Experimental Models of Vascular Occlusions for Evaluation of Thrombectomy Devices

Abstract

Stroke attributed to a large vessel occlusion is a multi-factorial disease and it has to be understood that one model does not exactly reproduce all the facets of ischemic stroke in humans. In this paper, we review currently available vascular occlusion models used for the assessment of thrombectomy devices. Vascular occlusions are often created in animal models such as rats, mice, rabbits, canine, swine and sheep. Depending on the source of the occlusion, two subtypes of vascular occlusion, thrombotic and embolic, are simulated in the aforesaid animal models. Embolic occlusion may also be reproduced in-vitro by injecting a clot into the vascular replica. In-vitro models are capable of simulating precisely human cerebrovascular anatomy and hemodynamics. Quantitative measurements, such as size and number of disrupted clots produced during the procedure, can be obtained in the in-vitro studies. Due to the small vessel size, occlusions created in rodents are not suitable for evaluation of thrombectomy devices. It is not feasible to create a focal intracranial vascular occlusion in the anterior circulation of sheep and swine amenable to thrombectomy due to the rete mirabile. An alternative is thrombectomy device testing in non-human primates, the posterior circulation of the dog, and extracranial circulation of the pig. Although the role of stroke models is not to perfectly mimic a human stroke with all its characteristics, choosing an appropriate model enables us to answer the unsolved questions in an objective manner.