In vitro evaluation of flow diverter performance using a human fibrinogen-based flow model.

OBJECTIVE: Fibrin deposition represents a key step in aneurysm occlusion, promoting endothelization of implants and connective tissue organization as part of the aneurysm-healing mechanism. In this study, the authors introduce a novel in vitro testing platform for flow diverters based on human fibrinogen. METHODS: A flow diverter was deployed in 4 different glass models. The glass models had the same internal parent artery (4 mm) and aneurysm (8 mm) diameters with varying parent artery angulations (paraophthalmic, sidewall, bifurcation, and slightly curved models). The neck size and area were 4 mm and 25 mm2, respectively. Human fibrinogen (330 mg/dl) was circulated within the glass models at varying flow rates (0, 3, 4, and 5 ml/sec) with or without heparin, calcium chloride, and thrombin for as long as 6 hours or until complete fibrin coverage of the flow diverter's neck was achieved. Aneurysm neck coverage was defined as macroscopic fibrin deposition occluding the flow diverters' pores. Flow characteristics after flow diverter deployment were assessed with computational fluid dynamics analysis. The effects of flow rates, heparin, calcium chloride, and thrombin on fibrin deposition rates were tested using 1-way ANOVA and the Tukey test. RESULTS: A total of 84 replicates were performed. Human fibrin did not accumulate on the flow diverter stents under static conditions. The fibrin deposition rate on the aneurysm neck was significantly greater with the 5 ml/sec flow rate as compared to 3 ml/sec for all models. The paraophthalmic model had the highest inflow velocity of 48.7 cm/sec. The bifurcation model had the highest maximum shear stress (SS) and maximum normalized shear stress values at the device cells at 843.3 dyne/cm2 and 35.1 SS/SSinflow, respectively. The fibrin deposition rates of the paraophthalmic and bifurcation models were significantly higher than those of sidewall and slightly curved models for all additive or flow rate comparisons (p = 0.001 for all comparisons). The incorporation of thrombin significantly increased the fibrin deposition rates across all models (p = 0.001 for all models). CONCLUSIONS: Rates of fibrin deposition varied widely across different configurations and additive conditions in this novel in vitro model system. Fibrin accumulation started at the aneurysm inflow zone where flow velocity and shear stress were the highest. The primary factors influencing fibrin deposition included flow velocities, shear stress, and the addition of thrombin at a physiological concentration. Further research is needed to test the clinical utility of fibrinogen-based models for patient-specific aneurysms.

Triple Aspiration Versus Conventional Aspiration Techniques: A Randomized In-Vitro Evaluation.

BACKGROUND AND PURPOSE: A single aspiration maneuver using a large volume syringe is a common and effective technique for aspiration thrombectomy. Multiple aspiration cycles using large aspiration syringes has been proposed as a means to improve efficacy over single aspiration. In this study, we sought to investigate the efficacy of a "triple aspiration technique" where a large volume syringe is cycled three times prior to catheter retraction during aspiration thrombectomy. MATERIALS AND METHODS: A 3D-printed adult vasculature was used as a benchtop thrombectomy platform. Fibrin-rich and red blood cell-rich clots were prepared in centrifuge tubes using human plasma, red blood cells, and calcium chloride. Next, clots were placed in the carotid terminus of the model, and the performances of three different aspiration techniques-triple syringe, single syringe, and continuous pump aspiration-were compared in a randomized manner (1:1:1). Outcomes of interest included first-pass efficacy (FPE), complete clot removal (final mTICI 2c/3), the number of thrombectomy attempts to achieve mTICI 2c/3, vacuum pressure, and distal embolization. The distal emboli were detected using a 70-micron cell strainer placed at the outflow of the model and quantified using an image processing algorithm. The vacuum pressures were measured using a pressure transducer (Honeywell, NC, USA). RESULTS: A total of 102 replicates were performed, 34 for each technique. The triple aspiration technique provided a significantly higher rate of FPE than the syringe and pump aspiration techniques (67.6% vs. 41.1%, p= 0.02). Additionally, the triple aspiration technique achieved complete clot removal with a significantly lower number of thrombectomy attempts compared to single syringe aspiration (1.2 ± 0.5 vs. 1.8 ± 0.8, p=0.005). The triple aspiration technique generated significantly higher vacuum pressure than both the single syringe and vacuum pump aspiration (28.3 ± 0.2 vs. 27.2 ± 0.3 (p= 0.002) and 26.2 ± 0.4 (p=0.001), respectively). The differences in complete clot removal and distal embolization parameters were not statistically significantly different across the groups. CONCLUSIONS: Our findings suggest that the triple aspiration technique can improve FPE rates and vacuum pressure in aspiration thrombectomy. Further studies are needed to examine the safety and efficacy of triple aspiration in the clinical setting. ABBREVIATIONS: AcommA = anterior communicating artery; FPE = first pass efficacy; ICA = internal carotid artery; MCA = middle cerebral artery; MT = mechanical thrombectomy; mTICI = modified thrombolysis in cerebral infarction scale; PcommA = posterior communicating artery.

Cyclic Aspiration in Mechanical Thrombectomy: Influencing Factors and Experimental Validation.

BACKGROUND AND PURPOSE: Mechanical thrombectomy is a fundamental intervention for acute ischemic stroke treatment. While conventional techniques are effective, cyclic aspiration (CyA) shows potential for better recanalization rates. We aim to investigate factors affecting CyA and compare them with static aspiration (StA). MATERIALS AND METHODS: StA setup consisted of an aspiration pump connected to pressure transducer. CyA was tested with five subsequent iterations: single solenoid valve with air+saline (1) or saline alone (2) as aspiration medium; two solenoid valves with air+saline (3) as aspiration medium; complete air removal and saline feeding (4); pressurized saline feeding (5). To assess the efficacy of clot ingestion, the pressure transducer was replaced with a distal aspiration catheter. Moderately stiff clot analogs (15 mm) were used to investigate the ingestion quantified as clot relative weight loss. Additionally, the aspiration flow rate was assessed for each setup. RESULTS: With CyA setup 1, the amplitude of the achieved negative pressure waves declined with increasing frequencies but progressively increased with each subsequent iteration, achieving a maximum amplitude of 81 kPa for setup 5 at 1Hz. Relative clot weight loss was significantly higher with setup 5 at 5Hz than with StA (100% vs. 37,8%; p=0.05). Aspiration flow rate was lower with CyA than with StA (setup 5 at 5Hz: 199,8ml/min vs. StA: 311ml/min; p<0.01). CONCLUSIONS: Cyclic aspiration with the appropriate setup may represent an encouraging innovation in mechanical thrombectomy, offering a promising pathway for improving efficacy in clot ingestion and recanalization. The observed benefits warrant confirmation in a clinical setting. ABBREVIATIONS: CyA -cyclic aspiration, StA - static aspiration, FPR -first pass reperfusion, MT -mechanical thrombectomy, DAC -distal aspiration catheter, LVO -large vessel occlusion.

Creating elastase aneurysms in rabbits: a video primer.

The New Zealand rabbit elastase-induced arterial aneurysm of the right common carotid artery remains a widely used model for assessing the effectiveness and safety of new neuroendovascular devices.1 This model offers a simple and reliable platform for pre-clinical in vivo investigations, crucial for comprehending the biological processes underlying aneurysm healing after endovascular treatment.2 Notably, the induced aneurysm exhibits morphological, hemodynamic, and histological characteristics similar to human intracranial aneurysms. The creation of the aneurysm is performed using open and endovascular techniques. Each step of the procedure requires a meticulous and controlled gesture to ensure reproducibility of the aneurysm and minimize animal misuse. In video 1 we present a step-by-step procedural guide for aneurysm creation and follow-up. We hope this resource will help in promoting this model and provide useful guidance for researchers in the field.neurintsurg;jnis-2024-021912v1/V1F1V1Video 1Surgical procedure of creating elastase-induced aneurysms in rabbits.

Efficacy and Safety of Imatinib Treatment in Elderly Patients With Chronic Myeloid Leukemia: Real-Life Data and a Single-Center Experience.

BACKGROUND: In the era of tyrosine kinase inhibitors (TKIs), chronic myeloid leukemia (CML) patients generally live close to a normal lifespan, and the number of elderly patients with CML with comorbidities is increasing. PATIENTS AND METHODS: We retrospectively compared the efficacy and safety of frontline imatinib between elderly patients (≥60 years old) and younger patients (<60 years old) with CML. RESULTS: The study included 33 elderly and 125 younger patients. Elderly patients had significantly higher Charlson comorbidity index (CCI) scores. Efficacy and toxicity were comparable among the older patients with CCI scores of 0 and ≥1. There were significantly more hematologic adverse events (AEs) in elderly patients (P = .005). Although not significant, nonhematologic AEs were also more common in older cases (P = .056). Elderly patients had significantly higher rates of imatinib dose reduction (P < .001). Cumulative response rates were similar in both groups. Event-free survival was comparable, and overall survival (OS)-when non-CML-related deaths were censored-was also similar. In the multivariate analysis, age at diagnosis and CCI were associated with OS, and patients ≥ 60 years of age had a 5.998-times higher risk of death compared with the patients < 60 years of age (P = .011). Similarly, patients with CCI scores ≥ 2 had a 3.758-times higher risk of death compared with patients with a CCI score of 0 (P = .033). CONCLUSIONS: Upfront imatinib was generally well tolerated among elderly Turkish patients with CML with non-inferior responses and long-term outcomes when compared with younger patients. Comorbidities can be problematic in elderly patients, and today the survival of patients with CML is determined mostly by comorbidities.