Browsing by Subject "Artery"
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Item CAROTID ARTERY ELASTICITY: Describing Elasticity in Healthy Children and Adults, and the Use of Atorvastatin to Modulate Elasticity in Adult Survivors of Childhood Cancer(2015-06) Marlatt, KaraCarotid artery elasticity has become a commonly assessed non-invasive marker of arterial health that is relatively easy to administer. Indeed, the loss of elastic properties within the larger and more elastic arteries like the carotid artery contributes substantially to the increase in systolic blood pressure as well as pulse pressure, which are known independent risk factors for the development of cardiovascular disease (CVD). Such risk factors can lead to compensatory remodeling of the carotid artery and nearby arterial beds, as well as create synergistic detriments to the arterial tree in the presence of other risk independent risk factors. Decreased carotid arterial elasticity and increased stiffness has been reported with advanced aging in both men and women; however, little research has examined artery elasticity measures by sex in otherwise healthy young adults, as well as children and adolescents. The purpose of the following dissertation was to examine the potential influences of sex, pubertal development, and age, on measures of carotid arterial elasticity in otherwise healthy children, adolescents, and adults, to lend further insight to the already existing body of research surrounding arterial elasticity and stiffness. Additionally, a separate study was further employed using HMG coenzyme A reductase inhibitors, or statins, to assess whether individuals at increased risk of CVD like childhood cancer survivors could potentially benefit from the known therapeutic effects of statins and subsequently improve carotid artery elasticity and stiffness. Given vascular dysfunction is considered an early manifestation of atherosclerosis, potential therapeutic remedies that dampen cardiovascular risk in populations that are at increased risk for vascular dysfunction are critical to explore.Item Experimental and Computational Mechanics of Arteries in Health and Disease: An Exploration of Complex Structures and Simple Mathematical Models(2021-05) Mahutga, RyanAortic aneurysm, or dilatation of the aorta, is a clinically significant pathology as the risk of potentially fatal rupture (through-thickness failure) or dissection (delamination of the layers) is the fifteenth leading cause of death in the U.S. [1], with just under 10,000 deaths occurring in 2017 [2]. Current diagnostics for assessing aneurysm risk are aortic size and growth rate [1, 3]. These criteria correlate with aneurysm risk but are not direct measures of tissue strength. These criteria are especially inadequate for rare disorders involving genetic anomalies, where population sizes are relatively small and disease severity can vary widely between individuals. Therefore, it is important that we recognize and understand the underlying pathology that makes one aneurysm different from another, especially in terms of mechanics as this is what dictates aneurysm rupture risk. In this thesis I explore several testing methods for assessing aortic properties in animal models of health and disease. I evaluate the simple ring pull test as a high-throughput mechanical testbed for circumferential mechanics and explore the use of ultrasound for the assessment of complex aortic structures including vessel bifurcations and the aortic arch. These techniques offer unique insights as screening tools for understanding mechanics and for evaluating therapeutics. In order to further understand how the different mechanics in healthy and diseased tissues arise, I created a novel micromechanical model of pathophysiologic remodeling. Using this model, I was able to show pathological differences in mechanical properties despite similar clinical growth parameters. I further developed a technique to model more complex geometries using a multiscale coupling to finite element models. These methods create a unique and useful tool for evaluating remodeling with complex geometries utilizing complex microstructural remodeling scenarios leading to improved understanding of the mechanics of healthy and diseased tissues, as well as being a convenient way to assess tissue-engineered therapies.Item Utility of the Visible Heart® and Micro-CT Imaging to Optimize the Treatments of Bifurcation Stenting(2021-05) Valenzuela, ThomasUsing the Visible Heart® Apparatus and methodologies allows for the ability to reanimate large mammalian hearts, including human, and thus to perform bifurcation stenting in an in vitro setting. This allows for novel uses of multimodal imaging for assessing/testing previous, current and future clinical recommendations for bifurcation techniques, without risking a living patient. After performing such procedures, high resolution 3D models were obtained via micro-CT imaging, which then allows for post implant device/tissue interface analyses. Utilizing reanimated swine hearts, we were able to uniquely visualize how the various bifurcation techniques performed could be optimized in specific anatomies. These findings again confirm that the Visible Heart® Apparatus is a valuable platform that should be used to further understand how next generation stents and/or bifurcation techniques can best be utilized. Recently, our laboratory also had the privilege to perform bifurcation stenting within three reanimated human hearts using the same methodologies. Additionally, similar PCI procedures were performed in three perfusion-fixed human hearts as further means to compare the differences in stenting technique and to identify potential differences between procedures performed in fixed versus reanimated human hearts. Also, it was identified that after the formalin fixation process, desecrations of the coronary vessels could readily be induced in healthy human hearts, while those presenting with coronary artery disease elicited little to no effects due to the plaque formations. If this holds true, this will open the Visible Heart® Laboratories’ human heart library of over 580 specimens, to perform clinically relevant bifurcation stenting techniques. Finally, a novel research method of detecting stent malappositions was created, as the current standard for intracoronary imaging, optical coherence tomography (OCT), has its limitations when there are multiple stents implanted. This method was then used alongside OCT in a step-by -step bifurcation intervention performed in a formalin fixed human heart. It was shown that stent apposition continuously improves if the operator adheres to the latest published guidelines; however future investigations should be performed in more diseased human hearts from the Visible Heart’s human heart library to focus on other bifurcation techniques and the consequences of straying from these guidelines in each case.