In this thesis focused ultrasound thrombolysis was investigated in vitro and in vivo. At high intensities it was demonstrated that clot breakdown only arises under the presence of inertial cavitation for longer pulse lengths, consistent with observations at significantly shorter pulse durations, and that the majority of clot debris is sub-capillary in size. Evidence of flow restoration was demonstrated in vivo by partially restoring flow to an occluded rabbit femoral artery. At slightly lower intensities it was observed that steady- state clot displacements scale linearly with power for clots treated with focused ultrasound pulses, and in some cases can reach magnitudes up to several hundred microns. It was demonstrated that the shear strain exerted on the clot by a focused ultrasound pulse scale with power, which may be implicated in enhancing drug permeation for studies in combination with lytic agents.

In this thesis focused ultrasound thrombolysis was investigated in vitro and in vivo. At high intensities it was demonstrated that clot breakdown only arises under the presence of inertial cavitation for longer pulse lengths, consistent with observations at significantly shorter pulse durations, and that the majority of clot debris is sub-capillary in size. Evidence of flow restoration was demonstrated in vivo by partially restoring flow to an occluded rabbit femoral artery. At slightly lower intensities it was observed that steady- state clot displacements scale linearly with power for clots treated with focused ultrasound pulses, and in some cases can reach magnitudes up to several hundred microns. It was demonstrated that the shear strain exerted on the clot by a focused ultrasound pulse scale with power, which may be implicated in enhancing drug permeation for studies in combination with lytic agents.

Among patients presenting acutely with ischaemic stroke who are being considered for intravenous thrombolysis, prompt brain imaging is used to exclude contraindications to treatment (chiefly haemorrhagic stroke or other conditions mimicking stroke) rather than to identify which patients are more or less likely to benefit from thrombolysis. For example, it is unclear whether the presence or absence of arterial obstruction on imaging should be used to guide thrombolysis treatment decisions. In this thesis I explore methods of imaging arterial patency among patients presenting acutely with ischaemic stroke and look for associations between these early imaging findings, response to intravenous thrombolysis and functional outcome six-months after stroke onset. I primarily use data from the Third International Stroke Trial (IST-3), the largest ever randomised-controlled trial testing the use of intravenous alteplase for the acute treatment of ischaemic stroke. I begin by summarising the main features of stroke, covering techniques for imaging the brain and for imaging arterial patency, and post-stroke outcomes. Next I describe two literature reviews which I compiled to increase my understanding of the topic with particular reference to imaging arterial patency. This is followed by a summary of IST-3. Then I describe the general methods I used to address my thesis aims exploring relationships between imaging characteristics of arterial patency, treatment with intravenous alteplase and functional outcome after ischaemic stroke. Specifically, I investigated the following imaging features: - The hyperattenuating artery sign (HAS), which is a non-contrast enhanced CT finding thought to be indicative of acute arterial obstruction by thrombus or embolus - Arterial patency or obstruction as demonstrated using contrast enhanced CT and MR angiographic imaging. In addition to providing better characterisation of the HAS and a better understanding of how angiography helps to assess ischaemic stroke patients, I found that arterial obstruction (however this is identified on imaging) is associated with more severe stroke at baseline and worse functional outcome six months after stroke. I also prove that intravenous alteplase is effective in the presence of arterial obstruction, counter to a widely held concern that it may not be effective in this context. Most of my work has been published in peer reviewed journals. My work should give front line clinicians greater confidence to use intravenous alteplase for the treatment of ischaemic stroke associated with arterial obstruction on imaging, but more work is needed to better understand the implications of apparently normal arterial patency on imaging among patients with ischaemic stroke.

Thrombotic disorders include myocardial infarction (MI), acute ischemic stroke (AIS) and venous thromboembolism (VTE), which encompasses pulmonary embolism (PE), and deep vein thrombosis (DVT). To prevent further complications or mortality in patients with MI and AIS, rapid restoration of blood flow is needed to minimize organ damage. Such treatment also is needed in patients with massive PE. Blood flow can be restored mechanically via percutaneous coronary intervention with stent implantation for MI and by thrombectomy in patients with AIS or PE. Alternatively, pharmacological reperfusion can be achieved by systemic administration of plasminogen activators (PAs). PAs convert plasminogen to the fibrinolytic enzyme, plasmin. Plasmin then degrades the clot into soluble fragments. Streptokinase (SK) and urokinase (UK) were the first therapeutic clot dissolving drugs but both lead to excessive bleeding complications because of non-specific effects. Current therapy focuses on clot specific agents such as recombinant tissue-PA (rt-PA) or tenecteplase (TNK), a rt-PA variant. However, there is a risk of intracranial bleeding in at least 1% of patients, which can be fatal or disabling. Thus, a need exists for new strategies to enable safer reperfusion that are not associated with potentially fatal side effects. This study focuses on the therapeutic role of alpha2-antiplasmin (α2AP). α2AP is the primary inhibitor of plasmin. One approach to thrombolysis is to attenuate α2AP with an inhibitory antibody (A2AP IgG). Inhibition of α2AP would enable clot lysis with lower doses of PAs, thereby reducing the risk of bleeding and serving as a safer approach to thrombolytic therapy. We aimed to characterize A2AP IgG and evaluate its effect on fibrinolysis in vitro and in vivo. A2AP IgG1 was selected and developed using phage display and an antibody gene library with human and rabbit α2AP as the antigen. Affinity maturation was performed and the Fc portion of the A2AP IgG1 was subsequently changed to the IgG4 isotype which yielded A2AP IgG4. A2AP IgG4 binds α2AP with 63-fold higher affinity than A2AP IgG1 as determined using surface plasmon resonance (SPR). SDS-PAGE and western blot analysis reveals that both antibodies bind to the plasmin-α2AP (PAP) complex, fibrinogen, and fragment X but not to α2AP; results confirmed by ELISA. In functional studies, A2AP IgG1 significantly reduced plasmin inhibition by α2AP by 5.5-fold. Both A2AP IgG1 and A2AP IgG4 shortened tissue-PA (t-PA)-mediated clot lysis in a concentration dependent manner. A2AP IgG4 was 2.2-fold more potent than A2AP IgG1 in human plasma and 1.4-fold more potent in rabbit plasma. Compared with t-PA or TNK alone, addition of either antibody enhanced the lysis of preformed plasma clots. Combining A2AP IgG4 with 10% of the highest t-PA or TNK dose produced more clot lysis than the highest dose of t-PA or TNK alone. In a rabbit jugular vein thrombosis model, A2AP IgG4 alone produced 20% lysis. When combined with a low dose of TNK, 40% clot lysis resulted, which was significantly greater than the 30% clot lysis observed with a higher dose of TNK. A2AP IgG4 alone or in combination with a lower dose of TNK did not cause significantly more bleeding than the higher dose of TNK alone and did not degrade circulating fibrinogen. Thus, we have shown that by inactivating α2AP, A2AP IgG attenuates α2AP activity, and accelerates clot lysis in vitro and in vivo. This demonstrates that antibody-mediated inhibition of α2AP, enhances thrombolysis and enables use of lower doses of PAs. / Thesis / Master of Science in Medical Sciences (MSMS)

Speech and language impairments after left hemisphere stroke are life altering. Neuroprotective interventions, such as tissue plasminogen activator, or tPA, are utilized to diminish the impact of the stroke on functional ability. The purpose of this study was to examine speech and language recovery in the first three months after stroke in individuals with aphasia and to further investigate any differences between individuals who did and individuals who did not receive tPA, using objective speech and language measures. Twenty-six individuals, thirteen of whom received tPA and thirteen who did not, suffering from first-ever left hemisphere stroke with resulting aphasia were enrolled and completed repeated speech and language assessments within 24 hours after stroke, at one and two weeks after stroke. A three month assessment also included an additional quality of life measure. Findings indicate that both individuals who did and those who did not receive tPA demonstrated significant gains in language skills. Results also suggest that the individuals who received tPA have better outcomes at three months compared to those who did not. This is clinically significant as it helps provide prognostic information about the use of tPA and informs decision making for speech pathologists within the acute care hospital.

BACKGROUND: Under the current treatment guidelines for acute ischemic stroke, intravenous alteplase may be used within 3-4.5 hours of symptom recognition or in cases of unknown onset if there is a small lesion on diffusion weighted imaging without increased signal on FLAIR sequence MRI. We seek to determine whether patients with lacunar strokes greater than 4.5 hours post onset with a DWI-FLAIR mismatch on imaging will benefit from thrombolysis with intravenous alteplase. METHODS: We will conduct a multicenter, randomized, double-blinded, placebo-controlled trial of patients presenting with acute ischemic stroke within 4.5 to 6 hours of symptom onset with DWI-FLAIR mismatch and without a large vessel occlusion. A target of 682 patients will be randomized to receive IV alteplase or placebo. The primary outcome is a favorable functional status as defined by a score of 0 or 1 on the modified Rankin scale (mRS) at 90 days. The secondary outcome is ordinal score on the modified Rankin scale at 90 days. The primary safety end points will be symptomatic intracranial hemorrhage (sICH) and death CONCLUSIONS: If intravenous (IV) alteplase is found to be an effective and safe treatment for lacunar stroke with DWI-FLAIR mismatch >4.5 hours from onset, these patients could have significantly reduced morbidity and improved long-term outcomes.

Several studies suggest that the use of ultrasound in conjunction with microbubbles (MBs) can induce the lysis of the blood clots through acoustic cavitation and through the production of microjets and microstreaming. However, there is no accordance about the optimal ultrasound parameters that have to be considered in order to achieve the maximum thrombolytic effect, neither a clear agreement about the type of MBs that have to be used. This project had two main goals: the design and optimization of an in-vitro set-up for the study of clot lysis within coronary arteries and its testing with ultrasound in conjunction with two different types of MBs. The MBs considered were the 3MiCRON MBs and the SonoVue MBs. The ultrasound sequence was developed using a programmable ultrasound architecture (Verasonics, Inc) and was tested using commercially available clinical transducers. Using the designed set-up and varying the ultrasound parameters (frequency, pulse length and pulse amplitude) it was possible to study the clot lysis effciency in conjunction with the two types of MBs. For the 3MiCRON MBs no increase in clot lysis was found with the implemented ultrasound parameters, while considering the SonoVue MBs, a 10% increase in clot lysis was found with 10ms long pulse delivered at 50V (peak-to peak value). The obtained set-up had several aspects in common with the real situation of occluded coronary arteries, although some limitations were present and further optimizations are required. Further work is required in order to assess if different combination of ultrasound parameters are able to lead to an increase in clot lysis when delivered with 3MiCRON or SonoVue MBs.

No description available.

No description available.

Diploma thesis "Quality of life of patients after systemic thrombolysis" is dealing with the impact of systemic thrombolysis to the quality of life of patients affected by the ischemic stroke (IS) and treated with intravenous administration of thrombolytics. The goal is to objectively assess quality of life resulting from health improvement after systemic thrombolysis. The work consists of theoretical and practical part. The theoretical part describes ischemic stroke, its etiology, symptoms and treatment options. The second chapter is devoted to the practical part of the term "quality of life", methods that are used to measure quality of life. This chapter also deals with the consequences of IS for patient's life. In the practical part we focused on monitoring the physical and mental health in patients with IS, who were treated with intravenous systemic thrombolysis, and in patients who have not undergone this treatment. Each study group of patients had 18 patients. The results of both groups we evaluated and compared. In the survey we used a retrospective analysis of medical data and a survey using the questionnaire SF-36 on the health-related quality of life. The survey results confirmed the assumption that patients treated with thrombolysis have less neurological deficit and thus better physical...