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Purpose: Knowledge about the localization and outcome of iatrogenic dissection (ID) during endovascular treatment of acute ischemic stroke (AIS) is limited. We aimed to determine the frequency, clinical aspects and morphology of ID in endovascular AIS treatment and to identify predictors of this complication., Methods: Digital subtraction angiography (DSA) of ID carried out during endovascular treatment between January 2000 and March 2012 have been re-evaluated. The ID localization and morphology were analyzed and related to the interventional techniques. Baseline clinical and radiological findings, treatment modality and outcome were compared with patients without ID., Results: Out of 866 patients 18 (2%) suffered an ID (44% female, median age 64 years). Localization was extracranial in 15 (83%, 14 internal carotid artery and 1 vertebral artery) and intracranial in 3 (17%; 1 vertebrobasilar dissection and 2 in the anterior circulation). Of the IDs 5 (28%) resulted in a high-degree, 3 (17%) in a moderate, 5 (28%) in a mild and 5 (28%) in no stenosis and 8 IDs were stented in the acute phase. At 3 months 7 (42%) patients had a favorable outcome (modified Rankin score mRS ≤ 2) and 6 (33%) patients had died. Patients with ID had a different stroke etiology (p = 0.041), were more likely to be smokers (44% versus 19%, p = 0.015) and were more likely to be treated with mechanical thrombectomy (100% versus 60%, p < 0.001). Although two ID patients had relevant complications, the outcome did not differ between the groups., Conclusion: The occurrence of ID is a rare complication of endovascular AIS treatment associated with smoking and mechanical thrombectomy.

The goal of acute stroke treatment with intravenous thrombolysis or endovascular recanalization techniques is to rescue the penumbral tissue. Therefore, knowing the factors that influence the loss of penumbral tissue is of major interest. In this study we aimed to identify factors that determine the evolution of the penumbra in patients with proximal (M1 or M2) middle cerebral artery occlusion. Among these factors collaterals as seen on angiography were of special interest. Forty-four patients were included in this analysis. They had all received endovascular therapy and at least minimal reperfusion was achieved. Their penumbra was assessed with perfusion- and diffusion-weighted imaging. Perfusion-weighted imaging volumes were defined by circular singular value decomposition deconvolution maps (Tmax > 6 s) and results were compared with volumes obtained with non-deconvolved maps (time to peak > 4 s). Loss of penumbral volume was defined as difference of post- minus pretreatment diffusion-weighted imaging volumes and calculated in per cent of pretreatment penumbral volume. Correlations between baseline characteristics, reperfusion, collaterals, time to reperfusion and penumbral volume loss were assessed using analysis of covariance. Collaterals (P = 0.021), reperfusion (P = 0.003) and their interaction (P = 0.031) independently influenced penumbral tissue loss, but not time from magnetic resonance (P = 0.254) or from symptom onset (P = 0.360) to reperfusion. Good collaterals markedly slowed down and reduced the penumbra loss: in patients with thrombolysis in cerebral infarction 2 b-3 reperfusion and without any haemorrhage, 27% of the penumbra was lost with 8.9 ml/h with grade 0 collaterals, whereas 11% with 3.4 ml/h were lost with grade 1 collaterals. With grade 2 collaterals the penumbral volume change was -2% with -1.5 ml/h, indicating an overall diffusion-weighted imaging lesion reversal. We conclude that collaterals and reperfusion are the main factors determining loss of penumbral tissue in patients with middle cerebral artery occlusions. Collaterals markedly reduce and slow down penumbra loss. In patients with good collaterals, time to successful reperfusion accounts only for a minor fraction of penumbra loss. These results support the hypothesis that good collaterals extend the time window for acute stroke treatment.

Background: The optimal treatment of asymptomatic carotid stenosis (ACS) is controversial. To optimize the risk-benefit ratio of carotid artery revascularization, it is crucial to identify ACS patients who are at increased stroke risk. Recent data suggest that plaque vulnerability depends on its composition. Therefore, we assessed plaque composition in ACS to determine predictors for ipsilateral cerebrovascular events., Methods: 62 patients with 65 ACS ≥50% underwent 3-T MRI of the carotid bifurcation (TOF, special dark-blood weighted noncontrast and contrast-enhanced T(1) and T(2) images) and of the brain. The different plaque components (lipid core, intraplaque hemorrhage, calcification and the status of the fibrous cap) were assessed. Furthermore, the plaque volume and the volume of clinically silent cortical and subcortical infarcts in the territory of the stenosed carotid artery as seen on FLAIR images were determined by using a semi-automated software. Carotid stenosis was considered asymptomatic if there had not been any clinically apparent ischemic events in the corresponding vascular territory within the previous 6 months. During follow-up, information on the occurrence of cerebrovascular events, medical treatment and sonographic changes of the stenosis was collected., Results: At baseline, 24 ACS (37%) were classified as high grade. A lipid-rich necrotic core was the dominant plaque component in 16 ACS (25%). The plaque volume was higher in ACS with a lipid-rich necrotic core as dominant plaque component (p = 0.002) and in patients with prior stroke/TIA (p = 0.010). After a median follow-up of 18.9 months (interquartile range 3.5-30.1) there were 2 ipsilateral strokes and 3 ipsilateral TIAs. The average annual event rate was 7.7%. A lipid-rich necrotic core (HR 7.21; 95% CI 1.12-46.28; p = 0.037), sonographic progression of the stenosis (HR 7.00; 95% CI 1.13-41.34; p = 0.036), history of stroke (HR 11.03; 95% CI 1.23-99.36; p = 0.032), and the volume of clinically asymptomatic ischemic brain lesions (HR 1.14/cm(3); 95% CI 1.03-1.25; p = 0.008) predicted cerebrovascular events. Patients on statin therapy at follow-up were at lower risk of events (HR 0.17; 95% CI 0.03-1.00; p = 0.05)., Conclusions: In addition to medical history and sonographic findings, a lipid-rich necrotic core within the plaque turned out as a predictor of cerebrovascular events. Therefore, MR imaging of carotid plaques deserves further attention and might be helpful to improve risk stratification of asymptomatic carotid disease. The identified predictors could be combined in a risk model and tested in larger prospective studies., (Copyright © 2012 S. Karger AG, Basel.)

Background and Purpose: The purpose of the study was to compare efficacy and potential complications of 2 commercially available devices for mechanical thromboembolectomy., Methods: Devices were tested in an established animal model allowing the use of routine angiography catheters and thrombectomy devices. Radio-opaque thrombi were used for visualization of thrombus-device interaction during angiography. The Merci Retrieval System and the Catch Thromboembolectomy System were assessed each in 10 vessel occlusions. For every occluded vessel up to 5 retrieval attempts were performed., Results: Sufficient recanalization was achieved with the Merci Retriever in 90% of occlusions, and with the Catch device recanalization was achieved in 70% of occlusions. Recanalization at the first attempt occurred significantly more often with the Merci Retriever compared to the Catch device (OR, 21; 95% CI, 1.78-248.11). Consequently, significantly more attempts (P=0.02) had to be performed with the Catch device; therefore, time to recanalization was longer. Thrombus fragmentations during retrieval were caused more often by the Catch device compared to the Merci Retriever (OR, 15.6; 95% CI, 1.73-140.84), resulting in a higher distal embolization rate. During retrieval both devices lost thrombotic material at the tip of the guide catheter, which was then aspirated in most cases., Conclusions: Both distal devices are effective for thromboembolectomy. To avoid loss of thrombotic material and distal embolization, the use of large luminal balloon guide catheters and aspiration during retrieval seems to be mandatory. The design of the Merci Retriever appears to be more efficient during thrombus mobilization and retrieval with less fragmentation compared to the Catch Thromboembolectomy System.

Background and Purpose: Although mechanical thrombectomy (MT) has an encouragingly high recanalization rate in treating stroke, it is associated with severe complications of which the underlying factors have yet to be identified. Because MT is a mechanical approach, the mechanical properties of the thrombus might be crucial for its success. The present study assesses the effect of thrombus length on the in vivo effectiveness and complication rate of MT., Materials and Methods: Angiography and embolization of 21 cranial vessels with radiopaque whole-blood thrombi 10, 20, and 40 mm in length (7 occlusions each) were performed in 7 swine. MT was carried out using a distal snarelike device (BCR Roadsaver) with proximal balloon occlusion. A total of 61 retrievals were attempted., Results: In the group of 10-mm occlusions, 77.8% of the attempts achieved complete recanalisation. For longer occlusions, the success rates decreased significantly to 20% of attempts for 20-mm occlusions (odds ratio [OR], 14; 95% confidence interval [CI], 2.2-89.2) and 11.1% for 40-mm occlusions (OR, 28; 95% CI, 3.9-202.2; P < .005). The low success rates were largely due to complications associated with thrombus compaction during retrieval. Similarly, the rate of thromboembolic events increased from 0% in 10-mm occlusions to 14.8% in 40-mm occlusions., Conclusions: MT using a distal device proved to be a fast, effective, and safe procedure for recanalizing short (10-mm) occlusions in the animal model. However, occlusion length emerged as a crucial determinant for MT with a significant decrease in recanalization success per attempt and increased complication rates. These findings suggest limitations of MT in the clinical application.

Background and Purpose: Mechanical thrombectomy is a promising new modality of interventional stroke treatment. The various devices differ with regard to where they apply force on the thrombus, taking a proximal approach such as aspiration devices or a distal approach such as basket-like devices. The study compares the in vivo effectiveness and thrombus-device interaction of these 2 approaches., Methods: Angiography and embolization with a radioopaque whole blood thrombus was performed in 10 swine. Mechanical thrombectomy was performed in 20 cranial vessels using a proximal aspiration device (Vasco35) and a distal basket-like device (Catch) with and without proximal balloon occlusion. Fifty-six retrieval attempts were made., Results: The proximal device allowed fast repeated application with a low risk of thromboembolic events (3%) and vasospasm, but it had a significantly lower success rate (39.4%) in retrieving thrombotic material than the distal device (DD) (82.6%; odds ratio, 7.3; 95% CI, 2.0 to 26.4). The compaction of the thrombus during retrieval with DD increased the risk of vessel wall irritation significantly (P<0.01) and complicated retrieval into the guiding catheter. The number of embolic events was significantly higher with DD (26%; odds ratio, 11.3; 95% CI, 1.35 to 101.6) unless proximal balloon occlusion was used., Conclusions: The proximal and the distal approaches to mechanical thrombectomy proved to be effective at achieving recanalization of cranial vessels. The proximal device is faster in application and allowed repeated attempts with a low complication rate. The DD is more successful at removing thrombotic material, but its method of application and attendant thrombus compaction increase the risk of thromboembolic events and vasospasms.

Background: Recent studies have focused on mechanical thrombectomy as a means to reduce the time required for revascularization and increase the revascularization rate in acute stroke. To date no systematic evaluation has been made of the different mechanical devices in this novel and fast-developing field of endovascular interventions. To facilitate such evaluations, we developed a specific in vivo model for mechanical thrombectomy that allows visualization of dislocation or fragmentation of the thrombus during angiographic manipulation., Methods: Angiography and embolization with a preformed thrombus was performed in 8 swine. The thrombus was generated by mixing 25 IU bovine thrombin and 10 mL autologous blood. For visualization during angiography, 1 g barium sulfate was added., Results: The preformed thrombus exhibited mechanical stability, reproducibility, and high radiographic absorption, providing excellent visibility during angiography. The setting allowed selective embolization of targeted vessels without thrombus fragmentation. Despite the application of barium sulfate no local or systemic reaction occurred. Histologic evaluation revealed no intimal damage caused by the thrombus or contrast agent washout., Conclusion: The model presented here allows selective and reliable thromboembolization of vessels that reproduce the anatomic and hemodynamic situation in acute cerebrovascular stroke. It permits visualization of the thrombus during angiography and intervention, providing unique insight into the behavior of both thrombus and device, which is potentially useful in the development and evaluation of mechanical clot retrieval in acute cerebrovascular stroke.

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 300 g of approximately 1 degrees C in 1 min, 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 hypothermia.

Interventional neuroradiological techniques are described, which are used for revascularisation of the intra-extracranial vessels in acute stroke. The results are based on our experience gained during the endovascular treatment of more than 300 patients suffering from acute stroke during the last years. Indication, procedures and results of intraarterial thrombolysis, thrombo-aspiration, percutaneous transluminal angioplasty, and implantation of stents in cases of occlusion or pseudoocclusion of brain supplying vessels are discussed. Furthermore first experiences with new techniques from other centers are presented, e.g., thrombolysis by ultrasound (sonothrombolysis), by angiojet aspiration, and laser evaporation of the thromboembolic occlusion of intra- and extracranial blood vessels.