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Elizabeth N. Alford, Lauren E. Rotman, Matthew S. Erwood, Robert A. Oster, Matthew C. Davis, H. Bruce C. Pittman, H. Evan Zeiger, and Winfield S. Fisher III

OBJECTIVE

The purpose of this study was to describe the development of a novel prognostic score, the Subdural Hematoma in the Elderly (SHE) score. The SHE score is intended to predict 30-day mortality in elderly patients (those > 65 years of age) with an acute, chronic, or mixed-density subdural hematoma (SDH) after minor, or no, prior trauma.

METHODS

The authors used the Prognosis Research Strategy group methods to develop the clinical prediction model. The training data set included patients with acute, chronic, and mixed-density SDH. Based on multivariate analyses from a large data set, in addition to review of the extant literature, 3 components to the score were selected: age, admission Glasgow Coma Scale (GCS) score, and SDH volume. Patients are given 1 point if they are over 80 years old, 1 point for an admission GCS score of 5–12, 2 points for an admission GCS score of 3–4, and 1 point for SDH volume > 50 ml. The sum of points across all categories determines the SHE score.

RESULTS

The 30-day mortality rate steadily increased as the SHE score increased for all SDH acuities. For patients with an acute SDH, the 30-day mortality rate was 3.2% for SHE score of 0, and the rate increased to 13.1%, 32.7%, 95.7%, and 100% for SHE scores of 1, 2, 3, and 4, respectively. The model was most accurate for acute SDH (area under the curve [AUC] = 0.94), although it still performed well for chronic (AUC = 0.80) and mixed-density (AUC = 0.87) SDH.

CONCLUSIONS

The SHE score is a simple clinical grading scale that accurately stratifies patients’ risk of mortality based on age, admission GCS score, and SDH volume. Use of the SHE score could improve counseling of patients and their families, allow for standardization of clinical treatment protocols, and facilitate clinical research studies in SDH.

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Daniel Gebrezgiabhier, Yang Liu, Adithya S. Reddy, Evan Davis, Yihao Zheng, Albert J. Shih, Aditya S. Pandey, and Luis E. Savastano

OBJECTIVE

Endovascular removal of emboli causing large vessel occlusion (LVO)–related stroke utilizing suction catheter and/or stent retriever technologies or thrombectomy is a new standard of care. Despite high recanalization rates, 40% of stroke patients still experience poor neurological outcomes as many cases cannot be fully reopened after the first attempt. The development of new endovascular technologies and techniques for mechanical thrombectomy requires more sophisticated testing platforms that overcome the limitations of phantom-based simulators. The authors investigated the use of a hybrid platform for LVO stroke constructed with cadaveric human brains.

METHODS

A test bed for embolic occlusion of cerebrovascular arteries and mechanical thrombectomy was developed with cadaveric human brains, a customized hydraulic system to generate physiological flow rate and pressure, and three types of embolus analogs (elastic, stiff, and fragment-prone) engineered to match mechanically and phenotypically the emboli causing LVO strokes. LVO cases were replicated in the anterior and posterior circulation, and thrombectomy was attempted using suction catheters and/or stent retrievers.

RESULTS

The test bed allowed radiation-free visualization of thrombectomy for LVO stroke in real cerebrovascular anatomy and flow conditions by transmural visualization of the intraluminal elements and procedures. The authors were able to successfully replicate 105 LVO cases with 184 passes in 12 brains (51 LVO cases and 82 passes in the anterior circulation, and 54 LVO cases and 102 passes in the posterior circulation). Observed recanalization rates in this model were graded using a Recanalization in LVO (RELVO) scale analogous to other measures of recanalization outcomes in clinical use.

CONCLUSIONS

The human brain platform introduced and validated here enables the analysis of artery-embolus-device interaction under physiological hemodynamic conditions within the unmodified complexity of the cerebral vasculature inside the human brain.

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Adithya S. Reddy, Yang Liu, Joshua Cockrum, Daniel Gebrezgiabhier, Evan Davis, Yihao Zheng, Aditya S. Pandey, Albert J. Shih, and Luis E. Savastano

OBJECTIVE

The development of new endovascular technologies and techniques for mechanical thrombectomy in stroke has greatly relied on benchtop simulators. This paper presents an affordable, versatile, and realistic benchtop simulation model for stroke.

METHODS

A test bed for embolic occlusion of cerebrovascular arteries and mechanical thrombectomy was developed with 3D-printed and commercially available cerebrovascular phantoms, a customized hydraulic system to generate physiological flow rate and pressure, and 2 types of embolus analogs (elastic and fragment-prone) capable of causing embolic occlusions under physiological flow.

RESULTS

The test bed was highly versatile and allowed realistic, radiation-free mechanical thrombectomy for stroke due to large-vessel occlusion with rapid exchange of geometries and phantom types. Of the transparent cerebrovascular phantoms tested, the 3D-printed phantom was the easiest to manufacture, the glass model offered the best visibility of the interaction between embolus and thrombectomy device, and the flexible model most accurately mimicked the endovascular system during device navigation. None of the phantoms modeled branches smaller than 1 mm or perforating arteries, and none underwent realistic deformation or luminal collapse from device manipulation or vacuum. The hydraulic system created physiological flow rate and pressure leading to iatrogenic embolization during thrombectomy in all phantoms. Embolus analogs with known fabrication technique, structure, and tensile strength were introduced and consistently occluded the middle cerebral artery bifurcation under physiological flow, and their interaction with the device was accurately visualized.

CONCLUSIONS

The test bed presented in this study is a low-cost, comprehensive, realistic, and versatile platform that enabled high-quality analysis of embolus–device interaction in multiple cerebrovascular phantoms and embolus analogs.

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Yang Liu, Yihao Zheng, Adithya S. Reddy, Daniel Gebrezgiabhier, Evan Davis, Joshua Cockrum, Joseph J. Gemmete, Neeraj Chaudhary, Julius M. Griauzde, Aditya S. Pandey, Albert J. Shih, and Luis E. Savastano

OBJECTIVE

This study’s purpose was to improve understanding of the forces driving the complex mechanical interaction between embolic material and current stroke thrombectomy devices by analyzing the histological composition and strength of emboli retrieved from patients and by evaluating the mechanical forces necessary for retrieval of such emboli in a middle cerebral artery (MCA) bifurcation model.

METHODS

Embolus analogs (EAs) were generated and embolized under physiological pressure and flow conditions in a glass tube model of the MCA. The forces involved in EA removal using conventional endovascular techniques were described, analyzed, and categorized. Then, 16 embolic specimens were retrieved from 11 stroke patients with large-vessel occlusions, and the tensile strength and response to stress were measured with a quasi-static uniaxial tensile test using a custom-made platform. Embolus compositions were analyzed and quantified by histology.

RESULTS

Uniaxial tension on the EAs led to deformation, elongation, thinning, fracture, and embolization. Uniaxial tensile testing of patients’ emboli revealed similar soft-material behavior, including elongation under tension and differential fracture patterns. At the final fracture of the embolus (or dissociation), the amount of elongation, quantified as strain, ranged from 1.05 to 4.89 (2.41 ± 1.04 [mean ± SD]) and the embolus-generated force, quantified as stress, ranged from 63 to 2396 kPa (569 ± 695 kPa). The ultimate tensile strain of the emboli increased with a higher platelet percentage, and the ultimate tensile stress increased with a higher fibrin percentage and decreased with a higher red blood cell percentage.

CONCLUSIONS

Current thrombectomy devices remove emboli mostly by applying linear tensile forces, under which emboli elongate until dissociation. Embolus resistance to dissociation is determined by embolus strength, which significantly correlates with composition and varies within and among patients and within the same thrombus. The dynamic intravascular weakening of emboli during removal may lead to iatrogenic embolization.

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Yang Liu, Yihao Zheng, Adithya S. Reddy, Daniel Gebrezgiabhier, Evan Davis, Joshua Cockrum, Joseph J. Gemmete, Neeraj Chaudhary, Julius M. Griauzde, Aditya S. Pandey, Albert J. Shih, and Luis E. Savastano

OBJECTIVE

This study’s purpose was to improve understanding of the forces driving the complex mechanical interaction between embolic material and current stroke thrombectomy devices by analyzing the histological composition and strength of emboli retrieved from patients and by evaluating the mechanical forces necessary for retrieval of such emboli in a middle cerebral artery (MCA) bifurcation model.

METHODS

Embolus analogs (EAs) were generated and embolized under physiological pressure and flow conditions in a glass tube model of the MCA. The forces involved in EA removal using conventional endovascular techniques were described, analyzed, and categorized. Then, 16 embolic specimens were retrieved from 11 stroke patients with large-vessel occlusions, and the tensile strength and response to stress were measured with a quasi-static uniaxial tensile test using a custom-made platform. Embolus compositions were analyzed and quantified by histology.

RESULTS

Uniaxial tension on the EAs led to deformation, elongation, thinning, fracture, and embolization. Uniaxial tensile testing of patients’ emboli revealed similar soft-material behavior, including elongation under tension and differential fracture patterns. At the final fracture of the embolus (or dissociation), the amount of elongation, quantified as strain, ranged from 1.05 to 4.89 (2.41 ± 1.04 [mean ± SD]) and the embolus-generated force, quantified as stress, ranged from 63 to 2396 kPa (569 ± 695 kPa). The ultimate tensile strain of the emboli increased with a higher platelet percentage, and the ultimate tensile stress increased with a higher fibrin percentage and decreased with a higher red blood cell percentage.

CONCLUSIONS

Current thrombectomy devices remove emboli mostly by applying linear tensile forces, under which emboli elongate until dissociation. Embolus resistance to dissociation is determined by embolus strength, which significantly correlates with composition and varies within and among patients and within the same thrombus. The dynamic intravascular weakening of emboli during removal may lead to iatrogenic embolization.