Search results for "FAILURE"
showing 10 items of 1977 documents
Fresh Human Orthotopic Ovarian Cortex Transplantation: Long-term Results
2006
An increasing number of young women are being diagnosed with cancer, and most cancer treatments have irreversibly negative effects on reproduction. Ovarian stimulation and preservation of oocytes or embryos is far from an ideal solution, in part because hormonal treatment may adversely affect some cancers. Another possibility is cryopreservation of ovarian tissue for later autotransplantation, but the ischemic damage caused by the procedure can lead to follicle loss. Using the ovarian medulla for orthotopic ovarian cortex transplantation might limit the risk of ischemia because the ovarian artery would assure a good blood supply. In addition, the medulla may have a role in follicular develo…
Computer Modeling for the Prediction of Thoracic Aortic Stent Graft Collapse
2011
OBJECTIVE: To assess the biomechanical implications of excessive stent protrusion into the aortic arch in relation to thoracic aortic stent graft (TASG) collapse by simulating the structural load and quantifying the fluid dynamics on the TASG wall protrusion extended into a model arch. METHODS: One-way coupled fluid-solid interaction analyses were performed to investigate the flow-induced hemodynamic and structural loads exerted on the proximal protrusion of the TASG and aortic wall reconstructed from a patient who underwent traumatic thoracic aortic injury repair. Mechanical properties of a Gore TAG thoracic endoprosthesis (W. L. Gore and Assoc, Flagstaff, Ariz) were assessed via experimen…
An In Vitro Phantom Study on the Role of the Bird-Beak Configuration in Endograft Infolding in the Aortic Arch.
2015
Purpose: To assess endograft infolding for excessive bird-beak configurations in the aortic arch in relation to hemodynamic variables by quantifying device displacement and rotation of oversized stent-grafts deployed in a phantom model. Methods: A patient-specific, compliant, phantom pulsatile flow model was reconstructed from a patient who presented with collapse of a Gore TAG thoracic endoprosthesis. Device infolding was measured under different flow and pressure conditions for 3 protrusion extensions (13, 19, and 24 mm) of the bird-beak configuration resulting from 2 TAG endografts with oversizing of 11% and 45%, respectively. Results: The bird-beak configuration with the greatest protr…
Framework for Fluid-Structure Interaction Analysis of Aortic Coarctation Resulting From Proximal Protusion of Thoracic Aortic Stent Graft Into the Ar…
2011
Thoracic aortic stent grafts (TASG) are commonly used to repair aortic anomalies or diseases in a minimally-invasive fashion. One complication of TASG is collapse, whereby blood is unable to completely flow through the graft as intended. Most TASG collapses occur in the setting of endovascular repair of traumatic thoracic aortic transection, where a typically smaller diameter aorta of pediatric patients is repaired with a relatively larger diameter endograft designed to treat aneurysmal disease [1]. It is hypothesized that the poor apposition of the leading edge of the proximal stent graft to the lesser curvature of the aortic arch can result increased hemodynamic force at the leading side …
Comparison of hemodynamic and structural indices of ascending thoracic aortic aneurysm as predicted by 2-way FSI, CFD rigid wall simulation and patie…
2018
Patient-specific computational modeling is increasingly being used to predict structural and hemodynamic parameters, especially when current clinical tools are not accessible. Indeed, pathophysiology of ascending thoracic aortic aneurysm (ATAA) has been simulated to quantify the risk of complications by novel prognostic parameters and thus to improve the clinical decision-making process related to the intervention of ATAAs. In this study, the relevance of aneurysmal wall elasticity in determining parameters of clinical importance, such as the wall shear stress (WSS), is discussed together with the significance of applying realistic boundary conditions to consider the aortic stretch and twis…
Regurgitant flow in apparently normal valve prostheses: improved detection and semiquantitative analysis by transesophageal two-dimensional color-cod…
1990
In 128 patients with apparently normally functioning prosthetic valves ( n = 136) in the aortic position ( n = 79) and the mitral position ( n = 57), the prevalence of transprosthetic regurgitant flow was studied by use of transthoracic and transesophageal two-dimensional color-coded Doppler echocardiography. With the transthoracic approach, regurgitant flow was detected in early systole or diastole for 28% of the mitral prostheses and for 29% of the aortic prostheses. With transesophageal color-coded Doppler echocardiography, regurgitant jets were visualized for 95% of the mitral prostheses and for 44% of the aortic prostheses. In 40% of the Bjork-Shiley prostheses and 88% of the St. Jude …
Constitutive modeling of ascending thoracic aortic aneurysms using microstructural parameters.
2016
Ascending thoracic aortic aneurysm (ATAA) has been associated with diminished biomechanical strength and disruption in the collagen fiber microarchitecture. Additionally, the congenital bicuspid aortic valve (BAV) leads to a distinct extracellular matrix structure that may be related to ATAA development at an earlier age than degenerative aneurysms arising in patients with the morphological normal tricuspid aortic valve (TAV). The purpose of this study was to model the fiber-reinforced mechanical response of ATAA specimens from patients with either BAV or TAV. This was achieved by combining image-analysis derived parameters of collagen fiber dispersion and alignment with tensile testing dat…
ON THE EFFECTS OF A CRACK PROPAGATING TOWARD THE INTERFACE OF A BIMATERIAL SYSTEM
2006
This paper deals with the influence of matrix cracks on the failure mode of bimaterial systems and composite materials. In order to investigate such an influence, the stress field near a crack embedded into the more yielding material and propagating perpendicularly to the interface, has been analyzed by using systematic numerical simulations. Such analysis has shown that the crack propagation give rises to transversal stresses that can damage the reinforcing materials when this has low modulus, as glass fibers, or low transversal strength, such as carbon fibers. Moreover, the longitudinal stress concentration can damage the reinforcing material only if this has high stiffness, as in the cas…
Arterial hypertension in cancer: The elephant in the room
2019
The great therapeutical success achieved by oncology is counterbalanced by growing evidences of cardiovascular (CV) toxicity due to many antineoplastic treatments. Cardiac adverse events may cause premature discontinuation of effective oncologic treatments or occur as late events undermining the oncologic success. Arterial hypertension is both the most common comorbidity in cancer patients and a frequent adverse effect of anticancer therapies. A pre-existing hypertension is known to increase the risk of other cardiac adverse events due to oncologic treatments, in particular heart failure. Moreover, as a strict association between cancer and CV diseases has emerged over the recent years, var…
A refugee newborn with heart failure and initial hydrops: Diagnostic clues of spectral Doppler examinations
2022
A newnborn admitted to NICU showed a severe clinical profile