MECHANICAL STRESSES ASSOCIATED WITH FLATTENING OF HUMAN FEMOROPOPLITEAL ARTERY SPECIMENS DURING PLANAR BIAXIAL TESTING AND THEIR EFFECTS ON THE CALCULATED PHYSIOLOGIC STRESS-STRETCH STATE

Planar biaxial testing is commonly used to characterize the mechanical properties of arteries, but stresses associated with specimen flattening during this test are unknown. We quantified flattening effects in human femoropopliteal arteries (FPAs) of different ages, and determined how they affect the calculated arterial physiologic stress-stretch state. Human FPAs from 472 tissue donors (age 12-82 years, mean 53±16 years) were tested using planar biaxial extension, and morphometric and mechanical characteristics were used to assess the flattening effects. Constitutive parameters for the invariant-based model were adjusted to account for specimen flattening, and used to calculate the physiologic stresses, stretches, axial force, circumferential stiffness, and stored energy for the FPAs in 7 age groups. Flattened specimens were overall 12±4% stiffer longitudinally and 19±11% stiffer circumferentially when biaxially tested. Differences between the stress-stretch curves adjusted and non-adjusted for the effects of flattening were relatively constant across all age groups longitudinally, but increased with age circumferentially. In all age groups these differences were smaller than the intersubject variability. Physiologic stresses, stretches, axial force, circumferential stiffness, and stored energy were all qualitatively and quantitatively similar when calculated with and without the flattening effects. Stresses, stretches, axial force, and stored energy reduced with age, but circumferential stiffness remained relatively constant between 25 and 65 years of age suggesting a homeostatic target of 0.75±0.02 MPa. Flattening effects associated with planar biaxial testing are smaller than the intersubject variability, and have little influence on the calculated physiologic stress-stretch state of human FPAs

Feasibility of Fluoroscopy-Free Endovascular Navigation in Subjects of Different Ages

https://digitalcommons.unmc.edu/emet_posters/1013/thumbnail.jp

In vivo three-dimensional blood velocity profile shapes in the human common, internal, and external carotid arteries

Objective: True understanding of carotid bifurcation pathophysiology requires a detailed knowledge of the hemodynamic conditions within the arteries. Data on carotid artery hemodynamics are usually based on simplified, computer-based, or in vitro experimental models, most of which assume that the velocity profiles are axially symmetric away from the carotid bulb. Modeling accuracy and, more importantly, our understanding of the pathophysiology of carotid bifurcation disease could be considerably improved by more precise knowledge of the in vivo flow properties within the human carotid artery. The purpose of this work was to determine the three-dimensional pulsatile velocity profiles of human carotid arteries. Methods: Flow velocities were measured over the cardiac cycle using duplex ultrasonography, before and after endarterectomy, in the surgically exposed common (CCA), internal (ICA), and external (ECA) carotid arteries (n = 16) proximal and distal to the stenosis/endarterectomy zone. These measurements were linked to a standardized grid across the flow lumina of the CCA, ICA, and ECA. The individual velocities were then used to build mean three-dimensional pulsatile velocity profiles for each of the carotid artery branches. Results: Pulsatile velocity profiles in all arteries were asymmetric about the arterial centerline. Posterior velocities were higher than anterior velocities in all arteries. In the CCA and ECA, velocities were higher laterally, while in the ICA, velocities were higher medially. Pre- and postendarterectomy velocity profiles were significantly different. After endarterectomy, velocity values increased in the common and internal and decreased in the external carotid artery. Conclusions: The in vivo hemodynamics of the human carotid artery are different from those used in most current computer-based and in vitro models. The new information on three-dimensional blood velocity profiles can be used to design models that more closely replicate the actual hemodynamic conditions within the carotid bifurcation. Such models can be used to further improve our understanding of the pathophysiologic processes leading to stroke and for the rational design of medical and interventional therapies

A method of assessing peripheral stent abrasiveness under cyclic deformations experienced during limb movement

Poor outcomes of peripheral arterial disease stenting are often attributed to the inability of stents to accommodate the complex biomechanics of the flexed lower limb. Abrasion damage caused by rubbing of the stent against the artery wall during limb movement plays a significant role in reconstruction failure but has not been characterized. Our goals were to develop a method of assessing the abrasiveness of peripheral nitinol stents and apply it to several commercial devices. Misago, AbsolutePro, Innova, Zilver, SmartControl, SmartFlex, and Supera stents were deployed inside electrospun nanofibrillar tubes with femoropopliteal artery-mimicking mechanical properties and subjected to cyclic axial compression (25%), bending (90°), and torsion (26°/cm) equivalent to five life-years of severe limb flexions. Abrasion was assessed using an abrasion damage score (ADS, range 1–7) for each deformation mode. Misago produced the least abrasion and no stent fractures (ADS 3). Innova caused small abrasion under compression and torsion but large damage under bending (ADS 7). Supera performed well under bending and compression but caused damage under torsion (ADS 8). AbsolutePro produced significant abrasion under bending and compression but less damage under torsion (ADS 12). Zilver fractured under all three deformations and severely abraded the tube under bending and compression (ADS 15). SmartControl and SmartFlex fractured under all three deformations and produced significant abrasion due to strut penetration (ADS 20 and 21). ADS strongly correlated with clinical 12- month primary patency and target lesion revascularization rates, and the described method of assessing peripheral stent abrasiveness can guide device selection and development

In situ longitudinal pre-stretch in the human femoropopliteal artery

In situ longitudinal (axial) pre-stretch (LPS) plays a fundamental role in the mechanics of the femoropopliteal artery (FPA). It conserves energy during pulsation and prevents buckling of the artery during limb movement. We investigated how LPS is affected by demographics and risk factors, and how these patient characteristics associate with the structural and physiologic features of the FPA. LPS was measured in n = 148 fresh human FPAs (14–80 years old). Mechanical properties were characterized with biaxial extension and histopathological characteristics were quantified with Verhoeff–Van Gieson Staining. Constitutive modeling was used to calculate physiological stresses and stretches which were then analyzed in the context of demographics, risk factors and structural characteristics. Age had the strongest negative effect (r = −0.812, p \u3c 0.01) on LPS and could alone explain 66% of LPS variability. Male gender, higher body mass index, hypertension, diabetes, coronary artery disease, dyslipidemia and tobacco use had negative effects on LPS, but only the effect of tobacco was not associated with aging. FPAs with less pre-stretch had thicker medial layers, but thinner intramural elastic fibers with less dense and more fragmented external elastic laminae. Elastin degradation was associated with decreased physiological tethering force and longitudinal stress, while circumferential stress remained constant. FPA wall pathology was negatively associated with LPS (r = −0.553, p \u3c 0.01), but the effect was due primarily to aging. LPS in the FPA may serve as an energy reserve for adaptive remodeling. Reduction of LPS due to degradation and fragmentation of intramural longitudinal elastin during aging can be accelerated in tobacco users

In situ longitudinal pre-stretch in the human femoropopliteal artery

In situ longitudinal (axial) pre-stretch (LPS) plays a fundamental role in the mechanics of the femoropopliteal artery (FPA). It conserves energy during pulsation and prevents buckling of the artery during limb movement. We investigated how LPS is affected by demographics and risk factors, and how these patient characteristics associate with the structural and physiologic features of the FPA. LPS was measured in n = 148 fresh human FPAs (14–80 years old). Mechanical properties were characterized with biaxial extension and histopathological characteristics were quantified with Verhoeff–Van Gieson Staining. Constitutive modeling was used to calculate physiological stresses and stretches which were then analyzed in the context of demographics, risk factors and structural characteristics. Age had the strongest negative effect (r = −0.812, p \u3c 0.01) on LPS and could alone explain 66% of LPS variability. Male gender, higher body mass index, hypertension, diabetes, coronary artery disease, dyslipidemia and tobacco use had negative effects on LPS, but only the effect of tobacco was not associated with aging. FPAs with less pre-stretch had thicker medial layers, but thinner intramural elastic fibers with less dense and more fragmented external elastic laminae. Elastin degradation was associated with decreased physiological tethering force and longitudinal stress, while circumferential stress remained constant. FPA wall pathology was negatively associated with LPS (r = −0.553, p \u3c 0.01), but the effect was due primarily to aging. LPS in the FPA may serve as an energy reserve for adaptive remodeling. Reduction of LPS due to degradation and fragmentation of intramural longitudinal elastin during aging can be accelerated in tobacco users

Outcomes of Aortic Surgery for Abdominal Aortic Graft Infections

Background: Literature on postoperative outcomes following aortic surgery for aortic graft infection (AGI) is limited by relatively small sample sizes, resulting in lack of national benchmarks for quality of care. We report in-hospital outcomes following abdominal aortic surgery for AGI and identify factors associated with postoperative complications using the Nationwide Inpatient Sample (NIS) database. Methods: Patients who underwent aortic graft resection for AGI were identified from the 2002 to 2008 NIS database, a multicenter database capturing 20% of all US admissions. Multivariable logistic regression analyses were performed. Results: Among 394 patients (men: 73.4%) who underwent abdominal aortic surgery for AGI, 53% of the admissions were emergent/urgent. A significant trend for decreasing number of abdominal aortic surgery for AGIs per year was observed (Pearson r correlation: -.96; P = .0006). Over the same time span, a significant correlation was also seen with decrease in open and increase in endovascular aortic aneurysm repairs in the NIS database. In-hospital rates of overall postoperative morbidity and mortality were 68.3% and 19.8%, respectively. In-hospital rates of postoperative respiratory failure, renal failure, and cardiac arrest were 35.5%, 14.2%, and 8.9%, respectively. Median length of stay was 26 days, with median hospital charges being US$184 162. On multivariable analysis, increase in age per year (odds ratio [OR] 1.07; 95% confidence interval [CI]: 1.03-1.12) was independently associated with postoperative morbidity, while higher hospital volume for this procedure was protective (OR: 0.71; 95% CI: 0.56-0.89). No preoperative factors were independently associated with postoperative mortality. Conclusion: Incidence of abdominal aortic surgery for AGI has progressively declined over the span of our study in association with decreased open and increased endovascular aortic aneurysm repairs. Aortic surgery for AGI is associated with very high morbidity and mortality rates along with prolonged lengths of stay and elevated hospital charges. The outcomes of operations for AGI are better in younger patients and higher volume hospitals

SS25. Cryopreserved Venous Allograft: An Alternative Conduit for Reconstruction of Infected Prosthetic Aortic Grafts

Olivé Milián, ArmandPla general picat del mosaic format per tres cercles: el central, amb un sol de color ocre sobre un cel blau. El sol, somrient, està encarat cap al sud. Aquest està envoltat d'un primer anell dentat i un segon on s'hi representen les fases d

MODEL-BASED SYSTEMS AND METHODS FOR ANALYZING AND PREDICTING OUTCOMES OF VASCULAR INTERVENTIONS AND RECONSTRUCTIONS

Systems and methods for analyzing and predicting treatment outcomes of medical procedures such as vascular interventions and reconstructions are disclosed. An illustrative system for analyzing and predicting therapeutic outcomes of medical procedures comprises a relational database configured for classifying and storing patient specific input data for multiple patients, a fluid-solid interaction biomechanical model configured for performing a biomechanics simulation and generating biomechanics data, and a graphical user interface