Mechanical Characterization of Thromboemboli in Acute Ischemic Stroke and Laboratory Embolus Analogs

A 65-year-old man (patient 5) presents with an AIS due to MCA occlusion and associated right ICA origin segmental stenosis (>90%) with intraluminal clot (A, arrow). The clot (B) is removed by using the aspiration device for characterization. A 53-year-old man (patient 11) with transient ischemic attacks has a clot located at the carotid bifurcation (C). After CEA, red thrombus (D) is collected for mechanical and structural analyses.

Morphologic features and composition of a variety of emboli from patients. A, Calcified embolus calcium-phosphate apatite is detected by the EDS scan (inset). B, An aged embolus has a compact structure with fissures that were occupied by the cholesterol crystals (arrows) and fibrin at the edge of the specimen (star). The SEM findings are related to the MSB result (×20; bar = 100 μm) shown in C. D, MSB results show that a red embolus is mainly composed of fibrin and erythrocytes (old fibrin in blue, erythrocytes in yellow, and erythrocyte-fibrin mixture in red) (×2, bar = 1 mm). E, Photomicrograph of a red embolus retrieved from the stroke patient (H&E ×10, bar = 200 μm) reveals that the leukocytes are distributed throughout the embolus. F, At ×10 magnification, erythrocytes and fibrin strands are arranged in a layer-by-layer manner in the red embolus (MSB, bar = 200 μm).

The engineering S-S curves show that at the end of the test, a 15-N force causes a 45.7% strain to a highly calcified embolus (black solid line) and a 64.4% strain to a partially calcified embolus (black dashed line). The same compression force results in a higher strain (>80%) on the other emboli.

A, Comparisons of thromboemboli from CEA and AIS in terms of E_0%–75% and E_75%–95%. Large variations are observed in the CEA groups. B, Strain recovery and length change of one of the thromboemboli during the stress relaxation test. The specimen has an initial length of 1.5 mm and was compressed to 60% strain for 5 minutes. Increases in length and strain recovery are seen after the load is removed.

A, A layer of fibrin is formed on the surface of the thrombin-induced bovine EA against the silicone tubing (star). MSB staining, bar = 10 μm. B, EA has a homogeneous structure, and is mainly composed of erythrocytes (shown in yellow) with fibrin clumps dispersed in it (arrows, bar = 10 μm). The corresponding SEM findings are presented in C (×5000) and D (×1000), respectively. E, Secondary electron image of the bovine EA with barium sulfate (×20 000). F, Mixed secondary and backscattered electron image of barium sulfate agglomerates (×20 000).