The human aorta is susceptible to both atherosclerotic plaque deposition and aneurysmal enlargement. While the specific causal mechanisms are unclear, biomechanical factors are thought to play an important role, particularly in the differing susceptibility of the thoracic and abdominal aorta to these degenerative changes. We developed a non-invasive magnetic resonance method to quantify aortic wall biomechanics in vivo and found that aortic wall motion and strain vary around the aortic circumference with significant local variation in aortic structure. This is consistent with clinical observations of eccentric plaque localization and focal aneurysm formation. Furthermore, aortic biomechanics are impacted by implanted endovascular devices such as stents and stent grafts which are used to treat occlusive disease and aneurysms of the aorta with unknown long term consequences. During this grant, we will relate varying aortic strain patterns measured in vivo to the 3-dimensional microarchitecture of normal porcine aortas. We will then implant endovascular aortic stents and stent grafts in experimental animals to modify aortic wall biomechanics. We will assess the acute and chronic impact on in vivo aortic wall biomechanics and long-term changes in aortic microstructure. We will utilize the same in vivo magnetic resonance imaging technique to assess aortic wall motion and cyclic strain in humans and quantitate the differences about the circumference and along the length of the aorta. We will study both young and elderly healthy volunteers in order to discern age and gender related differences in aortic wall biomechanics. These data will provide valuable insights into our understanding of the structure and compostition of the aorta in relation to biomechanical strain and will provide a means of assessing the impact on the aortic wall of interventional treatments using implanted aortic devices. Further, these studies will provide a framework to understand normal age-related and degenerative changes affecting the human aorta. Finally, it will provide a quantitative basis for application of aortic magnetic resonance imaging in larger human clinical trials involving patients with aneurysmal or occlusive disease of the aorta, both before and after endovascular treatment.
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