Acute Stroke: Present and Future of Catheter-Based Interventions

Abstract : Acute ischemic stroke is a major cause of morbidity and mortality in industrialized nations. The sequel of stroke ranges from mild to severe disability and even death. Since the impairment may be permanent, the costs to society from work incapacity and the need for long-term care can be high. Additionally, the burden of suffering associated with the disease may have devastating effects on individuals and families. Following the occlusion of a cerebral vessel, the full extent of the infarction may not become clinically and radiologically apparent until days after. By then, the surrounding watershed zone, or penumbra, either survives or succumbs to necrosis over time. The natural history of this "tissue at risk” is determined by two factors: the collateralization from other vascular territories and the possible occurrence of spontaneous recanalization of the occluded vessel. The current treatment options for acute ischemic stroke are aiming at an early and sustained restoration of flow to the penumbra. The effect of the treatment is therefore time-dependent and the neurologic outcome is a function of the time span between onset of symptoms and recanalization therapy as well as of the recanalization rate associated with a specific treatment. This report summarizes the results of the major trials on catheter-based interventions, either using thrombolytic drugs or novel mechanical approaches being developed to treat patients with acute ischemic strok

Frequency splitting of polarization eigenmodes in microscopic Fabry-Perot cavities

We study the frequency splitting of the polarization eigenmodes of the fundamental transverse mode in CO2 laser-machined, high-finesse optical Fabry-Perot cavities and investigate the influence of the geometry of the cavity mirrors. Their highly reflective surfaces are typically not rotationally symmetric but have slightly different radii of curvature along two principal axes. We observe that the eccentricity of such elliptical mirrors lifts the degeneracy of the polarization eigenmodes. The impact of the eccentricity increases for smaller radii of curvature. A model derived from corrections to the paraxial resonator theory is in excellent agreement with the measurements, showing that geometric effects are the main source of the frequency splitting of polarization modes for the type of microscopic cavity studied here. By rotating one of the mirrors around the cavity axis, the splitting can be tuned. In the case of an identical differential phase shift per mirror, it can even be eliminated, despite a nonvanishing eccentricity of each mirror. We expect our results to have important implications for many experiments in cavity quantum electrodynamics, where Fabry-Perot cavities with small mode volumes are required.Comment: 10 pages, 6 figure

A quantum network node with crossed optical fibre cavities

Quantum networks provide unique possibilities for resolving open questions on entanglement and promise innovative applications ranging from secure communication to scalable computation. While two quantum nodes coupled by a single channel are adequate for basic quantum communication tasks between two parties, fully functional large-scale quantum networks require a web-like architecture with multiply connected nodes. Efficient interfaces between network nodes and channels can be implemented with optical cavities. Using two optical fibre cavities coupled to one atom, we here realise a quantum network node that connects to two quantum channels. It functions as a passive, heralded and high-fidelity quantum memory that requires neither amplitude- and phase-critical control fields nor error-prone feedback loops. Our node is robust, fits naturally into larger fibre-based networks, can be scaled to more cavities, and thus provides clear perspectives for a quantum internet including qubit controlled quantum switches, routers, and repeaters.Comment: 12 pages, 8 figures (including Supplementary Information

Hydrology and nutrient spiralling at the forest groundwater – surface-water interface

Controls of stream and streambed metabolism were investigated at the reach and bedform-scale and methods to facilitate further understanding of these controls developed. Porewater concentrations of conservative and metabolically reactive (DOC, DIC, CH4) solutes along bedforms indicated that groundwater – surface-water mixing explained the majority of the spatial pattern of the reactive solutes. Therefore, our conceptual understanding of bedform-induced hyporheic exchange flow might need to be re-assessed. Hyporheic metabolism was only detected at a few locations with long porewater travel times. In addition, a small, low-cost conductance sensor was developed to measure high-resolution (temporal and spatial) porewater tracer breakthrough curves (BTC), without risking the induction of hyporheic flow. Based on the tracer BTCs, travel times during a storm event showed complex and hysteretic-like behaviour with discharge. During baseflow conditions, partly bedform-independent patterns of hyporheic travel times were observed, suggesting that small-scale streambed irregularities might be important. On a reach-scale, resazurin injections were conducted under contrasting discharge conditions along four consecutive reaches, with alternating flat and steep channel slopes. Metabolic transformation rates increased with discharge, but channel slope did not have a significant effect. Finally, a turbidity correction method for in situ fluorometers was developed, allowing their application during resazurin injections under variable discharge conditions

Thrombolyse der Arteria cerebri media

Zusammenfassung: In den ersten 3h nach Eintritt eines akuten ischämischen Hirninfarkts ist die intravenöse Thrombolyse (IVT) die evidenzbasierte Therapie (IVT 3-4,5h: "off-label use" mit Einverständnis des Patienten). Die intraarterielle Thrombolyse (IAT) führt in der A.cerebri media (ACM) allerdings häufiger zur Rekanalisation als die IVT. Daher ist die IAT in dafür ausgerüsteten Kliniken ergänzend oder alternativ zur IVT bis zu 6h nach Symptombeginn zu erwäge

The use of flat panel angioCT (DynaCT) for navigation through a deformed and fractured carotid stent

Navigation through a previously deployed and deformed stent is a difficult interventional task. Inadvertent navigation through the struts of a stent can potentially lead to incomplete secondary stent extension and vessel occlusion. Better visualisation of the pathway through the stent can reduce the risks of the procedural complications and reduce the reluctance of the interventionalist to navigate through a previously deployed stent. We describe a technique of visualisation of the pathway navigated by a guidewire through a previously deployed deformed and fractured carotid stent by the use of DynaCT. Three-dimensional reconstruction of the stent/microwire allows excellent visualisation of the correct pathway of the microwire within the sten

Closing the gap between coil and balloon in the neurointerventional armamentarium? Initial clinical experience with a nitinol vascular occlusion plug

Introduction: The use of vascular plug devices for the occlusion of high-flow lesions is a relatively new and successful procedure in peripheral and cardiopulmonary interventions. We report on the use and efficiency of the Amplatzer vascular plug in a small clinical series and discuss its potential for occlusion of large vessels and high-flow lesions in neurointerventions. Methods: Between 2005 and 2007 four patients (mean age 38.5years, range 16-62years) were treated with the device, in three patients to achieve parent artery occlusion of the internal carotid artery, in one patient to occlude a high-flow arteriovenous fistula of the neck. The application, time to occlusion, and angiographic and clinical results and the follow-up were evaluated. Results: Navigation, positioning and detachment of the device were satisfactory in all cases. No flow-related migration of the plug was seen. The cessation of flow was delayed by a mean of 10.5min after deployment of the first device. In the procedures involving vessel sacrifice, two devices had to be deployed to achieve total occlusion. No patient experienced new neurological deficits; the 3-month follow-up revealed stable results. Conclusion: The Amplatzer vascular plug can be adapted for the treatment of high-flow lesions and parent artery occlusions in the head and neck. In this small series the use of the devices was uncomplicated and safe. The rigid and large delivery device and the delayed cessation of flow currently limit the device's use in neurointervention

Age-dependent differences in demographics, risk factors, co-morbidity, etiology, management, and clinical outcome of acute ischemic stroke

Background : Comparisons between younger and older stroke patients including comorbidities are limited. Methods : Prospective data of consecutive patients with first ever acute ischemic stroke were compared between younger (≤ 45 years) and older patients (> 45 years). Results : Among 1004 patients, 137 (14 %) were ≤ 45 years. Younger patients were more commonly female (57 % versus 34 %; p < 0.0001), had a lower frequency of diabetes (1 % versus 15 %; p < 0.0001), hypercholesterolemia (26 % versus 56 %; p < 0.0001), hypertension (19 % versus 65 %; p < 0.0001), coronary heart disease (14 % versus 40 %; p < 0.0001), and a lower mean Charlson co-morbidity index (CCI), (0.18 versus 0.84; p < 0.0001). Tobacco use was more prevalent in the young (39 % versus 26 %; P < 0.0001). Large artery disease (2 % versus 21 %; p < 0.0001), small artery disease (3 % versus 12 %; p = 0.0019) and atrial fibrillation (1 % versus 17 %; p = 0.001) were less common in young patients, while other etiologies (31 % versus 9 %; p < 0.0001), patent foramen ovale or atrial septal defect (44 % versus 26 %; p < 0.0001), and cervical artery dissection (26 % versus 7 %; p < 0.0001) were more frequent. A favorable outcome (mRS 0 or 1) was more common (57.4 % versus 46.9 %; p = 0.023), and mortality (5.1 % versus 12 %; p = 0.009) was lower in the young. After regression analysis, there was no independent association between age and outcome (p = 0.206) or mortality (p = 0.073). Baseline NIHSS score (p < 0.0001), diabetes (p = 0.041), and CCI (p = 0.002) independently predicted an unfavorable outcome. Conclusions : Younger patients were more likely to be female, had different risk factors and etiologies and fewer co-morbidities. There was no independent association between age and clinical outcome or mortalit

Locally induced hypothermia for treatment of acute ischaemic stroke: a physical feasibility study

During the treatment of stroke by local intra-arterial thrombolysis (LIT) it is frequently possible to pass the blood clot with a micro-catheter, allowing perfusion of brain tissue distally to the occlusion. This possibility allows for new early treatments of ischaemic brain tissue, even before the blood clot has been removed. One potential new approach to preserve brain tissue at risk may be locally induced endovascular hypothermia. Physical parameters such as the required micro-catheter input pressure, output velocity and flow rates, and a heat exchange model, applicable in the case of a micro-catheter placed within a guiding catheter, are presented. Also, a simple cerebral temperature model is derived that models the temperature response of the brain to the perfusion with coolant fluids. Based on this model, an expression has been derived for the time needed to reach a certain cerebral target temperature. Experimental in vitro measurements are presented that confirm the usability of standard commercially available micro-catheters to induce local hypothermia of the brain. If applied in vivo, the model predicts a local cooling rate of ischaemic brain tissue of 300g of approximately 1°C in 1min, which is up to a factor 30-times faster than the time-consuming systemic hypothermia via the skin. Systemic body temperature is only minimally affected by application of local hypothermia, thus avoiding many limitations and complications known in systemic hypothermi