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.

Deep learning-based model for difficult transfemoral access prediction compared with human assessment in stroke thrombectomy.

BACKGROUND: In mechanical thrombectomy (MT), extracranial vascular tortuosity is among the main determinants of procedure duration and success. Currently, no rapid and reliable method exists to identify the anatomical features precluding fast and stable access to the cervical vessels. METHODS: A retrospective sample of 513 patients were included in this study. Patients underwent first-line transfemoral MT following anterior circulation large vessel occlusion stroke. Difficult transfemoral access (DTFA) was defined as impossible common carotid catheterization or time from groin puncture to first carotid angiogram >30 min. A machine learning model based on 29 anatomical features automatically extracted from head-and-neck computed tomography angiography (CTA) was developed to predict DTFA. Three experienced raters independently assessed the likelihood of DTFA on a reduced cohort of 116 cases using a Likert scale as benchmark for the model, using preprocedural CTA as well as automatic 3D vascular segmentation separately. RESULTS: Among the study population, 11.5% of procedures (59/513) presented DTFA. Six different features from the aortic, supra-aortic, and cervical regions were included in the model. Cross-validation resulted in an area under the receiver operating characteristic (AUROC) curve of 0.76 (95% CI 0.75 to 0.76) for DTFA prediction, with high sensitivity for impossible access identification (0.90, 95% CI 0.81 to 0.94). The model outperformed human assessment in the reduced cohort [F1-score (95% CI) by experts with CTA: 0.43 (0.37 to 0.50); experts with 3D segmentation: 0.50 (0.46 to 0.54); and model: 0.70 (0.65 to 0.75)]. CONCLUSIONS: A fully automatic model for DTFA prediction was developed and validated. The presented method improved expert assessment of difficult access prediction in stroke MT. Derived information could be used to guide decisions regarding arterial access for MT.

Modeling Robotic-Assisted Mechanical Thrombectomy Procedures with the CorPath GRX Robot: The Core-Flow Study.

BACKGROUND AND PURPOSE: Endovascular robotic devices may enable experienced neurointerventionalists to remotely perform endovascular thrombectomy. This study aimed to assess the feasibility, safety, and efficacy of robot-assisted endovascular thrombectomy compared with manual procedures by operators with varying levels of experience, using a 3D printed neurovascular model. MATERIALS AND METHODS: M1 MCA occlusions were simulated in a 3D printed neurovascular model, linked to a CorPath GRX robot in a biplane angiography suite. Four interventionalists performed manual endovascular thrombectomy (n = 45) and robot-assisted endovascular thrombectomy (n = 37) procedures. The outcomes included first-pass recanalization (TICI 2c-3), the number and size of generated distal emboli, and procedural length. RESULTS: A total of 82 experimental endovascular thrombectomies were conducted. A nonsignificant trend favoring the robot-assisted endovascular thrombectomy was observed in terms of final recanalization (89.2% versus manual endovascular thrombectomy, 71.1%; P = .083). There were no differences in total mean emboli count (16.54 [SD, 15.15] versus 15.16 [SD, 16.43]; P = .303). However, a higher mean count of emboli of > 1 mm was observed in the robot-assisted endovascular thrombectomy group (1.08 [SD, 1.00] versus 0.49 [SD, 0.84]; P = .001) compared with manual endovascular thrombectomy. The mean procedural length was longer in robot-assisted endovascular thrombectomy (6.43 [SD, 1.71] minutes versus 3.98 [SD, 1.84] minutes; P < .001). Among established neurointerventionalists, previous experience with robotic procedures did not influence recanalization (95.8% were considered experienced; 76.9% were considered novices; P = .225). CONCLUSIONS: In a 3D printed neurovascular model, robot-assisted endovascular thrombectomy has the potential to achieve recanalization rates comparable with those of manual endovascular thrombectomy within competitive procedural times. Optimization of the procedural setup is still required before implementation in clinical practice.

Partial (SAVE) versus Complete (Solumbra) Stent Retriever Retraction Technique for Mechanical Thrombectomy: A Randomized In Vitro Study.

BACKGROUND AND PURPOSE: Mechanical thrombectomy has become a first-line treatment for acute ischemic stroke. Several techniques combining stent retrievers and distal aspiration catheters have been described. We aimed to characterize the efficacy of 2 commonly used techniques according to clot characteristics. MATERIALS AND METHODS: Soft (mean stiffness = 95.77 [SD, 5.80] kPa) or stiff (mean stiffness = 205.63 [SD, 6.70] kPa) clots (3 × 10 mm and 2 × 10 mm, respectively) were embolized to the distal M1 segment of the MCA in an in vitro model. The technique was randomly allocated (1:1): stent retriever assisted vacuum-locked extraction (SAVE) versus complete retraction (Solumbra). The primary end point was the percentage of first-pass recanalization. Secondary end points were periprocedural distal embolization measures. RESULTS: A total of 130 mechanical thrombectomies were performed (50 for soft clots and 15 for stiff clots per arm). Overall, the rate of first-pass recanalizaton was 35% with Solumbra and 15% with SAVE (P < .01). For stiff clots, the first-pass recanalizaton was equal for both methods (27%; P = 1.00). With soft clots, the first-pass recanalizaton was higher with Solumbra (38%) than with SAVE (12%; P < .01). When we used soft clots, the maximum embolus size (mean, 1.19 [SD, 0.9] mm versus 2.16 [SD, 1.48] mm; P < .01) and total area of emboli (mean, 1.82 [SD, 2.73] versus 3.34 [SD, 3.2]; P = .01) were also lower with Solumbra than with SAVE. CONCLUSIONS: Clot characteristics may influence the efficacy of the thrombectomy technique. In occlusions caused by soft clots, complete retrieval into the distal aspiration catheters achieved higher rates of first-pass recanalizaton and lower embolization.

Impact on collateral flow of devices used for endovascular treatment of stroke: an in-vitro flow model.

BACKGROUND: Collateral blood supply of distal vessels has been linked to clinical outcome, infarct volume and recanalization rates in patients with large vessel occlusion. Our study aimed to explore the effects of catheterization during mechanical thrombectomy in collaterals. METHODS: We quantified the flow diversion effect secondary to arterial occlusions in an in vitro model which was connected in a flow-loop setup with a saline reservoir and a pump supplying pulsatile flow. Clot analogs were embolized to the middle cerebral artery (MCA) M1 or M2 segments. We used the same model with a clamped anterior communicating artery (AComA) to simulate its absence. An ultrasound flow sensor was placed at the vessel of interest. Flow rates and pressures were evaluated according to the following catheter locations: baseline (1) before and (2) after the occlusion; (3) 8F guiding catheter at the internal carotid artery (ICA) bulb; (4) at the cavernous segment; (5) at the cavernous segment a 0.071" distal access catheter at proximal M1; (6) 8F balloon guide catheter inflated. RESULTS: Collateral blood flow measured at distal anterior cerebral artery (ACA) (M1-MCA occlusion) and M2-MCA (M2-MCA occlusion) was progressively reduced as catheters were advanced through the ICA and MCA. In the lacking AComA model, the flow was further diminished as compared with the model with a patent AComA. CONCLUSION: Our in vitro study showed a progressive reduction of collateral blood flow due to the advance of catheters during mechanical thrombectomy.