Computational study of aortic hemodynamics: From simplified to patient-specific geometries

The investigation of aortic hemodynamics in physiological and pathological conditions by computational fluid dynamics is still one of the major topic of vascular biomechanics. In particular,thanks to the developments of new endovascular technologies such as Thoracic EndoVAscular Repair (TEVAR),a lot of attention is paid to the hemodynamics analysis of thoracic aorta. In this work,we aim at performing a sensitivity analysis of morphological aspects by comparing numerical results about three cases: (i) an idealized aortic arch with a candy cane shape; (ii) a patient-specific healthy arch; and (iii) a patient-specific dissected aorta. For the idealized aortic arch case we also compare the obtained results with respect to the theoretical and experimental literature dedicated to curved pipes

Computational methods in cardiovascular mechanics

The introduction of computational models in cardiovascular sciences has been progressively bringing new and unique tools for the investigation of the physiopathology. Together with the dramatic improvement of imaging and measuring devices on one side, and of computational architectures on the other one, mathematical and numerical models have provided a new, clearly noninvasive, approach for understanding not only basic mechanisms but also patient-specific conditions, and for supporting the design and the development of new therapeutic options. The terminology in silico is, nowadays, commonly accepted for indicating this new source of knowledge added to traditional in vitro and in vivo investigations. The advantages of in silico methodologies are basically the low cost in terms of infrastructures and facilities, the reduced invasiveness and, in general, the intrinsic predictive capabilities based on the use of mathematical models. The disadvantages are generally identified in the distance between the real cases and their virtual counterpart required by the conceptual modeling that can be detrimental for the reliability of numerical simulation

Benchmarking a hemodynamics application on Intel based HPC systems

Three different INTEL based HPC systems are used to benchmark an application of the LifeV library for running simulations of patient-specific cardiovascular hemodynamics. The targeted INTEL architectures rely on the Hashwell-Broadwell family of processors. Running times and scalability measures are collected with two real-size experiments. A third small-size test case is used to profile the code, exposing the effect of compiler vectorization, MPI efficiency and memory footprint. Profiling showed an unexpected low degree of floating point functional units usage, and a low percentage of effective vectorization. Extensive code redesign is likely necessary to best exploit the architectural features available in INTEL Knight Landing processors

Aortic hemodynamics after thoracic endovascular aortic repair, with particular attention to the bird-beak configuration

Purpose: To quantitatively evaluate the impact of thoracic endovascular aortic repair (TEVAR) on aortic hemodynamics, focusing on the implications of a bird-beak configuration. Methods: Pre- and postoperative CTA images from a patient treated with TEVAR for post-dissecting thoracic aortic aneurysm were used to evaluate the anatomical changes induced by the stent-graft and to generate the computational network essential for computational fluid dynamics (CFD) analysis. These analyses focused on the bird-beak configuration, flow distribution into the supra-aortic branches, and narrowing of the distal descending thoracic aorta. Three different CFD analyses (A: preoperative lumen, B: postoperative lumen, and C: postoperative lumen computed without stenosis) were compared at 3 time points during the cardiac cycle (maximum acceleration of blood flow, systolic peak, and maximum deceleration of blood flow). Results: Postoperatively, disturbance of flow was reduced at the bird-beak location due to boundary conditions and change of geometry after TEVAR. Stent-graft protrusion with partial coverage of the origin of the left subclavian artery produced a disturbance of flow in this vessel. Strong velocity increase and flow disturbance were found at the aortic narrowing in the descending thoracic aorta when comparing B and C, while no effect was seen on aortic arch hemodynamics. Conclusion: CFD may help physicians to understand aortic hemodynamic changes after TEVAR, including the change in aortic arch geometry, the effects of a bird-beak configuration, the supra-aortic flow distribution, and the aortic true lumen dynamics. This study is the first step in establishing a computational framework that, when completed with patient-specific data, will allow us to study thoracic aortic pathologies and their endovascular management