Value of pre-intervention CT perfusion imaging in acute ischemic stroke prognosis

Noninvasive imaging plays an important role in acute stroke towards diagnosis and ongoing management of patients. Systemic thrombolysis and endovascular thrombectomy (EVT) are proven treatments currently used in standards of care in acute stroke settings. The role of computed tomography angiography (CTA) in selecting patients with large vessel occlusion for EVT is well established. However, the value of CT perfusion (CTP) imaging in predicting outcomes after stroke remains ambiguous. This article critically evaluates the value of multimodal CT imaging in early diagnosis and prognosis of acute ischemic stroke with a focus on the role of CTP in delineating tissue characteristics, patient selection, and outcomes after reperfusion therapy. Insights on various technical and clinical considerations relevant to CTP applications in acute ischemic stroke, recommendations for existing workflow, and future areas of research are discussed.

Neuroimaging is currently the mainstay of acute stroke workflow as it is used to rule out hemorrhage and select patients eligible for systemic thrombolysis and endovascular thrombectomy (EVT) (1). Advanced imaging has shown promise in acute stroke; however, the prognostic utility of computed tomography perfusion (CTP) imaging has drawn considerable debate. Given that stroke is associated with long-term morbidity and mortality, efforts to develop diagnostic imaging biomarkers have been pursued. However, the clinical translation of certain imaging modalities has been limited, especially CTP imaging. This could be attributed to the limited availability of CTP in under-resourced settings, variations in the diagnostic accuracy of CTP maps, and differences in the thresholds used in creating perfusion maps. In this paper, we will present a comprehensive overview of various imaging modalities in acute stroke with a particular focus on the clinically relevant utility of CTP and provide roadmap for future research.     

Computed tomography perfusion imaging in acute stroke

The development of thrombolytic and neuroprotective agents for the treatment of acute stroke has created an imperative for improved imaging techniques in the assessment of acute stroke. Five cases are presented to illustrate the value of perfusion CT in the evaluation of suspected acute stroke. To obtain the perfusion data, a rapid series of images was acquired without table movement following a bolus of contrast medium. Cerebral blood flow, cerebral blood volume and mean transit time were determined by mathematically modelling the temporal changes in contrast enhancement in the brain and vascular system. Pixel-by-pixel analysis allowed generation of perfusion maps. In two cases, CT-perfusion imaging usefully excluded acute stroke, including one patient in whom a low-density area on conventional CT was subsequently proven to be tumour. Cerebral ischaemia was confirmed in three cases, one with an old and a new infarction, one with a large conventional CT abnormality but only a small perfusion defect, and one demonstrating infarct and penumbra. Perfusion CT offers the ability to positively identify patients with non-haemorrhagic stroke in the presence of a normal conventional CT, to select those cases where thrombolysis is appropriate, and to provide an indication for prognosis.     

急性后循环缺血机械取栓研究现状与进展

【摘要】　脑卒中已成为世界上第二大致死性疾病和最常见致残性疾病,其中约85%为缺血性脑卒中。开通闭塞血管是急性缺血性脑卒中关键治疗方法,主要包括静脉溶栓、动脉溶栓和机械取栓(MT)。随着溶取栓技术和器械不断发展,静脉溶栓联合血管内取栓桥接治疗逐渐成为急性颅内大血管闭塞首选治疗方法。MT治疗前循环缺血性脑卒中的安全性和有效性已有多项临床研究证实,MT也纳入相关指南。然而,目前尚缺乏后循环缺血性脑卒中血管内治疗的随机对照临床研究数据,以确定统一标准指导。该文就急性后循环缺血性脑卒中MT器械发展、影像学评估、预后、并发症及补救措施等研究现状与进展作一综述。     

Interventional neuroradiology of stroke,still not dead简

Since the National Institute of Neurological Disorders and Stroke trial, intravenous thrombolysis has been gaining wide acceptance as the modality of treatment for acute embolic stroke, with a current therapeutic window of up to 4.5 h. Both imaging [with either magnetic resonance imaging (MRI) or computed tomography (CT)] and interventional techniques (thrombolysis and/or thrombectomy) have since improved and provided us with additional imaging of the penumbra using CT or MRI and more advanced thrombolysis or thrombectomy strategies that have been embraced in many centers dealing with patients with acute cerebral ischemia. These techniques, however, have come under scrutiny due to their accrued healthcare costs and have been questioned following major recent studies. These studies basically showed that interventional techniques were not superior to the traditional intravenous thrombolysis techniques and that penumbra imaging could not determine what patients would benefit from more aggressive (i.e., interventional) treatment. We discuss this in the light of the latest developments in both diagnostic and interventional neuroradiology and point out why further studies are needed in order to define the right choices for patients with acute stroke. Indeed, these studies were in part conducted with suboptimal patient recruitment strategies and did not always use the latest interventional techniques available today. So, while these studies may have raised some relevant questions, at the same time, definitive answers have not been given, in our opinion.     

Brain perfusion-CT in acute stroke patients

The role of neuro-imaging in the evaluation of acute stroke has changed dramatically in the past decade. Previously, neuro-imaging was used in this setting to provide anatomic imaging that indicated the presence or absence of acute cerebral ischemia and excluded lesions that produce symptoms or signs mimicking those of stroke, such as hemorrhage and neoplasms. More recently, the introduction of thrombolysis has changed the goals of neuro-imaging from providing solely anatomic information to providing physiologic information that could help to determine which patients might benefit from therapy. In particular, significant emphasis has been placed on the delineation of the ischemic penumbra, also called tissue at risk. Modern CT survey, consisting of three indissociable elements: noncontrast CT (NCT) of course, perfusion-CT (PCT) and CT-angiography (CTA), fulfill all the requirements for hyperacute stroke imaging. CTA can define the occlusion site, depict arterial dissection, grade collateral blood flow, and characterize atherosclerotic disease, whereas PCT accurately delineates the infarct core and the ischemic penumbra. CT offers a number of practical advantages over other cerebral perfusion imaging methods, including its wide availability. Using PCT and CTA to define new individualized strategies for acute reperfusion will allow more acute stroke patients to benefit from thrombolytic therapy.     

Brain perfusion-CT in acute stroke patients

The role of neuro-imaging in the evaluation of acute stroke has changed dramatically in the past decade. Previously, neuro-imaging was used in this setting to provide anatomic imaging that indicated the presence or absence of acute cerebral ischemia and excluded lesions that produce symptoms or signs mimicking those of stroke, such as hemorrhage and neoplasms. More recently, the introduction of thrombolysis has changed the goals of neuro-imaging from providing solely anatomic information to providing physiologic information that could help to determine which patients might benefit from therapy. In particular, significant emphasis has been placed on the delineation of the ischemic penumbra, also called tissue at risk. Modern CT survey, consisting of three indissociable elements: noncontrast CT (NCT) of course, perfusion-CT (PCT) and CT-angiography (CTA), fulfill all the requirements for hyperacute stroke imaging. CTA can define the occlusion site, depict arterial dissection, grade collateral blood flow, and characterize atherosclerotic disease, whereas PCT accurately delineates the infarct core and the ischemic penumbra. CT offers a number of practical advantages over other cerebral perfusion imaging methods, including its wide availability. Using PCT and CTA to define new individualized strategies for acute reperfusion will allow more acute stroke patients to benefit from thrombolytic therapy.     

Feasibility and practicality of MR imaging of stroke in the management of hyperacute cerebral ischemia

BACKGROUND AND PURPOSE: Neuroimaging techniques such as diffusion- and perfusion-weighted MR imaging have been proposed as tools for advanced diagnosis in hyperacute ischemic stroke. There is, however, substantial doubt regarding the feasibility and practicality of applying MR imaging for the diagnosis of stroke on a routine basis, especially with respect to possible delay for specific treatment such as thrombolysis. In this study, we tested whether MR imaging of stroke is safe, fast, and accurate, and whether the gain in additional information can be used in the daily routine without a loss of time and a risk of suboptimal treatment for the patient with stroke. METHODS: Between September 1997 and August 1999, 64 patients with acute ischemic stroke were recruited for MR imaging (ie, diffusion-weighted imaging, perfusion-weighted imaging, MR angiography, T2-weighted imaging) after a baseline CT was performed. We evaluated practicality and feasibility of MR imaging of stroke by analyzing the intervals between symptom onset, arrival, CT, and MR imaging. RESULTS: Sixty-four patients (mean age, 60.9 years) underwent routine CT and MR imaging within 12 hours after stroke onset (n=25, < or =3 hr; n=26, 3-6 hr; n=13, 6-12 hr). Median times to arrival, start of CT, MR imaging, and between CT and MR imaging were 1.625 hours, 2 hours, 3.875 hours, and 1 hour, respectively. Intervals between symptom onset and MR imaging (P<.005), arrival and MR imaging (P<.002), and CT and MR imaging (P=.0007) differed significantly between the early phase of the study and after November 1998, whereas the intervals between symptom onset and arrival, symptom onset and CT, and arrival and CT did not. Hemorrhage could be excluded in all; a perfusion/diffusion match or mismatch could be shown in 63 of 64 patients. CONCLUSION: Practice and experience with MR imaging in a stroke team significantly reduce the time and effort required to perform this technique and thus make 24-hour availability for MR imaging of stroke practical. Assessment of patients with hyperacute stroke is rapid and comprehensive. Image quality can be substantially improved by head immobilization and by mild sedation, if necessary.     

Diagnostik der zerebralen Ischämie: Wann CT, wann MRT?

Rapid and effective diagnostic imaging is important for decision-making concerning thrombolysis in patients with acute ischemic stroke. Apart from excluding intracranial hemorrhage, CT and MRI provide multiple methodological options to define the extent of ischemic brain damage and the underlying vascular pathology. The aim of this article is to discuss the value of CT and MRI from a neurologicalneuroradiological point of view and to discuss which of the available imaging tools are really relevant for clinical decision making.     

动、静脉结合r-tPA溶栓治疗早期脑梗死

目的 评价动、静脉结合r-tPA溶栓治疗急性脑梗死的方法和临床疗效.方法 共15例急性脑梗死患者,术前均行CT、MR 和DSA检查证实颅内动脉闭塞部位：M1段4例,M2段2例,M3、4段2例,A1、2段1例,颈内动脉2例, P1段1例,豆纹动脉1例,其他穿支2例.其中术前经DSA证实12例.溶栓治疗时间在发病后3～7 h,采用动脉内药物灌注和机械疏通相结合方法溶栓,另外经静脉术前和术后持续滴注r-tPA辅助.术后观察临床症状和影像表现.结果 15例患者溶栓治疗中微导管和溶栓导管均到位满意,DSA所示闭塞段血管均有效再通.术后CT检查发现片状渗血2例,异位脑梗死1例.术后肢体功能即刻明显改善6例.临床观察3个月,症状基本完全恢复6例,较好改善7例,2例无明显改善;生活能力完全自理13例,有效率达87%（13/15）,生活能部分自理者1例,失去生活自理能力 1例,无患者死亡.结论 动、静脉结合溶栓治疗急性颅内动脉栓塞是一种有效、安全的治疗方法;局部动脉内灌注和机械疏通有效结合以及术前各项影像学检查的综合分析,将有利于动脉溶栓治疗的进行.     

MR imaging in hyperacute ischemic stroke

Brain and vascular imaging are required components of the emergency assessment of patients with suspected stroke. Either CT or MRI may be used as the initial imaging test. MRI is more sensitive to the presence of acute and chronic ischemic lesions, and chronic microbleeds, but CT remains the most practical and used initial brain imaging test. Although, a non-enhanced CT or T2* MRI sequence showing no haemorrhage is sufficient for deciding intravenous treatment eligibility within the first 4.5 h after stroke onset, a non-invasive intracranial vascular study is strongly recommended during the initial imaging evaluation of the acute stroke patient, particularly if mechanical thrombectomy is contemplated. Advanced imaging with multimodal MRI may facilitate accurate ischemic stroke diagnosis and characterization, and should be considered as an alternative to CT, especially for the selection of patients for acute reperfusion therapy in extended time windows, and in patients in which time of stroke onset is unknown. However, MRI should only be considered in the acute stroke workflow if centres are able to achieve speed and triaging efficiency similar to that which is currently available with CT-based imaging.     

Combined stent placement and thrombolysis in acute vertebrobasilar ischemic stroke

BACKGROUND AND PURPOSE: Acute vertebrobasilar ischemic stroke is often associated with high morbidity and mortality with limited therapeutic options. Endovascular treatment with thrombolysis has offered some hope for affected patients; however, overall outcomes have been less than satisfactory. In this report, we present the results of our approach in six consecutive cases of acute vertebrobasilar ischemic stroke by combined proximal vessel stent placement and thrombolysis. METHODS: Six consecutive cases were retrospectively reviewed for the clinical outcome of patients presenting to our institution with acute posterior circulation stroke who underwent cerebral revascularization including proximal arterial stent placement by using balloon-expandable coronary stents and intraarterial thrombolysis. All of these patients were initially evaluated by stroke team neurologists and imaged with MR, including diffusion-weighted imaging documenting acute posterior circulation stroke. MR angiography of the circle of Willis was also obtained. Short-term follow-up was conducted to assess National Institutes of Health stroke scores (NIHSS) and modified Rankin scores. RESULTS: In these six cases, a combined approach of proximal arterial stent placement (five cases of vertebral artery origin and one case of carotid and subclavian stent placement plus vertebral artery revascularization) and thrombolysis was performed at variable times after stroke onset (range, 30 hours to 5 days). Four of the six patients had good basilar artery recanalization (Thrombolysis in Myocardial Infarction [TIMI] grade 0-1 before tissue plasminogen activator thrombolysis and TIMI grade 2 after procedure). Four of six patients had excellent immediate recovery and were discharged to an acute rehabilitation unit or their homes with improved neurologic symptoms and functional status. Two patients died: one patient presented with coma at outset with an NIHSS of 38, and the other patient probably had reocclusion of the basilar artery within 24 hours despite initial postprocedural improvement. CONCLUSION: We demonstrate that, in the setting of acute stroke, stent placement in combination with revascularization and thrombolysis is practical and allows quick access to a clot and simultaneously increases perfusion through collaterals during the thrombolytic process. In particular, basilar thrombolysis may be facilitated by proximal vertebral stent placement as concomitant atheromatous vertebrobasilar stenosis is common.     

Imaging of stroke: Part 2, Pathophysiology at the molecular and cellular levels and corresponding imaging changes

OBJECTIVE: Stroke is the third leading cause of death and the leading cause of severe disability. During the "decade of the brain" in the 1990s, the most promising development was the treatment of acute ischemic stroke. It is thought to result from a cascade of events from energy depletion to cell death. In the initial minutes to hour, clinical deficit does not necessarily reflect irreversible damage. The final outcome and residual deficit will be decided by how fast reperfusion is achieved, which in turn depends on how early the diagnosis is made. This article explains the pathophysiology of stroke at the molecular and cellular levels with corresponding changes on various imaging techniques. CONCLUSION: The pathophysiology of stroke has several complex mechanisms. Understanding these mechanisms is essential to derive neuroprotective agents that limit neuronal damage after ischemia. Imaging and clinical strategies aimed at extending the therapeutic window for reperfusion treatment with mechanical and pharmacologic thrombolysis will add value to existing treatment strategies. Acute ischemic stroke is defined as abrupt neurologic dysfunction due to focal brain ischemia resulting in persistent neurologic deficit accompanied by characteristic abnormalities on brain imaging. Knowledge of the pathophysiologic mechanisms of neuronal injury in stroke is essential to target treatment. Neuroprotective and thrombolytic agents have been shown to improve clinical outcome. Physiologic imaging with diffusion-weighted imaging (DWI) and perfusion CT and MRI provide a pathophysiologic substrate of evolving ischemic stroke.     

Intracranial hemorrhage complicating acute stroke: how common is hemorrhagic stroke on initial head CT scan and how often is initial clinical diagnosis of acute stroke eventually confirmed?

BACKGROUND AND PURPOSE: Assessment of possible hemorrhage in acute stroke before appropriate therapy remains important. The aim of this study was to determine the frequency with which patients present with clinical stroke and have intracranial hemorrhage on initial noncontrast head CT scan (NCCT). In addition, we sought to determine the frequency with which initial clinical diagnosis acute stroke is confirmed in this group. METHODS: Medical records of 691 consecutive patients with admitting diagnosis of acute stroke were evaluated retrospectively. Results of initial NCCT performed within 24 hours after presentation were assessed. All patients were examined before anticoagulation or thrombolysis. Correlation with treatment and leading differential etiology was made. RESULTS: Twenty-five patients (25/691 [3.6%]) had hemorrhage. Twenty-three patients (23/25 [92%]) had intraparenchymal hemorrhage only. One patient (1/25 [4%]) had a combination of intraparenchymal and subarachnoid hemorrhage. One patient (1/25 [4%]) had subdural hemorrhage only. Twenty-two NCCT scans (22/25 [88%]) were performed within 6 hours of presentation. Seventeen NCCT scans (17/25 [68%]) were performed within 3 hours of presentation. CONCLUSION: Despite frequent concerns for intracranial hemorrhage complicating acute stroke and treatment, a low percentage of patients had this complication. Moreover, our frequency is much lower than the wide ranges reported elsewhere. The most common type of intracranial hemorrhage in this cohort was intraparenchymal, but subarachnoid and subdural hemorrhages were also diagnosed and must also be considered. Twenty-eight percent of patients with initial suspicion of acute ischemic stroke are eventually given other diagnoses. These results may have implications for use of CT imaging.     

Multimodal CT in the diagnostic workup of stroke

Stroke results in significant morbidity and mortality. Recent years have seen a revolution in the diagnosis and treatment of stroke, with advances in diagnostic imaging and improvements in early and specific treatment. Multimodal CT (unenhanced CT, perfusion CT, and CT angiography) is widely available, fast, and efficacious, all of which give it a key role in the early diagnosis of stroke and in the selection of patients who will benefit from thrombolytic treatment. Unenhanced CT is useful for ruling out hemorrhage or lesions that simulate stroke and for evaluating the presence of early signs. Perfusion CT enables us to know the presence and extension of infarcted ischemic tissue (irrecoverable) and of penumbra (tissue at risk that is potentially recoverable), thus ensuring more appropriate selection of candidates for treatment. Finally, CT angiography makes it possible to evaluate the intra- and extra-cranial circulation, to know the vascular alteration that originated the stroke, and to guide treatment (intra-arterial or mechanical thrombolysis).     

急性脑梗死动脉内溶栓治疗疗效观察

目的观察急性脑梗死患者行脑动脉内溶栓治疗的临床疗效。方法26例临床及头颅CT诊断为急性脑梗死患者用尿激酶行经动脉介入溶栓治疗(IATT)，治疗前后均作脑血管造影、复查CT及神经功能缺损评分。结果3例造影未见血管闭塞，23例患者即刻完全再通7例，部分再通11例，再通率78e。结论动脉溶栓疗法使84％的患者在15d内神经功能缺损得到改善，脑动脉内溶栓治疗是治疗急性脑梗死有效的方法之一。     

TC multimodal en el diagnóstico del código ictus

Stroke results in significant morbidity and mortality. Recent years have seen a revolution in the diagnosis and treatment of stroke, with advances in diagnostic imaging and improvements in early and specific treatment. Multimodal CT (unenhanced CT, perfusion CT, and CT angiography) is widely available, fast, and efficacious, all of which give it a key role in the early diagnosis of stroke and in the selection of patients who will benefit from thrombolytic treatment. Unenhanced CT is useful for ruling out hemorrhage or lesions that simulate stroke and for evaluating the presence of early signs. Perfusion CT enables us to know the presence and extension of infarcted ischemic tissue (irrecoverable) and of penumbra (tissue at risk that is potentially recoverable), thus ensuring more appropriate selection of candidates for treatment. Finally, CT angiography makes it possible to evaluate the intra- and extra-cranial circulation, to know the vascular alteration that originated the stroke, and to guide treatment (intra-arterial or mechanical thrombolysis).     

Evaluation of a new Spin-echo diffusion-weighted sequence on a 0.35 T open magnetic resonance imaging (MRI)-system: first experiences within 3 h after acute stroke

In acute stroke, diffusion-weighted magnetic resonance imaging helps to select patients who are eligible for thrombolysis, but is almost exclusively implemented on closed-bore scanners, which make monitoring of patients difficult. We developed and tested a cardiac gated Spin-echo diffusion-weighted sequence with prescan finetrim and motion correction on an open system with 0.35 T. Nineteen stroke patients appropriate for thrombolytic therapy by clinical criteria were enrolled in a prospective study on an intention-to-treat basis. In all but one patient, computed tomography and magnetic resonance imaging including the new diffusion-weighted sequence were performed within 3 h after symptom onset. Images were evaluated for acute cerebral ischemia and hemorrhage by two radiologists blinded to clinical information. Magnetic resonance imaging required a mean total acquisition time of 26 min. Sensitivity for early infarction was 94% in diffusion-weighted imaging and 73% in computed tomography. Six patients were excluded from thrombolysis due to an infarct size of more than 1/3 of the territory of the middle cerebral artery exclusively diagnosed with diffusion-weighted imaging. Hemorrhage was recognised by both, magnetic resonance imaging and computed tomography. We conclude that in acute stroke, diffusion-weighted imaging with an open system at 0.35 T is practicable. The implemented sequence reliably demonstrated the size of the infarction and improved the selection of patients who are eligible for thrombolysis.     

人工智能在急性缺血性脑卒中成像中的应用进展

人工智能（AI）技术可采用多种算法模拟人类认知和信息处理过程,与CT和MRI相结合可用于急性缺血性脑卒中成像,包括梗死灶的检测、影像分割、头颈大血管闭塞的检测和病人预后预测等。采用AI技术分析或构建模型有助于临床医师对脑卒中病人的尽早诊疗、及时干预和随访评估。概述AI的概念,并就其在急性缺血性脑卒中病人CT平扫、CT血管成像（CTA）、CT灌注成像（CTP）、MRI中的应用进展进行综述。     

Combined intraarterial/intravenous thrombolysis for acute ischemic stroke

BACKGROUND AND PURPOSE: The intravenous use of recombinant tissue-type plasminogen activator (rTPA) in acute ischemic stroke has been investigated in three large trials. Limited series have reflected outcome after local intraarterial thrombolysis (LIT) in the cerebral territory. The purpose of this study was to evaluate the safety and efficacy of combined intraarterial/intravenous thrombolysis using rTPA (actilyse) for acute ischemic stroke. METHODS: Forty-five patients with acute onset of severe hemispheric stroke and without signs of major cerebral infarction on early CT scans were randomized by order of admission. Twelve patients were treated with 50 mg actilyse (maximal dose, 0.7 mg/kg); three had occlusion of the internal carotid artery and nine had occlusion of the middle cerebral artery. Thrombolysis was started by LIT and continued intravenously within 6 hours of stroke onset. Outcome, assessed after 1 and 12 months according to the modified Rankin scale (MRS), was considered good (MRS score, 0-3) for patients who were functionally independent and poor (MRS score, 4-5) for those who were dependent or had died. RESULTS: In the thrombolysis group, outcome was good in eight patients at 1 month and in 10 patients at 12 months; in the control group, outcome was good in seven (21%) and 11 (33%) patients, respectively. Of the eight patients with a good outcome after thrombolysis, four had complete and one had partial recanalization. In the control group, the rate of intracerebral hemorrhage was 6%. Mortality at 1 month in the thrombolysis and control groups was 17% and 48%, respectively. CONCLUSIONS: Combined intraarterial/intravenous thrombolysis with low-dose rTPA may be a safe and effective treatment for acute ischemic stroke within 6 hours in carefully selected patients.     

Periprocedural aspects in mechanical recanalization for acute stroke: data from the ENDOSTROKE registry

Introduction

The ENDOSTROKE registry aims to accompany the spreading use of endovascular stroke treatment (EVT) in academic and non-academic hospitals. This analysis focuses on preprocedural imaging, patient handling and referral, as well as on different treatment modalities in mechanical recanalization.

Methods

Data for this study were from observational registry study in 12 stroke centers in Germany and Austria with online assessment of prespecified variables concerning endovascular stroke therapy.

Results

Data from 734 patients undergoing EVT were analyzed. Preferred imaging modality prior to EVT was CT (83 %) and CTA (78 %). In 95 %, EVT was performed under general anesthesia. In 55 % of patients, a combination of intravenous (IV) thrombolysis and EVT was used, followed by pure EVT (25 %), intra-arterial (IA) thrombolysis plus EVT (13 %) and IV?+?IA thrombolysis plus EVT (7 %). Intrahospital time delay until start of EVT was 91 and 99 min in anterior and vertebrobasilar circulation stroke, respectively. Average duration of EVT was 60 min. Overall thrombolysis in myocardial infarction grade 2/3 recanalization rate was 85 %. Stent retrievers were used in 75 %, being associated with higher recanalization rates than non-stent retrievers. Hemorrhagic complications (symptomatic and asymptomatic) occurred in 12 %. Overall vessel occlusion time was approximately 60 min longer in patients being referred from a primary care hospital for EVT.

Conclusion

This study gives an overview of procedure-related factors in current EVT practice. It gives estimates on preprocedural imaging modalities, periprocedural handling, and treatment combinations used for EVT. Patient referral for EVT from primary care hospitals is associated with longer vessel occlusion times.