Percutaneous transluminal angioplasty and stent placement in acute vessel occlusion: evaluation of new methods for interventional stroke treatment

Preclinical Evaluation of the NeVaTM Stent Retriever: Safety and Efficacy in the Swine Thrombectomy Model

Background

A novel stent retriever device with an enhanced radial force profile, enlarged offset openings, and a closed distal end has been developed.

Objective

Evaluate the safety and effectiveness of the NeVa^TM thrombectomy device in animal model of thrombo-occlusive disease.

Materials and Methods

Seven swine were used in safety and efficacy studies. Thrombo-occlusive disease was modeled using 4 emboli morphologies; 2 distinct models of autologous whole blood thrombi, plasma-enriched thrombi, and Onyx® emboli. A total of 35 vascular occlusions and retrievals were performed using emboli of variable sizes. Pre- and post-modified thrombolysis in cerebral ischemia (mTICI) scores, number of retrievals, and the presence of angiographic complications were recorded. In the safety study, a total of 6 clot retrievals were completed and the vascular territory examined grossly and harvested for histopathological evaluation. A semiquantitative vasospasm study was performed. Radial force testing was performed on NeVa^TM and control devices for comparison.

Results

Near-full or full reperfusion (mTICI 2b/3) was achieved in 34/35 occlusions after a mean of 1.2 passes. Full reperfusion (TICI 3) was achieved in 17/17 of whole blood clot occlusions (ranging between 10 and 20 mm) after a mean of 1.06 passes. The rate of mTICI 2b/3 reperfusion was 10/11 (mean, 1.6 passes) and 5/5 (mean, 1.0 passes) for Onyx® and plasma-enriched clot emboli, respectively. Histopathological vessel injury and vasospasm scores were comparable to predicate studies. Radial force curves demonstrated increased expansive radial force and similar compressive radial force compared to predicate devices.

Conclusions

Our preclinical results support the use of the NeVa^TM device in a clinical trial to determine if this novel design improves upon current stent retriever outcomes.

Incidence and Clinical Significance of Acute Reocclusion after Emergent Angioplasty or Stenting for Underlying Intracranial Stenosis in Patients with Acute Stroke

BACKGROUND AND PURPOSE

A major concern after emergent intracranial angioplasty in cases of acute stroke with underlying intracranial stenosis is the acute reocclusion of the treated arteries. This study reports the incidence and clinical outcomes of acute reocclusion of arteries following emergent intracranial angioplasty with or without stent placement for the management of patients with acute stroke with underlying intracranial atherosclerotic stenosis.

MATERIALS AND METHODS

Forty-six patients with acute stroke received emergent intracranial angioplasty with or without stent placement for intracranial atherosclerotic stenosis and underwent follow-up head CTA. Acute reocclusion was defined as "hypoattenuation" within an arterial segment with discrete discontinuation of the arterial contrast column, both proximal and distal to the hypoattenuated lesion, on CTA performed before discharge. Angioplasty was defined as "suboptimal" if a residual stenosis of ≥50% was detected on the postprocedural angiography. Clinical and radiologic data of patients with and without reocclusion were compared.

RESULTS

Of the 46 patients, 29 and 17 underwent angioplasty with and without stent placement, respectively. Acute reocclusion was observed in 6 patients (13%) and was more frequent among those with suboptimal angioplasty than among those without it (71.4% versus 2.6%, P < .001). The relative risk of acute reocclusion in patients with suboptimal angioplasty was 27.857 (95% confidence interval, 3.806-203.911). Furthermore, a good outcome was significantly less frequent in patients with acute reocclusion than in those without it (16.7% versus 67.5%, P = .028).

CONCLUSIONS

Acute reocclusion of treated arteries was common after emergent intracranial angioplasty with or without stent placement in patients with acute stroke with intracranial atherosclerotic stenosis and was associated with a poor outcome. Suboptimal results of angioplasty appear to be associated with acute reocclusion, irrespective of whether stent placement was performed.

Experimental evaluation of immediate recanalization effect and recanalization efficacy of a new thrombus retriever for acute stroke treatment in vivo

BACKGROUND AND PURPOSE

Currently, several new stent retriever devices for acute stroke treatment are under development and early clinical evaluation. Preclinical testing under standardized conditions is an important first step to evaluate the technical performance and potential of these devices. The aim of this study was to evaluate the immediate recanalization effect, recanalization efficacy, thrombus-device interaction, and safety of a new stent retriever intended for thrombectomy in patients with acute stroke.

MATERIAL AND METHODS

The pREset thrombectomy device (4 × 20 mm) was evaluated in 16 vessel occlusions in an established swine model. Radiopaque thrombi (10-mm length) were used for visualization of thrombus-device interaction during application and retrieval. Flow-restoration effect immediately after deployment and after 5-minute embedding time before retrieval, recanalization rate after retrieval, thromboembolic events, and complications were assessed. High-resolution FPCT was performed to illustrate thrombus-device interaction during the embedding time.

RESULTS

Immediate flow restoration was achieved in 75% of occlusions. An increase or stable percentage of recanalizations during embedding time before retrieval was seen in 56.3%; a decrease, in 12.5%; reocclusion of a previously recanalized vessel, in 18.8%; and no recanalization effect at all, in 12.5%. Complete recanalization (TICI 3) after retrieval was achieved in 93.8%; partial recanalization (TICI 2b), in 6.2%. No distal thromboembolic events were observed. High-resolution FPCT illustrated entrapment of the thrombus between the stent struts and compression against the contralateral vessel wall, leading to partial flow restoration. During retrieval, the thrombus was retained in a straight position within the stent struts.

CONCLUSIONS

In this experimental study, the pREset thrombus retriever showed a high recanalization rate in vivo. High-resolution FPCT allows detailed illustration of the thrombus-device interaction during embedding time and is advocated as an add-on tool to the animal model used in this study.

Passing the thrombus in endovascular treatment of acute ischemic stroke: do we penetrate the thrombus?

Mechanical thrombectomy is increasingly applied during the treatment of acute stroke. Various devices have been advocated with different sites of force effect at the thrombus. The purpose of this study was to evaluate the angiographic route of passing systematically and therefore to assess the site of deployment of mechanical devices in correlation to the thrombus in interventional stroke treatment. Twenty-one consecutive patients with endovascular treatment for acute ischemic stroke with 26 passing procedures were evaluated prospectively. Occlusion site was the M1-segment in 17 cases (65.4%), ICA termination in five cases (19.2%), M2-segment in two cases (7.7%), the A2-segment in one case (3.8%) and basilar artery in one case (3.8%). On angiographic images the microwire and microcatheter passage was evaluated by illustrating the entry point and course across the occlusion site in relation to the thrombus in different projections and in correlation to the recanalisation result. Results were correlated to the origin of the thrombi according to the TOAST criteria. In all cases the point of entry to the occlusion site was delineated laterally to the thrombus in at least one projection. The course of the wire across the occluded segment in relation to the thrombus was found to be laterally in 22 procedures (84.6%). In the majority of M1-occlusions (12/17, 70.6%) the passage was found in the cranial aspect of the thrombus. In four procedures (15.4%) angiograms in different projections did not unequivocally confirm a passage laterally to the thrombus. The route of passing the thrombus was independent of thrombus origin according to the TOAST criteria. In the majority of cases the complete route of passing the occlusion site was visualized angiographically. Entrance of the microwire and microcatheter at proximal surface of the thrombus takes place laterally to the thrombus and accordingly the passage takes place between the thrombus and the vessel wall independent of thrombus origin. A penetration of the thrombus was not observed. This route of passing has implications on deployment and transmission of force in relation to the thrombus in mechanical approaches and consequently on the development of retrieval devices.

Emergent angioplasty and stent placement recanalization without thrombolysis in acute middle cerebral artery occlusions

A significant proportion of patients with infarcts from large-vessel lesions have shown a poor response to systemic thrombolysis. Stents have been used to recanalize occluded or severely stenosed intracranial arteries in patients with acute stroke. This study evaluated the feasibility, efficacy, and safety of intracranial artery recanalization for acute middle cerebral artery (MCA) occlusion using emergent angioplasty and stent placement without thrombolysis. All patients from a retrospectively collected database who met the inclusion criteria and were treated with an intracranial stent for acute MCA occlusion were included. Treatment comprised angioplasty and stenting without interventional thrombolytic therapy. Recanalization was assessed by angiography immediately after stent placement based on the Thrombolysis in Myocardial Infarction (TIMI) score. Complications related to the procedure and outcomes were assessed. Neurologic status was evaluated before and after treatment. Eleven patients were treated with emergent angioplasty and stent placement. Partial or complete recanalization (TIMI 2 and 3) was achieved in 11 patients (100%) assessed by digital subtraction angiography immediately after MCA stenting. One patient died due to reocclusion of MCA 2 days after the procedure. Among the survivors, 7 patients (70%) had a good outcome (modified Rankin Scale score, 0-2) and 3 patients (30%) had a moderate outcome (modified Rankin Scale score, 3). Follow-up computed tomography angiography or magnetic resonance angiography revealed mild restenosis in 2 of the 10 patients. This preliminary experience demonstrates the technical feasibility and high rate of recanalization with emergent angioplasty and stenting without thrombolysis in patients with acute MCA occlusion.

Temporary Endovascular Bypass: Rescue Technique During Mechanical Thrombolysis

BACKGROUND

The goal of mechanical thrombolysis is to re-establish blood flow to a completely occluded artery in patients who fail intravenous thrombolytic therapy or who are outside the therapeutic window.

OBJECTIVE

We present our single-institution experience with the use of temporary, partial deployment of a self-expanding intracranial stent as a rescue technique for the treatment of acute stroke. The use of the Enterprise stent represents an off-label use of a humanitarian device exemption device.

METHODS

We performed a retrospective review of a prospective database of acute stroke patients treated with intra-arterial techniques at the Thomas Jefferson University Comprehensive Stroke Center from July 2009 to July 2010.

RESULTS

Seven patients were included, and we obtained a 100% recanalization rate to Thrombolysis in Myocardial Infarction grade 2 and 3 with a 28% asymptomatic hemorrhagic transformation. No device-related complications were encountered.

CONCLUSION

Temporary, partial deployment of a self-expanding intracranial stent as a rescue procedure is feasible, effective, and safe in the setting of endovascular intervention for acute stroke, although our experience is limited. This technique was used only as a rescue procedure when more established procedures failed.

In vivo evaluation of the first dedicated combined flow-restoration and mechanical thrombectomy device in a swine model of acute vessel occlusion

BACKGROUND AND PURPOSE

The use of self-expanding retrievable stents is an emerging and promising treatment strategy for acute stroke treatment. The concept combines the advantages of stent deployment with immediate flow-restoration and of mechanical thrombectomy with definitive thrombus removal. The present study was performed to gain more knowledge about the principle of combined flow restoration and thrombectomy in an established animal model using radiopaque thrombi evaluating efficiency, thrombus-device interaction and possible complications of the first dedicated flow-restoration and mechanical thrombectomy device.

MATERIALS AND METHODS

The Solitaire FR (4 × 20 mm) was evaluated in 15 vessel occlusions in an established animal model in swine. Flow-restoration effect at T0, T5, and T10; recanalization rate after retrieval; thromboembolic events; and complications were assessed. Radiopaque thrombi (10-mm length) were used for visualization of thrombus-device interaction during application and retrieval.

RESULTS

Immediate flow restoration was achieved in 80% of occlusions. Mean percentage of recanalization compared with the initial vessel diameter at T0 was 30.8%; at T5, 30.7%; and at T10, 25.4%. Re-occlusion occurred in 20.0% between T0 and T5 and in 13.3% between T5 and T10. Complete recanalization (TICI 3) after retrieval was achieved in 86.7%. In 2 cases (13.3%), partial recanalization was achieved, with the remaining thrombus in a side branch (TICI 2b). No thromboembolic event was observed. The assessment of thrombus-device interaction illustrated the compression of the thrombus against the vessel wall during deployment leading to partial flow restoration. During retrieval, the thrombus was retained by the stent struts even during the passage of vessel curvatures.

CONCLUSIONS

The Solitaire FR is a safe and effective combined flow-restoration and thrombectomy device in vivo. Partial flow restoration is achieved by thrombus compression immediately after deployment, but flow restoration decreases afterward until final retrieval results in maximal recanalization.

Use of the enterprise™ intracranial stent for revascularization of large vessel occlusions in acute stroke

BACKGROUND AND PURPOSE

Major cerebral thromboembolism often resists recanalization with currently available techniques. The authors present their initial experience with a self-expanding stent for use in intracranial vascular reconstruction, permitting immediate recanalization of acute thromboembolic occlusions of the anterior circulation.

PATIENTS AND METHODS

Patients treated with the Cordis Enterprise™ self-expanding intracranial stent system for acute thromboembolic occlusion of the major anterior cerebral arteries were included. Treatment comprised systemic and intraarterial thrombolysis, mechanical thrombectomy, and stent placement. Stent deployment, recanalization rate by means of Thrombolysis In Cerebral Infarction (TICI) scores and the clinical outcome were all assessed.

RESULTS

Six patients presenting with acute carotid T (n = 2) or proximal middle cerebral artery occlusion (n = 4) were treated. The mean National Institutes of Health Stroke Scale (NIHSS) score at presentation was 14; the mean age was 57 years. Successful stent deployment and immediate recanalization were achieved in all six with a TICI score of ≥ 2. Neither distal emboli nor any procedure-related complications were encountered. One patient developed symptomatic intracerebral hemorrhage and two patients needed decompressive craniectomy after treatment. The mean NIHSS score at 10 days was 10, but only one patient showed a complete recovery at 3 months.

CONCLUSION

Intracranial placement of the Enterprise™ self-expanding stent has proven to be feasible and efficient in achieving immediate recanalization of occluded main cerebral arteries. The use of antiplatelet therapy after treatment may, however, increase the risk of reperfusion intracerebral hemorrhage.

In vivo evaluation of the Phenox CRC mechanical thrombectomy device in a swine model of acute vessel occlusion

BACKGROUND AND PURPOSE

Mechanical thrombectomy in ischemic stroke is of increasing interest as it is a promising strategy for fast and efficient recanalization. Several thrombectomy devices have been introduced to the armentarium of mechanical thrombectomy. Currently, new devices are under development and are continuously added to the neurointerventional tool box. Each device advocated so far has a different design and mechanical properties in terms of thrombus-device interaction. Therefore, a systematic evaluation under standardized conditions in vivo of these new devices is needed. The purpose of this study was to evaluate the efficiency, thrombus-device interaction, and potential complications of the novel Phenox CRC for distal mechanical thrombectomy in vivo.

MATERIALS AND METHODS

The device was evaluated in an established animal model in the swine. Recanalization rate, thromboembolic events, vasospasm, and complications were assessed. Radiopaque thrombi (2 cm length) were used for the visualization of thrombus-device interaction during retrieval. The Phenox CRC (4 mm diameter) was assessed in 15 vessel occlusions. For every occlusion a maximum of 3 retrieval attempts were performed.

RESULTS

Complete recanalization (TICI 3/TIMI 3) was achieved in 86.7% of vessel occlusions. In 66.7% (10/15), the first retrieval attempt was successful, and in 20% (3/15), the second attempt led to complete recanalization of the parent artery. In 2 cases (13.3%) thrombus retrieval was not successful (TICI 0/TIMI 0). In 1 case (6.7%) a minor embolic event occurred in a small side branch. No distal thromboembolic event was observed during the study. Thrombus-device interaction illustrated the entrapment of the thrombus by the microfilaments and the proximal cage of the device. No significant thrombus compression was observed. No vessel perforation, dissection, or fracture of the device occurred.

CONCLUSIONS

In this small animal study, the Phenox CRC was a safe and effective device for mechanical thrombectomy. The unique design with a combination of microfilaments and proximal cage reduces thrombus compression with a consequently high recanalization and low complication rate.