MRI screening before standard tissue plasminogen activator therapy is feasible and safe

MRI vs CT for Baseline Imaging Evaluation in Acute Large Artery Ischemic Stroke: A Subanalysis of the SWIFT-DIRECT Trial

BACKGROUND AND OBJECTIVES

Whether MRI or CT is preferable for the evaluation of patients with suspected stroke remains a matter of debate, given that the imaging modality acquired at baseline may be a relevant determinant of workflow delays and outcomes with it, in patients with stroke undergoing acute reperfusion therapies.

METHODS

In this post hoc analysis of the SWIFT-DIRECT trial that investigated noninferiority of thrombectomy alone vs IV thrombolysis (IVT) + thrombectomy in patients with an acute ischemic anterior circulation large vessel occlusive stroke eligible to receive IVT within 4.5 hours after last seen well, we tested for a potential interaction between baseline imaging modality (MRI/MR-angiography [MRA] vs CT/CT-angiography [CTA]) and the effect of acute treatment (thrombectomy vs IVT + thrombectomy) on clinical and safety outcomes and procedural metrics (primary analysis). Moreover, we examined the association between baseline imaging modality and these outcomes using regression models adjusted for age, sex, baseline NIH Stroke Scale (NIHSS), occlusion location, and Alberta Stroke Program Early CT Score (ASPECTS) (secondary analysis). Endpoints included workflow times, the modified Rankin scale (mRS) score at 90 days, the rate of successful reperfusion, the odds for early neurologic deterioration within 24 hours, and the risk of symptomatic intracranial hemorrhage. The imaging modality acquired was chosen at the discretion of the treating physicians and commonly reflects center-specific standard procedures.

RESULTS

Four hundred five of 408 patients enrolled in the SWIFT-DIRECT trial were included in this substudy. Two hundred (49.4%) patients underwent MRI/MRA, and 205 (50.6%) underwent CT/CTA. Patients with MRI/MRA had lower NIHSS scores (16 [interquartile range (IQR) 12-20] vs 18 [IQR 14-20], p = 0.012) and lower ASPECTS (8 [IQR 6-9] vs 8 [IQR 7-9], p = 0.021) compared with those with CT/CTA. In terms of the primary analysis, we found no evidence for an interaction between baseline imaging modality and the effect of IVT + thrombectomy vs thrombectomy alone. Regarding the secondary analysis, MRI/MRA acquisition was associated with workflow delays of approximately 20 minutes, higher odds of functional independence at 90 days (adjusted odds ratio [aOR] 1.65, 95% CI 1.07-2.56), and similar mortality rates (aOR 0.73, 95% CI 0.36-1.47) compared with CT/CTA.

DISCUSSION

This post hoc analysis does not suggest treatment effect heterogeneity of IVT + thrombectomy vs thrombectomy alone in large artery stroke patients with different imaging modalities. There was no evidence that functional outcome at 90 days was less favorable following MRI/MRA at baseline compared with CT/CTA, despite significant workflow delays.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT03192332.

Understanding Delays in MRI-based Selection of Large Vessel Occlusion Stroke Patients for Endovascular Thrombectomy

PURPOSE

Given the efficacy of endovascular thrombectomy (EVT), optimizing systems of delivery is crucial. Magnetic resonance imaging (MRI) is the gold standard for evaluating tissue viability but may require more time to obtain and interpret. We sought to identify determinants of arrival-to-puncture time for patients who underwent MRI-based EVT selection in a real-world setting.

METHODS

Patients were identified from a prospectively maintained database from 2011-2019 that included demographics, presentations, treatments, and outcomes. Process times were obtained from the medical charts. MRI times were obtained from time stamps on the first sequence. Linear and logistic regressions were used to infer explanatory variables of arrival-to-puncture times and effects of arrival-to-puncture time on functional outcomes.

RESULTS

In this study 192 patients (median age 70 years, 57% women, 12% non-white) underwent MRI-based EVT selection. 66% also underwent computed tomography (CT) at the hub before EVT. General anesthesia was used for 33%. Among the entire cohort, the median arrival-to-puncture was 102 min; however, among those without CT it was 77 min. Longer arrival-to-puncture times independently reduced the odds of 90-day good outcome (∆mRS ≤ 2 from pre-stroke, aOR = 0.990, 95%CI = 0.981-0.999, p = 0.040) when controlling for age, NIHSS, and good reperfusion (TICI 2b-3). Independent determinants of longer arrival-to-puncture were CT plus MRI (β = 0.205, p = 0.003), non-white race/ethnicity (β = 0.162, p = 0.012), coronary disease (β = 0.205, p = 0.001), and general anesthesia (β = 0.364, p < 0.0001).

CONCLUSION

Minimizing arrival-to-puncture time is important for outcomes. Real-world challenges exist in an MRI-based EVT selection protocol; avoiding double imaging is key to saving time. Racial/ethnic disparities require further study. Understanding variables associated with delay will inform protocol changes.

MRI or CT for Suspected Acute Stroke: Association of Admission Image Modality with Acute Recanalization Therapies, Workflow Metrics and Outcomes

Objective

To examine rates of intravenous thrombolysis (IVT), mechanical thrombectomy (MT), door‐to‐needle (DTN) time, door‐to‐puncture (DTP) time, and functional outcome between patients with admission magnetic resonance imaging (MRI) versus computed tomography (CT).

Methods

An observational cohort study of consecutive patients using a target trial design within the nationwide Swiss‐Stroke‐Registry from January 2014 to August 2020 was carried out. Exclusion criteria included MRI contraindications, transferred patients, and unstable or frail patients. Multilevel mixed‐effects logistic regression with multiple imputation was used to calculate adjusted odds ratios with 95% confidence intervals for IVT, MT, DTN, DTP, and good functional outcome (mRS 0–2) at 90 days.

Results

Of the 11,049 patients included (mean [SD] age, 71 [15] years; 4,811 [44%] women; 69% ischemic stroke, 16% transient ischemic attack, 8% stroke mimics, 6% intracranial hemorrhage), 3,741 (34%) received MRI and 7,308 (66%) CT. Patients undergoing MRI had lower National Institutes of Health Stroke Scale (median [interquartile range] 2 [0–6] vs 4 [1–11]), and presented later after symptom onset (150 vs 123 min, p < 0.001). Admission MRI was associated with: lower adjusted odds of IVT (aOR 0.83, 0.73–0.96), but not with MT (aOR 1.11, 0.93–1.34); longer adjusted DTN (+22 min [13–30]), but not with longer DTP times; and higher adjusted odds of favorable outcome (aOR 1.54, 1.30–1.81).

Interpretation

We found an association of MRI with lower rates of IVT and a significant delay in DTN, but not in DTP and rates of MT. Given the delays in workflow metrics, prospective trials are required to show that tissue‐based benefits of baseline MRI compensate for the temporal benefits of CT. ANN NEUROL 2022;92:184–194

A Comparison of Time to Treatment between an Emergency Department Focused Stroke Protocol and Mobile Stroke Units

BACKGROUND

San Francisco (California USA) is a relatively compact city with a population of 884,000 and nine stroke centers within a 47 square mile area. Emergency Medical Services (EMS) transport distances and times are short and there are currently no Mobile Stroke Units (MSUs).

METHODS

This study evaluated EMS activation to computed tomography (CT [EMS-CT]) and EMS activation to thrombolysis (EMS-TPA) times for acute stroke in the first two years after implementation of an emergency department (ED) focused, direct EMS-to-CT protocol entitled "Mission Protocol" (MP) at a safety net hospital in San Francisco and compared performance to published reports from MSUs. The EMS times were abstracted from ambulance records. Geometric means were calculated for MP data and pooled means were similarly calculated from published MSU data.

RESULTS

From July 2017 through June 2019, a total of 423 patients with suspected stroke were evaluated under the MP, and 166 of these patients were either ultimately diagnosed with ischemic stroke or were treated as a stroke but later diagnosed as a stroke mimic. The EMS and treatment time data were available for 134 of these patients with 61 patients (45.5%) receiving thrombolysis, with mean EMS-CT and EMS-TPA times of 41 minutes (95% CI, 39-43) and 63 minutes (95% CI, 57-70), respectively. The pooled estimates for MSUs suggested a mean EMS-CT time of 35 minutes (95% CI, 27-45) and a mean EMS-TPA time of 48 minutes (95% CI, 39-60). The MSUs achieved faster EMS-CT and EMS-TPA times (P <.0001 for each).

CONCLUSIONS

In a moderate-sized, urban setting with high population density, MP was able to achieve EMS activation to treatment times for stroke thrombolysis that were approximately 15 minutes slower than the published performance of MSUs.

LDH and PDH Activities in the Ischemic Brain and the Effect of Reperfusion-An Ex Vivo MR Study in Rat Brain Slices Using Hyperpolarized [1-13C]Pyruvate

Ischemic stroke is a leading cause for neurologic disability worldwide, for which reperfusion is the only available treatment. Neuroimaging in stroke guides treatment, and therefore determines the clinical outcome. However, there are currently no imaging biomarkers for the status of the ischemic brain tissue. Such biomarkers could potentially be useful for guiding treatment in patients presenting with ischemic stroke. Hyperpolarized 13C MR of [1-13C]pyruvate is a clinically translatable method used to characterize tissue metabolism non-invasively in a relevant timescale. The aim of this study was to utilize hyperpolarized [1-13C]pyruvate to investigate the metabolic consequences of an ischemic insult immediately during reperfusion and upon recovery of the brain tissue. The rates of lactate dehydrogenase (LDH) and pyruvate dehydrogenase (PDH) were quantified by monitoring the rates of [1-13C]lactate and [13C]bicarbonate production from hyperpolarized [1-13C]pyruvate. 31P NMR of the perfused brain slices showed that this system is suitable for studying ischemia and recovery following reperfusion. This was indicated by the levels of the high-energy phosphates (tissue viability) and the chemical shift of the inorganic phosphate signal (tissue pH). Acidification, which was observed during the ischemic insult, has returned to baseline level following reperfusion. The LDH/PDH activity ratio increased following ischemia, from 47.0 ± 12.7 in the control group (n = 6) to 217.4 ± 121.3 in the ischemia-reperfusion group (n = 6). Following the recovery period (ca. 1.5 h), this value had returned to its pre-ischemia (baseline) level, suggesting the LDH/PDH enzyme activity ratio may be used as a potential indicator for the status of the ischemic and recovering brain.

In-hospital acute stroke workflow in acute stroke - Systems-based approaches

Clinical outcomes of acute ischaemic stroke patients have significantly improved with the advent of reperfusion therapy. However, time continues to be a critical factor. Reducing treatment delays by improving workflows can improve the efficacy of acute reperfusion therapy. Systems-based approaches have improved in-hospital temporal parameters, maximizing the utility of reperfusion therapies and improving clinical benefit to patients. However, studies aimed at optimizing and hence reducing treatment delays in emergency department (ED) settings are limited. The aim of this article is to discuss existing systems-based approaches to optimize ED acute stroke workflows and its value in reducing treatment delays and identify gaps in existing workflows that need optimization. Identifying gaps in acute stroke workflow, variations in processes and challenges in implementation, in the in-hospital settings, is essential for systems-based interventions to be effective in delivering improved outcomes for patients with acute ischaemic stroke.

Single Centre Experience on Decision Making for Mechanical Thrombectomy Based on Single-Phase CT Angiography by Including NCCT and Maximum Intensity Projection Images - A Comparison with Magnetic Resonance Imaging after Non-Contrast CT

Objective

The purpose of this study was to suggest that computed tomography angiography (CTA) is valuable as the only preliminary examination for mechanical thrombectomy (MT). MT after single examination of CTA including non-contrast computed tomography (NCCT) and maximum intensity projection (MIP) improves door-to-puncture time as well as results in favorable outcomes.

Methods

A total of 157 patients who underwent MT at Dong Kang Medical Center from April 2015 to March 2019 were divided into two groups based on the examination performed prior to MT : CTA group who underwent CTA with NCCT and MIP, and NCCT+magnetic resonance image (MRi) group who underwent MRI including perfusion images after NCCT. In the two groups, time to CTA imaging or NCCT+MRi imaging after symptom onset, and time to arterial puncture and reperfusion were characterized as time-related outcomes. The evaluation of vascular recanalization after MT was defined as a modified thrombolysis in cerebral infarction (mTICI) scale. National Institutes of Health Stroke Scale (NIHSS) was assessed at the time of the visit to the emergency room and modified Rankin Scale (mRS) was assessed after 90 days.

Results

Typically, there were 34 patients in the CTA group and 33 patients in the NCCT+MRi group. A significantly shorter delay for door-to-puncture time was observed (mean, 86±22.1 vs. 176±47.5 minutes; p<0.01). Also, a significantly shorter door-to-imege time in the CTA group was observed (mean, 13±6.8 vs. 93±30.8 minutes; p<0.01). Moreover, a significantly shorter onset-to-puncture time was observed (mean, 195±128.0 vs. 314±157.6 minutes; p<0.01). Reperfusion result of mTICI ≥2b was 100% (34/34) in the CTA group and 94% (31/33) in the NCCT+MRi group, and mTICI 3 in 74% (25/34) in the CTA group and 73% (24/33) in the NCCT+MRi group. Favorable functional outcomes (mRS score ≤2 at 90 days) were 68% (23/34) in the CTA group and 60% (20/33) in the NCCT+MRi group.

Conclusion

A single-phase CTA including NCCT and MIP images was performed as a single preliminary examination, which led to a reduction in the time of the procedure and resulted in good results of prognosis. Consequently, it is concluded that this method is of sufficient value as the only preliminary examination for decision making.

Impact of MRI Selection on Triage of Endovascular Therapy in Acute Ischemic Stroke: The MRI in Acute Management of Ischemic Stroke (MIAMIS) Registry

Background

The recently published multicenter randomized DAWN trial confirmed greater outcome benefit of endovascular therapy (ET) for anterior circulation large vessel occlusion ischemic stroke from 6 to 24 h from symptom onset compared to medical management in patients selected by advanced imaging with MRI or perfusion CT to identify mismatch between clinical deficit and infarct volume, which represents salvageable penumbra. The debate of CT over MRI is usually the potentially increase time consumption and the difficulty in establishing an adequate standardized workflow utilizing MRI during the hyperacute phase.

Purpose

While CT-based selection of patients is the current standard of care, we sought to determine the time impact of the alternative approach of MRI selection in the 0-12 h window.

Methods

In the MRI in Acute Management of Ischemic Stroke (MIAMIS) registry, we retrospectively analyzed 89 consecutive patients from January 2008 to January 2010 who presented with acute stroke symptoms with a National Institutes of Health Stroke Scale score ≥5 or aphasia within 0-12 h from symptom onset. The presence of penumbra was determined by MR perfusion-diffusion mismatch or clinical diffusion mismatch. Patients were stratified based on the presence of mismatch and clinical outcomes in patients who received ET. Imaging times were recorded.

Results

The MRI turnaround time was 95.5 ± 48.5 min. The total MRI time was 27.7 ± 12.8 min. Seventeen (19.1%) patients were found to have nonvascular etiology. Mismatch was found in 35 (48.6%) patients with acute ischemic stroke (AIS). Patients with nonvascular etiology were younger (55.7 vs. 65.6 years, p < 0.02), without any vessel occlusion or mismatch noticed in this group. We dichotomized the 39 AIS patients with vessel occlusion into two subgroups: these with mismatch and these without. Patients without mismatch were older (76.7 vs. 64.4 years, p < 0.05), more likely to have congestive heart failure (71.4 vs. 22%, p < 0.03), a higher total serum cholesterol level (196 vs. 156 mg/dL, p < 0.04), and medium to large lesions on diffusion-weighted imaging (DWI) (85.7 vs. 37.5%, p < 0.04).

Conclusions

Multimodality MRI screening for AIS symptoms for ET is feasible. Optimizing each center's protocol and the utilization of MRI with DWI only may be a time-saving alternative.

Choosing a Hyperacute Stroke Imaging Protocol for Proper Patient Selection and Time Efficient Endovascular Treatment: Lessons from Recent Trials

Recently, several prospective randomized control trials regarding endovascular treatment for patients with intracranial large artery occlusions causing acute ischemic stroke have been successfully reported. Effort to minimize time delays to endovascular treatment, patient selection and the use of retrievable stent were important factors for the success of these trials. The inclusion and exclusion criteria for each of these trials did include differences in imaging protocols. In this review, we focus on the importance of baseline non-invasive angiography prior to deciding endovascular treatment. Then imaging protocols are described for each trial according to measurement of infarct volume and collateral grading.

Relative CBV ratio on perfusion-weighted MRI indicates the probability of early recanalization after IV t-PA administration for acute ischemic stroke

BACKGROUND

We hypothesized that the relative cerebral blood volume (rCBV) ratio on perfusion-weighted imaging (PWI) using MRI might serve as a predictor of early recanalization (ER) after intravenous tissue plasminogen activator (IV t-PA) administration for acute ischemic stroke.

METHODS

Patients with acute middle cerebral artery (MCA) ischemic stroke (IS) were enrolled in the study. They were evaluated by MRI, including PWI and diffusion-weighted imaging, before administration of IV t-PA and underwent digital subtraction angiography (DSA) of the brain within 2 h after t-PA administration. We compared the rCBV ratio on PWI between patients with and without ER on DSA and investigated the proportion of patients with an excellent outcome at 90 days after t-PA administration (modified Rankin Scale score 0-1) among those with and without ER.

RESULTS

85 patients with acute MCA IS were included; 16 patients (18.8%) experienced ER on DSA after IV t-PA administration. Patients with ER more frequently had an excellent outcome at 90 days than those without ER. The rCBV ratio on PWI was higher in the ER group (1.01±0.21, p<0.01) than in the non-ER group (0.82±0.18). After adjusting for the presence of atrial fibrillation and the serum glucose level, the rCBV ratio on PWI (OR 1.07; 95% CI 1.02 to 1.12; p<0.01) was a significant independent indicator of ER.

CONCLUSIONS

The results of this study suggest that the rCBV ratio on PWI might serve as a useful indicator of ER after IV t-PA administration.

A systemized stroke code significantly reduced time intervals for using intravenous tissue plasminogen activator under magnetic resonance imaging screening

BACKGROUND

A stroke code can shorten time intervals until intravenous tissue plasminogen activator (IV t-PA) treatment in acute ischemic stroke (AIS). Recently, several reports demonstrated that magnetic resonance imaging (MRI)-based thrombolysis had reduced complications and improved outcomes in AIS despite longer processing compared with computed tomography (CT)-based thrombolysis.

METHODS

In January 2009, we implemented CODE RED, a computerized stroke code, at our hospital with the aim of achieving rapid stroke assessment and treatment. We included patients with thrombolysis from January 2007 to December 2008 (prestroke code period) and from January 2009 to May 2013 (poststroke code period). The IV t-PA time intervals and 90-day modified Rankin Scale (mRS) scores were collected.

RESULTS

During the observation period, 252 patients used IV t-PA under the CODE RED (MRI based: 208; CT based: 44). The remaining 71 patients (MRI based: 53; CT based: 18) received it before the implementation of our stroke code. After implementation of CODE RED, door-to-image time, door-to-needle time, and the onset-to-needle time were significantly reduced by 11, 18, and 22 minutes in MRI-based thrombolysis. Particularly, the proportion of favorable outcome (mRS score 0-2) was significantly increased (from 41.5% to 60.1%, P = .02) in poststroke than in prestroke code period in MRI-based thrombolysis. However, in ordinal regression, the presence of stroke code showed just a trend for favorable outcome (odds ratio, .99-2.87; P = .059) at 90 days of using IV t-PA after correction of age, sex, and National Institutes of Health Stroke Scale.

CONCLUSIONS

In this study, we demonstrated that a systemized stroke code shortened time intervals for using IV t-PA under MRI screening. Also, our results showed a possibility that a systemized stroke code might enhance the efficacy of MRI-based thrombolysis. In the future, we need to carry out a more detailed prospective study about this notion.

Sensitivity of diffusion- and perfusion-weighted imaging for diagnosing acute ischemic stroke is 97.5%

BACKGROUND AND PURPOSE

MRI using diffusion-weighted imaging (DWI) is the most sensitive diagnostic imaging modality for early detection of ischemia, but how accurate is it and how much does perfusion-weighted imaging (PWI) add to the sensitivity have to be known.

METHODS

In this single-center study, we collected epidemiological, imaging, and outcome data on all patients with stroke undergoing MRI-based treatment with intravenous tissue-type plasminogen activator at our center from 2004 to 2010. The DWI negative patients were identified, and we calculated the sensitivity and specificity of DWI and additional PWI for diagnosing acute ischemic stroke. We compared DWI positive and negative patients to identify characteristics associated with DWI negativity.

RESULTS

Five hundred sixty-nine consecutive patients were treated with intravenous tissue-type plasminogen activator on the basis of an acute MRI. A DWI lesion was evident in 518 patients. Forty-seven patients were DWI negative; however, a relevant PWI lesion was found in 33 of these patients. Four stroke mimics were treated with intravenous tissue-type plasminogen activator and 1 of these patients had a DWI lesion. Thus, 8% of all patients with stroke were DWI negative. The combination of DWI and PWI resulted in a sensitivity of 97.5% for the ischemic stroke diagnosis. DWI negativity was associated with less severe strokes, location in the posterior circulation, a longer time from onset to scan, and an improved 90-day outcome. The cause of small-vessel disease was more likely to be DWI negative.

CONCLUSIONS

The combination of DWI and PWI before intravenous tissue-type plasminogen activator confirms the diagnosis in 97.5% of all ischemic strokes.

The golden hour Performing an acute ischemic stroke workup

Ischemic stroke is a medical emergency resulting from an embolic or thrombotic occlusion of an intracranial artery. The purpose of this article is to provide acute care nurse practitioners a summary of recent updates on the rapid evaluation and workup for patient selection and treatment with I.V. fibrinolysis.

Magnetic resonance imaging in acute ischemic stroke treatment

Although intravenous administration of tissue plasminogen activator is the only proven treatment after acute ischemic stroke, there is always a concern of hemorrhagic risk after thrombolysis. Therefore, selection of patients with potential benefits in overcoming potential harms of thrombolysis is of great importance. Despite the practical issues in using magnetic resonance imaging (MRI) for acute stroke treatment, multimodal MRI can provide useful information for accurate diagnosis of stroke, evaluation of the risks and benefits of thrombolysis, and prediction of outcomes. For example, the high sensitivity and specificity of diffusion-weighted image (DWI) can help distinguish acute ischemic stroke from stroke-mimics. Additionally, the lesion mismatch between perfusion-weighted image (PWI) and DWI is thought to represent potential salvageable tissue by reperfusion therapy. However, the optimal threshold to discriminate between benign oligemic areas and the penumbra is still debatable. Signal changes of fluid-attenuated inversion recovery image within DWI lesions may be a surrogate marker for ischemic lesion age and might indicate risks of hemorrhage after thrombolysis. Clot sign on gradient echo image may reflect the nature of clot, and their location, length and morphology may provide predictive information on recanalization by reperfusion therapy. However, previous clinical trials which solely or mainly relied on perfusion-diffusion mismatch for patient selection, failed to show benefits of MRI-based thrombolysis. Therefore, understanding the clinical implication of various useful MRI findings and comprehensively incorporating those variables into therapeutic decision-making may be a more reasonable approach for expanding the indication of acute stroke thrombolysis.

Role of EPI-FLAIR in patients with acute stroke: a comparative analysis with FLAIR

BACKGROUND AND PURPOSE

Further improvement in acquisition speed is needed, if MR imaging is to compete with CT for evaluation of patients with acute ischemic stroke. The purpose of this study was to evaluate the feasibility of implementing an echo-planar fluid-attenuated inversion recovery (EPI-FLAIR) sequence into an acute MR stroke protocol with potential reduction in scan time and to compare the results with conventional FLAIR images.

MATERIALS AND METHODS

Fifty-two patients (28 men and 24 women; age range, 32-96 years) with acute ischemic stroke were prospectively evaluated with an acute stroke MR protocol, which included both conventional FLAIR and EPI-FLAIR imaging with integration of parallel acquisition. The image acquisition time was 52 seconds for EPI-FLAIR and 3 minutes for conventional FLAIR. FLAIR and EPI-FLAIR studies were assessed by 2 observers independently for image quality and conspicuity of hyperintensity in correlation with DWI and were rated as concordant or discordant. Coregistered FLAIR and EPI-FLAIR images were evaluated for signal intensity ratio of the DWI-positive lesion to contralateral normal white matter.

RESULTS

An estimated 96% of all FLAIR and EPI-FLAIR studies were rated of diagnostic image quality by both observers, with interobserver agreements of κ = 0.82 and κ = 0.63 for FLAIR and EPI-FLAIR, respectively. In 36 (95%) of 38 patients with acute infarction, FLAIR and EPI-FLAIR were rated concordant regarding DWI lesion. The mean ± standard deviation of the signal intensity ratio values on EPI-FLAIR and FLAIR for DWI-positive lesions were 1.28 ± 0.16 and 1.25 ± 0.17, respectively (P = .47), and demonstrated significant correlation (r = 0.899, z value = 8.677, P < .0001).

CONCLUSIONS

In patients with acute stroke, EPI-FLAIR is feasible with comparable qualitative and quantitative results to conventional FLAIR and results in reduced acquisition time.

Outcomes of antiplatelet therapy for haemorrhage patients after thrombolysis: a prospective study based on susceptibility-weighted imaging

PURPOSE

The authors evaluated the effect of susceptibility-weighted imaging (SWI) for antiplatelet therapy on post-thrombolysis microbleeds (MB).

MATERIALS AND METHODS

A total of 146 patients without symptomatic intracranial haemorrhage on computed tomography after thrombolysis were allocated to two groups: group A (n = 72) received antiplatelets 24 h after recombinant tissue plasminogen activator, regardless of SWI-detected haemorrhage; group B (n = 74) received antiplatelets for patients without SWI-visualised haemorrhage.

RESULTS

Haemorrhage was detected by SWI in 22 and 28 patients in groups A and B, respectively. The difference in mean NIHSS (National Institutes of Health Stroke Scale) score in group A between baseline and 6, 24 h, 7, 14 days was -1.6, -1.7, -3.6, -5.9, respectively; in group B, the difference in mean NIHSS score between baseline and 6, 24 h, 7, 14 days was -2.6, -3.3, -5.4, -8.7, respectively. The difference between groups in reduction of mean NIHSS score from baseline was 1.0 (p < 0.001) at 6 h, 1.6 (p < 0.001) at 24 h, 1.8 (p = 0.001) at 7 days and 2.8 (p < 0.001) at 14 days. NIHSS scores at 7, 14 days and modified Rankin scale at 90 days were significantly lower in haemorrhage patients in groups B than in A, whereas the hospital stay was shorter and the rate of favourable outcome at 90 days was higher.

CONCLUSION

Our results indicated that SWI was an effective approach for the guidance of antiplatelet therapy in post-thrombolysis MB.

Use of DWI-only MR protocol for screening stroke mimics

PURPOSE

Patients presenting with focal neurological symptoms may suffer from stroke or stroke mimics. Diffusion weighted MRI (DWI) is highly sensitive for identifying acute ischemia. Therefore, we aimed to explore whether a DWI-only protocol would help differentiate stroke from stroke mimics.

METHODS

We identified all patients with possible but not definite stroke that underwent DWI-only MRI between 6/2010 and 8/2011. Patients with a positive DWI lesion were compared to those with negative DWI findings on demographics, risk factor profile, final discharge diagnoses, and outcome.

RESULTS

A total of 124 patients were included with a median age of 63.5 (53% male). DWI MRI was positive for acute ischemia in 46 patients (37%). The most frequent stroke mimics were peripheral vertigo (n=19), acute confusion (n=10), seizures (n=9) and migraine with aura (n=8). Most ischemic lesions were small on DWI (<2 cm) and patients had minor disability (mean NIHSS 4.9±3.9) with 81% of patients having good outcomes (modified Rankin Score≤2) at 3 months. On univariate analysis patients with positive DWI studies had higher frequencies of having more than one clinical symptom (56% vs. 13% respectively; P<0.001) and this variable remained a significant predictor for stroke on multivariate analysis (OR 9.4 95% CI 3.8-23.5).

CONCLUSIONS

A short DWI-only MRI protocol can effectively differentiate stroke from stroke mimics and could be used in settings of the emergency department as well as later on for diagnostic purposes. The chances for finding positive DWI lesions are increased in patients with multiple symptoms and signs.

Advanced modality imaging evaluation in acute ischemic stroke may lead to delayed endovascular reperfusion therapy without improvement in clinical outcomes

PURPOSE

Advanced neuroimaging techniques may improve patient selection for endovascular stroke treatment but may also delay time to reperfusion. We studied the effect of advanced modality imaging with CT perfusion (CTP) or MRI compared with non-contrast CT (NCT) in a multicenter cohort.

MATERIALS AND METHODS

This is a retrospective study of 10 stroke centers who select patients for endovascular treatment using institutional protocols. Approval was obtained from each institution's review board as only de-identified information was used. We collected demographic and radiographic data, selected time intervals, and outcome data. ANOVA was used to compare the groups (NCT vs CTP vs MRI). Binary logistic regression analysis was performed to determine factors associated with a good clinical outcome.

RESULTS

556 patients were analyzed. Mean age was 66 ± 15 years and median National Institutes of Health Stroke Scale score was 18 (IQR 14-22). NCT was used in 286 (51%) patients, CTP in 190 (34%) patients, and MRI in 80 (14%) patients. NCT patients had significantly lower median times to groin puncture (61 min, IQR (40-117)) compared with CTP (114 min, IQR (81-152)) or MRI (124 min, IQR (87-165)). There were no differences in clinical outcomes, hemorrhage rates, or final infarct volumes among the groups.

CONCLUSIONS

The current retrospective study shows that multimodal imaging may be associated with delays in treatment without reducing hemorrhage rates or improving clinical outcomes. This exploratory analysis suggests that prospective randomised studies are warranted to support the hypothesis that advanced modality imaging is superior to NCT in improving clinical outcomes.

The clinical value of antiplatelet therapy for patients with hemorrhage after thrombolysis based on susceptibility-weighted imaging: a prospective pilot study

PURPOSE

To evaluate treatment decision-making based on susceptibility-weighted imaging (SWI) in patients with hemorrhage after thrombolysis.

MATERIALS AND METHODS

One hundred and forty-six patients without intracranial hemorrhage on CT after receiving recombinant tissue plasminogen activator (rt-PA) were allocated to two groups: antiplatelets (n=72), who received antiplatelet therapy 24h after rt-PA for 10 days; and non-antiplatelets (n=74), who received no antiplatelet therapy. Twenty-two patients with SWI-detected microbleeds (MBs) or hemorrhagic transformation (HT) in the antiplatelets group (Group A) and 28 with MB or HT in the non-antiplatelets group (Group B) were included in this study.

RESULTS

Sixteen patients had MB and six HT in Group A; 18 had MB, six HT, and four parenchymal hemorrhage (PH) in Group B. National Institutes of Health Stroke Scale (NIHSS) scores at 7 and 14 days and the Modified Rankin Scale (mRS) at 90 days post-rt-PA were significantly lower in Group B than in Group A, duration of hospitalization was significantly shorter, and the favorable outcome rate was higher at 90 days (P<0.05). There were no other significant differences. SWI evaluation at 14 days revealed eight patients with MB, 11 HT, and three PH in Group A; in Group B, 16 had MB, five HT, and one PH, with resolution of hemorrhage in six patients.

CONCLUSIONS

Treatment decision-making based on SWI in acute stroke after thrombolysis was validated by the significantly reduced NIHSS score after 7/14 days, improved outcome, and reduced mRS in hemorrhage patients without antiplatelet therapy.

Early ischemic change on CT versus diffusion-weighted imaging for patients with stroke receiving intravenous recombinant tissue-type plasminogen activator therapy: stroke acute management with urgent risk-factor assessment and improvement (SAMURAI) rt-PA registry

BACKGROUND AND PURPOSE

Alberta Stroke Programme Early CT Score (ASPECTS) is a quantitative topographical score to evaluate early ischemic change in the middle cerebral arterial territory on CT as well as on diffusion-weighted imaging (DWI). The aim of the present study was to elucidate the relationship between CT-ASPECTS and DWI-ASPECTS for patients with hyperacute stroke and their associations with outcomes after recombinant tissue-type plasminogen activator therapy based on a multicenter registry.

METHODS

ASPECTS was assessed on both CT and DWI before intravenous 0.6 mg/kg alteplase in 360 patients with stroke (119 women, 71 ± 11 years old). The outcomes were symptomatic intracerebral hemorrhage within 36 hours and independence at 3 months defined by a modified Rankin Scale score of 0 to 2.

RESULTS

DWI-ASPECTS was positively correlated with CT-ASPECTS (ρ=0.511, P<0.001) and was lower than CT-ASPECTS (median 8 [interquartile range, 6 to 9] versus 9 [8 to 10], P<0.001). Higher baseline National Institutes of Health Stroke Scale score (standardized partial regression coefficient [β] 0.061, P<0.001) and cardioembolic stroke (β 0.35, P<0.001) were related to this discrepancy. The area under the receiver operating characteristic curve for predicting sICH (12 patients) using ASPECTS was 0.673 (95% CI, 0.503 to 0.807) by CT and 0.764 (95% CI, 0.635 to 0.858) by DWI (P=0.275). The area for predicting independence at 3 months (192 patients) was 0.621 (0.564 to 0.674) by CT and 0.639 (0.580 to 0.694) by DWI (P=0.535).

CONCLUSIONS

For patients with hyperacute stroke, DWI-ASPECTS scored approximately 1 point lower than CT-ASPECTS. Both CT-ASPECTS and DWI-ASPECTS were useful predictors of symptomatic intracerebral hemorrhage and independence at 3 months after recombinant tissue-type plasminogen activator.

Thrombolysis in acute ischaemic stroke: an update

Stroke is a major cause of mortality and morbidity, and thrombolysis has served as a catalyst for major changes in the management of acute ischaemic stroke. Intravenous alteplase (recombinant tissue plasminogen activator) is the only approved thrombolytic agent at present indicated for acute ischaemic stoke. While the licensed time window extends to 3h from symptom onset, recent data suggest that the trial window can be extended up to 4.5 h with overall benefit. Nonetheless, 'time is brain' and every effort must be made to reduce the time delay to thrombolysis. Intracranial haemorrhage is the major complication associated with thrombolysis, and key factors increasing risk of haemorrhage include increasing age, high blood pressure, diabetes and stroke severity. Currently, there is no direct evidence to support thrombolysis in patients >80 years of age, with a few case series indicating no overt harm. Identification of viable penumbra based on computed tomography/magnetic resonance imaging may allow future extension of the time window. Adjuvant transcranial Doppler ultrasound has the potential to improve reperfusion rates. While intra-arterial thrombolysis has been in vogue for a few decades, there is no clear advantage over intravenous thrombolysis. The evidence base for thrombolysis in specific situations (e.g. dissection, pregnancy) is inadequate, and individualized decisions are needed, with a clear indication to the patient/carer about the lack of direct evidence, and the risk-benefit balance. Patient-friendly information leaflets may facilitate the process of consent for thrombolysis. This article summarizes the recent advances in thrombolysis for acute ischaemic stroke. Key questions faced by clinicians during the decision-making process are answered based on the evidence available.

Multimodal imaging does not delay intravenous thrombolytic therapy in acute stroke

BACKGROUND AND PURPOSE

Patients with acute ischemic stroke require immediate medical treatment, and a CT to rule out hemorrhage is required before tPA. We adapted our protocol to include multimodal CT: unenhanced CT, CTA, and PCT. The purpose of this study was to determine whether multimodal CT imaging delays initiation of IV tPA beyond 60 minutes from hospital arrival.

MATERIALS AND METHODS

All patients admitted during 3 years through the ED with a stroke alert and time from symptom onset to hospital arrival <2.5 hours were included. We examined 2 subgroups (multimodal CT versus unenhanced CT) to determine whether multimodal CT delayed tPA administration. Logistic regression was used to identify variables that predicted tPA within 60 minutes.

RESULTS

There were 123 patients in the analysis, including 108 patients who were examined with multimodal CT. The median time from arrival to tPA was 56 minutes and was shorter for patients examined with multimodal CT (55 versus 78 minutes, P = .02). After adjustment, variables that were associated with tPA administration within 60 minutes included prehospital stroke alert (OR = 3.47, P = .03), time to CT (OR = 0.94, P = .01), and onset-to-arrival time (OR = 1.02, P = .04). There was no statistically significant difference in the odds of receiving timely tPA for multimodal versus unenhanced CT (OR = 3.99, P = .07).

CONCLUSIONS

In our single-center experience, the use of multimodal imaging in patients with acute stroke did not delay IV tPA beyond 60 minutes. Further study is needed to assess the feasibility of the routine use of multimodal imaging in the acute stroke setting.

Early experience of translating pH-weighted MRI to image human subjects at 3 Tesla

BACKGROUND AND PURPOSE

In acute stroke, mismatch between lesions seen on diffusion- (DWI) and perfusion-weighted (PWI) MRI has been used to identify ischemic tissue before irreversible damage. Nevertheless, the concept of PWI/DWI mismatch is oversimplified and the ischemic tissue metabolic status and outcome are often heterogeneous. Tissue pH, a well-regulated physiological index that alters on disrupted tissue metabolism, may provide a surrogate metabolic imaging marker that augments the DWI and PWI for penumbra imaging.

METHODS

pH-weighted MRI was obtained by probing the pH-dependent amide proton transfer between endogenous mobile proteins/peptides and tissue water. The technique was validated using animal stroke models, optimized for human use, and preliminarily tested for imaging healthy volunteers.

RESULTS

pH-weighted MRI is sensitive and specific to ischemic tissue acidosis. pH MRI can be optimized for clinical use, and a pilot human study showed it is feasible using a standard 3 Tesla MRI scanner.

CONCLUSIONS

Ischemic acidosis can be imaged via an endogenous pH-weighted MRI technique, which complements conventional PWI and DWI for penumbra imaging. pH-weighted MRI has been optimized and appears feasible and practical in imaging human subjects. Additional study is necessary to elucidate the diagnostic use of pH MRI in stroke patients.

Comparison between MRI screening and CT-plus-MRI screening for thrombolysis within 3 h of ischemic stroke

BACKGROUND AND PURPOSE

Although MRI may provide much information on brain pathology to aid in patient selection for thrombolysis, the concern remains that MRI screening may increase time-to-treatment. We hypothesized that CT-plus-MRI screening might be a valuable time-efficient alternative for selection of patients requiring thrombolysis.

METHODS

We reviewed acute stroke patients who received intravenous tissue plasminogen activator (tPA) (with or without intra-arterial urokinase) initiated within 3 h of stroke between March 2004 and March 2007. MRI was the routine screening imaging employed until November 2005. Thereafter, CT-plus-MRI screening was performed; tPA of 0.6 mg/kg was infused intravenously after exclusion of hemorrhage by CT screening, and subsequently a further decision on thrombolysis (i.e., intravenous tPA of 0.3 mg/kg, or intra-arterial urokinase) was made after MRI screening. We compared times-to-treatment and clinical outcomes between MRI screening and CT-plus-MRI-screening groups, and identified factors associated with good clinical outcome (modified Rankin Scale < or =2 at 3 months).

RESULTS

Eighty-nine patients were included in the analysis; 43 were MRI-screened, and 46 were CT-plus-MRI-screened. Although the MRI-screening group had a longer door-to-needle time (p<0.001), these patients showed better 3-month outcomes compared to CT-plus-MRI-screening group (p=0.01). Multivariate analysis showed that MRI screening (odds ratio 3.97, 95% confidence interval 1.30-12.17, p=0.02) was independently associated with a good outcome at 3 months. In CT-plus-MRI-screening group, although time-to-initial imaging and time-to-tPA were shorter, time-to-MRI and time-to-additional thrombolysis were delayed.

CONCLUSION

These results suggest that early patient selection using MRI may be more effective than reduction of times-to-treatment in improvement of thrombolytic outcomes.

Feasibility and logistics of MRI before thrombolytic treatment

OBJECTIVES

The study analyzes feasibility and time-delays in Magnetic resonance imaging (MRI) based thrombolysis and estimate the impact of MRI on individual tissue plasminogen activator (rtPA) treatment.

MATERIALS AND METHODS

Feasibility of MRI and time logistics were prospectively recorded in patients referred with presumed acute stroke over a 2 year time period. Door-to-needle-times (DNT) were compared with those of patients treated with rtPA after conventional CT during the same time period, and to published open label studies.

RESULTS

We received 174 patients with presumed stroke. MRI was feasible in 141 of 161 (88%) of those requiring acute imaging. MRI supported the decision to treat 11 patients with mild symptoms or seizures, and not to treat four patients with extensive infarctions. Median 'door-to-needle time' (DNT) in MR scanned patients (70 min), did not differ significantly from DNT after conventional CT (n = 17, DNT = 66 min, P = 0.27) or the Safe Implementation of Thrombolysis in Stroke (SITS-MOST) registry (DNT = 68 min).

CONCLUSIONS

Magnetic resonance imaging can be performed in the majority of acute stroke patients without delaying treatment. MRI may affect decision making in a large proportion of patients.

Imaging the penumbra - strategies to detect tissue at risk after ischemic stroke

The aim of thrombolytic therapy after acute ischemic stroke is salvage of the ischemic penumbra. Several imaging techniques have been used to identify the penumbra in patients who may benefit from reperfusion beyond the currently narrow 3-hour time-window for thrombolysis. We discuss the advantages and disadvantages of positron emission tomography (PET), single photon emission computed tomography (SPECT), MRI and CT scans. We comment on concepts of clinical-imaging mismatch models and we explore the implications for clinical trials.

Focal fluid-attenuated inversion recovery hyperintensity within acute diffusion-weighted imaging lesions is associated with symptomatic intracerebral hemorrhage after thrombolysis

BACKGROUND AND PURPOSE

We investigated whether focal hyperintensity on fluid-attenuated inversion recovery image within acute infarcts is associated with symptomatic intracerebral hemorrhage (SICH) after thrombolysis.

METHODS

Patients with acute ischemic stroke who underwent MRI screening before thrombolysis were enrolled. The presence of focal fluid-attenuated inversion recovery hyperintensity within acute infarcts did not preclude thrombolysis. SICH was defined as hemorrhagic transformation with any neurological decline (SICH-1) or with an increase in National Institutes of Health Stroke Scale of >or=4 (SICH-2) within 48 hours.

RESULTS

Among 88 included patients, focal fluid-attenuated inversion recovery hyperintensity within acute infarct lesions was observed in 27 (30.7%) patients. Multivariate analysis showed that focal fluid-attenuated inversion recovery hyperintensity was independently associated with SICH-1 (OR, 13.64; 95% CI, 1.51 to 123.28) and SICH-2 (OR, 10.44; 95% CI, 1.11 to 98.35).

CONCLUSIONS

The presence of focal fluid-attenuated inversion recovery hyperintensity within acute infarcts may increase the risk of symptomatic intracerebral hemorrhage after thrombolysis.

T2' imaging predicts infarct growth beyond the acute diffusion-weighted imaging lesion in acute stroke

PURPOSE

To show that measurement of the transverse relaxation time that characterizes signal loss caused by local susceptibilities (T2') is sensitive to an increased deoxyhemoglobin concentration in the brain, indicating tissue at risk for infarction.

MATERIALS AND METHODS

The study was approved by the local institutional review board; patients or their guardians provided informed consent. Magnetic resonance (MR) imaging was performed within 6 hours of symptom onset and again 1-11 days thereafter in 100 consecutive stroke patients, all of whom received intravenous thrombolytic therapy (mean age, 67 years). The MR imaging protocol included diffusion- and perfusion-weighted imaging for determination of apparent diffusion coefficient (ADC) and time to peak (TTP), along with quantitative T2 and T2* imaging. T2' maps were calculated and visually compared with ADC and TTP lesions by two independent observers.

RESULTS

A T2'>ADC mismatch was observed by reader 1 in 73 (73%) of 100 patients, and by reader 2 in 65 (65%) patients. Respective sensitivities of T2'>ADC and of TTP>ADC mismatches for later infarct growth were 0.87 and 0.98 for reader 1 and 0.78 and 0.98 for reader 2, with respective specificities of 0.42 and 0.04 for reader 1 and 0.46 and 0.04 for reader 2. The odds ratios for infarct growth in the presence of a T2'>ADC mismatch were 4.59 (reader 1 P = .002) and 3.10 (reader 2 P = .012), while the odds ratios for TTP>ADC mismatch were 2.22 (reader 1 P = .606) and 1.73 (reader 2 P > .999).

CONCLUSION

The presence of a T2'>ADC mismatch is a more specific predictor of infarct growth than is TTP>ADC mismatch and hence may be of clinical value in patient selection for acute stroke therapies in the future.