Mechanical Thrombolysis in Acute Ischemic Stroke With Endovascular Photoacoustic Recanalization

Fabrication of Shape Memory Polymer Endovascular Thrombectomy Device for Treating Ischemic Stroke

Stroke is the second result for death and ischemic stroke constitutes most of all stroke cases. Ischemic stroke takes place when blood clot or embolus blocks cerebral vessel and interrupts blood flow, which often leads to brain damage, permanent disability, or death. There is a 4.5-h (golden hour) treatment window to restore blood flow prior to permanent neurological impairment results. Current stroke treatments consist mechanical system or thrombolytic drug therapy to disrupt or dissolve thrombus. Promising method for stroke treatment is mechanical retrieving of thrombi employing device deployed endovascularly. Advent of smart materials has led to research fabrication of several minimally invasive endovascular devices that take advantage of new materials capabilities. One of these capabilities is shape memory, is capability of material to store temporary form, then activate to primary shape as subjected to stimuli. Shape memory polymers (SMPs) are employed as good materials for thrombectomy device fabrication. Therefore, current review presents thrombectomy device development and fabrication with SMPs. Design, performance, limitations, and in vitro or in vivo clinical results of SMP-based thrombectomy devices are identified. Review also sheds light on SMP's future outlook and recommendations for thrombectomy device application, opening a new era for advanced materials in materials science.

Ischemic stroke and diabetes: a TLR4-mediated neuroinflammatory perspective

Ischemic stroke is the major contributor to morbidity and mortality in people with diabetes mellitus. In ischemic stroke patients, neuroinflammation is now understood to be one of the main underlying mechanisms for cerebral damage and recovery delay. It has been well-established that toll-like receptor 4 (TLR4) signaling pathway plays a key role in neuroinflammation. Emerging research over the last decade has revealed that, compared to ischemic stroke without diabetes mellitus, ischemic stroke with diabetes mellitus significantly upregulates TLR4-mediated neuroinflammation, increasing the risk of cerebral and neuronal damage as well as neurofunctional recovery delay. This review aims to discuss how ischemic stroke with diabetes mellitus amplifies TLR4-mediated neuroinflammation and its consequences. Additionally covered in this review is the potential application of TLR4 antagonists in the management of diabetic ischemic stroke.

Use of quantitative angiographic methods with a data-driven model to evaluate reperfusion status (mTICI) during thrombectomy

PURPOSE

Intra-procedural assessment of reperfusion during mechanical thrombectomy (MT) for emergent large vessel occlusion (LVO) stroke is traditionally based on subjective evaluation of digital subtraction angiography (DSA). However, semi-quantitative diagnostic tools which encode hemodynamic properties in DSAs, such as angiographic parametric imaging (API), exist and may be used for evaluation of reperfusion during MT. The objective of this study was to use data-driven approaches, such as convolutional neural networks (CNNs) with API maps, to automatically assess reperfusion in the neuro-vasculature during MT procedures based on the modified thrombolysis in cerebral infarction (mTICI) scale.

METHODS

DSAs from patients undergoing MTs of anterior circulation LVOs were collected, temporally cropped to isolate late arterial and capillary phases, and quantified using API peak height (PH) maps. PH maps were normalized to reduce injection variability. A CNN was developed, trained, and tested to classify PH maps into 2 outcomes (mTICI 0,1,2a/mTICI 2b,2c,3) or 3 outcomes (mTICI 0,1,2a/mTICI 2b/mTICI 2c,3), respectively. Ensembled networks were used to combine information from multiple views (anteroposterior and lateral).

RESULTS

The study included 383 DSAs. For the 2-outcome classification, average accuracy was 81.0% (95% CI, 79.0-82.9%), and the area under the receiver operating characteristic curve (AUROC) was 0.86 (0.84-0.88). For the 3-outcome classification, average accuracy was 64.0% (62.0-66.0), and AUROC values were 0.85 (0.83-0.87), 0.74 (0.71-0.77), and 0.78 (0.76-0.81) for the mTICI 0,1,2a, mTICI 2b, and mTICI 2c,3 classes, respectively.

CONCLUSION

This study demonstrated the feasibility of using hemodynamic information in API maps with data-driven models to autonomously assess intra-procedural reperfusion during MT.

The feasibility of ultrasound-assisted endovascular laser thrombolysis in an acute rabbit thrombosis model

PURPOSE

This study aimed to test the feasibility of combined ultrasound and laser technique, namely, ultrasound-assisted endovascular laser thrombolysis (USELT), for thrombolysis by conducting in vivo tests in a rabbit thrombosis model.

MATERIALS AND METHODS

An acute thrombus was created in the right jugular vein of rabbit and then was treated with ultrasound only, laser only, and USELT to dissolve the blood clot. A total of 20 rabbits were used. Out of which, the first three rabbits were used to titrate the laser and ultrasound parameters. Then, five rabbits were treated with ultrasound only, five rabbits were treated with laser only, and seven rabbits were treated with USELT. During USELT, 532-nm laser pulses were delivered endovascularly directly to the clot through a fiber optic, and 0.5 MHz ultrasound pulses were applied noninvasively to the same region. A laser fluence of 4 to 12 mJ/cm² and ultrasound amplitude of 1 to 2 MPa were used. Recanalization of the jugular vein was assessed by performing ultrasound Doppler imaging immediately after the treatment. The maximum blood flow speed after the treatment as compared to its value before the treatment was used to calculate the blood flow recovery in vessel.

RESULTS

The blood flow was fully recovered (100%) in three rabbits, partially recovered in two rabbits (more than 50% and less than 100%) with mean percentage recovery of 69.73% and poorly recovered in two rabbits (<50%) with mean percentage recovery of 6.2% in the USELT group. In contrast, the treatment group with ultrasound or laser alone did not show recanalization of vein in any case, all the five rabbits were poorly/not recovered with a mean percentage recovery of 0%.

CONCLUSIONS

The USELT technology was shown to effectively dissolve the blood clots in an acute rabbit jugular vein thrombosis model.

Ultrasound-assisted laser thrombolysis with endovascular laser and high-intensity focused ultrasound

PURPOSE

The combination of laser and ultrasound can significantly improve the efficiency of thrombolysis through an enhanced cavitation effect. We developed a fiber optics-based laser-ultrasound thrombolysis device and tested the feasibility and efficiency of this technology for restoring blood flow in an in vitro blood clot model.

METHODS

An in vitro blood flow-clot model was setup, and then an endovascular laser thrombolysis system was combined with high-intensity focused ultrasound to remove the clot. The laser and ultrasound pulses were synchronized and delivered to the blood clot concurrently. The laser pulses of 532 nm were delivered to the blood clot endovascularly through an optical fiber, whereas the ultrasound pulses of 0.5 MHz were applied noninvasively to the same region. Effectiveness of thrombolysis was evaluated by the ability to restore blood flow, which was monitored by ultrasound Doppler.

RESULTS

As laser powers increased, the ultrasound threshold pressures for effective thrombolysis decreased. For laser fluence levels of 0, 2, and 4 mJ/cm² , the average negative ultrasound threshold pressures were 1.26 ± 0.114, 1.05 ± 0.181, and 0.59 ± 0.074 MPa, respectively. The periods of time needed to achieve effective thrombolysis were measured at 0.8, 2, and 4 mJ/cm² laser fluence levels and 0.42, 0.70, and 0.98 MPa negative ultrasound pressures. In general, thrombolysis could be achieved more rapidly with higher laser powers or ultrasound pressures.

CONCLUSIONS

Effective thrombolysis can be achieved by combining endovascular laser with noninvasive ultrasound at relatively low power and pressure levels, which can potentially improve both the treatment efficiency and safety.

Targeting the Immune System for Ischemic Stroke

Stroke is responsible for almost 6 million deaths and more than 10% of all mortalities each year, and two-thirds of stroke survivors remain disabled. With treatments for ischemic stroke still limited to clot lysis and/or mechanical removal, new therapeutic targets are desperately needed. In this review, we provide an overview of the complex mechanisms of innate and adaptive immune cell-mediated inflammatory injury, that exacerbates infarct development for several days after stroke. We also highlight the features of poststroke systemic immunodepression that commonly leads to infections and some mortalities, and argue that safe and effective therapies will need to balance pro- and anti-inflammatory mechanisms in a time-sensitive manner, to maximize the likelihood of an improved long-term outcome.

Photoacoustic image-guided interventions

Photoacoustic imaging has demonstrated its potential for diagnosis over the last few decades. In recent years, its unique imaging capabilities, such as detecting structural, functional and molecular information in deep regions with optical contrast and ultrasound resolution, have opened up many opportunities for photoacoustic imaging to be used during image-guided interventions. Numerous studies have investigated the capability of photoacoustic imaging to guide various interventions such as drug delivery, therapies, surgeries, and biopsies. These studies have demonstrated that photoacoustic imaging can guide these interventions effectively and non-invasively in real-time. In this minireview, we will elucidate the potential of photoacoustic imaging in guiding active and passive drug deliveries, photothermal therapy, and other surgeries and therapies using endogenous and exogenous contrast agents including organic, inorganic, and hybrid nanoparticles, as well as needle-based biopsy procedures. The advantages of photoacoustic imaging in guided interventions will be discussed. It will, therefore, show that photoacoustic imaging has great potential in real-time interventions due to its advantages over current imaging modalities like computed tomography, magnetic resonance imaging, and ultrasound imaging.

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.

Endovascular Stroke Therapy Focused on Stent Retriever Thrombectomy and Direct Clot Aspiration: Historical Review and Modern Application

Intravenous recombinant tissue plasminogen activator had been the only approved treatment for acute ischemic stroke since its approval in 1995. However, the restrictive time window, numerous contraindications, and its low recanalization rate were all limitations of this modality. Under those circumstances, endovascular stroke therapy went through a great evolution during the past two decades of intravenous thrombolysis. The results of the 2013 randomized trials for endovascular stroke therapy were neutral, although they were limited by insufficient imaging screening at enrollment, early-generation devices with less efficacy, and treatment delays. Huge progress was made in 2015, as there were five randomized clinical trials which all demonstrated the safety and efficacy of endovascular stroke treatment. Despite differences in detail patient enrollment criteria, all 5 trials employed key factors for good functional recovery; (1) screening with non-invasive imaging to identify the proximal occlusion and exclude a large infarct core, (2) using highly effective modern thrombectomy devices mainly with stent retriever, and (3) establishment of a fast workflow to achieve effective reperfusion. The results of those trials indicate that modern thrombectomy devices can allow for faster and more effective reperfusion, which can lead to improved clinical outcomes compared to intravenous thrombolysis alone. These advances in mechanical thrombectomy are promising in the global fight against ischemic stroke-related disability and mortality. Two current mainstreams among such mechanical thrombectomy techniques, “stent retriever thrombectomy” and “direct clot aspiration”, are the topic of this review. Stent retriever thrombectomy using Solitaire and Trevo retriever will be firstly discussed. And, the commonalities and the differences between two major clot aspiration thrombectomy techniques; a direct aspiration first pass technique (ADAPT) and forced arterial suction thrombectomy (FAST), will be additionally explained. Finally, details regarding the combination of direct clot aspiration and stent retriever thrombectomy, the switching strategy and the Solumbra technique, will be described.

Update on Endovascular Treatment of Cerebrovascular Diseases

Several developments in endovascular technology have greatly expanded the application of these techniques to treat extra- and intracranial cerebrovascular diseases. This review explores the indications, techniques, and clinical results for endovascular treatment of ischemic stroke and intracranial stenoses, aneurysms, and arteriovenous malformations.

Endovascular revascularization for basilar artery occlusion

Basilar artery occlusion is one of the most devastating neurological conditions known to man. Though rare, patients with clinical syndromes localized to this anatomical region are often referred to acute stroke and endovascular units. Recent studies evaluating the efficacy of endovascular approaches to stroke have focused on anterior circulation syndromes. In this review, we examine the approaches to stroke syndromes due to basilar artery thrombosis. We share the relevant data for intravenous and intra-arterial tissue plasminogen activator as well as mechanical approaches to restoring perfusion in this critical area of the brain.

Intraarterial mechanical thrombectomy for the treatment of postoperative cerebral infarction: a case report

Perioperative ischemic stroke is an uncommon event associated with significant morbidity and mortality. The complexity of the surgical procedure and surgery induced hypercoagulable status also influence the incidence of stroke. The management of stroke involves a decision regarding the quickest suitable revascularization method. Endovascular mechanical thrombectomy, such as intra-arterial mechanical thrombectomy (IAMT), can restore vascular patency of the vessels, providing an alternative or synergistic method to restore blood flow. Although, there are no recommended treatment guidelines, IAMT is eligible to be a treatment of choice for perioperative ischemic stroke. We experienced a case of a patient who demonstrated hemiplegia and aphasia, the early symptom of acute ischemic stroke, in the post-anesthesia care unit and performed IAMT successfully. Thus we report the case with a review of the relevant literature.

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.

Advances in revascularization for acute ischemic stroke treatment

Intravenous thrombolysis with recombinant tissue plasminogen activator is the established treatment for acute ischemic stroke patients presenting within 3 h after stroke onset. In a significant number of patients, however, intravenous thrombolysis with recombinant tissue plasminogen activator remains ineffective. New thrombolytic agents, such as reteplase, tenecteplase or desmoteplase, offer pharmacokinetic and dynamic advantages over recombinant tissue plasminogen activator and have been or are currently being tested for safety and efficacy in clinical trials. Endovascular revascularization is an evolving treatment option enabling mechanical clot disruption or extraction in combination with thrombolysis. Several new endovascular devices have been successfully tested for safety in acute ischemic stroke patients and are now being tested for efficacy in larger clinical trials. Continued innovation and refinement of endovascular technology and techniques is expected to increase technical success with a minimal procedure-related morbidity in the treatment of acute ischemic stroke.

Structural and functional photoacoustic molecular tomography aided by emerging contrast agents

Photoacoustic tomography (PAT) can offer structural, functional and molecular contrasts at scalable observation level. By ultrasonically overcoming the strong optical scattering, this imaging technology can reach centimeters penetration depth while retaining high spatial resolution in biological tissue. Recent extensive research has been focused on developing new contrast agents to improve the imaging sensitivity, specificity and efficiency. These emerging materials have substantially accelerated PAT applications in signal sensing, functional imaging, biomarker labeling and therapy monitoring etc. Here, the potentials of different optical probes as PAT contrast agents were elucidated. We first describe the instrumental embodiments and the measured functional parameters, then focus on emerging contrast agent-based PAT applications, and finally discuss the challenges and prospects.

A feasibility study on femtosecond laser thrombolysis

OBJECTIVE

In this feasibility study, we investigate possible femtosecond laser thrombolysis.

BACKGROUND DATA

Because of low pulse energies, femtosecond laser surgery inherently minimizes side effects on the surrounding tissue. Moreover, current femtosecond laser sources as well as fiber technology allow consideration of catheter-based treatments.

METHODS

Two femtosecond laser systems (λ=800 nm, λ=1030 nm) along with a three dimensional (3D) scanner system (NA ~0.1) were used in this study. In vitro experiments were performed on porcine thrombi and blood vessels. Ablation thresholds were determined in air, by determining the pulse energy at which single shot ablation was visible under the optical microscope. Ablation rates were determined in physiological saline. Additionally, ablation of thrombi and blood vessels was monitored by means of a fiber spectrometer.

RESULTS

Depending upon the scan velocity, typical ablation rates for thrombi were ~0.04 mm(3)/sec. Ablation thresholds of thrombi and blood vessels differ by factors of 3 and 1.5 at laser wavelengths of 800 and 1030 nm, respectively. At a distance of 5 mm above the surface, second harmonic generation was observed in blood vessels, but not within thrombi.

CONCLUSIONS

The results show that a typical thrombus volume can be destroyed within a reasonable time frame. Because of the higher threshold difference of thrombi and blood vessels, the use of a laser wavelength of 800 nm is preferable. Furthermore, the detection of the second harmonic could provide a feedback mechanism to protect the vascular wall from mechanical and laser damage.

Neurothrombectomy in the treatment of acute ischaemic stroke

Major ischaemic stroke is a leading cause of morbidity and mortality in industrialized countries. For patients with acute stroke, fast and effective vessel recanalization is important for successful treatment. Neurothrombectomy--that is, angiographically performed mechanical thrombus removal from intracranial arteries--results in higher recanalization rates than with pharmaceutical thrombolysis alone, but the value of this treatment in terms of clinical outcome remains to be established. This article summarizes the history of intra-arterial stroke treatment, outlines the recent developments and the different techniques used, and discusses the results of current studies on neurothrombectomy. Owing to the high morphological and clinical variability of stroke, careful patient selection in future randomized controlled trials will be crucial for assessment of the true potential of neurothrombectomy.

Multimodality molecular imaging of stem cells therapy for stroke

Stem cells have been proposed as a promising therapy for treating stroke. While several studies have demonstrated the therapeutic benefits of stem cells, the exact mechanism remains elusive. Molecular imaging provides the possibility of the visual representation of biological processes at the cellular and molecular level. In order to facilitate research efforts to understand the stem cells therapeutic mechanisms, we need to further develop means of monitoring these cells noninvasively, longitudinally and repeatedly. Because of tissue depth and the blood-brain barrier (BBB), in vivo imaging of stem cells therapy for stroke has unique challenges. In this review, we describe existing methods of tracking transplanted stem cells in vivo, including magnetic resonance imaging (MRI), nuclear medicine imaging, and optical imaging (OI). Each of the imaging techniques has advantages and drawbacks. Finally, we describe multimodality imaging strategies as a more comprehensive and potential method to monitor transplanted stem cells for stroke.

[Mechanical recanalization in acute stroke. Torture or choice]

CLINICAL/METHODICAL ISSUE

Stroke is the third most common cause of death in the developed world and the leading cause of disability worldwide. The present demographic development will lead to increased numbers of stroke patients in the future.

STANDARD RADIOLOGICAL METHODS

Patient selection takes place by using various computer tomographic (CT) or magnetic resonance (MR) imaging modalities. For endovascular stroke treatment a modern biplane angiography suite is recommended.

METHODICAL INNOVATIONS

Intra-arterial chemical thrombolysis was shown to be effective in achieving recanalization and improving clinical outcome. Mechanical devices were introduced in the late 1990s and the highly effective stent retriever was recently included.

PERFORMANCE

Mechanical devices allows a recanalization rate of up to 90 % of affected brain vessels.

ACHIEVEMENTS

The advantage of a stent retriever compared to other mechanical devices seems to be an improvement in good clinical outcome.

PRACTICAL RECOMMENDATIONS

Currently, the stent retriever seems to be the definitive first choice in the use of mechanical devices for intra-arterial recanalization treatment in acute ischemic stroke.

Endovascular neuroradiological treatment of acute ischemic stroke: techniques and results in 350 patients

BACKGROUND AND OBJECTIVES

Randomized trials have demonstrated the benefit of intra-arterial thrombolysis (IAT) for treatment of acute ischemic stroke, if performed within 6 hours of symptom onset.

METHODS

We report our experience with 350 acute stroke patients who were treated with IAT using urokinase at a single center. Predictors of favorable outcome were low National Institute of Health Stroke Scale (NIHSS) at admission (p<0.001), good collaterals (p<0.001) and successful endovascular recanalization (p<0.001). Recanalization rates of more than 75% could be achieved, when additional endovascular techniques such as mechanical fragmentation of the thrombus, thromboaspiration, percutaneous transluminal angioplasty, and implantation of stents were used.

RESULTS AND CONCLUSIONS

Predictors of unfavorable outcome were diabetes mellitus (p<0.001) and symptomatic hemorrhages (p<0.001). The latter occurred in 5% of our population. Preliminary results of new techniques including sonothrombolysis, angiojet aspiration, and laser recanalization of thromboembolic occlusions are discussed.

Acute vertebrobasilar occlusion: current treatment strategies

Acute vertebrobasilar occlusion (VBO) remains a disease with a high mortality. Local intraarterial fibrinolysis (LIF) can reduce the mortality rate from about 90 to 60%. The combined therapy of i.v. Abciximab and i.a. rt-PA with additional PTA/stenting may improve neurological outcome and significantly reduce mortality, despite an increase of overall bleeding complications. Additional PTA/stenting is an important treatment factor in cases of atherothrombotic occlusion. In embolic occlusions, mechanical catheter devices, such as basket or snare devices or rheolytic systems, are promising therapies for the near future. This article describes diagnostic criteria and treatment factors in acute VBO. Different treatment strategies, such as i.v. and i.a. fibrinolysis, adjunctive application of GP IIb/IIIa inhibitors, PTA/stenting and mechanical embolectomy are addressed in detail.

The quest for arterial recanalization in acute ischemic stroke-the past, present and the future

Ischemic stroke is one of the major causes of mortality and long-term disability. In the recent past, only very few treatment options were available and a considerable proportion of stroke survivors remained permanently disabled. However, over the last 2 decades rapid advances in acute stroke care have resulted in a corresponding improvement in mortality rates and functional outcomes. In this review, we describe the evolution of systemic thrombolytic agents and various interventional devices, their current status as well as some of the future prospects. We reviewed literature pertaining to acute ischemic stroke reperfusion treatment. We explored the current accepted treatment strategies to attain cerebral reperfusion via intravenous modalities and compare and contrast them within the boundaries of their clinical trials. Subsequently we reviewed the trials for interventional devices for acute ischemic stroke, categorizing them into thrombectomy devices, aspiration devices, clot disruption devices and thrombus entrapment devices. Finally we surveyed several of the alternative reperfusion strategies available. We also shed some light on the controversies surrounding the current strategies of treatment of acute ischemic stroke. Acute invasive interventional strategies continue to improve along with the noninvasive modalities. Both approaches appear promising. We conducted a comprehensive chronological review of the existing treatments as well as upcoming remedies for acute ischemic stroke.

Endovascular thrombectomy following acute ischemic stroke: a single-center case series and critical review of the literature

Acute ischemic stroke (AIS) due to thrombo-embolic occlusion in the cerebral vasculature is a major cause of morbidity and mortality in the United States and throughout the world. Although the prognosis is poor for many patients with AIS, a variety of strategies and devices are now available for achieving recanalization in patients with this disease. Here, we review the treatment options for cerebrovascular thromboembolic occlusion with a focus on the evolution of strategies and devices that are utilized for achieving endovascular clot extraction. In order to demonstrate the progression of this treatment strategy over the past decade, we will also present a single-center case series of AIS patients treated with endovascular thrombectomy.

Development of endovascular vibrating polymer actuator probe for mechanical thrombolysis: in vivo study

In this study, we propose a new method for the enhancement of intraarterial thrombolysis by use of an endovascular vibrating polymer actuator probe (VPAP), which is fabricated from an ionic polymer metal composite (IPMC) actuator. The endovascular VPAP was fabricated by combining 0.8 × 0.8 × 10 mm3 IPMC samples, 0.22 mm × 50 cm copper wires, and 40 cm of Teflon tube. The purpose of this study was to evaluate the thrombolysis efficiency of an endovascular VPAP in a dog model. Both renal arteries of the enrolled dogs (n = 5) were used in the current study. A distal portion of the renal artery in a mongrel dog was occluded by a blood clot from autologous venous whole blood. Intraarterial thrombolysis was performed by use of a VPAP without the actuation force (control group), by a VPAP-only (VPAP-only group), or with a combination of recombinant tissue plasminogen activator (rtPA) and a VPAP (VPAP + rtPA group). The thrombolysis efficiency was evaluated by the modified Thrombolysis in Myocardial Infarction (TIMI) grading system based on the consensus between two radiologists. The grading scales were compared according to each intraarterial thrombolysis method. The VPAP + rtPA and VPAP-only groups showed a significantly higher thrombolysis efficiency than did the control group (p < 0.05). The VPAP-only group also showed a significantly higher thrombolysis efficiency than did the control group (p < 0.05). The VPAP+ rtPA group showed a significantly higher thrombolysis efficiency than did the VPAP-only group (p < 0.05). The use of an endovascular VPAP was a feasible and useful method for intraarterial thrombolysis, and it enhanced the thrombolysis efficiency when combined with the thrombolytic agent rtPA.

Guidelines for acute ischemic stroke treatment: part II: stroke treatment

The second part of these Guidelines covers the topics of antiplatelet, anticoagulant, and statin therapy in acute ischemic stroke, reperfusion therapy, and classification of Stroke Centers. Information on the classes and levels of evidence used in this guideline is provided in Part I. A translated version of the Guidelines is available from the Brazilian Stroke Society website (www.sbdcv.com.br).

Beyond the time window of intravenous thrombolysis: standing by or by stenting?

Intravenous administration of tissue plasminogen activator within 4.5 h of symptom onset is presently the 'golden rule' for treating acute ischemic stroke. However, many patients miss the time window and others reject this treatment due to a long list of contraindications. Mechanical embolectomy has recently progressed as a potential alternative for treating patients beyond the time window for IV thrombolysis. In this paper, recent progress in mechanical embolectomy, angioplasty, and stenting in acute stroke is reviewed. Despite worries concerning the long-term clinical outcomes and increased risk of intracranial hemorrhage, favorable clinical outcomes may be achieved after mechanical embolectomy in carefully selected patients even 4.5 h after stroke onset. Potential steps should be prepared and attempted in these patients whose opportunity for recovery will elapse in a flash.

Endovascular treatment strategies for acute ischemic stroke

The limitations of intravenous thrombolysis therapy have paved the way for the development of novel endovascular technologies for use in the setting of acute stroke. These technologies range from direct intraarterial thrombolysis to various thrombus disruption or retrieval devices to angioplasty and stenting. The tools in the armamentarium of the neuroendovascular interventionalist enable fast, effective revascularization to be offered to a wider population of patients that may otherwise have few therapeutic options available to them. In this paper, we review the current state-of-the-art in neuroendovascular intervention for acute ischemic stroke. Particular emphasis is placed on delineating the indications and outcomes for use of these various technologies.

In vivo imaging of cell transplants in experimental ischemia

The therapeutic potential of stem cells for regeneration after cerebral lesion has become of great interest. This is particularly so for neurodegenerative diseases as well as for stroke. Contrary to more conventional, cerebroprotective treatment approaches, the focus of regeneration lies in a longer time window during the chronic phase of the lesion evolution. Thus, in order to assess the true potential of a treatment strategy and to investigate the underlying mechanisms, observation of the temporal profile of both the cell dynamics as well as the organ response to the treatment is of paramount importance. This need for intraindividual longitudinal studies can be optimally met by the application of noninvasive imaging modalities. This chapter presents in breadth the potential of noninvasive imaging modalities for cell tracking with application focus to experimental stroke. While the lion's share of discussed studies is based on MRI, we have also included the contributions of positron emission tomography and of the increasingly important optical imaging modality.

Reperfusion Strategies for Acute Ischemic Stroke

Stroke remains a major cause of morbidity and mortality worldwide. Despite preventive measures, effective management strategies are needed to reduce the morbidity and mortality associated with this devastating condition. While the management of hemorrhagic stroke is mostly limited to supportive care, reperfusion strategies in ischemic stroke have been developed and continue to evolve. Conceptually, the pathophysiology of ischemic stroke is similar to that of acute myocardial infarction and the objective of management is similar (ie, to rapidly restore normal flow to reduce permanent damage). It is, therefore, not surprising that the management of acute ischemic stroke includes intravenous (IV) thrombolysis, the only Food and Drug Administration (FDA)-approved strategy at this point. In addition, there are a myriad of emerging endovascular interventional techniques. We review the current literature and discuss some of the technical aspects of endovascular therapy in the setting of acute ischemic stroke.

Outcomes of mechanical endovascular therapy for acute ischemic stroke: a clinical registry study and systematic review

BACKGROUND AND PURPOSE

Recanalization is a powerful predictor of stroke outcome in patients with arterial occlusion. Intravenous recombinant tissue plasminogen activator is limited by its recanalization rate, which may be improved with mechanical endovascular therapy (MET). However, the benefit and safety of MET remain to be determined. The aim of this study was to give reliable estimates of efficacy and safety outcomes of MET.

METHODS

We analyzed data from our prospective clinical registry and conducted a systematic review of all previous studies using MET published between January 1966 and November 2009.

RESULTS

From April 2007 to November 2009, 47 patients with acute stroke were treated with MET at Bichat Hospital. The literature search identified 31 previous studies involving a total of 1066 subjects. In the meta-analysis, including our registry data, the overall recanalization rate was 79% (95% CI, 73-84). Meta-analysis of clinical outcomes showed a pooled estimate of 40% (95% CI, 34-46; 27 studies) for favorable outcome, 28% (95% CI, 23-33; 28 studies) for mortality, and 8% (95% CI, 6-10; 27 studies) for symptomatic intracranial hemorrhage. The likelihood of a favorable outcome increased with the use of thrombolysis (OR, 1.99; 95% CI, 1.23-3.22) and with proportion of patients with isolated middle cerebral artery occlusion (OR per 10% increase, 1.14; 95% CI, 1.04-1.25).

CONCLUSIONS

MET is associated with acceptable safety and efficacy in stroke patients, and it may be a therapeutic option in those presenting with isolated middle cerebral artery occlusion.

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.

Classification for carotid artery stenting complications: manifestation, management, and prevention

Carotid artery stenting is a rapidly evolving method for treating carotid artery disease. Various intraprocedural and postprocedural complications have been reported in the literature. However, the absence of a unified classification scheme for these complications makes it difficult, if not impossible, to study their precise incidence, predictors, and management. The aim of this article is to propose the first joint classification of periprocedural complications, to analyze their incidence and etiology, and suggest possible ways to manage and prevent them. This classification is intended to be used as a common platform for prompt recognition, evaluation, treatment, and universal study of the complications during carotid stenting procedures. For this purpose, the opinions of the major experts on carotid interventions worldwide were merged with all the available information reported in the English-language literature to present as accurately as possible the management and prevention of carotid stenting complications according to this proposed classification.

Current endovascular treatment of acute stroke and future aspects

Acute ischemic stroke remains a condition of high morbidity and mortality. Until now, the only established therapy has been intravenous (IV) tissue-type plasminogen activator (tPA). Only 3-10% of patients with acute ischemic stroke receive this treatment. On the basis of data from part 3 of the European Collaborative Acute Stroke Study (ECASS III), the time window for beneficial treatment of ischemic stroke with IV tPA has been extended from 3 to 4.5h after the onset of stroke symptoms. Beyond that window of opportunity, and additionally to IV treatment, interventional stroke therapy has assumed an important role for the treatment of acute ischemic stroke. Currently, new promising pharmacological and mechanical treatment options are being established as routine procedures to achieve a further improved outcome for stroke patients.

Development of a catheter for combined intravascular ultrasound and photoacoustic imaging

Atherosclerosis is characterized by formation and development of the plaques in the inner layer of the vessel wall. To detect and characterize atherosclerotic plaques, we previously introduced the combined intravascular ultrasound (IVUS) and intravascular photoacoustic (IVPA) imaging capable of assessing plaque morphology and composition. The utility of IVUS/IVPA imaging has been demonstrated by imaging tissue-mimicking phantoms and ex vivo arterial samples using laboratory prototype of the imaging system. However, the clinical realization of a IVUS/IVPA imaging requires an integrated intravascular imaging catheter. In this paper, two designs of IVUS/IVPA imaging catheters--side fire fiber-based and mirror-based catheters--are reported. A commercially available IVUS imaging catheter was utilized for both pulse-echo ultrasound imaging and detection of photoacoustic transients. Laser pulses were delivered by custom-designed fiber-based optical systems. The optical fiber and IVUS imaging catheter were combined into a single device. Both designs were tested and compared using point targets and tissue-mimicking phantoms. The results indicate applicability of the proposed catheters for clinical use.

Effect of Blood Soluble Clotting Factors on Coagulation Profile

Objective: Recently, mechanical thrombolytic therapy has been introduced as an alternative or adjunct to pharmaceutical thrombolytic therapy in removing thrombus from vascular system. Recurrent thrombosis has been a challenge for thrombolytic therapies. We hypothesize that soluble clotting factors released during a mechanical thrombectomy procedure may be responsible for creating a localized hypercoagulable state and could be one of the underlying causes of recurrent thrombosis. Method: Blood samples were obtained from 20 participants with no history of hypertension, vascular disease, and antiplatelet/anticoagulation therapy. For each whole blood (WB) sample, we measured activated clotting time (ACT) and clotting rate (CR) at the baseline and then with added agitated and nonagitated clot serums. The same set of measurements was performed on platelet-rich plasma (PRP) samples of each participant. We tested for changes in coagulation profile between baseline samples and those with added supernatant serums obtained from autologous blood clot. Result: We observed a significant decrease in ACT for WB with agitated and nonagitated clot serums (49%, P < .0001 and 25%, P = .01, respectively) compared to the baseline WB. The same trend was observed for PRP samples with agitated and nonagitated clot serums (28%, P = .002 and 18%, P = .05, respectively). The CR was increased (a steeper slope) by 83% for samples with added agitated clot serum only (P = .007). Conclusion: We observed a significant change for ACT in WB samples with added clot serums as compared to the baseline WB samples. The results of this study suggest that the soluble substances released from clotting blood have profound procoagulant effects.

[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.

Endovascular approaches to acute stroke, part 1: Drugs, devices, and data

Despite years of research and pioneering clinical work, stroke remains a massive public health concern. Since 1996, we have lived in the era of US Food and Drug Administration-approved intravenous (i.v.) recombinant tissue plasminogen activator (rtPA). This treatment, despite its promise, continues to exhibit its limitations. Endovascular therapy has several theoretic advantages over i.v. rtPA, including site specificity, longer treatment windows, and higher recanalization rates. In this article, we will review the various pharmacologic strategies for acute stroke treatment, providing both a historic context and the state of the art. The drugs will be classified on the basis of their theoretic rationale for therapy. Next, we will review the various devices and strategies for mechanical revascularization with an aim toward comprehensiveness. These range from wire disruption of thrombus to preclinical trials for novel mechanical solutions. This first installment of this 2-part series will end with an analysis of retrograde reperfusion techniques.