Experimental Direct Measurement of Clot-Capturing Ability of Stent Retrievers

Repeated Middle Cerebral Artery Occlusion Possibly Caused by Endoluminal Injury Due to Stent Clot Retriever: A Case Report

In acute ischemic stroke, various endovascular approaches have been reported with high recanalization rates and good clinical outcomes. However, the best device or technique for the first attempt at mechanical thrombectomy remains a matter of debate. We report a case in which endoluminal injury from initial stent clot retrieval possibly caused repeated middle cerebral artery occlusion. A 74-year-old man presented with left-sided hemiplegia and was diagnosed with a right internal carotid artery occlusion. He underwent endovascular thrombectomy using a stent clot retriever. Although complete recanalization was achieved in the first pass, repeated middle cerebral artery occlusion occurred. Angiography revealed an irregular inner surface and thrombus formation in the superior branch of the second segment of the right middle cerebral artery. There is a risk of endoluminal injury due to stent retrieval, especially using a large sized stent against small branches. Antiplatelet therapy may be effective for preventing recurrent occlusion. Key Messages  We report a case in which endoluminal injury from initial stent clot retrieval possibly caused repeated middle cerebral artery occlusion. There is a risk of endoluminal injury due to stent retrieval, especially using a large sized stent against nonvisible small branches.

Endovascular treatment of acute ischemic stroke with a fully radiopaque retriever: A randomized controlled trial

Objective

The Neurohawk retriever is a new fully radiopaque retriever. A randomized controlled non-inferiority trial was conducted to compare the Neurohawk and the Solitaire FR in terms of safety and efficacy. In order to evaluate the efficacy and safety of endovascular treatment in acute ischemic stroke (AIS) caused by intracranial atherosclerotic disease (ICAD) larger vessel occlusion (LVO), a sub-analysis was performed.

Methods

Acute ischemic stroke patients aged 18-80 years with LVO in the anterior circulation were randomly assigned to undergo thrombectomy with either the Neurohawk or the Solitaire FR. The primary efficacy endpoint was successful reperfusion (mTICI 2b-3) rate by the allocated retriever. A relevant non-inferiority margin was 12.5%. Safety outcomes were symptomatic intracranial hemorrhage (sICH) and all-cause mortality within 90 days. Secondary endpoints included first-pass effect (FPE), modified FPE, and favorable outcomes at 90 days. In subgroup analysis, the patients were divided into the ICAD group and non-ICAD group according to etiology, and baseline characteristics, angiographic, and clinical outcomes were compared.

Results

A total of 232 patients were involved in this analysis (115 patients in the Neurohawk group and 117 in the Solitaire group). The rates of successful reperfusion with the allocated retriever were 88.70% in the Neurohawk group and 90.60% in the Solitaire group (95%CI of the difference, -9.74% to 5.94%; p = 0.867). There were similar results in FPE and mFPE in both groups. The rate of sICH seemed higher in the Solitaire group (13.16% vs. 7.02%, p = 0.124). All-cause mortality and favorable outcome rates were comparable as well. In subgroup analysis, 58 patients were assigned to the ICAD group and the remaining 174 to the non-ICAD group. The final successful reperfusion and favorable outcome rates showed no statistically significant differences in two groups. Mortality within 90 days was relatively lower in the ICAD group (6.90% vs. 17.24%; p = 0.054).

Conclusion

The Neurohawk retriever is non-inferior to the Solitaire FR in the mechanical thrombectomy of large vessel occlusion-acute ischemic stroke (LVO-AIS). The sub-analysis suggested that endovascular treatment including thrombectomy with the retriever and essential rescue angioplasty is effective and safe in AIS patients with intracranial atherosclerotic disease-larger vessel occlusion (ICAD-LVO).

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT04995757, number: NCT04995757.

Experimental Validation of Pullout Resistance for Stent Retrievers and Aspiration Catheters

Objective

Stretching or avulsion of a small perforating artery caused by mechanical traction contributes to intracranial hemorrhagic complications in mechanical thrombectomy, especially for medium and small-vessel occlusions. This study aimed to measure the pullout resistance during stent retriever (SR) traction and aspiration catheter (AC) traction with or without thrombi and characterize the mechanical properties of each device.

Methods

We placed the thrombectomy device in the area corresponding to the insular segment of the middle cerebral artery of a silicon carotid artery model. The thrombectomy device was automatically pulled out at a constant velocity using a horizontal motorized test stand, and pullout resistance was continuously measured 2000 times per second using a digital force gauge. Five types of SRs and two types of ACs with or without thrombus were evaluated. The data were divided into four groups for analysis: SR without clot, SR with clot, AC without clot, and AC with clot.

Results

The line graph was a jagged waveform during SR traction, and it was a gentle curve during AC traction. The maximum pullout resistance was higher in the SR with clot group than the other groups. The coefficient of variation was higher in the SR group than the AC group, with or without clot.

Conclusion

The pullout resistance during SR traction was more fluctuated than that during AC traction. In the presence of a thrombus, pullout resistance for SR was substantially increased, whereas AC resistance was less susceptible to thrombi. The differences in characteristics may reflect differences in the frequency of mechanical traction injury between the devices during clinical use.

In vitro and in silico modeling of endovascular stroke treatments for acute ischemic stroke

Acute ischemic stroke occurs when a thrombus obstructs a cerebral artery, leading to sub-optimal blood perfusion to brain tissue. A recently developed, preventive treatment is the endovascular stroke treatment (EVT), which is a minimally invasive procedure, involving the use of stent-retrievers and/or aspiration catheters. Despite its increasing use, many critical factors of EVT are not well understood. In this respect, in vitro, and in silico studies have the great potential to help us deepen our understanding of the procedure, perform further device and procedural optimization, and help in clinical training. This review paper provides an overview of the previous in vitro and in silico evaluations of EVT treatments, with a special emphasis on the four main aspects of the adopted experimental and numerical set-ups: vessel, thrombus, device, and procedural settings.

A Method to Evaluate Vessel Deviation during Withdrawal of a Stent Retriever Using a Silicon Vascular Model

Objective

Catastrophic complications may develop because of vessel deviation during device delivery into intracranial vessels for neurointerventions. We report a novel method using a silicon model capable of evaluating vessel deviation as a numerical value.

Methods

In all, 10 tiny markers, each with a pitch of approximately 5 mm, were attached to the vessel model along the long axis. We used a high-resolution camera to record movies of the deviation of the vessel model while employing different stent retrievers. The movies were reviewed to determine the maximum deviation of each marker on the vessel model.

Results

As expected, stent retrievers of the same type exhibited more vessel shifts when they had a larger diameter and longer length. On the other hand, stents with a segmental structure demonstrated less vessel deviation than those with a tubular structure, regardless of the large lumen and long length.

Conclusion

If the degree of vessel stress can be represented by a numerical value, areas where the careful use of different devices for neurointerventions is required may be able to be identified. Moreover, this method may be useful for training.

Applicability assessment of a stent-retriever thrombectomy finite-element model

An acute ischaemic stroke appears when a blood clot blocks the blood flow in a cerebral artery. Intra-arterial thrombectomy, a mini-invasive procedure based on stent technology, is a mechanical available treatment to extract the clot and restore the blood circulation. After stent deployment, the clot, trapped in the stent struts, is pulled along with the stent towards a receiving catheter. Recent clinical trials have confirmed the effectiveness and safety of mechanical thrombectomy. However, the procedure requires further investigation. The aim of this study is the development of a numerical finite-element-based model of the thrombectomy procedure. In vitro thrombectomy tests are performed in different vessel geometries and one simulation for each test is carried out to verify the accuracy and reliability of the proposed numerical model. The results of the simulations confirm the efficacy of the model to replicate all the experimental setups. Clot stress and strain fields from the numerical analysis, which vary depending on the geometric features of the vessel, could be used to evaluate the possible fragmentation of the clot during the procedure. The proposed in vitro/in silico comparison aims at assessing the applicability of the numerical model and at providing validation evidence for the specific in vivo thrombectomy outcomes prediction.

Ideas Developed from the Routine Use of Problem-solving Skills in Neuroendovascular Therapy

Objective

All physicians should endeavor to perform safe and rapid neuroendovascular operations. We describe the process of identifying novel methods and highlight some representative clinical examples from our practice.

Methods

We made a habit of asking questions regarding problems encountered during operations. Potential solutions are often identified and noted in our smartphones or as memos. These solutions are then evaluated by experiments in vascular models before assessing their efficacy in clinical settings.

Results

Some ideas based on our process of raising problems and finding solutions were published, and found to be relevant to the wider scientific community. Moreover, all ideas were applicable in most settings due to the use of conventional, familiar, and cheap methods and equipment. The paper rail method, modified pigtail shape microguidewire, microcatheter in vivo printing method, microcatheter shaping cast, and wireless trans-cell approach are presented as representative ideas.

Conclusions

We reported methods of neuroendovascular therapy identified through the routine practice of problem-solving by our team.