A Comparison of Computed Tomography Perfusion-Guided and Time-Guided Endovascular Treatments for Patients With Acute Ischemic Stroke

CTP-guided reperfusion therapy in acute ischemic stroke: a meta-analysis

BACKGROUND

Computed tomography perfusion (CTP) imaging could be useful in guiding reperfusion therapy or patient selection in acute ischemic stroke (AIS) patients. The aim of the current study was to determine the efficacy of the CTP-guided reperfusion therapy in AIS by performing a systematic review and meta-analysis.

METHODS

Medline/PubMed, Embase, and the Cochrane library were searched using the terms: "CT perfusion", "acute stroke" and "reperfusion therapy". The following studies were included: (a) studies reporting original data; (b) patients aged 18 years or above; (c) patients diagnosed with anterior circulation AIS; and (d) studies with good methodological design.

RESULTS

Twenty-two studies were finally included in the metanalysis with a total of 5, 687 patients. CTP-guided reperfusion therapy was associated with increased odds of good functional outcome without significant difference in safety profile.

CONCLUSIONS

CTP-guided reperfusion therapy improved functional outcomes in AIS, with increased benefits to patients treated with endovascular thrombectomy.

Prospective Endovascular Treatment in Acute Ischemic Stroke Evaluating Non-Contrast Head CT versus CT Perfusion (PLEASE No CTP)

Background

Studies have shown a lack of agreement of computed tomography perfusion (CTP) in the selection of acute ischemic stroke (AIS) patients for endovascular treatment.

Purpose

To demonstrate whether non-contrast computed tomography (CT) within 8 h of symptom onset is comparable to CTP imaging.

Methods

Prospective study of consecutive anterior circulation AIS patients with a National Institute of Health Stroke Scale (NIHSS) score > 7 presenting within 8 h of symptom onset with endovascular treatment. All patients had non-contrast CT, CT angiography, and CTP. The neuro-interventionalist was blinded to the results of the CTP and based the treatment decision using the Alberta Stroke Program Early CT score (ASPECTS). Baseline demographics, co-morbidities, and baseline NIHSS scores were collected. Outcomes were modified Rankin scale (mRS) score at discharge and in-hospital mortality. Good outcomes were defined as a mRS score of 0-2.

Results

283 AIS patients were screened for the trial, and 119 were enrolled. The remaining patients were excluded for: posterior circulation stroke, no CTP performed, could not obtain consent, and NIHSS score < 7. Mean -NIHSS score at admission was 16.8 ± 3, and mean ASPECTS was 8.4 ± 1.4. There was no statistically significant correlation with CTP penumbra and good outcomes: 50 versus 47.8% with no penumbra present (p = 0.85). In patients without evidence of CTP penumbra, there was 22.5% mortality compared to 22.1% mortality in patients with a CTP penumbra. If ASPECTS ≥7, 64.6% had good outcome versus 13.3% if ASPECTS < 7 (p < 0.001). Patients with an ASPECTS ≥7 had 10% mortality versus 51.4% in patients with an ASPECTS < 7 (p < 0.001).

Conclusions

CTP penumbra did not identify patients who would benefit from endovascular treatment when patients were selected with non-contrast CT ASPECTS ≥7. There is no correlation of CTP penumbra with good outcomes or mortality. Larger prospective trials are warranted to justify the use of CTP within 6 h of symptom onset.

Diagnosis and Management of Acute Ischemic Stroke

Acute ischemic stroke (AIS) is among the leading causes of death and long-term disability. Intravenous tissue plasminogen activator has been the mainstay of acute therapy. Recently, several prospective randomized trials documented the value of endovascular revascularization in selected patients with large-vessel occlusion within the anterior circulation. This finding has led to a paradigm shift in the management of AIS, including wide adoption of noninvasive neuroimaging to assess vessel patency and tissue viability, with the supplemental and independent use of intravenous tissue plasminogen activator to improve clinical outcomes. In this article, we review the landmark studies on management of AIS and the current position on the diagnosis and management of AIS. The review also highlights the importance of early stabilization and prompt initiation of therapeutic interventions before, during, and after the diagnosis of AIS within and outside of the hospital.

Computed Tomographic Perfusion Selection and Clinical Outcomes After Endovascular Therapy in Large Vessel Occlusion Stroke

Background and Purpose—

Different imaging paradigms have been used to select patients for endovascular therapy in stroke. We sought to determine whether computed tomographic perfusion (CTP) selection improves endovascular therapy outcomes compared with noncontrast computed tomography alone.

Methods—

Review of a prospectively collected registry of anterior circulation stroke patients undergoing stent-retriever thrombectomy at a tertiary care center between September 2010 and March 2016. Patients undergoing CTP were compared with those with noncontrast computed tomography alone. The primary outcome was the shift in the 90-day modified Rankin scale (mRS).

Results—

A total of 602 patients were included. CTP-selected patients (n=365, 61%) were younger ( P =0.02) and had fewer comorbidities. CTP selection (n=365, 61%) was associated with a favorable 90-day mRS shift (adjusted odds ratio [aOR]=1.49; 95% confidence interval [CI], 1.06–2.09; P =0.02), higher rates of good outcomes (90-day mRS score 0–2: 52.9% versus 40.4%; P =0.005), modified Thrombolysis in Cerebral Infarction-3 reperfusion (54.8% versus 40.1%; P <0.001), smaller final infarct volumes (24.7 mL [9.8–63.1 mL] versus 34.6 mL [13.1–88 mL]; P =0.017), and lower mortality (16.6% versus 26.8%; P =0.005). When matched on age, National Institutes of Health Stroke Scale (NIHSS) score, and glucose (n=424), CTP remained associated with a favorable 90-day mRS shift ( P =0.016), lower mortality ( P =0.02), and higher rates of reperfusion ( P <0.001). CTP better predicted functional outcomes in patients presenting after 6 hours (as assessed by comparison of logistic regression models: Akaike information criterion: 199.35 versus 287.49 and Bayesian information criterion: 196.71 versus 283.27) and those with an Alberta Stroke Program Early Computed Tomography Score ≤7 (Akaike information criterion: 216.69 versus 334.96 and Bayesian information criterion: 213.6 versus 329.94).

Conclusions—

CTP selection is associated with a favorable mRS shift in patients undergoing stent-retriever thrombectomy. Future prospective studies are warranted.

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.

Detection of Intraparenchymal Hemorrhage After Endovascular Therapy in Patients with Acute Ischemic Stroke Using Immediate Postprocedural Flat-Panel Computed Tomography Scan

PURPOSE

To assess the diagnostic value of parenchymal hyperdense lesions visualized on the flat-panel CT scan in detecting/excluding intraparenchymal hemorrhage (IPH) after the endovascular treatment of acute stroke patients.

METHODS

Two separate cohorts of acute ischemic stroke patients who underwent endovascular treatment were evaluated. In the first group, patients were evaluated for hyperdense parenchymal lesions immediately after the treatment with flat-panel CT scan; whereas, in the second group, patients underwent multidetector CT scan post procedure. IPH was defined as hyperdensity that persisted for >24 hours on follow up CT scan.

RESULTS

A total of 30 patients were evaluated with flat panel, and 135 with multidetector CT scan immediately after the endovascular treatment. Hyperdense lesions were visualized on 7/30 (23%) of those evaluated with flat-panel CT versus 74/135 (55%) of those evaluated with multidetector CT scan. Based on 24-hour follow up imaging, hyperdense parenchymal lesions on immediate postprocedural flat-panel or multidetector CT studies had 100% sensitivity and negative predictive value for IPH; whereas, the specificity, and positive predictive value of such lesions were 88% and, 57% on the flat panel; and 53% and, 27% on the multidetector CT study, respectively.

CONCLUSION

The absence of hyperdense lesions on immediate postprocedural flat-panel CT scan of ischemic stroke patients can exclude IPH with a high sensitivity and negative predictive value. The hyperdense parenchymal lesions visualized on flat-panel versus multidetector CT studies may have comparable sensitivity and negative predictive value for the detection of IPH.

Physiologic imaging in acute stroke: Patient selection

Treatment of acute stroke is changing, as endovascular intervention becomes an important adjunct to tissue plasminogen activator. An increasing number of sophisticated physiologic imaging techniques have unique advantages and applications in the evaluation, diagnosis, and treatment-decision making of acute ischemic stroke. In this review, we first highlight the strengths, weaknesses, and possible indications for various stroke imaging techniques. How acute imaging findings in each modality have been used to predict functional outcome is discussed. Furthermore, there is an increasing emphasis on using these state-of-the-art imaging modalities to offer maximal patient benefit through IV therapy, endovascular thrombolytics, and clot retrieval. We review the burgeoning literature in the determination of stroke treatment based on acute, physiologic imaging findings.

A critical analysis of intra-arterial thrombolytic doses in acute ischemic stroke treatment

BACKGROUND

Intra-arterial thrombolytics (IAT) such as Alteplase, Tenecteplase, and Reteplase are currently used in patients with acute ischemic stroke in varying doses. We evaluated the relationship of IA thrombolytic dose with angiographic recanalization, intracerebral hemorrhage (ICH) rates, and clinical outcomes at three comprehensive stroke centers.

METHODS

We stratified patients who underwent endovascular treatment into tertiles based on intra-arterial thrombolytic dose administered: lower tertile (range 1.5-5 mg), middle tertile (range 6-10 mg), and upper tertile (range 10.3-68.5 mg) of rt-PA equivalent. The rates of angiographic recanalization, ICH, and favorable clinical outcomes (discharge modified Rankin score [mRS] = 0-2) were ascertained and compared within the three tertiles. Logistic regression analyses were performed to determine the association between IA thrombolytic dosages and angiographic recanalization, ICH, and favorable clinical outcomes after adjusting for potential confounders.

RESULTS

A total of 197 patients were treated with IAT; mean age ±SD was 65.6 ± 16 years; 105 (53.3%) were women. Ninety-one (46.2%) patients received both IVT and IAT. IA rt-PA equivalent dose was not different between the patients with and without ICH [mean (mg) ± SD, 9.8 ± 6.1 versus 9.8 ± 9.5, p = 0.9]. We did not find any relation between increasing doses of IAT (from 2 to 69 mg rt-PA equivalent) and symptomatic or asymptomatic ICH: (p = 0.1630) and (p = 0.6702), respectively. Multivariate analysis demonstrated that IAT dose was not associated with ICH (OR 1.0, 95% CI 0.97-1.07, p = 0.3919) or favorable outcome (OR, 1.00, 95% CI 0.95-1.06, p = 0.7375). In a subset analysis of IVT patients, total doses ranged from 48.2 to 149 mg and were not associated with either symptomatic (p = 0.23) or asymptomatic (p = 0.24) ICHs.

CONCLUSION

Our study demonstrates that IAT in doses up to 69 mg is safe without any evidence of dose-related ICHs even in those patients who had received IVT.

Big and bigger data in endovascular stroke therapy

More than 30 years after initial reports demonstrated the feasibility of intra-arterial or endovascular therapies for the treatment of acute ischemic stroke, big data have finally established requisite evidence for the safety and efficacy of thrombectomy. Cautious enthusiasm for this breakthrough is tempered, as we await the bigger data of these trials to understand the constellation of variables that ensured success. Noninvasive imaging, including multimodal computed tomography and MRI as used in recent endovascular trials, has dramatically advanced since that time, providing snapshots or profiles of the collaterome in a given patient. Data-driven analyses will provide the most potent argument to distinguish comprehensive stroke centers from interventional-ready sites. These trials may provide insight on the future role of telestroke, for intravenous thrombolysis and remote imaging review of multimodal computed tomography or MRI to streamline patient transfer for endovascular therapy. Rather than concluding that recent trials have answered the most important question regarding endovascular therapy, even more data are needed to effectively translate such success and extend such potential benefit to the greatest number of stroke patients encountered on a daily basis.

Middle Cerebral Artery Residual Contrast Stagnation on Noncontrast CT Scan Following Endovascular Treatment in Acute Ischemic Stroke Patients

BACKGROUND AND PURPOSE

We evaluated the relationship between middle cerebral artery (MCA) residual contrast stagnation on immediate postprocedural noncontrast CT scan and intraparenchymal hemorrhage (IPH) after endovascular treatment in acute ischemic stroke patients.

METHODS

The clinical and imaging data from patients with acute unilateral MCA M1 occlusion who underwent endovascular treatment over a 3.5-year period were reviewed. Bilateral M1 segments were selected on the first postangiography CT scan, and average attenuation was determined in Hounsfield units (HU); the difference between average HU values was calculated. Postprocedural CT scans were also evaluated for presence of IPH, defined as hyperdensity persisting on follow-up CT scans obtained >24-hours postprocedure.

RESULTS

Of 80 patients included in our series; 10/80 developed IPH on immediate postprocedural CT scan. Patients with IPH had a higher (ipsilateral-contralateral) M1 residual attenuation difference (P < .001). An average ipsilateral M1 attenuation which was ≥5 HU greater than contralateral artery had a 3.8 times increase in relative risk of IPH (95% confidence interval: 2-7.1).

CONCLUSION

On immediate postprocedural noncontrast CT scan of stroke patients with acute MCA M1 occlusion after endovascular treatment, higher residual contrast stagnation in the affected MCA, compared to contralateral artery, is associated with an increased risk of IPH.

Multimodal CT versus MRI in Selecting Acute Stroke Patients for Endovascular Treatment

Arterial revascularization is the most effective therapy for acute stroke patients. Systemic thrombolysis with recombinant tissue plasminogen activator based on baseline non-contrast CT (NCCT) imaging criteria is the only treatment approved to date, which is limited by severe timing and medical restrictions, and a narrow efficacy. The simple imaging methodology required contrast with the current wide range of imaging modalities available, which permits the physician to rapidly obtain an estimation of the most relevant pathophysiological factors involved in an acute stroke, overcoming the limited capability of NCCT. Multimodal CT and MRI combine techniques that aim to depict the neurovasculature and the status of the brain parenchyma, including the presence of hemorrhage and infarction, as well as the viability of the cerebral ischemic areas involved. These additional imaging procedures have been explored in clinical studies and trials to guide intravenous thrombolysis in acute stroke patients beyond the currently established time windows, with inconclusive results. However, emergent endovascular materials and techniques are evolving, showing promising results with increasing rates of arterial recanalization with an acceptable safety profile, therefore becoming a potential alternative and complimentary treatment, although the current lack of a high level of evidence is limiting their use in routine clinical practice. Nevertheless, these advanced neuroimaging methods can be used to improve the selection of candidates for these novel invasive therapies and, moreover, to help the interventionist to design a faster and safer procedure. In this article, we review the basic aspects of both CT and MRI modalities and the state of the evidence of these imaging tools to guide endovascular therapy, as well as the advantages and disadvantages of each method.

Multimodal Computed Tomography Based Definition of Cerebral Imaging Profiles for Acute Stroke Reperfusion Therapy (CT-DEFINE): Results of a Prospective Observational Study

PURPOSE

To prospectively evaluate the prognostic impact of multimodal computed tomography-based imaging in ischemic stroke patients potentially eligible for reperfusion therapy.

METHODS

Anterior circulation stroke patients underwent non-contrast CT (NCCT), CT-angiography, and CT-perfusion within 12 h from symptom-onset. Patients could be treated with intravenous-tissue plasminogen activator (IV-tPA), endovascular or combined reperfusion therapies. Cerebral imaging profiles (IP) were NCCT-Alberta Stroke Program Early CT Score (ASPECTS) > 7 (IP1); NCCT-ASPECTS > 5 and proximal occlusion on CT-angiography (IP2); CT-perfusion mismatch between cerebral blood volume (CBV)-ASPECTS, and cerebral blood flow (CBF)-ASPECTS ≥ 2 (IP3). Favorable outcome was defined as modified Rankin Scale ≤ 2 at 3 months.

RESULTS

Of 102 included patients, 62 (61%) received any reperfusion therapy. In IP2 and IP3, favorable outcome was more frequent in patients with reperfusion therapy than in those without; however, this did not reach statistical significance (IP2: 39% vs 15%, p = 0.26; IP3: 50% vs 17 %; p = 0.31). No difference was seen in IP1 (58% vs 58%, p = 1.0). In IP2, patients with IV-tPA alone achieved better functional outcome (50% vs 11%, p = 0.03) and lower mortality (0% vs 28%, p = 0.045) than those without.

CONCLUSIONS

Our results suggest a benefit with imaging profile selection based upon the combination of a small-to-moderate-sized infarction and a visible intracranial occlusion in patients receiving IV-tPA. Reperfusion therapy may be futile in patients without proven vessel occlusion.

Differentiating intraparenchymal hemorrhage from contrast extravasation on post-procedural noncontrast CT scan in acute ischemic stroke patients undergoing endovascular treatment

INTRODUCTION

This study aimed to identify the imaging characteristics that can help differentiate intraparenchymal hemorrhage from benign contrast extravasation on post-procedural noncontrast CT scan in acute ischemic stroke patients after endovascular treatment.

METHODS

We reviewed the clinical and imaging records of all acute ischemic stroke patients who underwent endovascular treatment in two hospitals over a 3.5-year period. The immediate post-procedural CT scan was evaluated for the presence of hyperdense lesion(s). The average attenuation of the lesion(s) was measured. Intraparenchymal hemorrhage was defined as a persistent hyperdensity visualized on follow-up CT scan, 24 h or greater after the procedure.

RESULTS

Of the 135 patients studied, 74 (55%) patients had hyperdense lesion(s) on immediate post-procedural CT scan. Follow-up scans confirmed the diagnosis of intraparenchymal hemorrhage in 20 of these 74 patients. A receiver operating characteristic analysis showed that the average attenuation of the most hyperdense lesion can differentiate intraparenchymal hemorrhage from contrast extravasation with an area under the curve of 0.78 (p = 0.001). An average attenuation of <50 Hounsfield units (HU) in the most visually hyperattenuating hyperdense lesion had 100 % specificity and 56% sensitivity for identification of contrast extravasations. Petechial hyperdensity was seen in 46/54 (85%) patients with contrast extravasation versus 9/20 (45%) patients with intraparenchymal hemorrhage on the immediate post-procedural CT scan (p < 0.001).

CONCLUSION

An average attenuation <50 HU of the most hyperattenuating hyperdense parenchymal lesion on immediate post-procedural CT scan was very specific for differentiating contrast extravasation from intraparenchymal hemorrhage in acute ischemic stroke patients after endovascular treatment.

Perfusion-based selection for endovascular reperfusion therapy in anterior circulation acute ischemic stroke

BACKGROUND AND PURPOSE

Controversy exists about the role of perfusion imaging in patient selection for endovascular reperfusion therapy in acute ischemic stroke. We hypothesized that perfusion imaging versus noncontrast CT- based selection would be associated with improved functional outcomes at 3 months.

MATERIALS AND METHODS

We reviewed consecutive patients with anterior circulation strokes treated with endovascular reperfusion therapy within 8 hours and with baseline NIHSS score of ≥8. Baseline clinical data, selection mode (perfusion versus NCCT), angiographic data, complications, and modified Rankin Scale score at 3 months were collected. Using multivariable logistic regression, we assessed whether the mode of selection for endovascular reperfusion therapy (perfusion-based versus NCCT-based) was independently associated with good outcome.

RESULTS

Two-hundred fourteen patients (mean age, 67.2 years; median NIHSS score, 18; MCA occlusion 74% and ICA occlusion 26%) were included. Perfusion imaging was used in 76 (35.5%) patients (39 CT and 37 MR imaging). Perfusion imaging-selected patients were more likely to have good outcomes compared with NCCT-selected patients (55.3 versus 33.3%, P = .002); perfusion selection by CT was associated with similar outcomes as that by MR imaging (CTP, 56.; MR perfusion, 54.1%; P = .836). In multivariable analysis, CT or MR perfusion imaging selection remained strongly associated with good outcome (adjusted OR, 2.34; 95% CI, 1.22-4.47), independent of baseline severity and reperfusion.

CONCLUSIONS

In this multicenter study, patients with acute ischemic stroke who underwent perfusion imaging were more than 2-fold more likely to have good outcomes following endovascular reperfusion therapy. Randomized studies should compare perfusion imaging with NCCT imaging for patient selection for endovascular reperfusion therapy.

CT perfusion-guided versus time-guided mechanical recanalization in acute ischemic stroke patients

OBJECTIVE

Perfusion studies are increasingly used to triage acute stroke patients for endovascular recanalization therapies. We compare the safety and efficacy of CT perfusion (CTP)-guided to time-guided mechanical recanalization in acute ischemic stroke (AIS) patients.

METHODS

A review was conducted on 132 patients, 94 undergoing CTP-guided and 38 undergoing time-guided (maximum 8h from symptom onset) mechanical recanalization at our institution.

RESULTS

The rate of partial-to-complete recanalization did not differ between the CTP and the non-CTP group (78.7% vs. 81.6%, respectively, p=0.71). ICH occurred respectively in 18.1% in the CTP group versus 31.6% in the non-CTP group (p=0.06). The overall in-hospital mortality rate was significantly lower in the CTP group (15.9% vs. 36.8%, p=0.04). In multivariable analysis, CTP-guided patient selection was an independent negative predictor of in-hospital mortality (OR=3.2; p=0.01). CTP-guided patient selection, however, was not a predictor of favorable outcome (Modified Rankin Scale 0-2 or 0-3).

CONCLUSIONS

CTP-based patient selection was associated with lower ICH and mortality rates. Favorable outcomes, however, did not differ between the 2 groups. These results may suggest a possible benefit in terms of in-hospital mortality with CTP-guided triage of AIS patients for endovascular treatment.

Advanced neuroimaging to guide acute stroke therapy

Traditionally non-contrast CT has been considered the first choice imaging modality for acute stroke. Acute ischemic stroke patients presenting to the hospital within 3-hours from symptom onset and without any visible hemorrhages or large lesions on CT images are considered optimum reperfusion therapy candidates. However, non-contrast CT alone has been unable to identify best reperfusion therapy candidates outside this window. New advanced imaging techniques are now being used successfully for this purpose. Non-invasive CT or MR angiography images can be obtained during initial imaging evaluation for identification and characterization of vascular lesions, including occlusions, aneurysms, and malformations. Either CT-based perfusion imaging or MRI-based diffusion and perfusion imaging performed immediately upon arrival of a patient to the hospital helps estimate the extent of fixed core and penumbra in ischemic lesions. Patients having occlusive lesions with small fixed cores and large penumbra are preferred reperfusion therapy candidates.

Computed Tomography Workup of Patients Suspected of Acute Ischemic Stroke

Background and Purpose—

To determine whether perfusion computed tomography (PCT) adds value to noncontrast head CT (NCT), CT angiogram (CTA), and clinical assessment in patients suspected of acute ischemic stroke.

Methods—

We retrospectively reviewed 165 patients with acute ischemic stroke. PCT was used to calculate the volumes of infarct core and ischemic penumbra on admission. Other imaging data included Alberta Score Program Early CT Score, site of occlusion, and collateral flow. Clinical data included age, time, National Institutes of Health Stroke Scale at baseline, treatment type, and modified Rankin score (mRS) at 90 days. Recanalization status was assessed on follow-up imaging. In a first multivariate regression analysis, we assessed whether volumes of PCT penumbra and infarct core could be predicted from clinical variables, NCT, or CTA, or whether they represented independent information. In a second multivariate regression analysis, we used mRS at 90 days as outcome and determined which variables predicted it best.

Results—

Of 165 patients identified, 76 had a mRS score of 0 to 2 at 90 days, 89 had a mRS score >2. PCT infarct could be predicted by clinical data, NCT, CTA, and combinations of this data ( P <0.05). PCT penumbra could not be predicted by clinical data, NCT, and CTA. All of the variables but NCT and CTA were significantly associated with 90-day mRS outcome. The single most important predictor was recanalization status ( P <0.001). PCT penumbra volume ( P =0.001) was also a predictor of clinical outcome, especially when considered in conjunction with recanalization through an interaction term ( P <0.001).

Conclusions—

PCT penumbra represents independent information, which cannot be predicted by clinical, NCT, and CTA data. PCT penumbra is an important determinant of clinical outcome and adds relevant clinical information compared with a stroke CT workup, including NCT and CTA.

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.

Microcatheter to recanalization (procedure time) predicts outcomes in endovascular treatment in patients with acute ischemic stroke: when do we stop?

BACKGROUND AND PURPOSE

Endovascular treatment for acute ischemic stroke consists of various mechanical and pharmacologic modalities used for recanalization of arterial occlusions. We performed this study to determine the relationship among procedure time, recanalization, and clinical outcomes in patients with acute ischemic stroke undergoing endovascular treatment.

MATERIALS AND METHODS

We analyzed data from consecutive patients with acute ischemic stroke who underwent endovascular treatment during a 6-year period. Demographic characteristics, NIHSS score before and 24 hours after the procedure, and discharge mRS score were ascertained. Procedure time was defined by the time interval between microcatheter placement and recanalization or completion of the procedure. We estimated the procedure time after which favorable clinical outcome was unlikely, even after adjustment for age, time from symptom onset, and admission NIHSS scores.

RESULTS

We analyzed 209 patients undergoing endovascular treatment (mean age, 65 ± 16 years; 109 [52%] men; mean admission/preprocedural NIHSS score, 15.3 ± 6.8). Complete or partial recanalization was observed in 176 (84.2%) patients, while unfavorable outcome (mRS 3-6) was observed in 138 (66%) patients at discharge. In univariate analysis, patients with procedure time ≤30 minutes had lower rates of unfavorable outcome at discharge compared with patients with procedure time ≥30 minutes (52.3% versus 72.2%, P = .0049). In our analysis, the rates of favorable outcomes in endovascularly treated patients after 60 minutes were lower than rates observed with placebo treatment in the Prourokinase for Acute Ischemic Stroke Trial. In logistic regression analysis, unfavorable outcome was positively associated with age (P = .0012), admission NIHSS strata (P = .0017), and longer procedure times (P = .0379).

CONCLUSIONS

Procedure time in patients with acute ischemic stroke appears to be a critical determinant of outcomes following endovascular treatment. This highlights the need for procedure time guidelines for patients being considered for endovascular treatment in acute ischemic stroke.

Standardization of Stroke Perfusion CT for Reperfusion Therapy

With the advances in terms of perfusion imaging, the "time is brain" approach used for acute reperfusion therapy in ischemic stroke patients is slowly being replaced by a "penumbra is brain" or "imaging is brain" approach. But the concept of penumbra-guided reperfusion therapy has not been validated. The lack of standardization in penumbral imaging is one of the main contributing factors for this absence of validation. This article reviews the issues underlying the lack of standardization of perfusion-CT for penumbra imaging, and offers avenues to remedy this situation.

Contrast stasis on noncontrast computed tomography as a predictor of stroke postthrombolysis

Multimodal endovascular intervention is becoming more commonplace for the acute intervention of ischemic stroke. Hyperdensity in a portion of the treated territory is a common finding on postthrombolytic noncontrast CT (NCCT), but its significance is poorly understood. The authors conducted a single-institution, retrospective chart review of patients who had intraarterial thrombolysis of the anterior circulation between 2010 and 2011 with evidence of hyperdensity on NCCT following recanalization. Eighteen patients had evidence of postoperative contrast stasis causing hyperdensity on NCCT. One hundred percent of the patients had MR imaging evidence of completed strokes postoperatively in the same distribution as the stasis. Stasis on NCCT after intervention had a sensitivity and specificity of 82% and 0% for predicting stroke, respectively. Furthermore, the positive predictive value was 100%. The presence of contrast stasis on postthrombolytic NCCT correlates well with stroke seen on subsequent MR imaging.

Computed tomography perfusion–based selection of patients for endovascular recanalization

Intravenous and intraarterial recombinant tissue plasminogen activator remains underutilized in the treatment of acute ischemic stroke, largely due to strict adherence to the concept of the therapeutic time window for administration. Recent efforts to expand the number of patients eligible for thrombolysis have been mirrored by an evolution in endovascular recanalization technology and techniques. As a result, there is a growing need to establish efficient and reliable means by which to select candidates for endovascular intervention beyond the traditional criteria of time from symptom onset. Perfusion imaging techniques, particularly CT perfusion used in combination with CT angiography, represent an increasingly recognized means by which to identify those patients who stand to benefit most from endovascular recanalization. Additionally, CT perfusion and CT angiography appear to provide sufficient data by which to exclude patients in whom there is little chance of neurological recovery or a substantial risk of postprocedure symptomatic intracranial hemorrhage. The authors review the current literature as it pertains to the limitations of time-based selection of patients for intervention, the increasing utilization of endovascular therapy, and the development of a CT perfusion-based selection of acute stroke patients for endovascular recanalization. Future endeavors must prospectively evaluate the utility and safety of CT perfusion-based selection of candidates for endovascular intervention.