Adapa, Arjun R.

Abstract BACKGROUND Appropriate thrombus-device interaction is critical for recanalization. Histology can serve as a proxy for mechanical properties, and thus inform technique selection. OBJECTIVE To investigate the value of histologic characterization, we conducted a systematic review and meta-analysis on the relationship between thrombus histology and recanalization, technique, etiology, procedural efficiency, and imaging findings. METHODS In this meta-analysis, we identified studies published between March 2010 and March 2020 reporting findings related to the histologic composition of thrombi in large vessel occlusion stroke. Studies with at least 10 patients who underwent mechanical thrombectomy using stent retriever or aspiration were considered. Only studies in which retrieved thrombi were histologically processed were included. Patient-level data were requested when data could not be directly extracted. The primary outcome assessed was the relationship between thrombus histology and angiographic outcome. RESULTS A total of 22 studies encompassing 1623 patients met inclusion criteria. Clots associated with good angiographic outcome had higher red blood cell (RBC) content (mean difference [MD] 9.60%, 95% CI 3.85-15.34, P = .008). Thrombi retrieved by aspiration had less fibrin (MD −11.39, 95% CI −22.50 to −0.27, P = .046) than stent-retrieved thrombi. Fibrin/platelet-rich clots were associated with longer procedure times (MD 13.20, 95% CI 1.30-25.10, P = .037). Hyperdense artery sign was associated with higher RBC content (MD 14.17%, 95% CI 3.07-25.27, P = .027). No relationship was found between composition and etiology. CONCLUSION RBC-rich thrombi were associated with better recanalization outcomes and shorter procedure times, suggesting that preinterventional compositional characterization may yield important prognostic and therapeutic guidance.

Introduction: Recent studies suggest that suction based thrombectomy leads to better recanalization with RBC-rich clots while stent-retrievers perform better with fibrin-rich clots. The ability to determine real-time histology of clots, in the setting of large vessel occlusion (LVO), could potentially lead to improved recanalization and better clinical outcomes while simultaneously reducing procedural costs. There is an unmet need for technology that would allow for accurate assessment of real-time clot histology in LVOs. Hypothesis: Bioimpedance measurements can be used to predict real-time clot histology. Methods: We constructed an in vitro test bed to measure the bioimpedance of clot analogs with different RBC percentages. The test bed includes a cylindrical chamber with a gold electrode embedded at the bottom. A mixture of human RBCs and plasma was injected into the chamber and coagulation was induced by adding calcium chloride solution. After coagulation, another gold electrode was used to sandwich the clot. Both electrodes were connected to an inductance, capacitance, and resistance (LCR) meter and a low-voltage (10 mV) excitation was sent to the clot at 1 to 201 kHz. We fabricated 5 types of clot analogs by mixing human RBCs and plasma with different RBC percentages (10%, 30%, 50%, 70%, and 90%). Clot types were measured 3 times. The Pearson correlation coefficient was calculated and used to evaluate the relationship between clot bioimpedance and RBC percentage. Results and Conclusions: Clot impedance decreases with the excitation frequency and clots with higher RBC percentages had higher impedance at all excitation frequencies (Fig. 1). The impedance was strongly and positively related to the RBC percentage ( r = .996, p = .0004). By minimizing the electrode size and integrating them into catheters, stents, or wires, such technology could inform clinicians of clot composition and guide device selection for optimum recanalization.