Endovascular Mechanical Recanalization Research Articles

Impact of Mechanical Thrombectomy Device on Thrombus Histology in Acute Embolic Stroke

Although many studies have evaluated the retrieved thrombus to assess the cause of stroke after mechanical thrombectomy for acute large vessel occlusion, the results remain controversial. We investigated the hypothesis that histology of the retrieved thrombus is enhanced by mechanical thrombectomy devices. Thrombi were collected from consecutive patients who had undergone endovascular mechanical recanalization for large intracranial vessel occlusion. The mechanical thrombectomy device used was either an aspiration catheter or a stent retriever. The hematoxylin and eosin-stained specimens were quantitatively analyzed with respect to the relative fractions of the main constituents (erythrocytes and fibrin). Clinical and radiologic findings were also evaluated. Of 65 patients, an aspiration catheter was used in 27, and a stent retriever was used in 38. The presence of a preoperative susceptibility vessel sign on magnetic resonance imaging was not correlated with the percentage of erythrocytes. Thrombus cross-sectional area was larger in the aspiration group than in the stent group (P < 0.01). Conversely, the percentage of the fibrin component was higher in the stent group (P < 0.001). Preoperative intravenous administration of recombinant tissue plasminogen activator reduced thrombus cross-sectional area with a trend of increased percentage of fibrin and reduced percentage of erythrocyte in the stent group. Histologic differences in retrieved thrombi are enhanced by mechanical thrombectomy devices. Stent retrievers may crush the thrombus, which may have a synergistic effect with recombinant tissue plasminogen activator. Histology of the retrieved thrombi might be different from histology of the original thrombi.

Combined local hypothermia and recanalization therapy for acute ischemic stroke: Estimation of brain and systemic temperature using an energetic numerical model.

Local brain hypothermia is an attractive method for providing cerebral neuroprotection for ischemic stroke patients and at the same time reducing systemic side effects of cooling. In acute ischemic stroke patients with large vessel occlusion, combination with endovascular mechanical recanalization treatment could potentially allow for an alleviation of inflammatory and apoptotic pathways in the critical phase of reperfusion. The direct cooling of arterial blood by means of an intra-carotid heat exchange catheter compatible with recanalization systems is a novel promising approach. Focusing on the concept of "cold reperfusion", we developed an energetic model to calculate the rate of temperature decrease during intra-carotid cooling in case of physiological as well as decreased perfusion. Additionally, we discussed and considered the effect and biological significance of temperature decrease on resulting brain perfusion. Our model predicted a 2 °C brain temperature decrease in 8.3, 11.8 and 26.2 min at perfusion rates of 50, 30 and 10ml100g⋅min, respectively. The systemic temperature decrease - caused by the venous blood return to the main circulation - was limited to 0.5 °C in 60 min. Our results underline the potential of catheter-assisted, intracarotid blood cooling to provide a fast and selective brain temperature decrease in the phase of vessel recanalization. This method can potentially allow for a tissue hypothermia during the restoration of the physiological flow and thus a "cold reperfusion" in the setting of mechanical recanalization.

Mechanical thrombeсtomy and trombaspiration in stroke. Problem claims

Objective — to evaluate the effectiveness of endovascular mechanical recanalization methods in ischemic stroke and the analysis of problem cases.Materials and methods. A retrospective analysis of the results of treatment of 33 patients with acute ischemic stroke due to occlusion of a large vessel was performed. There were 18 (54.5 %) men and 15 (45.5 %) women. Endovascular interventions were performed in all patients to restore cerebral arteries patency using various methods and techniques of mechanical thrombectomy. All patients underwent neuroimaging (CT of the brain and selective cerebral subtraction angiography). A topographical assessment of early CT-changes in ischemic stroke was performed using the ASPECTS scale. The severity of neurological symptoms in the acute period of ischemic stroke was assessed according to the NIHSS score. The severity of the condition – on the NIHSS score. The mTICI scale was used to assess the success of recanalization (reperfusion) after mechanical thrombectomy.Results. Successful recanalization (mTICI 2b-3) with the use of stent retrievers and distal aspiration catheters was achieved in 22 (66.7 %) cases. The total number of intraoperative complications was 12.0 %. Mortality rate – 12.0 %.Conclusions. Endovascular reperfusion methods using stent retrievers and distal aspiration catheters for acute ischemic stroke are effective. Endovascular reperfusion advisable to start with a mechanical thrombus aspiration. When performing endovascular recanalization, the use of stent retrievers in combination with guide balloon catheters only without distal aspiration catheters increases the risk of distal reembolism and embolism of other arterial basins.

Worse endovascular mechanical recanalization results for patients with in-hospital onset acute ischemic stroke.

Strokes with onset inside the hospital account for approximately 2-17% of all acute ischemic strokes. The few existing studies addressing these in-hospital strokes lack a thorough analysis of patients who underwent endovascular mechanical thrombectomy-the state of the art therapy for acute strokes due to large vessel occlusions. The objective of the study was to evaluate the efficacy and safety of mechanical revascularization therapy in in-hospital stroke patients. In a single-center case-control study, a propensity score-matched analysis in a 1:2 ratio with the covariates sex, age, type of occluded large vessel, i.v. thrombolysis, and National Institutes of Health Stroke Scale prior to endovascular mechanical thrombectomy was performed. All identified in-hospital stroke patients between 2010 and 2017 were matched to two consecutive out-of-hospital stroke patients. 27 in-hospital strokes were compared to 54 out-of-hospital strokes. After propensity score matching, the baseline characteristics were well balanced between these groups. The times for symptom onset to alarm, symptom onset to imaging, symptom onset/alarm to start of recanalization and symptom onset to final recanalization respectively were faster in in-hospital stroke patients. In contrast, the recanalization procedure itself took significantly longer in in-house patients and had a significantly lower rate of technical success resulting in significantly worse clinical outcomes. The recognition, assessment and pre-interventional procedures of patients with in-hospital strokes and subsequent mechanical thrombectomy are favorable. Nevertheless, in-hospital stroke patients display inferior recanalization results and poorer clinical outcomes. Furthermore, we find mechanical thrombectomy seems safe for treatment of in-hospital strokes.

Current status and prospects of endovascular mechanical thrombectomy for treatment of acute ischemic stroke

Acute ischemic stroke has already become common cause of death in our country. Until now, the intravenous thrombolysis therapy produces a limited therapeutic efficacy in patients with acute ischemic stroke, because the recanalization rate is very low in patients with large vessel occlusion, especially with interal carotid artery occlusion. As a novel modality of primary treatment, endovascular mechanical recanalization using clot removal has become a noticeably efficient intervention and a hot research focus of acute ischemic stroke. In this paper, we reviewed recent large multicenter trials of endovascular mechanical recanalization in the world. Key words: Acute ischemic stroke; Large-vessel occlusion; Endovascular treatment; Stent

Endovascular Cooling Catheter for Selective Brain Hypothermia: An Animal Feasibility Study of Cooling Performance

Therapeutic hypothermia represents a promising neuroprotective treatment in acute ischemic stroke. Selective cerebral hypothermia applied early, prior to and during endovascular mechanical recanalization therapy, may be beneficial in the critical phase of reperfusion. We aimed to assess the feasibility of a new intracarotid cooling catheter in an animal model. Nine adult sheep were included. Temperature probes were introduced into the frontal and temporal brain cortices bilaterally. The cooling catheter system was introduced into a common carotid artery. Selective blood cooling was applied for 180 minutes. Systemic and local brain temperatures were measured during cooling and rewarming. Common carotid artery diameters and flow were measured angiographically and by Doppler sonography. The common carotid artery diameter was between 6.7 and 7.3 mm. Common carotid artery blood flow velocities increased moderately during cooling and after catheter removal. Maximum cerebral cooling in the ipsilateral temporal cortex was -4.7°C (95% CI, -5.1 to -4.0°C). Ipsilateral brain temperatures dropped significantly faster and became lower compared with the contralateral cortex with maximum temperature difference of -1.3°C (95% CI, -1.5 to -1.0°C; P < .0001) and compared with systemic temperature (-1.4°C; 95% CI, -1.7 to -1.0°C; P < .0001). Sheep proved a feasible animal model for the intracarotid cooling catheter. Fast induction of selective mild hypothermia was achieved within the cooled cerebral hemisphere, with stable temperature gradients in the contralateral brain and systemic blood. Further studies are required to demonstrate any therapeutic benefit of selective cerebral cooling in a stroke model.

A numerical framework to investigate hemodynamics during endovascular mechanical recanalization in acute stroke.

Ischemic stroke, caused by embolism of cerebral vessels, inflicts high morbidity and mortality. Endovascular aspiration of the blood clot is an interventional technique for the recanalization of the occluded arteries. However, the hemodynamics in the Circle of Willis (CoW) are not completely understood, which results in medical misjudgment and complications during surgeries. In this study we establish a multiscale description of cerebral hemodynamics during aspiration thrombectomy. First, the CoW is modeled as a 1D pipe network on the basis of computed tomography angiography (CTA) scans. Afterwards, a vascular occlusion is placed in the middle cerebral artery and the relevant section of the CoW is transferred to a 3D computational fluid dynamic (CFD) domain. A suction catheter in different positions is included in the CFD simulations. The boundary conditions of the 3D domain are taken from the 1D domain to ensure system coupling. A Eulerian-Eulerian multiphase simulation describes the process of thrombus aspiration. The physiological blood flow in the 1D and 3D domains is validated with literature data. Further on, it is proved that domain reduction and pressure coupling at the boundaries are an appropriate method to reduce computational costs. Future work will apply the developed framework to various clinical questions.

Utility of a rescue endovascular therapy for the treatment of major strokes refractory to full-dose intravenous thrombolysis

Large artery occlusion (LAO) in patients with major stroke predicts poor revascularization by intravenous thrombolysis (IVT) and more likely results in a poor outcome. We focused on the effects of intra-arterial thrombolysis (IAT) and endovascular mechanical recanalization (EMR) as rescue therapies in major strokes refractory to IVT. A retrospective analysis of 87 patients (National Institutes of Health Stroke Scale >20), who did not respond to full-dose IVT due to LAO, was performed based on their endovascular therapy status. IAT was performed as an intraclot infusion of alteplase, and EMR was provided by the Solitaire device™ (Covidien, Dubin, Ireland). The recanalization and 3-month outcome rates after IAT/EMR were correlated with a group of patients who were scheduled to receive endovascular treatment but who underwent only IVT. We achieved successful recanalization by IAT and EMR in 68.7% and 76.1% of patients, respectively. Despite no significant differences in mortality between IAT and EMR, a trend towards better outcomes after IAT and a statistically significant increase for outcome-modified Rankin scale (mRS) 0-3 (45.7%) and mRS 0-2 (34.9%) after EMR was noted when compared with IVT. The degree of recanalization did not correlate with the functional results except for the good-moderate outcome after successful recanalization by EMR. EMR by the Solitaire device is a safe and beneficial method for the rescue treatment of patients with major stroke whose neurological status does not improve and who fail to recanalize the LAO after a 1-h full dose of IVT. The article verifies efficiency of the Solitaire device in major strokes.

Comparison of Endovascular Treatment Versus Conservative Medical Treatment in Patients With Acute Basilar Artery Occlusion

Basilar artery occlusion (BAO) causes mortality up to 90%. A total of 99 patients with BAO received either endovascular (endovascular mechanical recanalization and/or intra-arterial with optional intravenous thrombolysis [IVT] as bridging concept) or conservative medical treatment (IVT and/or medical oral therapy). Outcome parameters were measured in accordance with the thrombolysis in cerebral infarction (TICI), National Institutes of Health Stroke Scale (NIHSS), and modified Rankin Scale (mRS) scores. In all, 78% underwent endovascular and 22% conservative medical treatment. The NIHSS at admission was 20 in both the groups. Postprocedurally, 36% (95% confidence interval: 26%-48%) of the endovascular group and 9% (21%-64%) of the conservative group reached TICI 3 (P = .017). In all, 30% of the endovascular group and 9% of the conservative group were documented with TICI 2b (P = .057). At 90 days follow-up, 45% (31%-60%) of the endovascular-treated patientsand no patient (0%-25%) of the conservative-treated group reached mRS ≤2 (P = .012). Endovascular treatment of BAO provides a better chance to survive this severe condition with good clinical outcome.

Comparison of Stent-Retriever Devices versus the Merci Retriever for Endovascular Treatment of Acute Stroke

Revascularization of large cerebral artery occlusion is the therapeutic goal in stroke therapy. Currently, many recanalization devices are in clinical use. This study compares the outcome parameters, efficacy, and safety of the new generation of stent-retriever devices with the well-established Merci retriever. All patients who received endovascular mechanical recanalization therapy were prospectively registered. One hundred twenty-two patients were treated with either new stent retrievers, including the Trevo and Solitaire devices, or the Merci retriever system. Recanalization of the occluded vessel was assessed in accordance with the modified TICI score, and outcome parameters, including the NIHSS and mRS scores, were documented. Clinical status was recorded after neurointervention, at time of discharge, and after 90 days. The mean age of all patients was 68 years; 54% were male, with no statistical differences in demographics between both groups. Successful recanalization (TICI 3 and TICI 2b) was achieved in 82% of patients treated with stent retrievers compared with 62% of patients treated with Merci retrievers (P = .016). In the 90-day follow-up, 65% of patients treated with stent retrievers and 35% of those treated with the Merci had achieved a good (mRS = 0-2) clinical outcome (P = .002). Patients treated with stent retrievers had a significantly shorter treatment time (72 versus 122 minutes, P < .01) and less severe intracerebral hemorrhages (10% versus 28%, P < .01). Patients treated with Trevo and Solitaire stents had a better revascularization rate, better clinical outcome, and lower complication rate than patients treated with the Merci retriever.

Preceding Intravenous Thrombolysis Facilitates Endovascular Mechanical Recanalization in Large Intracranial Artery Occlusion

Acute occlusions of the large intracranial arteries are relatively resistant to intravenous thrombolysis. Therefore, multimodal approaches combining intravenous thrombolysis with endovascular mechanical recanalization are increasingly being applied. In this setting, intravenous thrombolysis may facilitate subsequent mechanical thrombectomy. To test this hypothesis, we analyzed the influence of intravenous thrombolysis on net intervention time in subsequent endovascular mechanical recanalization. In this retrospective single-center analysis, we compared net intervention time with and without preceding intravenous thrombolysis in patients treated by endovascular mechanical recanalization between 01/2003 and 06/2010. The net intervention time was defined as the interval between the onset of endovascular thrombus manipulation and successful vessel recanalization. We identified 65 eligible patients, 35 of whom were treated by intravenous thrombolysis before mechanical therapy. Recanalization was achieved in 26 patients with (74%) and 23 patients without preceding intravenous thrombolysis (77%). In the case of successful recanalization, the net intervention time was significantly shorter in patients with preceding intravenous thrombolysis (24·8 ± 22·8 vs. 44·2 ± 40·5 min; P<0·05). This difference remained significant after restricting the analysis to the patients treated by the Penumbra Stroke System(©) (n=32). After three-months, patients with preceding intravenous thrombolysis were more likely to be functionally independent (modified Rankin Scale≤2) than those without (P<0·05). Our findings suggest that preceding intravenous thrombolysis may reduce the intervention time in patients treated by endovascular mechanical recanalization. However, due to the retrospective design of our study, these findings have to be interpreted with caution and need confirmation in a larger patient population.

Drip, Ship, and Retrieve

In acute basilar artery occlusion, intra-arterial thrombolysis or endovascular mechanical recanalization may result in higher recanalization rates than intravenous thrombolysis. However, many patients are admitted to community hospitals, where endovascular therapy is usually not readily available. We initiated a "drip, ship, and retrieve" cooperative treatment protocol in 2006, in which thrombolysis was initiated in the community hospital with simultaneous referral to our stroke center and the use of endovascular mechanical recanalization as required. The outcome of all consecutive patients treated by this protocol between 2006 and June 2009 was compared with that of a similar population of referred patients who had received primary intra-arterial therapy with or without tirofiban bridging at our center between 2003 and 2005. In both groups, 26 patients were identified. The rate of symptomatic intracranial hemorrhage was 12% in previous patients and 8% in those treated under the new protocol. Recanalization rates were similar: 92% in previous patients and 85% with the new protocol; 38% of these had recanalization after intravenous thrombolysis alone. Functional outcome was better among those treated with the new protocol, with more patients achieving a modified Rankin scale score < or = 2 (38% versus 12%; P=0.03) and < or = 3 (50% versus 23%; P=0.04). "Drip, ship, and retrieve" seems to be feasible and safe in acute basilar artery occlusion. Patients appear to benefit from initiation of intravenous thrombolysis in the community hospital before transfer. Randomized controlled trials will have to confirm the expected benefit of subsequent on-demand mechanical recanalization on clinical outcome.

Approval of the MERCI Clot Retriever

Section Editors: Marc Fisher MD Antoni Davalos MD The Food and Drug Administration (FDA) evaluates applications for new human drugs, biologics, and complex medical devices. Companies must obtain FDA approval to legally market these products. In August, the FDA gave Concentric Medical clearance to market its Merci Retriever system to “remove blood clots from the brain in patients experiencing an ischemic stroke.” Given that the FDA is charged with “protecting the public health by assuring the safety, efficacy, and security of… biological products and medical devices…, ” “advancing public health by helping to speed innovations that make medicines … more effective, safer, and more affordable,” and “helping the public get the accurate, science-based information they need to use medicines … to improve their health,”1 the FDA’s decision to approve the Merci Retriever system is of concern. The pathways to approval are reviewed by Felten et al in the accompanying article and are outlined in Figure 1. Figure 1. Potential pathways for device approval. The decision to approve the Merci Retriever was based on data from the MERCI (Mechanical Embolus Removal in Cerebral Ischemia) Trial; the approval was granted through the 510(k) process. The Merci Retriever system includes a flexible nickel titanium (nitinol) wire that obtains a helical shape once it is passed through the tip of the guidance catheter. In practice, the catheter/wire is passed distal to the thrombus, the catheter is removed, and the helical configuration assumed by the wire; the clot is then trapped in the helix and withdrawn from the vasculature (Figure 2). The 510(k) clearance means that the Merci Retriever was felt to be substantially equivalent to a predicate device. In this case, the predicate device was the Concentric Retriever, which itself received 510(k) clearance by the FDA in May 2001 for “use in …

Improving the Assessment of Outcomes in Stroke: Use of a Structured Interview to Assign Grades on the Modified Rankin Scale

Improving the Assessment of Outcomes in Stroke: Use of a Structured Interview to Assign Grades on the Modified Rankin Scale