and surgical treatment of aneurysm. Several techniques have been used to study the flow patterns in simplified models of vascular anastomose and aneurysm. In the present investigation, Computational Fluid Dynamics (CFD) is used to analyze the flow patterns in AVF and aneurysm through the velocity waveform obtained from experimental surgeries in dogs (Galego et al., 2000), as well as intra-operative blood flow recordings of patients with radiocephalic AVF (Sivanesan et al., 1999b) and physiological pulses (Aires, 1991), respectively. The flow patterns in AVF for dog and patient surgeries data are qualitatively similar. Perturbation, recirculation and separation zones appeared during cardiac cycle, and these were intensified in the diastole phase for the AVF and aneurysm models. The values of wall shear stress presented in this investigation of AVF and aneurysm models oscillated in the range that can both cause damage to endothelial cells and develop atherosclerosis.

Numerical Analysis on the Blood Flow Characteristic in the Arteriovenous Graft for Different Injection Method of Blood

“…Unsteady profile period 0.758 s Artery outlet 12.8% of Artery inlet Velocity profile Needle (suction) -400 mL/min Needle (injection) 400 mL/min Vein outlet Pressure-outlet Wall Rigid body [19][20][21][22]. 또 한 활성화된 백혈구는 항원반응 발현을 증가시키게 하여 내 피세포에 혈소판의 부착 및 염증작용을 야기하며, 혈전 형성 에 중요한 역할을 한다 [22].…”

Biomechanical Factors Analysis in Aneurysm

“…These studies occur in ideal symmetric and nonsymmetric shapes of fusiform aneurysms and in realistic geometries obtained from high-resolution CT and angiographies (Egelhoff et al 1999, Finol & Amon 2003, Salsac et al 2006, Bessa & Ortiz 2009, Legendre 2010. Although, these studies show limitations about the appropriate initial and boundary conditions, as well as account for the precise elastic properties of the wall, they clearly show that once a fusiform aneurysm forms, the flow is dominated by the onset of an unsteady, massive separation from the walls that occurs immediately after the peak systole.…”

“…When the flow separates from the walls during the deceleration portion of the cardiac cycle, a relatively coherent array of large vortices forms and the blood flow slowly recirculates (Lasheras, 2007). Bessa & Ortiz (2009) showed that occur massive separation from the walls and the velocity profile becomes inverted inside of the aneurysm, forming a vortex in the bottom and in the top of the aneurysm. After that, the velocity profile has been completely inverted and the vortex pair travels towards to the center of the aneurysm (Figure 8).…”

Concepção de bancada e montagem de experimento para a análise in vitro de próteses cardíacas mitrais

“…The final design of the testing bench (SME / EPUSP) is based on experience in monitoring the activities of the Dante Pazzanese Institute of Cardiology with artificial hearts in master's and doctoral works previously developed by Silva et al [23], Leal [24], Bessa & Ortiz [28] and Legendre [29], adapting them to pulsatile flow through prosthetic heart valves and in the literature review on the subject. In particular, it meets the requirements of international standard ISO 5840:2005 for pulsed flow regime [25] and includes the views of the benches using the deformable model of the left ventricle (silicone) and the disposition of the prosthetic valves in geometries similar those occurring in vivo [11][12][13].…”

“…In order to give subsidies to the interpretation of results and help in optimization of these prostheses, the information obtained in the experimental simulations will be used to adjust a computer model [28].…”