Quantification of Particle Residence Time in Abdominal Aortic Aneurysms Using Magnetic Resonance Imaging and Computational Fluid Dynamics

Suh, Ga-Young; Les, Andrea S.; Tenforde, Adam S.; Shadden, Shawn C.; Spilker, Ryan L.; Yeung, Janice J.; Cheng, Christopher P.; Herfkens, Robert J.; Dalman, Ronald L.; Taylor, Charles A.

doi:10.1007/s10439-010-0202-4

Cited by 76 publications

(60 citation statements)

References 42 publications

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“…It has been suggested that larger aneurysms are associated with increased convection flow, which, in the context of an aorta with normally very fast-flowing blood, leads to local pockets of reduced flow and shear stress. 31,32 This reduced flow, in combination with the propensity of patients with large aneurysms to form denser clots that are slower to lyse, could significantly increase the prothrombotic burden in the aneurysmal aorta. Furthermore, it is possible that a more densely packed clot may trap and accumulate a greater number of polymorphonuclear leukocytes, which in turn release biologically active proteases, causing AAA dilatation.…”

Section: Discussionmentioning

confidence: 99%

Clot Architecture Is Altered in Abdominal Aortic Aneurysms and Correlates With Aneurysm Size

Scott

Prasad

Philippou

et al. 2011

ATVB

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Objective-Abdominal aortic aneurysm (AAA) is characterized by widening of the aorta. Once the aneurysm exceeds 5.5 cm, there is a 10% risk of death due to rupture. AAA is also associated with mortality due to other cardiovascular disease. Our aim was to investigate clot structure in AAA and its relationship to aneurysm size. Methods and Results-Plasma was obtained from 49 controls, 40 patients with small AAA, and 42 patients with large AAA. Clot formation was studied by turbidity, fibrin pore structure by permeation, and time to half lysis by turbidity with tissue plasminogen activator. Plasma clot pore size showed a stepwise reduction from controls to small to large AAA. Lag phase for plasma clot formation and time to half lysis were prolonged, with smaller AAA samples showing intermediate response. Clot structure was normal in clots made with fibrinogen purified from patients compared with controls, suggesting a role for other plasma factors. Endogenous thrombin potential and turbidity using tissue factor indicated that the effects were independent of changes in thrombin generation. Conclusion-Patients

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Section: Discussionmentioning

confidence: 99%

Clot Architecture Is Altered in Abdominal Aortic Aneurysms and Correlates With Aneurysm Size

Scott

Prasad

Philippou

et al. 2011

ATVB

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“…One might find this analogous to the normalization of residence time or exposure time by the volume in discrete methods. 13,14,16 Considering the schematic shown in Figure 4 and Eqs. (9), (10), (16) and setting n = u u gives…”

Section: Point-wise Rtmentioning

confidence: 99%

“…To obtain a measure of RT in a region of interest, most prior studies have proposed a discrete formulation in which particles are released in the flow and their locations are traced over time. [13][14][15][16][17] RT is then calculated based on the time each individual particle spends in the region of interest. RT results obtained from these approaches depend on the number of particles used, often requiring a large number of particles to obtain a smooth spatial distribution.…”

Section: Introductionmentioning

confidence: 99%

“…Results can also be highly effected by seeding location, which is typically upstream of the region of interest, inside the region of interest, or at the model inlet. 13,14,16 Typically, several particle-tracking simulations are needed for pulsatile flow conditions, since the particle initiation time (e.g., relative to the cardiac cycle) affects the results of the RT calculation. 13,14 To mitigate this drawback, particles are often continuously released at the inflow boundary; however, the spatial distribution of seeded particles may not follow the non-uniform velocity distribution at the inlet.…”

Section: Introductionmentioning

confidence: 99%

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A non-discrete method for computation of residence time in fluid mechanics simulations

2013

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Cardiovascular simulations provide a promising means to predict risk of thrombosis in grafts, devices, and surgical anatomies in adult and pediatric patients. Although the pathways for platelet activation and clot formation are not yet fully understood, recent findings suggest that thrombosis risk is increased in regions of flow recirculation and high residence time (RT). Current approaches for calculating RT are typically based on releasing a finite number of Lagrangian particles into the flow field and calculating RT by tracking their positions. However, special care must be taken to achieve temporal and spatial convergence, often requiring repeated simulations. In this work, we introduce a non-discrete method in which RT is calculated in an Eulerian framework using the advection-diffusion equation. We first present the formulation for calculating residence time in a given region of interest using two alternate definitions. The physical significance and sensitivity of the two measures of RT are discussed and their mathematical relation is established. An extension to a point-wise value is also presented. The methods presented here are then applied in a 2D cavity and two representative clinical scenarios, involving shunt placement for single ventricle heart defects and Kawasaki disease. In the second case study, we explored the relationship between RT and wall shear stress, a parameter of particular importance in cardiovascular disease. C 2013 AIP Publishing LLC. [http://dx

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“…Degradation of the aortic wall, inflammation with immune responses, and biochemical wall stress are mechanisms that promote AAA initiation, influenced by molecular genetics (1). After the irreversible process of aneurysm formation, the dilated vessel creates an environment with complex blood flow and wall shear stress distribution (4,5,9,14,22,37,38), which is thought to perpetuate aneurysm progression.The presence of intraluminal thrombus (ILT) complicates AAA growth. ILT is fibrin structure compound of platelets, blood cells, blood proteins, and cellular debris (20).…”

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confidence: 99%

A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms

Arzani

Suh

Dalman

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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(ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2-to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (Ͼ0.4) and low TAWSS (Ͻ1 dyn/cm 2 ) did not appear to coincide with locations of thrombus deposition. computational fluid dynamics; hemodynamics; oscillatory shear index; thrombosis; wall shear stress ABDOMINAL AORTIC ANEURYSM (AAA) is a permanent dilation (50% greater than the normal arterial wall diameter) of the abdominal aorta. The disease is progressive and fatal if untreated. Between 11,000 and 17,000 patients die annually in the United States (18a) from AAA rupture following progressive, often asymptomatic, enlargement, and only invasive treatments have proven effective at preventing rupture and premature death (13). Male gender, age, smoking, genetic factors, hypertension, and high cholesterol are among known risk factors (10), and diabetes is a negative risk factor (47). Degradation of the aortic wall, inflammation with immune responses, and biochemical wall stress are mechanisms that promote AAA initiation, influenced by molecular genetics (1). After the irreversible process of aneurysm formation, the dilated vessel creates an environment with complex blood flow and wall shear stress distribution (4,5,9,14,22,37,38), which is thought to perpetuate aneurysm progression.The presence of intraluminal thrombus (ILT) complicates AAA growth. ILT is fibrin structure compound of platelets, blood cells, blood proteins, and cellular debris (20). ILT is more frequent in larger AAA since most patients develop thrombus as the aneurysm progresses. It has been proposed that platelets activate in regions of high shear and are subsequently advected towards the aneurysm wall where they accumulate in regions of low shear and form thrombus (8), with a possible role played by the vortical structures formed inside the aneurysm (9). It has also been shown that the flow field inside AAA may promote ILT formation by increasing residence time and trapping blood particles (7,37,38).The effect of ILT on AAA progression and rupture remains controversial (48). ILT may deprive the aneurysm wall of oxygen, which may exacerba...

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Quantification of Particle Residence Time in Abdominal Aortic Aneurysms Using Magnetic Resonance Imaging and Computational Fluid Dynamics

Cited by 76 publications

References 42 publications

Clot Architecture Is Altered in Abdominal Aortic Aneurysms and Correlates With Aneurysm Size

Clot Architecture Is Altered in Abdominal Aortic Aneurysms and Correlates With Aneurysm Size

A non-discrete method for computation of residence time in fluid mechanics simulations

A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms

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