Four panels showing removal of clots from blood vessels

The Science of Mechanical Thrombectomy: Biomechanics, Test Models and New Platform Technology

Endovascular removal of emboli causing large vessel occlusion (LVO) stroke is a new standard of care. Despite high recanalization rates (~85%), 40% of stroke patients still experience poor neurological outcomes as many cannot be fully recanalized after the first attempt. The development of new endovascular technologies and techniques for mechanical thrombectomy requires more-sophisticated testing platforms that overcome the limitations of phantom-based simulators. To this end, in our laboratory we have:

  • Conducted mechanistic research to understand the forces driving the complex mechanical interaction between embolic material and current stroke thrombectomy devices by analyzing the histological composition and strength of emboli retrieved from patients and evaluating the mechanical forces necessary for retrieval of such emboli in a middle cerebral artery bifurcation model
  • Generated a library of histologically and mechanically validated emboli analogs derived from human blood to match emboli causing large vessel occlusion strokes
  • Developed a test bed for embolic occlusion of cerebrovascular arteries and mechanical thrombectomy with 3D-printed and commercially available cerebrovascular phantoms, a customized hydraulic system to generate physiological flow rate and pressure, and embolus analogs capable of causing embolic occlusions under physiological flow
  • Constructed the first-in-kind test bed for embolic occlusion of cerebrovascular arteries and mechanical thrombectomy with cadaveric human brains
  • Presented the first-in-kind cadaveric human head and neck model pressurized under physiological conditions to mimic the cerebrovascular conditions encountered in patients.

These models have been instrumental in the iterative design process of endovascular technologies invented in the lab, and equally importantly, they have facilitated engagement with industry for preclinical testing of their technologies. These academic-industry partnerships have been instrumental in keeping the Translational Neurosurgery and Biotechnology Lab at the forefront of medical innovation.

Leveraging the new knowledge about biomechanics in large vessel occlusion (LVO) stroke and the testing platforms, the team has developed an entirely new class of thrombectomy system that ingests emboli by the generation of a unique and powerful whirlpool. We conducted preliminary computational simulations, prototyping and bench testing of this new device that suggested that this disruptive mechanism could be translated into a new-generation, low-profile and atraumatic thrombectomy technology. Then, employing the multiple preclinical testing platforms developed in-house including phantoms, human cadaveric models and in vivo translational animal models, we showed that this device had extensive superiority in safety and efficacy compared with commercially available technologies.

This awarded platform technology, protected by multiple granted patents and several more in the pipeline, was licensed to Endovascular Engineering Inc., and it is expected to be used in patients by the end of 2021. Additionally, many other technologies are currently under development in our lab.

Related publications

Gebrezgiabhier D, Liu Y, Reddy AS, Davis E, Zheng Y, Arturo Larco JL, Shih AJ, Pandey AS, Savastano LE. A human brain test bed for research in large vessel occlusion stroke. Journal of Neurosurgery. 2021; doi:10.3171/2020.7.JNS202278.

Liu Y, Reddy A, Cockrum J, Ajulufoh MC, Zheng Y, Shih AS, Pandey AS, Savastano LE. Standardized fabrication method of human-derived emboli with histologic and mechanical quantification for stroke research. Journal of Stroke and Cerebrovascular Diseases. 2020; doi:10.1016/j.jstrokecerebrovasdis.2020.105205.

Reddy A, Liu Y, Cockrum J, Gebrezgiabhier D, Davis E, Zheng Y, Pandey AS, Shih AJ, Savastano LE. Construction of a comprehensive endovascular test bed for research and device development in mechanical thrombectomy in stroke. Journal of Neurosurgery 2021; doi:10.3171/2020.1.JNS192732.

Liu Y, Zheng Y, Reddy AS, Gebrezgiabhier D, Davis E, Cockrum J, Gemmete JJ, Chaudhary N, Griauzde JM, Pandey AS, Shih AJ, Savastano LE. Analysis of human emboli and thrombectomy forces in large-vessel occlusion stroke. Journal of Neurosurgery. 2021; doi:10.3171/2019.12.JNS192187.

Liu Y, Zheng Y, Li ADR, Liu Y, Savastano LE, Shih AJ. Cutting of blood clots — Experiment and smooth particle Galerkin modelling. CIRP Annals. 2019; doi:10.1016/j.cirp.2019.04.025.

Stroke technology wins 2019 biomedical innovation cup. Michigan Medicine News. 2019;

Cision PR Newswire. Clot buster wins the 35th annual Pryor-Hale Award at the Michigan Business Challenge. 2018;