Conferencias y Seminarios

Abstract: Mechanical circulatory support (MCS) devices provide both short and long term hemodynamic support for advanced heart failure patients. Unfortunately these devices remain plagued by thromboembolic complications associated with chronic platelet activation – mandating complex, lifelong anticoagulation therapy. To address the unmet need for enhancing the thromboresistance of these devices to extend their long term use, we developed a universal predictive methodology entitled Device Thrombogenicity Emulation (DTE) that facilitates optimizing the thrombogenic performance of any MCS device – ideally to a level that may obviate the need for mandatory anticoagulation. DTE combines in silico numerical simulations with in vitro measurements by correlating device hemodynamics with platelet activity coagulation markers – before and after iterative design modifications aimed at achieving optimized thrombogenic performance. The application of this breakthrough optimization methodology is demonstrated in Mechanical Heart Valves and in by comparing two rotary Left Ventricular Assist Devices (LVAD) (DeBakey vs Heart Assist V, Micromed Houston, TX), the latter a version of the former- following optimization of geometrical features implicated in device thrombogenicity. Cumulative stresses that may drive platelets beyond their activation threshold were calculated along multiple flow trajectories – collapsed into probability density functions (PDFs) representing the device ‘thrombogenic footprint’, indicate significantly reduced thrombogenicity for the optimized design. Platelet activity measurements performed in the actual pump prototypes operating under clinical conditions in circulation flow loops - before and after the optimization with the DTE methodology, show an order of magnitude lower platelet activity rate for the optimized device. The robust capability of this predictive technology – demonstrated here for attaining safe and cost-effective pre-clinical MCS thrombo-optimization, indicates its potential for reducing device thrombogenicity to a level that may liberate their recipients from anticoagulation.
Another study is aimed at enhancing cardiovascular disease diagnostics using patient specific numerical modeling and biomechanical analysis approach. Patient specific FSI simulations were conducted in vulnerable plaque- a pathology that prompts strokes and fatal heart attacks (sudden cardiac death) in geometries retrieved from patients with Intravascular Ultrasound (IVUS), and in abdominal aortic aneurysms (AAA) reconstructed from patients CT images, in order to predict plaque vulnerability and AAA risk of rupture. For the vulnerable plaque the analysis indicates regions where a combination of elevated strains in the vessel wall and shear stresses induced by the flow, combined with stresses that develop withing the fibrous cap, enhance the plaque vulnerability and may lead to rapid thrombus formation. The role of calcification in the plaque was examined, indicating that it significantly increases the plaque vulnerability. For the AAA, the role of intraluminal (ILT) thrombus in the AAA and calcifications was examined and used to predict potential rupture locations, using anisotropic (orthotropic) material models derived from experimental data. The rupture prediction capabilities were validated by reconstructing specific ruptured AAAs cases, demonstrating that our models can predict the AAA rupture location Abstract: Recently, there is an increased interest in numerical methods which make use of tensors. In particular, for high spatial dimensions one must take care that the numerical cost (in time and storage) is linear in the space dimension and does not increase exponentially. Even for three spatial dimensions, these methods can be implied with great success.
In the present work we introduce the minimal subspaces for Topological Tensor Product Spaces in order to develop numerical algorithms for solving problems in high-dimensions.
It is a joint work with Wolfgang Hackbush.