Felix C. Ng

Perfusion‐Derived Dynamic 4D CT Angiography Identifies Carotid Pseudo‐Occlusion in Hyperacute Stroke

Differentiation between true acute tandem occlusion involving the extracranial internal carotid artery (ICA) from pseudotandem occlusion with a patent extracranial ICA has important prognostic and therapeutic implications. We explored the utility of perfusion‐derived 4‐dimensional CT angiogram (4D‐CTA) in identifying carotid pseudo‐occlusion in a single‐center pilot study.

Deconstruction of Interhospital Transfer Workflow in Large Vessel Occlusion: Real-World Data in the Thrombectomy Era

Background and Purpose— Interhospital transfer is a critical component in the treatment of acute anterior circulation large vessel occlusive stroke transferred for mechanical thrombectomy. Real-world data for benchmarking and theoretical modeling are limited. We sought to characterize transfer workflow from primary stroke center (PSC) to comprehensive stroke center after the publication of positive thrombectomy trials. Methods— Consecutive patients transferred from 3 high-volume PSCs to a single comprehensive stroke center between January 2015 and August 2016 were included in a retrospective study. Factors associated with key time metrics were analyzed with emphasis on PSC intrahospital workflow. Results— Sixty-seven patients were identified. Median age was 74 years (interquartile range [IQR], 63.5–78) and National Institutes of Health Stroke Scale 17 (IQR, 12–21). Median transfer time measured by PSC-door-to-comprehensive stroke center-door was 128 minutes (IQR, 107–164), of which 82.8% was spent at PSCs (door-in-door-out [DIDO]; 106 minutes; IQR, 86–143). The lengthiest component of DIDO was computed-tomography-to-retrieval-request (median 59.5 minutes; IQR, 44–83). The 37.3% had DIDO exceeding 120 minutes. DIDO times differed significantly between PSCs (P=0.01). In multivariate analyses, rerecruiting the initial ambulance crew for transfer (P<0.01) and presentation during working hours (P=0.04) were associated with shorter DIDO times. Conclusions— In a metropolitan hub-and-spoke network, PSC-door-to-comprehensive stroke center-door and DIDO times are long even in high-volume PSCs. Improving PSC workflow represents a major opportunity to expedite mechanical thrombectomy and improve patient outcomes.

Adverse clinical outcomes after dabigatran reversal with idarucizumab to facilitate acute stroke thrombolysis

Intravenous tissue plasminogen activator (tPA) thrombolysis remains the only proven pharmacological treatment for acute ischemic stroke [1]. A common clinical scenario is where a patient with atrial fibrillation (AF) on therapeutic anticoagulation presents with an acute ischemic stroke but thrombolysis is absolutely contraindicated due to hemorrhagic risk. Recently, dabigatran reversal with idarucizumab to facilitate thrombolysis in acute stroke patients on dabigatran has been proposed [2]. We present two patients, the first outside Europe, managed with this approach (Fig. 1). Case 1 A well 85-year-old presented with a severe dominant hemispheric stroke with a National Institutes of Health Stroke Scale (NIHSS) of 30 within 17 h of last dabigatran dose. Computed Tomography (CT) with angiogram and perfusion studies showed a tandem left Internal Carotid Artery and Middle Cerebral Artery (ICAMCA) occlusion with minimal established infarction and a large salvageable penumbra. Coagulation studies revealed isolated elevated Thrombin Time ([60 s, normal range \21 s) consistent with active dabigatran anticoagulation. 5 g of idarucizumab followed by tPA were administered at 167 min from symptoms onset. Mechanical thrombectomy was not possible as the patient arrived at an endovascularcapable centre outside the 6 h therapeutic time window after urgent inter-hospital transfer post-thrombolysis. Day1 CT showed a large hemispheric infarct with significant hemorrhage and mass effect. He progressively deteriorated and died on day 4. Case 2 A 46-year-old with AF presented with left hemiparesis (admission NIHSS 5) within 1 h of dabigatran intake. Multimodal CT revealed a right frontal ischemic penumbra without large vessel occlusion or stenosis. Idarucizumab and immediate tPA were administered at 178 min from onset with near-total resolution of symptoms (NIHSS 1). Follow-up CT confirmed a small area of right frontal infarction. At 30 h, he developed a severe contralateral left hemispheric stroke (NIHSS 18) secondary to a left M2 segment MCA thrombus which was too distal for endovascular clot retrieval. With the recent stroke contraindicating further thrombolysis, he was conservatively treated. Subsequent echocardiogram did not reveal intracardiac thromboses or valvular lesions. He remained aphasic and bed-bound for 3 months. Idarucizumab, a humanised monoclonal antibody fragment, was approved by the European Medicine Agency in 2015 as a reversal agent in patients on dabigatran requiring emergency procedures, or with life-threatening bleeding [3]. In-vitro and in vivo studies with healthy controls have shown immediate normalization of dabigatran-induced anticoagulation following idarucizumab without & Felix C. Ng ng.fcffelix@gmail.com

Utility of Computed Tomographic Perfusion in Thrombolysis for Minor Stroke

Background and Purpose— The use of thrombolysis in acute minor ischemic stroke (MIS) remains controversial. We sought to determine the safety and efficacy of intravenous tissue-type plasminogen activator (IV-tPA) in acute MIS patients with demonstrable penumbra on computed tomographic perfusion study. Methods— Consecutive MIS patients with National Institutes of Health Stroke Scale ⩽3 were identified from a prospective single tertiary-center database over a 4.5-year period (2011–2015). Cases with demonstrable penumbra were analyzed according to treatment received: IV-tPA versus standard stroke-unit care without thrombolysis. Results— Seventy-three patients of 195 acute MIS admissions had a demonstrable penumbra (34 IV-tPA versus 39 standard stroke-unit care). Overall median National Institutes of Health Stroke Scale and premorbid modified Rankin Scale were 2 and 0, respectively. Median age was 73.2 (interquartile range, 67.3–82.8) years. There were no differences in baseline demographics, risk factors, stroke localization and cause, rates of vascular occlusion (38.2% versus 38.5%; P=1.000), or mean penumbral volume (41.3 versus 25.1 mL; P=0.150; IV-tPA versus standard stroke-unit care) between groups. There were no symptomatic intracerebral hemorrhages in either group. Patients treated with IV-tPA were more likely to have an excellent functional outcome at discharge (88.2% versus 53.9%; P=0.002) and 90 days (91.2% versus 71.8%; P=0.042). Ordinal analysis demonstrated a favorable shift in modified Rankin Scale with IV-tPA both at discharge (odds ratio, 5.23; 95% confidence interval, 1.83–12.20) and 90 days (odds ratio, 4.35; 95% confidence interval, 1.77–11.36). Conclusions— In selected MIS patients with demonstrable penumbra on computed tomographic perfusion, IV-tPA is safe and associated with significant improvement in functional outcome at discharge and 90 days.

Time-Resolved 4-Dimensional Computed-Tomography Angiography Can Correctly Identify Carotid Pseudo-Occlusion

Correct identification of symptomatic high-grade internal carotid artery stenosis from low-grade or total chronic occlusion is critical for patient selection for urgent carotid endarterectomy. Carotid pseudo-occlusion is a flow-related artifact on noninvasive imaging that can lead to an incorrect diagnosis of total internal carotid artery occlusion, thereby denying an eligible patient for appropriate surgical treatment. We present an 82-year-old man with a symptomatic critical internal carotid artery, which was detected on time-resolved 4-dimensional computed-tomography angiography, whereas single-phase computed-tomography angiography, magnetic resonance angiography, and Doppler ultrasonography suggested apparent occlusion. To our understanding, the use of 4-dimensional computed-tomography angiography to identify carotid pseudo-occlusion has not been previously reported.

CT perfusion predicts tissue injury in TIA and minor stroke

Diffusion-weighted imaging (DWI) changes in transient ischaemic attack and minor ischaemic stroke (TIA/MIS) patients predict a poorer prognosis with increased risk of recurrent strokes and persistent disability [1, 2]. Identifying these patients in the hyperacute setting may allow early risk stratification to aid clinical decision making. Recent reports evaluating the prognostic value of CT perfusion studies (CTP) have predominantly focused on moderate to severe stroke patients [3, 4]. In this study, we sought to determine the utility of CTP as a prognostic modality in TIA/MIS patients by investigating the association between acute ischaemic changes on CTP and the presence of abnormal restricted diffusion on follow-up DWI magnetic resonance imaging (DWI-positive). We compared the prevalence of a DWI-positive result between patients with and without a CTP ischaemic lesion among 138 consecutive TIA/MIS patients identified from a prospective tertiary stroke centre database over 4.5 years (2011–2015). The main inclusion criteria were (1) presentation within 4.5 h of symptoms onset, (2) NIH Stroke Scale B3, (3) underwent CTP while symptomatic and (4) had follow-up DWI. CTP ischaemic lesion was defined as an area of prolonged time-to-peak corresponding to the presenting symptoms as assessed by two experienced raters blinded to all other clinical information. TIA was defined using time-based criteria as a focal cerebral ischaemic event with symptoms lasting less than 24 h. T test, Fisher exact test and logistic regression were used for statistical analysis. Overall, the mean age was 71.8 years (standard deviation 13.3), and the median presenting NIH Stroke Scale was 2 [interquartile range (IQR) 1–3] (Table 1). Median symptoms duration was 110 min (IQR 78–145) among twenty-nine TIA patients (21.0%). Sixty-two patients had a CTP ischaemic lesion in the study cohort. Twenty-eight patients (20.3%) received intravenous alteplase thrombolysis at the discretion of the treating neurologist. Among non-thrombolysed patients (n = 110), those with CTP ischaemic lesions were significantly more likely to have a DWI-positive result (100% vs, 49.3%, p\ 0.01), have atrial fibrillation (AF) (34.3% vs. 16.0%, p = 0.046) and be disabled on discharge (modified Rankin Scale C2) (40.6% vs. 25.6%, p = 0.04) compared to patients with a normal CTP. In addition, CTP ischaemic lesion was associated with a significant shift in the distribution of modified Rankin Scale towards higher disability at discharge (odds ratio 3.33; 95% confidence interval, 1.56–7.09). There were no differences between groups among baseline demographics, presenting NIH Stroke Scale domains involved, stroke location, cardiovascular risk factors and CTP ischaemic lesion volume. CTP had high specificity (100%, 95% confidence interval 89.3–100%), high positive predictive value (100%, 95% confidence interval 87.7–100%) but moderate sensitivity (48.6%, 95% confidence interval 36.7–60.7%) in detecting a DWI-positive result in non-thrombolysed patients. All patients with CTP ischaemic lesions developed abnormal restricted diffusion unless alteplase thrombolysis was administered (100 vs. 77.8%; p\ 0.01). & Felix C. Ng ng.fcffelix@gmail.com

Prehospital idarucizumab prior to intravenous thrombolysis in a mobile stroke unit

Background Administration of intravenous idarucizumab to reverse dabigatran anticoagulation prior to thrombolysis for patients with acute ischemic stroke has been previously described, but not in the prehospital setting. The speed and predictability of idarucizumab reversal is well suited to prehospital treatment in a mobile stroke unit and allows patients with recent dabigatran intake to access reperfusion therapy. Aims To describe feasibility of prehospital idarucizumab administration prior to thrombolysis on the Melbourne mobile stroke unit. Methods The Melbourne mobile stroke unit is a specialized stroke ambulance servicing central metropolitan Melbourne, Australia and provides prehospital assessment, scanning and treatment with an integrated CT scanner and multidisciplinary stroke team. All cases were identified through the mobile stroke unit treatment registry since launch in November 2017. Results Of a total of n = 20 thrombolysis cases in the first 4 months of operation, three patients (15%) received intravenous idarucizumab 5 g for dabigatran reversal prior to thrombolysis. Mean time between idarucizumab administration and thrombolysis was approximately 10 minutes. Two of the three patients were shown to have large vessel occlusion on CTA in the mobile stroke unit and proceeded to endovascular thrombectomy. At 24 hours, only one patient had a small amount of asymptomatic petechial hemorrhage on follow-up imaging. All patients demonstrated substantial neurological recovery and were discharged to inpatient rehabilitation. Conclusions Rapid treatment with prehospital administration of idarucizumab prior to thrombolysis using a mobile stroke unit is feasible and facilitates hyperacute treatment.

Letter by Ng et al Regarding Article, “Cervical Carotid Pseudo-Occlusions and False Dissections: Intracranial Occlusions Masquerading as Extracranial Occlusions”

We read with interest the recent study of Grossberg et al1 on cervical carotid pseudo-occlusion (PO) showing that PO is relatively common in patients with isolated intracranial internal carotid artery occlusion. We are writing to further highlight the clinical relevance of this poorly recognized entity and the need for an alternative noninvasive diagnostic modality for early detection. Misdiagnoses of PO as true occlusions may affect acute clinical decision making in the era of endovascular clot retrieval. When a chronic carotid occlusion is incorrectly suspected, or when a technically challenging procedure too prolonged for timely …