Evaluation of the Circulatory Dynamics by using the Windkessel Model in Different Body Positions

2011 ◽  
Vol 131 (1) ◽  
pp. 140-145
Author(s):  
Kiyoshi Kotani ◽  
Fumiaki Iida ◽  
Yutaro Ogawa ◽  
Kiyoshi Takamasu ◽  
Yasuhiko Jimbo
2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad Amin Abazari ◽  
Deniz Rafieianzab ◽  
M. Soltani ◽  
Mona Alimohammadi

AbstractAortic dissection (AD) is one of the fatal and complex conditions. Since there is a lack of a specific treatment guideline for type-B AD, a better understanding of patient-specific hemodynamics and therapy outcomes can potentially control the progression of the disease and aid in the clinical decision-making process. In this work, a patient-specific geometry of type-B AD is reconstructed from computed tomography images, and a numerical simulation using personalised computational fluid dynamics (CFD) with three-element Windkessel model boundary condition at each outlet is implemented. According to the physiological response of beta-blockers to the reduction of left ventricular contractions, three case studies with different heart rates are created. Several hemodynamic features, including time-averaged wall shear stress (TAWSS), highly oscillatory, low magnitude shear (HOLMES), and flow pattern are investigated and compared between each case. Results show that decreasing TAWSS, which is caused by the reduction of the velocity gradient, prevents vessel wall at entry tear from rupture. Additionally, with the increase in HOLMES value at distal false lumen, calcification and plaque formation in the moderate and regular-heart rate cases are successfully controlled. This work demonstrates how CFD methods with non-invasive hemodynamic metrics can be developed to predict the hemodynamic changes before medication or other invasive operations. These consequences can be a powerful framework for clinicians and surgical communities to improve their diagnostic and pre-procedural planning.


2021 ◽  
Author(s):  
Kleoniki Baxevanaki ◽  
Stavroula Kapoulea ◽  
Costas Psychalinos ◽  
Ahmed S. Elwakil

2009 ◽  
Vol 3 (1) ◽  
Author(s):  
Qiang Wang ◽  
Fernando Jaramillo ◽  
Yasushi Kato ◽  
Leonard Pinchuk ◽  
Richard T. Schoephoerster

Implantation methods for commercially available heart valve prostheses require open-chest access to the heart to perform the suturing process. In order to alleviate this complicated surgical implant technique, a “stent-valve” design was developed that will provide a less cumbersome implantation method and therefore a less invasive access to the heart. The purpose of this study is to verify its hydrodynamic performance and migration characteristics to assess its feasibility for use as a replacement heart valve. Hydrodynamic evaluation of the novel stent-valve combination device was carried out using a Vivitro left heart simulator and by setting up a comparison with the same 19 mm trileaflet valve under a traditional implantation (suture) method. To assess implantation ability under normal physiological conditions, porcine aortic root tissue was mounted into the left heart simulator to replace the original glass sinus. A comparison experiment was conducted to study the change in the total compliance and resistance of the testing system using the modified Windkessel model. For the range of test conditions investigated, the stent-valve combination device produced an average pressure gradient of 41.2 mm Hg(±19.6 mm Hg), an average effective orifice area (EOA) of 1.06 cm2(±0.08 cm2), and an average regurgitation percentage of 4.5% (±3.3%), while the sutured valve produced an average pressure gradient of 48.7 mm Hg(±17.4 mm Hg), an average EOA of 0.88 cm2(±0.14 cm2), and an average regurgitation percentage of 0.8% (±0.4%). The total compliance and resistance of the system was 0.37 ml/mm Hg(±0.01 ml/mm Hg) and 1.1 mm Hg/ml/s(±0.29 mm Hg/ml/s), with the original Windkessel model, and 0.33 ml/mm Hg(±0.01 ml/mm Hg) and 1.1 mm Hg/ml/s(±0.24 mm Hg/ml/s) for the system with the aortic tissue. The stent-valve combination device has demonstrated favorable hydrodynamic performance when compared with the same trileaflet valve under the traditional suturing method, and the arterial stent makes it possible to secure the valve at its required position without migration.


2002 ◽  
Vol 282 (2) ◽  
pp. R611-R622 ◽  
Author(s):  
Mette S. Olufsen ◽  
Ali Nadim ◽  
Lewis A. Lipsitz

The dynamic cerebral blood flow response to sudden hypotension during posture change is poorly understood. To better understand the cardiovascular response to hypotension, we used a windkessel model with two resistors and a capacitor to reproduce beat-to-beat changes in middle cerebral artery blood flow velocity (transcranial Doppler measurements) in response to arterial pressure changes measured in the finger (Finapres). The resistors represent lumped systemic and peripheral resistances in the cerebral vasculature, whereas the capacitor represents a lumped systemic compliance. Ten healthy young subjects were studied during posture change from sitting to standing. Dynamic variations of the peripheral and systemic resistances were extracted from the data on a beat-to-beat basis. The model shows an initial increase, followed approximately 10 s later by a decline in cerebrovascular resistance. The model also suggests that the initial increase in cerebrovascular resistance can explain the widening of the cerebral blood flow pulse observed in young subjects. This biphasic change in cerebrovascular resistance is consistent with an initial vasoconstriction, followed by cerebral autoregulatory vasodilation.


1982 ◽  
Vol 33 (3) ◽  
pp. 258-266 ◽  
Author(s):  
Kiyoshi Haneda ◽  
Murray P. Sands ◽  
Robert Thomas ◽  
Scot H. Merrick ◽  
Eugene A. Hessel ◽  
...  

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