Alexander D. Kaiser is an applied mathematician who researches modeling and simulation of heart mechanics. His doctoral work focused on the mitral valve. He currently works in the Stanford Cardiovascular Biomechanics Computation Laboratory, led by Alison Marsden, on modeling cardiac disease.
Honors & Awards
Mechanisms and Innovation in Cardiovascular Disease T32 training grant, Cardiovascular Institute, Stanford University (6/2018)
Kurt O. Friedrichs Prize for Outstanding Dissertation in Mathematics, Courant Institute of Mathematical Sciences, New York University (4/2018)
Thomas Tyler Bringley Fellowship, Courant Institute of Mathematical Sciences, New York University (4/2016)
Math Master’s Thesis Prize, Courant Institute of Mathematical Sciences, New York University (4/2014)
NSF Graduate Research Fellowship, National Science Foundation (4/2013)
Boards, Advisory Committees, Professional Organizations
Postdoctoral scholar, Institute for Computational & Mathematical Engineering, Stanford University (2018 - Present)
Postdoctoral scholar, Cardiovascular Institute, Stanford University (2018 - Present)
Doctor of Philosophy, New York University, Mathematics (2017)
Master of Science, New York University, Mathematics (2013)
Bachelor of Arts, University of California, Berkeley, Mathematics (2009)
Use of patient-specific computational models for optimization of aortic insufficiency after implantation of left ventricular assist device.
The Journal of thoracic and cardiovascular surgery
Aortic incompetence (AI) is observed to be accelerated in the continuous-flow left ventricular assist device (LVAD) population and is related to increased mortality. Using computational fluid dynamics (CFD), we investigated the hemodynamic conditions related to the orientation of the LVAD outflow in these patients.We identified 10 patients with new aortic regurgitation, and 20 who did not, after LVAD implantation between 2009 and 2018. Three-dimensional models of patients' aortas were created from their computed tomography scans. The geometry of the LVAD outflow graft in relation to the aorta was quantified using azimuth angles (AA), polar angles (PAs), and distance from aortic root. The models were used to run CFD simulations, which calculated the pressures and wall shear stress (rWSS) exerted on the aortic root.The AA and PA were found to be similar. However, for combinations of high values of AA and low values of PA, there were no patients with AI. The distance from aortic root to the outflow graft was also smaller in patients who developed AI (3.39 ± 0.7 vs 4.07 ± 0.77 cm, P = .04). There was no significant difference in aortic root pressures in the 2 groups. The rWSS was greater in AI patients (4.60 ± 5.70 vs 2.37 ± 1.20 dyne/cm2, P < .001). Qualitatively, we observed a trend of greater perturbations, regions of high rWSS, and flow eddies in the AI group.Using CFD simulations, we demonstrated that patients who developed de novo AI have greater rWSS at the aortic root, and their outflow grafts were placed closer to the aortic roots than those patients without de novo AI.
View details for DOI 10.1016/j.jtcvs.2020.04.164
View details for PubMedID 32653292
Modeling the mitral valve.
International journal for numerical methods in biomedical engineering
This work is concerned with modeling and simulation of the mitral valve, one of the four valves in the human heart. The valve is composed of leaflets, the free edges of which are supported by a system of chordae, which themselves are anchored to the papillary muscles inside the left ventricle. First, we examine valve anatomy and present the results of original dissections. These display the gross anatomy and information on fiber structure of the mitral valve. Next, we build a model valve following a design-based methodology, meaning that we derive the model geometry and the forces that are needed to support a given load, and construct the model accordingly. We incorporate information from the dissections to specify the fiber topology of this model. We assume the valve achieves mechanical equilibrium while supporting a static pressure load. The solution to the resulting differential equations determines the pressurized configuration of the valve model. To complete the model we then specify a constitutive law based on a stress-strain relation consistent with experimental data that achieves the necessary forces computed in previous steps. Finally, using the immersed boundary method, we simulate the model valve in fluid in a computer test chamber. The model opens easily and closes without leak when driven by physiological pressures over multiple beats. Further, its closure is robust to driving pressures that lack atrial systole or are much lower or higher than normal.
View details for DOI 10.1002/cnm.3240
View details for PubMedID 31330567