Approval of the MERCI Clot Retriever

Updates in mechanical thrombectomy

Stroke is a leading cause of morbidity and mortality. The advent of mechanical thrombectomy has largely improved patient outcomes. This article reviews the features and outcomes associated with aspiration, stent retrievers, and combination catheters used in current practice. There is also a discussion on clinical considerations based on anatomical features and clot composition. The reperfusion grading scale and outcome metrics commonly used following thrombectomy when a patient is still in the hospital are reviewed. Lastly, there are proposed discharge and outpatient follow-up goals in caring for patients hospitalized for a stroke.

Food and Drug Association Approval Process for Devices Used in Endovascular Treatment of Stroke

PURPOSE OF THE REVIEW

This article reviews the Food and Drug Administration's (FDA's) process for approval of new medical devices and describes the evolution of endovascular devices used for the treatment of acute ischemic stroke.

RECENT FINDINGS

Several recent studies have established the benefit of endovascular treatment of acute ischemic stroke from emergent large vessel occlusion. This has led to endovascular treatment becoming the usual care in acute stroke management and has generated greater-than-ever interest in the development of newer and more effective devices.

SUMMARY

In the United States, the FDA is the regulatory authority that is empowered with the approval and monitoring of new medical devices for widespread use in the population. The FDA categorizes medical devices into 3 classes based mainly on their potential risks to patients and/or users; class I devices pose the least risk and have the least stringent approval process, while class III devices pose the highest risk and undergo the most stringent and time-consuming approval process. There are 4 main pathways to approval: premarket notification, also known as the 510(k) pathway; premarket approval (PMA), de novo, and Humanitarian Device Exemption pathway. These pathways are described in detail in the article. The FDA also mandates postmarketing surveillance to identify any untoward and unexpected long-term complications.

A pilot protocol and review of triple neuroprotection with targeted hypothermia, controlled induced hypertension, and barbiturate infusion during emergency carotid endarterectomy for acute stroke after failed tPA or beyond 24-hour window of opportunity

An alternative to tissue plasminogen activator (tPA) failure has been a daunting challenge in ischemic stroke management. As tPA is time-dependent, delays can occur in definitive treatment while passively waiting to observe a clinical response to intravenous thrombolysis. Until today, uncertainty exists in the management strategy of wake-up stroke patients or those presenting beyond the therapeutic tPA window. Clinical dilemmas in these situations can prolong the transitional period of inertia, resulting in an adverse neurological outcome. We propose and review an innovative approach called triple neuro-protection (TNP), which encompasses three technical domains-targeted hypothermia, systemic induced hypertension, and barbiturates infusion, to protect the brain during carotid endarterectomy after failed tPA and/or beyond the 24-hour therapeutic mechanical thrombectomy window. This proposal assimilates discussion on the clinical evidence of the individual domains of TNP with our own clinical experience with TNP. Our first TNP was successfully employed in a 55-year-old man in 2015 while performing emergency carotid endarterectomy after he was referred to us 72 hours post tPA failure. The patient had a successful clinical outcome despite being in therapeutic inertia with 90–99% ipsilateral carotid stenosis and contralateral occlusion on presentation. In the last five years, we have safely used TNP in 25 selected cases with favourable clinical outcomes.

Thrombectomy for Distal, Medium Vessel Occlusions: A Consensus Statement on Present Knowledge and Promising Directions

Endovascular thrombectomy (EVT) is well established as a highly effective treatment for acute ischemic stroke (AIS) due to proximal, large vessel occlusions (PLVOs). With iterative further advances in catheter technology, distal, medium vessel occlusions (DMVOs) are now emerging as a promising next potential EVT frontier. This consensus statement integrates recent epidemiological, anatomic, clinical, imaging, and therapeutic research on DMVO-AIS and provides a framework for further studies. DMVOs cause 25% to 40% of AISs, arising as primary thromboemboli and as unintended consequences of EVT performed for PLVOs, including emboli to new territories (ENTs) and emboli to distal territories (EDTs) within the initially compromised arterial field. The 6 distal medium arterial arbors (anterior cerebral artery [ACA], M2–M4 middle cerebral artery [MCA], posterior cerebral artery [PCA], posterior inferior cerebellar artery [PICA], anterior inferior cerebellar artery [AICA], and superior cerebellar artery [SCA]) typically have 25 anatomic segments and give rise to 34 distinct arterial branches nourishing highly differentiated, largely superficial cerebral neuroanatomical regions. DMVOs produce clinical syndromes that are highly heterogenous but frequently disabling. While intravenous fibrinolytics are more effective for distal than proximal occlusions, they fail to recanalize one-half to two-thirds of DMVOs. Early clinical series using recently available, smaller, more navigable stent retriever and thromboaspiration devices suggest EVT for DMVOs is safe, technically efficacious, and potentially clinically beneficial. Collaborative investigations are desirable to enhance imaging recognition of DMVOs; advance device design and technical efficacy; conduct large registry studies using harmonized, common data elements; and complete formal randomized trials, improving treatment of this frequent mechanism of stroke.

Endovascular Stroke Therapy

Ischemic stroke is a leading cause of death and disability throughout the world and is both preventable and treatable. This review focuses on the treatment of the most severe form of ischemic stroke, namely large-vessel ischemic stroke, using endovascular techniques. Such therapies were proven effective in 2015. These therapies are among the most beneficial surgical therapies ever subjected to randomized clinical trials. Recent research has explored treating patients up to 24 h following the onset of stroke using advanced imaging techniques to select patients with brain tissue still at risk. These new findings suggest there exists a tissue clock rather than a time clock when selecting patients for therapy. Stroke systems throughout the world are now embracing endovascular stroke therapy. Improving regional stroke systems of care and expanding eligibility for patients are a major focus of current research.

Endovascular Metal Devices for the Treatment of Cerebrovascular Diseases

Cerebrovascular disease involves various medical disorders that obstruct brain blood vessels or deteriorate cerebral circulation, resulting in ischemic or hemorrhagic stroke. Nowadays, platinum coils with or without biological modification have become routine embolization devices to reduce the risk of cerebral aneurysm bleeding. Additionally, many intracranial stents, flow diverters, and stent retrievers have been invented with uniquely designed structures. To accelerate the translation of these devices into clinical usage, an in-depth understanding of the mechanical and material performance of these metal-based devices is critical. However, considering the more distal location and tortuous anatomic characteristics of cerebral arteries, present devices still risk failing to arrive at target lesions. Consequently, more flexible endovascular devices and novel designs are under urgent demand to overcome the deficiencies of existing devices. Herein, the pros and cons of the current structural designs are discussed when these devices are applied to the treatment of diseases ranging broadly from hemorrhages to ischemic strokes, in order to encourage further development of such kind of devices and investigation of their use in the clinic. Moreover, novel biodegradable materials and drug elution techniques, and the design, safety, and efficacy of personalized devices for further clinical applications in cerebral vasculature are discussed.

Quinolinyl Nitrone RP19 Induces Neuroprotection after Transient Brain Ischemia

There is a need to develop additional effective therapies for ischemic stroke. Nitrones, which were first developed as reactive oxygen species (ROS)-trapping compounds, have been proposed as neuroprotective agents for ischemic stroke, a ROS-related disorder. The previous reported ROS-trapping compound, quinolyl nitrone RP19, is here being assayed to induce neuroprotection to ischemia-reperfusion injury in three experimental ischemia models: (i) oxygen-glucose deprivation (OGD) on primary neuronal cultures; (ii) transient global cerebral ischemia in four-vessel occlusion model; and (iii) transient focal cerebral ischemia in middle cerebral artery occlusion (tMCAO) model. RP19 (50 μM) induced long-term neuroprotection at 5 days of recovery after OGD in primary neuronal cultures, evaluated by cell viability assay, and decreased both ROS formation and lipid peroxidation upon recovery after OGD. Furthermore, treatment of animals with RP19 at the onset of reperfusion after either global or focal ischemia, at the dose range that was demonstrated to be neuroprotective in neuronal cultures, decreased neuronal death and apoptosis induction, reduced the size of infarct, and improved the neurological deficit scores after 48 h or 5 days of reperfusion after ischemia. The molecule proposed, quinolyl nitrone RP19, induced substantial neuroprotection on experimental ischemia in neuronal cells, and against ischemic injury following transient brain ischemia in treated animals. This molecule may have potential therapeutic interest in ischemic stroke and to reduce the reoxygenation-induced injury after induced reperfusion.

[Mechanical thrombectomy for acute ischemic stroke : current evidence and open questions]

OBJECTIVE

To determine the importance of mechanical thrombectomy (MT) in the treatment of ischemic stroke.

MATERIAL AND METHODS

Analysis and comparison of randomized controlled trials (RCT) of MT versus i.v. thrombolysis (IVT) considering pathophysiological and logistic aspects.

RESULTS

The use of MT is more effective than IVT for internal carotid artery terminus (ICAT), M1 segment and tandem occlusions, i.e. proximal internal carotid artery (ICA) occlusion or stenosis, even in patients older than 75-80 years of age. Due to the small sample sizes this question cannot be answered for patients with M2 occlusions. It is still uncertain whether MT is needed in patients with a low National Institutes of Health stroke scale (NIHSS) score, whether IVT is needed before MT and what type of imaging should be performed. Approximately one third of eligible patients currently undergo MT in Germany. Results from RCTs with stent retrievers for patients with vertebrobasilar artery occlusions are lacking.

CONCLUSION

After becoming established as a first-line therapy for patients with ICAT, M1 segment and tandem occlusions, the effectiveness of MT with stent retrievers has to proven in patients with more distal occlusions, low NIHSS scores and even vertebrobasilar artery occlusions.

A critical analysis of intra-arterial thrombolytic doses in acute ischemic stroke treatment

BACKGROUND

Intra-arterial thrombolytics (IAT) such as Alteplase, Tenecteplase, and Reteplase are currently used in patients with acute ischemic stroke in varying doses. We evaluated the relationship of IA thrombolytic dose with angiographic recanalization, intracerebral hemorrhage (ICH) rates, and clinical outcomes at three comprehensive stroke centers.

METHODS

We stratified patients who underwent endovascular treatment into tertiles based on intra-arterial thrombolytic dose administered: lower tertile (range 1.5-5 mg), middle tertile (range 6-10 mg), and upper tertile (range 10.3-68.5 mg) of rt-PA equivalent. The rates of angiographic recanalization, ICH, and favorable clinical outcomes (discharge modified Rankin score [mRS] = 0-2) were ascertained and compared within the three tertiles. Logistic regression analyses were performed to determine the association between IA thrombolytic dosages and angiographic recanalization, ICH, and favorable clinical outcomes after adjusting for potential confounders.

RESULTS

A total of 197 patients were treated with IAT; mean age ±SD was 65.6 ± 16 years; 105 (53.3%) were women. Ninety-one (46.2%) patients received both IVT and IAT. IA rt-PA equivalent dose was not different between the patients with and without ICH [mean (mg) ± SD, 9.8 ± 6.1 versus 9.8 ± 9.5, p = 0.9]. We did not find any relation between increasing doses of IAT (from 2 to 69 mg rt-PA equivalent) and symptomatic or asymptomatic ICH: (p = 0.1630) and (p = 0.6702), respectively. Multivariate analysis demonstrated that IAT dose was not associated with ICH (OR 1.0, 95% CI 0.97-1.07, p = 0.3919) or favorable outcome (OR, 1.00, 95% CI 0.95-1.06, p = 0.7375). In a subset analysis of IVT patients, total doses ranged from 48.2 to 149 mg and were not associated with either symptomatic (p = 0.23) or asymptomatic (p = 0.24) ICHs.

CONCLUSION

Our study demonstrates that IAT in doses up to 69 mg is safe without any evidence of dose-related ICHs even in those patients who had received IVT.

State-of-the-art endovascular treatment of acute ischemic stroke

Stroke is the third leading cause of death in the USA. An estimated 795,000 new or recurrent stroke events occur annually, mostly ischemic in nature. Arterial recanalization and subsequent reperfusion performed shortly after symptom onset can help to restore brain function in acute ischemic stroke (AIS). The only treatment currently approved by the United States Food and Drug Administration is intravenous tissue plasminogen activator, administered within 4.5 h of symptom onset. However, this short window often precludes effective intervention. Mechanical neurothrombectomy devices offer many potential advantages over pharmacologic thrombolysis, including more rapid achievement of recanalization, enhanced efficacy in treating large-vessel occlusions, and a potentially lower risk of hemorrhagic events. The goal of this chapter is to describe the state-of-the-art neurothrombectomy devices and stenting techniques for endovascular treatment of acute ischemic stroke, as well as to highlight recent advances in reperfusion therapies. Ongoing clinical trials, some with randomized, controlled designs, are included.

Reperfusion therapies of acute ischemic stroke: potentials and failures

Over the past 20 years, clinical research has focused on the development of reperfusion therapies for acute ischemic stroke (AIS), which include the use of systemic intravenous thrombolytics (alteplase, desmoteplase, or tenecteplase), the augmentation of systemic intravenous recanalization with ultrasound, the bridging of intravenous with intra-arterial thrombolysis, the use of multi-modal approaches to reperfusion including thrombectomy and thromboaspiration with different available retrievers. Clinical trials testing these acute reperfusion therapies provided novel insight regarding the comparative safety and efficacy, but also raised new questions and further uncertainty on the field. Intravenous alteplase (tPA) remains the fastest and easiest way to initiate acute stroke reperfusion treatment, and should continue to be the first-line treatment for patients with AIS within 4.5 h from onset. The use of tenecteplase instead of tPA and the augmentation of systemic thrombolysis with ultrasound are both novel therapeutical modalities that may emerge as significant options in AIS treatment. Endovascular treatments for AIS are rapidly evolving due to technological advances in catheter-based interventions and are currently emphasizing speed in order to result in timely restoration of perfusion of still-salvageable, infarcted brain tissue, since delayed recanalization of proximal intracranial occlusions has not been associated with improved clinical outcomes. Comprehensive imaging protocols in AIS may enable better patient selection for endovascular interventions and for testing multi-modal combinatory strategies.

Evolution of practice during the Interventional Management of Stroke III Trial and implications for ongoing trials

BACKGROUND AND PURPOSE

We explored changes in the patient population and practice of endovascular therapy during the course of the Interventional Management of Stroke (IMS) III Trial.

METHODS

Changes in baseline characteristics, use of baseline CT angiography, treatment times and specifics, and outcomes were compared between the first 4 protocols and the fifth and final protocol.

RESULTS

Compared with subjects treated in the first 4 protocol versions (n=610), subjects treated in fifth and final protocol (n=46) were older (75 versus 68 years, P<0.0002) and less likely to have a pretreatment Rankin of 0 (76% versus 89%, P=0.01), were more likely to have a pretreatment CT angiography (65% versus 45%, P=0.009), had quicker median times in the endovascular arm from onset to start of intra-arterial therapy (209 versus 250 minutes, P=0.002) and to reperfusion (269 versus 344 minutes, P<0.0001), had a higher mean dose of total tissue-type plasminogen activator in the endovascular arm (74.0 versus 63.7 mg, P<0.0001), and were less likely to receive intra-arterial tissue-type plasminogen activator as part of the endovascular procedure (16% versus 44%, P=0.015). There were no significant differences in functional and safety outcomes between subjects treated in the 2 treatments arms in either the first 4 protocols or fifth protocol although the small sample size in the fifth protocol provided limited power.

CONCLUSIONS

Endovascular technology and diagnostic approaches to acute stroke patients changed substantially during the IMS III Trial. Efforts to decrease the time to delivery of endovascular therapy were successful.

Machine learning for outcome prediction of acute ischemic stroke post intra-arterial therapy

Introduction

Stroke is a major cause of death and disability. Accurately predicting stroke outcome from a set of predictive variables may identify high-risk patients and guide treatment approaches, leading to decreased morbidity. Logistic regression models allow for the identification and validation of predictive variables. However, advanced machine learning algorithms offer an alternative, in particular, for large-scale multi-institutional data, with the advantage of easily incorporating newly available data to improve prediction performance. Our aim was to design and compare different machine learning methods, capable of predicting the outcome of endovascular intervention in acute anterior circulation ischaemic stroke.

Method

We conducted a retrospective study of a prospectively collected database of acute ischaemic stroke treated by endovascular intervention. Using SPSS®, MATLAB®, and Rapidminer®, classical statistics as well as artificial neural network and support vector algorithms were applied to design a supervised machine capable of classifying these predictors into potential good and poor outcomes. These algorithms were trained, validated and tested using randomly divided data.

Results

We included 107 consecutive acute anterior circulation ischaemic stroke patients treated by endovascular technique. Sixty-six were male and the mean age of 65.3. All the available demographic, procedural and clinical factors were included into the models. The final confusion matrix of the neural network, demonstrated an overall congruency of ∼80% between the target and output classes, with favourable receiving operative characteristics. However, after optimisation, the support vector machine had a relatively better performance, with a root mean squared error of 2.064 (SD: ±0.408).

Discussion

We showed promising accuracy of outcome prediction, using supervised machine learning algorithms, with potential for incorporation of larger multicenter datasets, likely further improving prediction. Finally, we propose that a robust machine learning system can potentially optimise the selection process for endovascular versus medical treatment in the management of acute stroke.

Thrombolytic and newer mechanical device treatment for acute ischemic stroke

For 8 years, only intravenous tissue plasminogen activator was approved by the US FDA for acute stroke treatment. The US FDA has now cleared the Merci Retriever (Concentric Medical, Inc.), a corkscrew-like device attached to a catheter, for the removal of clots causing ischemic strokes. Since the clearance was based on nonrandomized treatment trials, practitioners must scrutinize available data describing effects of the device on recanalization of the vessel, outcomes and important adverse events, such as symptomatic intracranial hemorrhage. This article reviews the study findings that are likely to contribute to current treatment decisions.

Retrievable stent thrombectomy in the treatment of acute ischemic stroke: analysis of a revolutionizing treatment technique

Acute ischemic stroke resulting from intracranial vessel occlusion is associated with high morbidity and mortality. The mainstays of therapy are fibrinolytics and mechanical thrombectomy in properly selected patients. A new Food and Drug Administration-approved technology to perform thrombectomy, retrievable stenting, may provide superior revascularization rates and improved patient outcomes. We analyzed the cumulative human experience reported for the Trevo Pro Retrieval System (Stryker, Kalamazoo, MI, USA) and the Solitaire FR Revascularization Device (ev3, Irvine, CA, USA) as the definitive treatment for acute ischemic stroke. A literature search was undertaken to identify studies using the retrievable stents published up to September 2012. Nineteen studies identified a total of 576 patients treated with either the Trevo (n=221) or Solitaire (n=355) devices. Pooled data analysis identified median baseline National Institutes of Health Stroke Scale scores of 18.5 ± 0.289 (standard error of the mean) and 17.9 ± 0.610, and time to recanalization of 53.9 ± 23.6 minutes and 59.0 ± 8.0 minutes for the Trevo and Solitaire groups, respectively. Recanalization was variably defined by individual studies, most commonly achieving at least a thrombolysis in cerebral infarction score of 2a-3 or a thrombolysis in myocardial infarction score of 2-3. Revascularization (83%, 82%), mortality (31%, 14%), hemorrhage (8%, 6%), device complications (5%, 6%), and good patient outcomes (51%, 47%) were found with the Trevo and Solitaire devices, respectively. Preliminary analysis reveals excellent clinical outcomes for retrievable stent technology. This may be attributable to both high rates of revascularization with a relatively short time to perfusion restoration.

Unanswered questions in thrombolytic therapy for acute ischemic stroke

This article reviews some of the current literature in support or against extension of the intravenous tissue plasminogen activator window, use of intra-arterial therapy or devices, as well alternative pharmacologic therapies that may extend the window for treatment of patients with acute ischemic stroke, with consideration of the relative risk of thrombolytic complications, factors for worse outcomes, and unclear stroke onset, as seen in patients with wake-up stroke. The issue of newer concomitant antithrombotic therapies as they affect the decision for acute ischemic stroke thrombolytic therapy is also explored.

Population-based estimates of neuroendovascular procedures: results of a state-wide study

BACKGROUND

The Brain Attack Coalition identified the availability of neuroendovascular procedures as an essential component of a comprehensive stroke center.

OBJECTIVE

To provide population-based estimates of neuroendovascular procedures.

METHODS

State-wide estimates of cervicocerebral angiograms, endovascular ischemic stroke treatments, carotid angioplasty and stent placements, intracranial angioplasty and stent placements, endovascular treatment of intracranial aneurysms, and endovascular treatment of intracranial arteriovenous malformations (AVMs) were obtained. We calculated the annual incidence rates of various neuroendovascular and neurosurgical procedures (per 100,000 persons). For the denominator, total persons in each year were categorized in 10-year age intervals.

RESULTS

The incidence of carotid endarterectomy (387.6 per 100,000 persons) and carotid stent placement (34.7 per 100,000 persons) peaked at 75-84 years. The incidence of aneurysm embolization also peaked in that population bracket (67.9 per 100,000 persons), yet there was a dramatic reduction in the incidence of surgical aneurysm treatment (3.6 per 100,000 persons) in those aged 75-84 years. There was a prominent reduction in the incidence of all procedures in the population aged ≥85 years, except for intravenous/intra-arterial thrombolytic use in ischemic stroke. The incidence of ischemic stroke increased almost by 50% in the population aged ≥85 years compared to those aged 75-84 years. However, the incidence of endovascular procedures for acute ischemic stroke decreased from 22.8 per 100,000 persons in the population aged 75-84 years to 13.2 per 100,000 persons in the population aged ≥85 years.

CONCLUSIONS

A marked disproportion of neuroendovascular procedures performed and disease prevalence was noted in persons aged ≥85 years, an increasing segment of the population according to recent Census.

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

Background and aims

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.

Methods

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.

Results

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).

Conclusions

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.

Ischemic stroke: emergencies and management

The past 40 years have seen the evolution of acute ischemic stroke management from unproven therapies du jour, such as steroids, heparin for stroke in evolution, and hypervolemic-hemodilution, to more of a scientific basis for our decision-making process. This evolution is directly related to the advancements in imaging of stroke. It is also related to carefully designed, controlled clinical trials of potential therapies, which have led to the recognition of the benefits of thrombolytic therapy in the acute setting but have also caused confusion and frustration over the lack of benefit for potential neuroprotective agents that once seemed promising.

CT and MRI early vessel signs reflect clot composition in acute stroke

BACKGROUND AND PURPOSE

The purpose of this study was to provide the first correlative study of the hyperdense middle cerebral artery sign (HMCAS) and gradient-echo MRI blooming artifact (BA) with pathology of retrieved thrombi in acute ischemic stroke.

METHODS

Noncontrast CT and gradient-echo MRI studies before mechanical thrombectomy in 50 consecutive cases of acute middle cerebral artery ischemic stroke were reviewed blinded to clinical and pathology data. Occlusions retrieved by thrombectomy underwent histopathologic analysis, including automated quantitative and qualitative rating of proportion composed of red blood cells (RBCs), white blood cells, and fibrin on microscopy of sectioned thrombi.

RESULTS

Among 50 patients, mean age was 66 years and 48% were female. Mean (SD) proportion was 61% (±21) fibrin, 34% (±21) RBCs, and 4% (±2) white blood cells. Of retrieved clots, 22 (44%) were fibrin-dominant, 13 (26%) RBC-dominant, and 15 (30%) mixed. HMCAS was identified in 10 of 20 middle cerebral artery stroke cases with CT with mean Hounsfield Unit density of 61 (±8 SD). BA occurred in 17 of 32 with gradient-echo MRI. HMCAS was more commonly seen with RBC-dominant and mixed than fibrin-dominant clots (100% versus 67% versus 20%, P=0.016). Mean percent RBC composition was higher in clots associated with HMCAS (47% versus 22%, P=0.016). BA was more common in RBC-dominant and mixed clots compared with fibrin-dominant clots (100% versus 63% versus 25%, P=0.002). Mean percent RBC was greater with BA (42% versus 23%, P=0.011).

CONCLUSIONS

CT HMCAS and gradient-echo MRI BA reflect pathology of occlusive thrombus. RBC content determines appearance of HMCAS and BA, whereas absence of HMCAS or BA may indicate fibrin-predominant occlusive thrombi.

Recanalization therapy for acute ischemic stroke, part 2: mechanical intra-arterial technologies

Stroke therapy has been revolutionized in the past two decades with the widespread implementation of chemical thrombolysis for acute stroke. However, chemical thrombolysis continues to be limited in its efficacy secondary to relatively short time windows and a high associated risk of hemorrhage. In an attempt to minimize hemorrhagic complications and extend the available therapeutic window, mechanical devices designed specifically for thrombus removal, clot obliteration, and arterial revascularization have experienced a recent surge in development and utilization. As such, chemical thrombolytics now represent only one of many options in acute stroke therapy. These new mechanical devices have extended the potential treatment window and now provide alternatives to patients who do not respond to conventional intravenous thrombolysis. This review will discuss the development of these devices, supporting literature, and the individual strengths that each engenders towards a life-saving therapy for stroke.

Intravenous rt-PA versus endovascular therapy for acute ischemic stroke

The influence of baseline stroke severity on outcome makes comparisons between nonrandomized studies of intravenous and intra-arterial (IA) therapy problematic. Using pooled data from the placebo arms of randomized trials in acute ischemic stroke, we derived predictive functions for outcome. We then compared the outcomes from published trials to these functions. Net benefit was calculated by comparison of the individual study with the predicted outcome based on the therapeutic time window. Similar net benefit for IA therapy and intravenous therapy was found at 3 hours and 6 hours; a slight advantage for IA therapy was mitigated by an increase in mortality at 6 hours and by publication bias. No net benefit for IA therapy was shown in the time window greater than 6 hours. Conclusive evidence for the superiority of either therapy awaits prospective randomized trials.

Percutaneous balloon angioplasty for acute occlusion of intracranial arteries

BACKGROUND

The benefits of intravenous thrombolysis for acute ischemic stroke are still limited.

OBJECTIVE

To evaluate the safety and efficacy of double-lumen balloon catheter-based reperfusion therapy with or without intra-arterial thrombolysis for acute occlusion of intracranial arteries.

METHODS

Fifty-nine patients with acute occlusion of intracranial arteries were enrolled. A Gateway balloon catheter was used to disrupt clots or dilate atheromatous plaques in every patient. The technical details, technique-related complications, recanalization rates, and clinical outcomes were analyzed.

RESULTS

The occlusion sites were internal carotid arteries in 17 patients, M1 segments in 32 patients, the M2 segment in 1 patient, a vertebral artery in 1 patient, and basilar arteries in 8 patients. Twenty-four patients (41%) were treated with thrombolysis first, and 20 patients (34%) were treated with percutaneous transluminal angioplasty (PTA) followed by thrombolysis. PTA alone was performed in 15 patients (25%). The mean dose of urokinase was 205 x 10 U. The extent of recanalization was complete (Thrombolysis in Myocardial Infarction [TIMI] score of 3) in 17 patients (29%), and partial (TIMI 1/2) in 28 patients (47%). Functional independence at discharge was preserved in 76%, 25%, and 7% of patients with TIMI 3, TIMI 1/2, and TIMI 0, respectively. A combination of PTA and thrombolysis resulted in a significantly higher recanalization rate than PTA only. Seven patients (12%) experienced hemorrhagic events after treatment. Severe parenchymal hemorrhage with neurologic deterioration was observed in 2 patients (4%), and vessel rupture was encountered in 1 atherosclerotic case.

CONCLUSIONS

Mechanical angioplasty using a Gateway catheter combined with a low-dose thrombolytic agent is a safe and effective treatment for acute intracranial embolic and atherosclerotic occlusion with a low risk of hemorrhagic complications.

The endovascular management of intracranial vascular disease including the MERCI device

The prompt and aggressive management of acute stroke has become the standard of care as public awareness and the available successful treatment options both increase. The intravenous administration of tissue plasminogen activator within an established treatment window has been determined through large well-designed studies. The endovascular strategies for acute stroke have evolved significantly over the past 5 years and have been prompted by the limits of the intravenous treatment, as well as by the desire to demonstrate improved recanalization rates and improved long-term outcomes. Among these interventional treatment options are the intra-arterial administration of tissue plasminogen activator and newer antiplatelet agents, mechanical thrombectomy with the MERCI device, and intracranial angioplasty and stenting. This article outlines the major studies that have defined the current field of acute stroke management and discusses the basic treatment paradigms that are commonly used today.

Current and future recanalization strategies for acute ischemic stroke

In a quest for stroke treatment, reperfusion proved to be the first key to the puzzle. Systemic tissue plasminogen activator (tPA), the first and currently the only approved treatment, is also the fastest way to initiate thrombolyis for acute ischemic stroke. tPA works by induction of mostly partial recanalization since stroke patients often have large thrombus burden. Thus, early augmentation of fibrinolysis and multi-modal approach to improve recanalization are desirable. This review focuses on the following strategies available to clinicians now or being tested in clinical trials: (a) faster initiation of tPA infusion; (b) sonothrombolysis; (c) intra-arterial revascularization, bridging intravenous and intra-arterial thrombolysis, mechanical thrombectomy and aspiration; and (d) novel experimental approaches. Despite these technological advances, no single strategy was yet proven to be a 'silver bullet' solution to reverse acute ischemic stroke. Better outcomes are expected with faster treatment leading to early, at times just partial flow improvement rather than achieving complete recanalization with lengthy procedures. Arterial re-occlusion can occur with any of these approaches, and it remains a challenge since it leads to poor outcomes and no clinical trial data are available yet to determine safe strategies to prevent or reverse re-occlusion.

From presentation to follow-up: diagnosis and treatment of cerebral venous thrombosis

Cerebral venous thrombosis is an uncommon cause of stroke but remains a challenge for physicians faced with this diagnosis largely due to the variability in presentation. Anticoagulation, typically with intravenous heparin, remains the mainstay of treatment for stable patients and is sufficient in the majority of cases. However, a significant mortality rate exists for cerebral venous thrombosis due to patients who deteriorate or do not adequately respond to initial treatments. It is in these patients that more aggressive interventions must be undertaken. The neurosurgeon is often called on, either acutely for initial evaluation of the stroke or venous hemorrhage or after the failure of initial therapy for clot evacuation, hemicraniectomy, or thrombectomy. A proper workup must include a search for an underlying, correctable cause as well as thorough follow-up with correction of identified risk factors to decrease the risk of recurrent disease.

Recanalization therapies in acute ischemic stroke: pharmacological agents, devices, and combinations

The primary aim of thrombolysis in acute ischemic stroke is recanalization of an occluded intracranial artery. Recanalization is an important predictor of stroke outcome as timely restoration of regional cerebral perfusion helps salvage threatened ischemic tissue. At present, intravenously administered tissue plasminogen activator (IV-TPA) remains the only FDA-approved therapeutic agent for the treatment of ischemic stroke within 3 hours of symptom onset. Recent studies have demonstrated safety as well as efficacy of IV-TPA even in an extended therapeutic window. However, the short therapeutic window, low rates of recanalization, and only modest benefits with IV-TPA have prompted a quest for alternative approaches to restore blood flow in an occluded artery in acute ischemic stroke. Although intra-arterial delivery of the thrombolytic agent seems effective, various logistic constraints limit its routine use and as yet no lytic agent have not received full regulatory approval for intra-arterial therapy. Mechanical devices and approaches can achieve higher rates of recanalization but their safety and efficacy still need to be established in larger clinical trials. The field of acute revascularization is rapidly evolving, and various combinations of pharmacologic agents, mechanical devices, and novel microbubble/ultrasound technologies are being tested in multiple clinical trials.

Revascularization in acute ischaemic stroke using the penumbra system: the first single center experience

BACKGROUND AND PURPOSE

This is the first single center experience illustrating the effectiveness of the penumbra system (PS) in the treatment of large vessel occlusive disease in the arena of acute ischaemic stroke. The PS is an innovative mechanical thrombectomy device, employed in the revascularization of large cerebral vessel occlusions in patients via the utilization of an aspiration platform.

METHODS

This is a prospective, non-randomized controlled trial evaluating the clinical and functional outcome in 29 patients with acute intra-cranial occlusions consequent to mechanical thrombectomy by the PS either as mono-therapy or as an adjunct to current standard of care. Patients were evaluated by a neurologist and treated by our in house interventional neuro-radiologists. Primary end-points were revascularization of the occluded target vessel to TIMI grade 2 or 3 and neurological outcome as measured by an improvement in the NIH Stroke Scale (NIHSS) score after the procedure.

RESULTS

Complete revascularization (TIMI 3) was achieved in 21/29 (72.4%) of patients. Partial revascularization (TIMI 2) was established in 4/29 (13.8%) of patients. Revascularization failed in four (13.8%) patients. Nineteen (19) patients (65.5%) had at least a four-point improvement in NIHSS scores. Modified Rankin scale scores of < or =2 were seen in 37.9% of patients. There were no device-related adverse events. Symptomatic intra-cranial hemorrhage occurred in 7% of patients.

CONCLUSIONS

The PS has the potential of exercising a significant impact in the interventional treatment of ischaemic stroke in the future.

Stroke Therapy Academic Industry Roundtable (STAIR) recommendations for extended window acute stroke therapy trials

The Stroke Therapy Academic Industry Roundtable (STAIR) meetings focus on helping to advance the development of acute stroke therapies. Further extending the time window for acute stroke therapies is an important endeavor for increasing the number of stroke patients who might benefit from treatment. The STAIR group recommends that future extended time window trials initially should focus on selected patient groups most likely to respond to investigational therapies and that penumbral imaging is one tool that may identify such patients. The control group in these trials should receive best locally available medical care; if regulatory approval for intravenous (i.v.) tPA is extended to 4.5 hours, then tPA will become the most appropriate comparator in trials conducted within this time window. In future well-designed extended window clinical trials randomization is appropriate and should not be precluded by using unproven treatment with intraarterial (i.a.) thrombolysis or mechanical devices. For proof of concept, extended time window, phase II trials of i.v. thrombolysis, or mechanical devices in which early recanalization/reperfusion is the primary end point, rescue therapy/bailout treatment with i.a. thrombolysis or devices may be acceptable. Statistical considerations and definitions of successful recanalization/reperfusion are suggested for these trials.

[Mechanical recanalization]

Although several studies and registries have focused on new interventional systems for the treatment of acute ischemic stroke, a standard procedure has not yet been established. The procedure itself is still controversially discussed but studies have shown that patients who were successfully treated with mechanical recanalization had a better clinical outcome.

Retrieval of a Migrated Coil Using an X6 MERCI Device

SUMMARY

Coil migration is a recognised but rare complication of endovascular coiling. Many techniques are available commercially for coil retrieval. We report the case of an acute subarachnoid hemorrhage in a 54-year-old woman in which a migrated coil was successfully retrieved using an X6 MERCI device.