Introduction Advances in pump design make aspiration patterns programmable, producing an infinite combination of cyclical aspiration profiles for clot removal during treatment of acute ischemic stroke (AIS). However, little is known about how clots respond to different aspiration patterns. The goal of this study is to assess the structural and mechanical changes of the clot under aspiration. It is our hypothesis that a decreased fibrin pore size correlates to a higher aspiration efficacy.
Materials and methods A fibrin-rich bovine clot was used to create an MCA occlusion in a patient-specific silicone model and underwent thromboaspiration via a 6F Sofia Plus catheter (MicroVention, Tustin, CA). Three sets of the retrieved clots were prepared for scanning electron microscopy (SEM) analysis, including clots lodged at the MCA without aspiration (control) as well as clots subjected to static (28 mmHg) or cyclic aspiration (amplitude: 18 to 27 mmHg) for 2 minutes (CLEARTM Aspiration System, Insera Therapeutics, LLC, Sacramento, CA). All the clot samples were fixed, dehydrated and frozen fractured. Surfaces of the fractured clots were imaged at 20 Kx at four different locations to obtain pore-size estimates of fibrin networks using ImageJ. Dynamic mechanical analysis (DMA) was conducted to understand the viscoelastic behavior of the clots obtained from patients with AIS under cyclic loading conditions.
Results The fibrin-rich clot was corked in the distal tip of the aspiration catheter during clot retrieval. The average clot diameter measured proximally was 3.5 mm, 2.3 mm and 1.8 mm for the control, static and cyclic groups, respectively. Mechanical loading-unloading-reloading on the clot resulted in clot deformations; however, the changes in the clot dimension were less pronounced as the mechanical stimulus continued during the DMA tests. Clot deformation during aspiration was accompanied by a reduction in the average pore size in the fibrin-rich clot. The figure 1 demonstrates that the fibrin pore size measured from the proximal end of the clot was significantly reduced after aspiration when compared to the control clot (control: 857µm2, cyclic: 434µm2, static: 420 µm2). No significant differences in fibrin pore size were observed between the cyclic and static groups; however, it should be noted that the smallest pore size measurement was found in the cyclic group.
Conclusion Applying cyclic or static aspiration to the fibrin-rich clot forms a denser fibrin mesh and results in clot stiffening. A comprehensive study is ongoing to study the structural changes of different clot models under aspiration at various frequencies and amplitudes.
Disclosures M. Marosfoi: 2; C; Stryker Neurovascular and InNeuroCo Inc. L. Strittmatter: None. R. Arslanian: None. C. Raskett: None. M. Gounis: 1; C; the National Institutes of Health, Israel Binational Science Foundation, Anaconda, Cerenovus, Cook Medical, Gentuity, Imperative Care, InNeuroCo, Magneto, Microvention, Medtronic Neurovascular, MIVI Neurosciences, Neuravi, Neurogami, Philips Healthcare, Rapid Medical, Route 92 Medical, Stryker Neurovascular, Syntheon, and the Wyss Institute. 2; C; Cerenovus, Imperative Care, MIVI Neurosciences, phenox, Route 92 Medical, Stryker Neurovascular. 4; C; Imperative Care and Neurogami. A. Puri: 1; C; Medtronic Neurovascular and Stryker Neurovascular. 2; C; Medtronic Neurovascular and Stryker Neurovascular. F. Massari: None. K. De Macedo Rodrigues: None. J. Singh: None. J. Chueh: 2; C; Stryker Neurovascular and InNeuroCo Inc.
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