Treatment of acute ischemic stroke: feasibility of primary or secondary use of a self-expanding stent (Neuroform) during local intra-arterial thrombolysis

Stentrievers : An engineering review

The advent of endovascular therapy for acute large vessel occlusion has revolutionized stroke treatment. Timely access to endovascular therapy, and the ability to restore intracranial flow in a safe, efficient, and efficacious manner has been critical to the success of the thrombectomy procedure. The stentriever has been a mainstay of endovascular stroke therapy, and current guidelines recommend the usage of stentrievers in the treatment of large vessel occlusion stroke. Despite the success of existing stentrievers, there continues to be significant development in the field, with newer stentrievers attempting to improve on each of the three key aspects of the thrombectomy procedure. Here, we elucidate the technical requirements that a stentriever must fulfill. We then review the basic variables of stent design, including the raw material and its form, fabrication method, geometric configuration, and further additions. Lastly, a selection of stentrievers from successive generations are reviewed using these engineering parameters, and clinical data is presented. Further avenues of stentriever development and testing are also presented.

Reperfusion therapy in acute ischemic stroke: dawn of a new era?

Following the success of recent endovascular trials, endovascular therapy has emerged as an exciting addition to the arsenal of clinical management of patients with acute ischemic stroke (AIS). In this paper, we present an extensive overview of intravenous and endovascular reperfusion strategies, recent advances in AIS neurointervention, limitations of various treatment paradigms, and provide insights on imaging-guided reperfusion therapies. A roadmap for imaging guided reperfusion treatment workflow in AIS is also proposed. Both systemic thrombolysis and endovascular treatment have been incorporated into the standard of care in stroke therapy. Further research on advanced imaging-based approaches to select appropriate patients, may widen the time-window for patient selection and would contribute immensely to early thrombolytic strategies, better recanalization rates, and improved clinical outcomes.

Recanalization and Reperfusion Therapies of Acute Ischemic Stroke: What have We Learned, What are the Major Research Questions, and Where are We Headed?

Two placebo-controlled trials have shown that early administration of intravenous recombinant tissue plasminogen activator (rt-PA) after ischemic stroke improves outcomes up to 4.5 h after symptoms onset; however, six other trials contradict these results. We also know from analysis of the pooled data that benefits from treatment decrease as time from stroke onset to start of treatment increases. In addition to time, another important factor is patient selection through multimodal imaging, combining data from artery status, and salvageable tissue measures. Nonetheless, at the present time randomized controlled trials (RCTs) cannot demonstrate any beneficial outcomes for neuroimaging mismatch selection after 4.5 h from symptoms onset. By focusing on cases of large arterial occlusion, we know that recanalization is crucial, so endovascular treatment is an approach of interest. The use of intra-arterial thrombolysis was tested in two small RCTs that demonstrated clear benefits in terms of higher recanalization and also in clinical outcomes. But a new paradigm of stroke treatment may have begun with mechanical thrombectomy. In this field, Merci devices have been overtaken by fully deployed closed-cell self-expanding stents (stent-retrievers or “stent-trievers”). However, despite the high rate of recanalization achieved with stent-retrievers compared with other recanalization treatments, the use of these devices cannot clearly demonstrate better outcomes. Thus, futile recanalization occurs when successful recanalization fails to improve functional outcome. Recently, three RCTs, namely synthesis, IMS-III, and MR-rescue, have not been demonstrated any clear benefit for endovascular treatment. Most likely, these trials were not adequately designed to prove the superiority of endovascular treatment because they did not use optimal target populations, vascular status was not evaluated in all patients, relatively high rates of patients did not have enough mismatch, time from baseline neuroimaging to recanalization were too long or the devices used are now obsolete relative to stent-retrievers. Several RCTs currently underway are trying to determine whether bridging therapy is more effective than intravenous treatment and if mechanical thrombectomy is more effective than best medical treatment in patients ineligible for intravenous thrombolysis.

Mechanical Thrombectomy Using the Solitaire FR system for Occlusion of the Top of the Basilar Artery: Intentional Detachment of the Device after Partial Retrieval

Acute, distal, basilar artery occlusion is a challenging neurovascular emergency. There have been several reports regarding the successful application of the Solitaire FR device for treating this lesion. However, due to the lack of a suitable, balloon-tipped, guiding catheter for the vertebral artery, during this procedure we frequently experience the occurrence of clot fragmentation and distal migration. There may be some technical solutions to solve this problem. The purpose of this report is to present a technical variation of using the Solitaire FR, and which is referred to as the 'intentional device detachment technique.' As a clot tends to re-embolize during its passage through the tortuous cranio-cervical junction level of the vertebral artery or its passage through the tip of the guiding catheter, due to the lack of proximal flow arrest, we thought that not removing the stent segment of the device which is capturing the clot could avoid this problem. We were able to successfully apply this technique in two cases. We believe that this technique can be a possible technical option for using the Solitaire FR device when a patient has little concern regarding the subsequent use of antiplatelets.

Evaluation of the Solitaire system in a canine arterial thromboembolic occlusion model: is it safe for the endothelium?

The Solitaire system has recently been increasingly used for acute stroke treatment in which the endothelial safety immediately after its use has not been evaluated. This study was performed to evaluate the endothelial status when using a Solitaire system in a canine arterial occlusion model. Thromboembolic occlusion of both internal maxillary arteries was achieved in five mongrel dogs. In each animal, the Solitaire system (ev3, Irvine, CA, USA) was used for primary thrombectomy on the right side and for temporary stenting on the left side. Efficacy was assessed by comparing the recanalization rates, and safety was assessed using angiographic and microscopic assessments. Endothelial injuries were evaluated with light microscopy (LM) and scanning electron microscopy (SEM). Successful revascularizations were observed following primary thrombectomy in all five animals (100%) and after temporary stenting in two (40%). There was no incidence of vasospasm or vessel perforation in either group. Distal migration of the clot occurred in two animals that underwent primary thrombectomy. Endothelial injury was seen after primary thrombectomy in two animals (40%) and after temporary stenting in one (20%). The lesions presented as defects of the internal elastic lamina on LM and denudation of the wavy endothelial surface on SEM. During mechanical thrombectomy, the Solitaire system can cause endothelial injury both in primary thrombectomy and temporary stenting. Primary thrombectomy is likely to have a higher recanalization rate with increased endothelial injury.

Multimodal endovascular management of acute ischemic stroke in patients over 75 years old is safe and effective

Introduction

Greater attention has been directed to endovascular recanalization of acute ischemic stroke in septuagenarians and above.

Technique

A retrospective chart review was conducted to include patients treated for acute ischemic stroke from 2006 to 2012. All patients underwent initial neurological assessment and non-contrast head CT. Patients treated from 2009 to 2012 additionally received emergent CT angiogram and CT perfusion. 51 patients met the clinical and radiographic criteria and underwent multimodal endovascular revascularization for acute ischemic events.

Results

All patients underwent cerebral angiography and met angiographic criteria for endovascular thrombolysis. 34 patients (67%) were older than 80 years of age. 23 patients (45%) received intravenous tissue plasminogen activator prior to admission. Eight (16%) patients underwent stent placement after intra-arterial thrombolysis, 10 (20%) underwent balloon angioplasty and seven (14%) underwent both angioplasty and stent placement. 21 (41%) required only intra-arterial thrombolytics. An improvement in Thrombolysis in Myocardial Infarction score was noted in 34 patients (67%). The average modified Rankin Scale score on discharge was 3.9. Symptomatic intracranial hemorrhage occurred in three patients (6%); none required surgery. One patient (1.9%) had a postoperative retroperitoneal hematoma, which was managed conservatively. Two fatalities resulted from intraoperative vessel rupture (3.9%), with a combined morbidity and mortality of 27.5%.

Conclusions

Multimodal endovascular recanalization of acute ischemic stroke is a relatively safe treatment option in patients older than 75 years of age. Careful patient selection by clinical and radiographic inclusion criteria is necessary for the successful management of stroke in this age group.

Early venous drainage after successful endovascular recanalization in ischemic stroke -- a predictor for final infarct volume?

INTRODUCTION

Peri-ischemic early venous filling (PEVD) has been reported to occur at certain stages of brain infarction and has previously been termed as "luxury perfusion". We report on the significance of PEVD after a successful endovascular recanalization.

METHODS

We retrospectively evaluated all patients who underwent endovascular stroke treatment from February 2006 to April 2010 in two centers. PEVD was rated as present or absent. Infarction was evaluated on computed tomography (CT) ≥ 18 h post-treatment. Localization of the PEVD and the infarction was noted for the anterior and posterior circulation; for the anterior circulation, also deep and superficial veins/brain regions were defined.

RESULTS

A total of 151 of the 175 patients developed an infarct. Of these 151 patients, 118 had PEVD (sensitivity 78.1%); meanwhile, 20 of 24 patients without an infarction had no PEVD (specificity 83.3%). Consistent localization of the PEVD and the infarct was seen in 107/151 patients (70.9%); in 28 of these 107 cases, the territory of PEVD was smaller than the infarct (26.2%) and exceeded it in 7/107 patients (5.6%). Territorial congruency of the PEVD and the final infarct was 57.6-75% for deep/superficial brain regions of the anterior, but only 16.7% for the posterior circulation. Separate evaluation for the anterior circulation resulted in a 94.9% sensitivity and an 81.0% specificity.

CONCLUSION

PEVD is a potential angiographic predictor for irreversible regional tissue damage and subsequent infarction despite successful recanalization. This finding deserves further studies and may influence therapeutic decisions such as post-treatment anticoagulative medication. It may also be considered in potential refined classifications of angiographic reperfusion success in the future.

Intra-arterial adjuvant tirofiban after unsuccessful intra-arterial thrombolysis of acute ischemic stroke: preliminary experience in 16 patients

INTRODUCTION

Intra-arterial (IA) thrombolysis with plasminogen activator is well-known, but the use of IA tirofiban as an adjuvant for IA thrombolysis is not well-known. We investigated the feasibility of IA tirofiban as an adjuvant after unsuccessful IA recanalization with urokinase (UK) for acute ischemic stroke.

METHODS

We retrospectively analyzed all 16 consecutive patients (11 men and five women; mean age, 61.3 years; range, 36-85 years) who were treated with IA tirofiban after isolated IA thrombolysis with UK or bridging therapy with systemic recombinant tissue plasminogen activator (rt-PA; 0.6 mg/Kg) and IA UK for acute ischemic stroke. Outcome measures included angiographic recanalization (thrombolysis in cerebral infarction, TICI), symptomatic and asymptomatic intracerebral hemorrhage (ICH), mortality, and functional independence at 3 months (modified Rankin Scale, 0-2).

RESULTS

Among the 16 patients treated with IA tirofiban as an adjuvant, 10 patients had conventional dose (<25 ug/kg, bolus) and six patients had high dose (≥25 ug/kg, bolus) of IA tirofiban after unsuccessful IA thrombolysis whether systemic rt-PA used or not. Successful angiographic recanalization (TICI grade 2b or 3) was achieved in 13 patients (13/16) and a functional independence at 3 months in eight patients (8/16). Three months after therapy, three patients had died. There were two patients of symptomatic ICH and four asymptomatic ICH.

CONCLUSION

Conventional dose of IA tirofiban as an adjuvant during IA thrombolysis for acute ischemic stroke seems feasible. However, further dose escalation studies should be performed regarding the IA use of tirofiban for acute ischemic stroke.