Computational Fluid Dynamics and Solid Mechanics Analyses of a Patient-Specific AAA Pre- and Post-EVAR

2004 ◽  
Author(s):  
Christine M. Scotti ◽  
Ender A. Finol ◽  
Siddharth Viswanathan ◽  
Aleksandr Shkolnik ◽  
Elena S. DiMartino ◽  
...  
Keyword(s):  
Arterial Wall ◽  
Solid Mechanics ◽  
Morphological Changes ◽  
Thrombus Formation ◽  
Endovascular Aneurysm Repair ◽  
Aneurysm Rupture ◽  
Patient Specific ◽  
Minimally Invasive Surgical ◽  
Increased Risk ◽  
Risk Of Rupture

The establishment of a new pathway for blood flow immediately following endovascular aneurysm repair (EVAR) results in morphological changes and remodeling of the aneurismal sac. While EVAR is a minimally invasive surgical intervention, failure of the endovascular graft (EVG) may occur in which there is downstream migration and endoleak formation, creating a repressurization of the aneurismal sac and an increased risk of rupture. While the mechanism of aneurysm rupture and EVG failure is fundamental in nature, the factors that most significantly contribute to the end result are not yet fully understood. Mechanically, both are the consequence of an exerted force or disturbance exceeding the strength of a given material, whether it is the aneurismal arterial wall or the interaction that exists between the graft and wall. Embedded within this causal relationship are the contributions of arterial wall remodeling, intraluminal thrombus formation, and the dynamics that exists within the lumen. Several studies have been performed to examine these factors individually as they affect shear stress, the development of vortices, and the mechanical stress experienced along the arterial wall. However, a complete investigation is needed to study an anatomically realistic geometry operating under physiological conditions. The computational analyses conducted in this investigation address the confluence of these factors as they are modeled within an accurate patient-specific abdominal aortic aneurysm (AAA) reconstructed from CT scan data prior to and after EVAR. Our results verify the pressure-dominated characteristic of the flow and the negligible contribution of the dynamic and frictional force components; both are in good agreement with previously published results for analytical estimation of flow-induced forces in EVGs. [1]

Patient-Specific Modelling of Intracranial Aneurysm Evolution

2011 ◽  
Author(s):  
Paul N. Watton ◽  
Marc Homer ◽  
Justin Penrose ◽  
Harry Thompson ◽  
Haoyu Chen ◽  
...  
Keyword(s):  
Arterial Wall ◽  
Adult Population ◽  
Computational Simulation ◽  
Clinical Intervention ◽  
Patient Specific ◽  
Computational Framework ◽  
Important Concern ◽  
Risk Of Rupture ◽  
Appropriate Therapy ◽  
Insight Into

Intracranial aneurysms appear as sac-like outpouchings of the cerebral vasculature wall; inflated by the pressure of the blood that fills them. They are relatively common and affect up to 5% of the adult population. Fortunately, most remain asymptomatic. However, there is a small but inherent risk of rupture: 0.1% to 1% of detected aneurysms rupture every year. If rupture does occur there is a 30% to 50% chance of fatality. Consequently, if an aneurysm is detected, clinical intervention may be deemed appropriate. Therapy is currently aimed at pre-rupture detection and preventative treatment. However, interventional procedures are not without risk to the patient. The improvement and optimization of interventional techniques is an important concern for patient welfare and is necessary for rationalisation of healthcare priorities. Hence there is a need to develop methodologies to assist in identifying those ICAs most at risk of rupture. We focus on the mathematical modelling and computational simulation of ICA evolution. Models must take into consideration: (i) the biomechanics of the arterial wall; (ii) the biology of the arterial wall and (iii) the complex interplay between (i) and (ii), i.e. the mechanobiology of the arterial wall. The ultimate ambition of such models is to aid clinical diagnosis on a patient-specific basis. However, due to the significant biological complexity coupled with limited histological information such models are still in their relative infancy. Current research focuses on simulating the evolution of an ICA with an aim to yield insight into the growth and remodelling (G&R) processes that give rise to inception, enlargement, stabilisation and rupture. We present a novel Fluid-Structure-Growth computational framework for modelling aneurysm evolution.

WHICH MORPHOLOGIC AND HEMODYNAMIC CHARACTERISTICS PREDICT INTRACRANIAL FUSIFORM ANEURYSMS RUPTURE? A PATIENT-SPECIFIC COMPUTATIONAL FLUID DYNAMICS STUDY

2017 ◽  
Vol 17 (03) ◽  
pp. 1750070
Author(s):  
YAN CHEN ◽  
YI-BIN FANG ◽  
PENG-FEI YANG ◽  
QING-HAI HUANG ◽  
JIAN-MIN LIU
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Patient Specific ◽  
Parent Artery ◽  
Cross Sectional ◽  
3D Angiography ◽  
Cross Section Area ◽  
Increased Risk ◽  
Risk Of Rupture

To identify hemodynamic and morphological parameters leading to increased risk of intracranial fusiform aneurysms (IFA) rupture using computational fluid dynamics (CFDs). A total of 24 patient-specific fusiform aneurysms models on vertebral artery were reconstructed from 3D angiography images. 11 ruptured cases and 13 unruptured cases were included. Morphologic parameters were measured and CFD parameters were calculated using CFD simulation. The length of the aneurysm is significantly shorter in ruptured group than in unruptured group. The ratio of the width to the length of an aneurysm (WLR) and the ratio of the cross-section area to the length of an aneurysm (ALR) to the averaged cross sectional areas of the inlet and outlet of the parent artery (ALaR) were significantly higher in ruptured group compared with unruptured group. Wall shear stress (WSS) of the aneurysm was normalized to the WSS of the parent artery. Hemodynamically, only low WSS was associated with higher risk of rupture. Ruptured IFAs are shorter, have bigger WLR, ALaR, and lower WSS, compared with unruptured IFAs.

scholarly journals PHASES Score for Prediction of Intracranial Aneurysm Growth

Stroke ◽  
2015 ◽  
Vol 46 (5) ◽  
pp. 1221-1226 ◽  
Author(s):  
Daan Backes ◽  
Mervyn D.I. Vergouwen ◽  
Andreas T. Tiel Groenestege ◽  
A. Stijntje E. Bor ◽  
Birgitta K. Velthuis ◽  
...  
Keyword(s):  
Intracranial Aneurysm ◽  
Cox Regression ◽  
Continuous Variable ◽  
Aneurysm Rupture ◽  
Hazard Ratios ◽  
Unruptured Intracranial Aneurysms ◽  
Increased Risk ◽  
Risk Of Rupture ◽  
Aneurysm Growth

Background and Purpose— Growth of an intracranial aneurysm occurs in around 10% of patients at 2-year follow-up imaging and may be associated with aneurysm rupture. We investigated whether PHASES, a score providing absolute risks of aneurysm rupture based on 6 easily retrievable risk factors, also predicts aneurysm growth. Methods— In a multicenter cohort of patients with unruptured intracranial aneurysms and follow-up imaging with computed tomography angiography or magnetic resonance angiography, we performed univariable and multivariable Cox regression analyses for the predictors of the PHASES score at baseline, with aneurysm growth as outcome. We calculated hazard ratios and corresponding 95% confidence intervals (CI), with the PHASES score as continuous variable and after division into quartiles. Results— We included 557 patients with 734 unruptured aneurysms. Eighty-nine (12%) aneurysms in 87 patients showed growth during a median follow-up of 2.7 patient-years (range 0.5–10.8). Per point increase in PHASES score, hazard ratio for aneurysm growth was 1.32 (95% CI, 1.22–1.43). With the lowest quartile of the PHASES score (0–1) as reference, hazard ratios were for the second (PHASES 2–3) 1.07 (95% CI, 0.49–2.32), the third (PHASES 4) 2.29 (95% CI, 1.05–4.95), and the fourth quartile (PHASES 5–14) 2.85 (95% CI, 1.43–5.67). Conclusions— Higher PHASES scores were associated with an increased risk of aneurysm growth. Because higher PHASES scores also predict aneurysm rupture, our findings suggest that aneurysm growth can be used as surrogate outcome measure of aneurysm rupture in follow-up studies on risk prediction or interventions aimed to reduce the risk of rupture.

scholarly journals Propose a Wall Shear Stress Divergence to Estimate the Risks of Intracranial Aneurysm Rupture

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Y. Zhang ◽  
H. Takao ◽  
Y. Murayama ◽  
Y. Qian
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intracranial Aneurysm ◽  
Risk Estimation ◽  
Aneurysm Rupture ◽  
Patient Specific ◽  
Luminal Surface ◽  
Risk Of Rupture ◽  
Computational Fluid Dynamics Cfd ◽  
Wall Shear

Although wall shear stress (WSS) has long been considered a critical indicator of intracranial aneurysm rupture, there is still no definite conclusion as to whether a high or a low WSS results in aneurysm rupture. The reason may be that the effect of WSS direction has not been fully considered. The objectives of this study are to investigate the magnitude of WSS (WSS) and its divergence on the aneurysm surface and to test the significance of both in relation to the aneurysm rupture. Patient-specific computational fluid dynamics (CFD) was used to compute WSS and wall shear stress divergence (WSSD) on the aneurysm surface for nineteen patients. Our results revealed that if highWSSis stretching aneurysm luminal surface, and the stretching region is concentrated, the aneurysm is under a high risk of rupture. It seems that, by considering both direction and magnitude of WSS, WSSD may be a better indicator for the risk estimation of aneurysm rupture (154).

scholarly journals Clinical relevance of short-term follow-up of unruptured intracranial aneurysms

2019 ◽  
Vol 47 (1) ◽  
pp. E7 ◽  
Author(s):  
Rob Molenberg ◽  
Marlien W. Aalbers ◽  
Jan D. M. Metzemaekers ◽  
Aryan Mazuri ◽  
Gert-Jan Luijckx ◽  
...  
Keyword(s):  
Clinical Relevance ◽  
Intracranial Aneurysms ◽  
Significant Risk ◽  
Patient Specific ◽  
Rupture Risk ◽  
Short Term ◽  
Unruptured Intracranial Aneurysms ◽  
Increased Risk ◽  
Risk Of Rupture

OBJECTIVEUnruptured intracranial aneurysms are common incidental findings on brain imaging. Short-term follow-up for conservatively treated aneurysms is routinely performed in most cerebrovascular centers, although its clinical relevance remains unclear. In this study, the authors assessed the extent of growth as well as the rupture risk during short-term follow-up of conservatively treated unruptured intracranial aneurysms. In addition, the influence of patient-specific and aneurysm-specific factors on growth and rupture risk was investigated.METHODSThe authors queried their prospective institutional neurovascular registry to identify patients with unruptured intracranial aneurysms and short-term follow-up imaging, defined as follow-up MRA and/or CTA within 3 months to 2 years after initial diagnosis. Medical records and questionnaires were used to acquire baseline information. The authors measured aneurysm size at baseline and at follow-up to detect growth. Rupture was defined as a CT scan–proven and/or CSF-proven subarachnoid hemorrhage (SAH).RESULTSA total of 206 consecutive patients with 267 conservatively managed unruptured aneurysms underwent short-term follow-up at the authors’ center. Seven aneurysms (2.6%) enlarged during a median follow-up duration of 1 year (range 0.3–2.0 years). One aneurysm (0.4%) ruptured 10 months after initial discovery. Statistically significant risk factors for growth or rupture were autosomal-dominant polycystic kidney disease (RR 8.3, 95% CI 2.0–34.7), aspect ratio > 1.6 or size ratio > 3 (RR 10.8, 95% CI 2.2–52.2), and initial size ≥ 7 mm (RR 10.7, 95% CI 2.7–42.8).CONCLUSIONSSignificant growth of unruptured intracranial aneurysms may occur in a small proportion of patients during short-term follow-up. As aneurysm growth is associated with an increased risk of rupture, the authors advocate that short-term follow-up is clinically relevant and has an important role in reducing the risk of a potential SAH.

Morphological and hemodynamic analysis of posterior communicating artery aneurysms prone to rupture: a matched case–control study

2014 ◽  
Vol 8 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Guoli Duan ◽  
Nan Lv ◽  
Jianhua Yin ◽  
Jinyu Xu ◽  
Bo Hong ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Regression Analysis ◽  
Logistic Regression Analysis ◽  
Conditional Logistic Regression ◽  
Aneurysm Rupture ◽  
Posterior Communicating Artery ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Conditional Logistic Regression Analysis ◽  
Risk Of Rupture

ObjectivesWe evaluated the correlation between posterior communicating artery (PcomA) aneurysm rupture and morphological and hemodynamic parameters to assess related rupture risk indices.MethodsSix patients with PcomA aneurysms that ultimately ruptured (cases) were studied after initially being included in a prospective database including their three-dimensional (3D) imaging before rupture. For each case, four incidental stable unruptured aneurysms (controls) were randomly selected and matched based on clinical factors. The 3D images from all patients were reconstructed to establish the patient-specific model. Six morphologic parameters and three hemodynamic parameters were measured and calculated. A conditional logistic regression analysis was used to assess the individual risk of rupture.ResultsThe analysis demonstrated a larger aneurysm size (p=0.001), higher aspect ratio (p=0.018), ellipticity index (p<0.001), undulation index (p=0.005), percentage of low wall shear stress (WSS) area (LSA%) (p=0.010), and a lower normalized WSS (p=0.005) in the case group. The multivariate conditional logistic regression analysis demonstrated that only normalized WSS was significantly associated with the rupture of PcomA aneurysms (OR 0.151; 95% CI 0.025 to 0.914; p=0.040).ConclusionsHemodynamics and morphology are closely associated with aneurysm rupture, and WSS may be a more reliable parameter characterizing the rupture status of PcomA aneurysms.

The Importance of Proliferation of the Arterial Wall in Formation of Saccular Cerebral Aneurysms

2008 ◽  
Author(s):  
Y. Shimogonya ◽  
T. Ishikawa ◽  
Y. Imai ◽  
D. Mori ◽  
T. Yamaguchi
Keyword(s):  
Cerebral Aneurysm ◽  
Poor Prognosis ◽  
Arterial Wall ◽  
Cerebral Aneurysms ◽  
Aneurysm Rupture ◽  
Preventative Treatment ◽  
Unruptured Aneurysms ◽  
Unruptured Cerebral Aneurysm ◽  
Risk Of Rupture ◽  
Annual Risk

Cerebral aneurysms are an important cerebrovascular condition because aneurysm rupture is the most common cause of subarachnoid hemorrhage, which has a high mortality rate and a poor prognosis. Since the mechanism of cerebral aneurysm pathogenesis has not yet been understood, the preventative treatment for unruptured aneurysms is surgery only; however, the morbidity of the surgery is as high as over 10% [1]. On the other hand, the annual risk of rupture of cerebral aneurysms is not so high, reported to be 1.9% [2]. Consequently, it is difficult to judge whether a patient with an unruptured cerebral aneurysm should undergo surgery, when it is detected. Thus, it is important to develop a better understanding of the mechanism of cerebral aneurysm pathogenesis.

Development of an Abdominal Aortic Aneurysm Ruptures Mechanism Using a Geometric Analytical Technique

2014 ◽  
Author(s):  
A. H. Embong ◽  
A. M. Al-Jumaily ◽  
G. Mahadevan ◽  
A. Lowe ◽  
S. Sugita
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
Aneurysm Rupture ◽  
Aortic Aneurysms ◽  
Patient Specific ◽  
Analytical Technique ◽  
Abdominal Aortic ◽  
Risk Of Rupture ◽  
Wall Deformation ◽  
Rupture Mechanism

Current ultrasound approaches practice probe for diagnosing instantaneous abdominal aortic aneurysms (AAA) based on arterial tissue deformation. However, tracking the progression of potential aneurysms, and predicting the risk of rupture is based on the diameter of the aneurysm and is still an insufficient method: Larger diameter aneurysms do not always lead to ruptures, and smaller diameter aneurysms unexpectedly rupture. In order to improve diagnostic accuracy of ultrasound imaging techniques, this paper presents geometric analyses of patient-specific instant deformations as a means to develop an aneurysm rupture mechanism. Segmented AAA images were used to analyze dependent elements that contribute to a three-dimensional (3-D) aneurysm reconstructive model using proposed Patient-Specific Aneurysm Rupture Predictor (P-SARP) method. The outcomes indicate that the proposed technique has the ability to associate the distortion of wall deformation with geometric analyses. This method can positively be integrated with established ultrasound techniques for improvements in the accuracy of future diagnoses of potential AAA ruptures.

Risk Assessment of Hemorrhage of Posterior Inferior Cerebellar Artery Aneurysms in Posterior Fossa Arteriovenous Malformations

2017 ◽  
Vol 14 (4) ◽  
pp. 359-366 ◽  
Author(s):  
Alice L Hung ◽  
Wuyang Yang ◽  
Maria Braileanu ◽  
Tomas Garzon-Muvdi ◽  
Justin M Caplan ◽  
...  
Keyword(s):  
Treatment Outcomes ◽  
Posterior Fossa ◽  
Arteriovenous Malformations ◽  
Aneurysmal Subarachnoid Hemorrhage ◽  
Posterior Inferior Cerebellar Artery ◽  
Aneurysm Rupture ◽  
Acute Hydrocephalus ◽  
Increased Risk ◽  
Cerebellar Artery ◽  
Risk Of Rupture

Abstract BACKGROUND Posterior fossa arteriovenous malformations (AVMs) are associated with increased risk of rupture and severe consequences from such rupture. The hemorrhagic risk of prenidal aneurysms (anr) on the posterior inferior cerebellar artery (PICA) may exceed that of the AVM in posterior fossa AVMs fed by PICA (PICA-AVM). OBJECTIVE To characterize the relative risks of aneurysm and AVM hemorrhage in patients with posterior fossa AVMs. METHODS We retrospectively reviewed patients diagnosed with AVM. Patients with posterior fossa AVMs were divided into 3 groups: PICA-AVM with prenidal aneurysm (PICA-AVM-anr group), PICA-AVM without prenidal aneurysm (PICA-AVM group), and AVMs without PICA feeder with/without aneurysm (AVM-only group). Patient and lesion characteristics and treatment outcomes were compared. ANOVA and chi squared tests were used for statistical analyses. RESULTS Our cohort included 85 patients. Mean age was 45.3 ± 18.1 yr, with 43(50.6%) female patients. Fifty-one patients (60.0%) had hemorrhagic presentation, and 27 (31.8%) experienced acute hydrocephalus. Patients in the PICA-AVM-anr group (n = 11) were more likely to present with aneurysmal subarachnoid hemorrhage (SAH; P = .005) and less likely to have AVM rupture (P &lt; .001). Ten (90.9%) patients presented with hemorrhage, 6 (60.0%) of which resulted from aneurysm rupture. Of these 6, 5 (83.3%) had acute hydrocephalus. No patients with AVM rupture had hydrocephalus. Eight (72.7%) received aneurysm treatment prior to AVM treatment. There were no significant differences in post-treatment outcomes dependent on treatment order. CONCLUSION In addition to relatively higher risk of AVM rupture from infratentorial location and prenidal aneurysm, a higher risk of aneurysm rupture rather than AVM rupture was observed in patients with PICA-AVM-anr complex.

Bowel ischaemia after endovascular aneurysm repair

VASA ◽  
2018 ◽  
Vol 47 (4) ◽  
pp. 273-277
Author(s):  
Christopher Lowe ◽  
Oussama El Bakbachi ◽  
Damian Kelleher ◽  
Imran Asghar ◽  
Francesco Torella ◽  
...  
Keyword(s):  
Case Reports ◽  
Endovascular Aneurysm Repair ◽  
Artery Occlusion ◽  
Bibliographic Databases ◽  
Bowel Ischaemia ◽  
Prophylactic Measures ◽  
Increased Risk ◽  
Prisma Statement ◽  
Meta Analyses ◽  
Aneurysm Repair

Abstract. The aim of this review was to investigate presentation, aetiology, management, and outcomes of bowel ischaemia following EVAR. We present a case report and searched electronic bibliographic databases to identify published reports of bowel ischaemia following elective infra-renal EVAR not involving hypogastric artery coverage or iliac branch devices. We conducted our review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement standards. In total, five cohort studies and three case reports were included. These studies detailed some 6,184 infra-renal elective EVARs, without procedure-related occlusion of the hypogastric arteries, performed between 1996 and 2014. Bowel ischaemia in this setting is uncommon with an incidence ranging from 0.5 to 2.8 % and includes a spectrum of severity from mucosal to transmural ischaemia. Due to varying reporting standards, an overall proportion of patients requiring bowel resection could not be ascertained. In the larger series, mortality ranged from 35 to 80 %. Atheroembolization, hypotension, and inferior mesenteric artery occlusion were reported as potential causative factors. Elderly patients and those undergoing prolonged procedures appear at higher risk. Bowel ischaemia is a rare but potentially devastating complication following elective infra-renal EVAR and can occur in the setting of patent mesenteric vessels and hypogastric arteries. Mortality ranges from 35 to 80 %. Further research is required to identify risk factors and establish prophylactic measures in patients that have an increased risk of developing bowel ischaemia after standard infra-renal EVAR.

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