Introduction/purpose Despite significant advances in the recanalization rates of large vessel occlusions, significant challenges remain, with ~25% of occlusions not achieving TICI 2 b-3 reperfusion, or occlusions requiring multiple passes to reopen. Observations from clinical experience can be translated to in-vitro models, where device-clot interactions which are not visible in a clinical setting can be studied. Such models may inform both technology development and technique refinement.

Materials and methods Clots retrieved from patients in known challenging cases were observed macroscopically, and their composition was quantified histologically. This information was used to reverse engineer clot analogues which were then introduced into patient-specific in-vitro neurovascular models which replicated the anatomy of the challenging clinical cases, as well as physiological flow and pressure conditions. Simulated thrombectomies were performed and recorded under high magnification to closely observe the physical interaction between the challenging clot and the device. Specific mechanical properties of the clot analogues were also measured.

Results Reverse engineered clot analogues have been combined with in-vitro vascular models to successfully simulate a number of challenging clinical scenarios, and the behavior observed in-vitro appears to closely replicate that observed clinically. Fibrin rich clot has involved in several of the challenging clinical cases studied by the authors. Clot analogues simulating such thrombi were produced in the laboratory with a low erythrocyte and high fibrin content. Physical properties of the resultant clots were studied, and higher than normal frictional characteristics were observed. Analysis of in-vitro thrombectomy procedures with these clots showed a number of mechanisms at play, with the frictional properties of the clot having a significant impact on the ability (or number of passes required) to successfully recanalise the occluded vessel. The observed clot/device/vessel interaction and consequent clot retrieval outcomes appeared to closely match the recorded details of the clinical cases in question.

Conclusion In-vitro modelling may provide valuable insights into the mechanisms behind failed and challenging thrombectomy cases. The direct visualization of device-clot interaction that is possible in a transparent in-silico model allows a thrombectomy procedure to be witnessed in a different way than is possible in-vivo. Reverse engineering of retrieved clots to generate realistic clot analogues can help to enhance the clinical relevance of these in-vitro models. Better understanding of the detailed mechanisms of action in mechanical thrombectomy procedures may help in the optimization of procedural techniques as well as the design of improved devices.

Disclosures M. Gilvarry: 5; C; Neuravi Ltd. D. Vale: 5; C; Neuravi Ltd.