Influence of Recanalization and Time of Cerebral Ischemia on Tissue Outcome after Endovascular Stroke Treatment on Computed Tomography Perfusion

High relative cerebral blood volume is associated with good long term clinical outcomes in acute ischemic stroke: a retrospective cohort study

BACKGROUND

Endovascular therapy for acute ischemic stroke has been shown to be highly effective in selected patients. However, the ideal criteria for patient selection are still debated. It is well known that collateral flow is an important factor, but the assessment is often subjective and time-consuming. Relative cerebral blood volume (rCBV) is a putative indicator of collateral capacity and can be quickly and easily determined by automated quantitative analysis. We investigated the relationship between rCBV of the affected region and clinical outcome in patients with acute ischemic stroke after endovascular therapy.

METHODS

We conducted a retrospective study on consecutive patients between January 2017 and May 2019. Patients with acute ischemic stroke of the anterior circulation who underwent imaging including computed tomography perfusion and were treated with mechanical thrombectomy (MT) were eligible for inclusion. rCBV was calculated automatically with RAPID software by dividing the average cerebral blood volume (CBV) of the affected region (time-to-maximum (Tmax) > 6 s) by the CBV of the unaffected contralateral side. The primary outcome was determined by the modified Rankin Scale (mRS) after 90 days. Good clinical outcome was defined as mRS ≤ 2. We compared means, performed mono- and multivariate logistical regression and calculated a receiver operating characteristic (ROC)-analysis to determine the ideal cutoff value to predict clinical outcomes.

RESULTS

155 patients were enrolled in this study. 66 patients (42.58%) had good clinical outcomes. Higher rCBV was associated with good clinical outcome (p < 0.001), even after adjustment for the patients' status according to mRS and National Institute of Health Stroke Scale (NIHSS) age and Alberta stroke program early computed tomography score (ASPECTS) at baseline (p = 0.006). ROC-analysis revealed 0.650 (confidence interval: 0.616-0.778) as the optimal cutoff value.

CONCLUSION

Higher rCBV at baseline is associated with good clinical long-term outcomes in patients with acute ischemic stroke treated by MT. In this study we provide the biggest collective so far that gives evidence that rCBV can be a valuable tool to identify patients who might benefit from MT and are able give a threshold to help to offer patients MT in borderline cases.

Cerebral circulation time on DSA after thrombectomy associated with hemorrhagic transformation in acute ischemic stroke

BACKGROUND

To investigate the association between cerebral circulation time (CCT) on digital subtraction angiography immediately after thrombectomy and hemorrhagic transformation (HT) in acute ischemic stroke (AIS).

METHODS

Retrospectively enrolled consecutive AIS patients presented with large vessel occlusion who received thrombectomy and achieved successful recanalization between January 2019 and June 2021. The time interval from the beginning of the siphon segment of internal carotid artery visualization until the end of the arterial phase during cerebral angiography was calculated as CCT. The independent association of CCT with HT was evaluated using logistic regression analyses. The receiver operating characteristic curve was analyzed to evaluate the association between CCT and HT.

RESULTS

Two hundred and twenty-four patients were included, of whom 86 (38.4%) suffered HT. Compared with patients without HT, patients with HT were of advanced age, less commonly male, had more diabetes mellitus, had higher baseline National Institutes of Health Stroke Scale score, lower Alberta Stroke Program Early Computed Tomographic Score, and shorter CCT (P < 0.05). Multivariable logistic regression suggested that CCT was independently associated with HT (adjusted odds ratio, 0.170; 95% confidence interval, 0.004-0.450; P < 0.001). According to the receiver operating characteristic curve, the optimal cut-off value for the strong correlation between CCT and HT was 1.72 s, which had 76.6% sensitivity, 81.6% specificity, and the area under the curve was 0.846.

CONCLUSION

Shorter post-thrombectomy CCT was independently associated with HT.

Optimizing the Definition of Ischemic Core in CT Perfusion: Influence of Infarct Growth and Tissue-Specific Thresholds

BACKGROUND AND PURPOSE

CTP allows estimating ischemic core in patients with acute stroke. However, these estimations have limited accuracy compared with MR imaging. We studied the effect of applying WM- and GM-specific thresholds and analyzed the infarct growth from baseline imaging to reperfusion.

MATERIALS AND METHODS

This was a single-center cohort of consecutive patients (n = 113) with witnessed strokes due to proximal carotid territory occlusions with baseline CT perfusion, complete reperfusion, and follow-up DWI. We segmented GM and WM, coregistered CTP with DWI, and compared the accuracy of the different predictions for each voxel on DWI through receiver operating characteristic analysis. We assessed the yield of different relative CBF thresholds to predict the final infarct volume and an estimated infarct growth-corrected volume (subtracting the infarct growth from baseline imaging to complete reperfusion) for a single relative CBF threshold and GM- and WM-specific thresholds.

RESULTS

The fixed threshold underestimated lesions in GM and overestimated them in WM. Double GM- and WM-specific thresholds of relative CBF were superior to fixed thresholds in predicting infarcted voxels. The closest estimations of the infarct on DWI were based on a relative CBF of 25% for a single threshold, 35% for GM, and 20% for WM, and they decreased when correcting for infarct growth: 20% for a single threshold, 25% for GM, and 15% for WM. The combination of 25% for GM and 15% for WM yielded the best prediction.

CONCLUSIONS

GM- and WM-specific thresholds result in different estimations of ischemic core in CTP and increase the global accuracy. More restrictive thresholds better estimate the actual extent of the infarcted tissue.

Artery diameter ratio after recanalization in endovascular therapy for acute ischemic stroke: a new predictor of clinical outcomes

PURPOSE

This study aimed to investigate the relationship between the artery diameter ratio (ADR) after recanalization and clinical outcomes.

METHODS

Patients with middle cerebral artery occlusion confirmed by DSA from 1 January 2018, to 31 December 2019, were retrospectively analyzed. All patients confirmed TICI grade 2b or 3. The ADR was calculated as M2 segment diameter/M1 segment diameter. Multivariate regression analysis was used to describe clinical outcomes of two groups (ADR < 0.6 and ≥ 0.6). ROC curves were used to compare different models and find the best cutoff.

RESULTS

A total of 143 patients were included in the study, including 77 males and 66 females, with an average age of 67.79 ± 12 years. The NIHSS at discharge was significantly higher in the ADR < 0.6 group than another group (mean, 16.37 vs. 6.19, P < 0.001). At 90 days, the cases of functional independence was significantly less in the ADR < 0.6 group (20.97% vs. 83.95%, OR 0.05, 95% CI 0.02-0.12, P < 0.001). The ADR < 0.6 group had a higher incidence of cerebral edema (P = 0.027) and sICH (P = 0.038). The ADR had the strongest power to distinguish mRS > 2 (AUC = 0.851) and DC (AUC = 0.805), and the best cutoff value are 0.6 (specificity 85.19%, sensitivity 75.81%) and 0.58 (specificity 65.96%, sensitivity 100%), respectively.

CONCLUSION

The low ADR is associated with poor outcomes. The decrease in ADR may be an indirect manifestation of the loss of cerebrovascular autoregulation.

Effect of different thresholds for CT perfusion volumetric analysis on estimated ischemic core and penumbral volumes

Purpose

This single-center study compared three threshold settings for automated analysis of the ischemic core (IC) and penumbral volumes using computed tomographic perfusion, and their accuracy for predicting final infarct volume (FIV) in patients with anterior circulation acute ischemic stroke (AIS).

Methods

Fifty-two consecutive AIS patients undergoing mechanical thrombectomy (November 2015–March 2018) were included. Perfusion images were retrospectively analyzed using a single CT Neuro perfusion application (syngo.via 4.1, Siemens Healthcare GmbH). Three threshold values (S1–S3) were derived from another commercial package (RAPID; iSchema View) (S1), up-to-date syngo.via default values (S2), and adapted values for syngo.via from a reference study (S3). The results were compared with FIV determined by non-contrast CT.

Results

The median IC volume (mL) was 24.6 (interquartile range: 13.7–58.1) with S1 and 30.1 (20.1–53.1) with S2/S3. After removing the contralateral hemisphere from the analysis, the median IC volume decreased by 1.33(0–3.14) with S1 versus 9.13 (6.24–14.82) with S2/S3. The median penumbral volume (mL) was 74.52 (49.64–131.91), 77.86 (46.56–99.23), and 173.23 (125.86–200.64) for S1, S2, and S3, respectively. Limiting analysis to the affected hemisphere, the penumbral volume decreased by 1.6 (0.13–9.02), 19.29 (12.59–26.52), and 58.33 mL (45.53–74.84) for S1, S2, and S3, respectively. The correlation between IC and FIV was highest in patients with successful recanalization (n = 34, r = 0.784 for S1; r = 0.797 for S2/S3).

Conclusion

Optimizing thresholds significantly improves the accuracy of estimated IC and penumbral volumes. Current recommended values produce diversified results. International guidelines based on larger multicenter studies should be established to support the standardization of volumetric analysis in clinical decision-making.

Recent Administration of Iodinated Contrast Renders Core Infarct Estimation Inaccurate Using RAPID Software

BACKGROUND AND PURPOSE

Automated CTP software is increasingly used for extended window emergent large-vessel occlusion to quantify core infarct. We aimed to assess whether RAPID software underestimates core infarct in patients with an extended window recently receiving IV iodinated contrast.

MATERIALS AND METHODS

We reviewed a prospective, single-center data base of 271 consecutive patients who underwent CTA ± CTP for acute ischemic stroke from May 2018 through January 2019. Patients with emergent large-vessel occlusion confirmed by CTA in the extended window (>6 hours since last known well) and CTP with RAPID postprocessing were included. Two blinded raters independently assessed CT ASPECTS on NCCT performed at the time of CTP. RAPID software used relative cerebral blood flow of <30% as a surrogate for irreversible core infarct. Patients were dichotomized on the basis of receiving recent IV iodinated contrast (<8 hours before CTP) for a separate imaging study.

RESULTS

The recent IV contrast and contrast-naïve cohorts comprised 23 and 15 patients, respectively. Multivariate linear regression analysis demonstrated that recent IV contrast administration was independently associated with a decrease in the RAPID core infarct estimate (proportional increase = 0.34; 95% CI, 0.12-0.96; P = .04).

CONCLUSIONS

Patients who received IV iodinated contrast in proximity (<8 hours) to CTA/CTP as part of a separate imaging study had a much higher likelihood of core infarct underestimation with RAPID compared with contrast-naïve patients. Over-reliance on RAPID postprocessing for treatment disposition of patients with extended window emergent large-vessel occlusion should be avoided, particularly with recent IV contrast administration.

Perfusion Computed Tomography in Acute Ischemic Stroke

Occlusion of a cervical or cerebral artery may cause acute ischemic stroke (AIS). Recent advances in AIS treatment by endovascular thrombectomy have led to more widespread use of advanced computed tomography (CT) imaging, including perfusion CT (PCT). This article reviews PCT for the evaluation of AIS patients.

Radiologic Cerebral Reperfusion at 24 h Predicts Good Clinical Outcome

Cerebral reperfusion and arterial recanalization are radiological features of the effectiveness of thrombolysis in acute ischemic stroke (AIS) patients. Here, an investigation of the prognostic role of early recanalization/reperfusion on clinical outcome was performed. In AIS patients (n = 55), baseline computerized tomography (CT) was performed ≤ 8 h from symptom onset, whereas CT determination of reperfusion/recanalization was assessed at 24 h. Multiple linear and logistic regression models were used to correlate reperfusion/recanalization with radiological (i.e., hemorrhagic transformation, ischemic core, and penumbra volumes) and clinical outcomes (assessed as National Institutes of Health Stroke Scale [NIHSS] reduction ≥ 8 points or a NIHSS ≤ 1 at 24 h and as modified Rankin Scale [mRS] < 2 at 90 days). At 24 h, patients achieving radiological reperfusion were n = 24, while the non-reperfused were n = 31. Among non-reperfused, n = 15 patients were recanalized. Radiological reperfusion vs. recanalization was also confirmed by early increased levels of circulating inflammatory biomarkers (i.e., serum osteopontin). In multivariate analysis, ischemic lesion volume reduction was associated with both recanalization (β = 0.265; p = 0.014) and reperfusion (β = 0.461; p < 0.001), but only reperfusion was independently associated with final infarct volume (β = - 0.333; p = 0.007). Only radiological reperfusion at 24 h predicted good clinical response at day 1 (adjusted OR 16.054 [1.423-181.158]; p = 0.025) and 90-day good functional outcome (adjusted OR 25.801 [1.483-448.840]; p = 0.026). At ROC curve analysis the AUC of reperfusion was 0.777 (p < 0.001) for the good clinical response at 24 h and 0.792 (p < 0.001) for 90-day clinical outcome. Twenty-four-hour radiological reperfusion assessed by CT is associated with good clinical response on day 1 and good functional outcome on day 90 in patients with ischemic stroke.

Ghost Infarct Core and Admission Computed Tomography Perfusion: Redefining the Role of Neuroimaging in Acute Ischemic Stroke

Background

Determining the size of infarct extent is crucial to elect patients for reperfusion therapies. Computed tomography perfusion (CTP) based on cerebral blood volume may overestimate infarct core on admission and consequently include ghost infarct core (GIC) in a definitive lesional area.

Purpose

Our goal was to confirm and better characterize the GIC phenomenon using CTP cerebral blood flow (CBF) as the reference parameter to determine infarct core.

Methods

We performed a retrospective, single-center analysis of consecutive thrombectomies of middle cerebral or intracranial internal carotid artery occlusions considering noncontrast CT Alberta Stroke Program Early CT Score ≥6 in patients with pretreatment CTP. We used the RAPID® software to measure admission infarct core based on initial CBF. The final infarct was extracted from follow-up CT. GIC was defined as initial core minus final infarct > 10 mL.

Results

A total of 123 patients were included. The median National Institutes of Health Stroke Scale score was 18 (13-20), the median time from symptoms to CTP was 188 (67-288) min, and the recanalization rate (Thrombolysis in Cerebral Infarction score 2b, 2c, or 3) was 83%. Twenty patients (16%) presented with GIC. GIC was associated with shorter time to recanalization (150 [105-291] vs. 255 [163-367] min, p = 0.05) and larger initial CBF core volume (38 [26-59] vs. 6 [0-27] mL, p < 0.001). An adjusted logistic regression model identified time to recanalization < 302 min (OR 4.598, 95% CI 1.143-18.495, p = 0.032) and initial infarct volume (OR 1.01, 95% CI 1.001-1.019, p = 0.032) as independent predictors of GIC. At 24 h, clinical improvement was more frequent in patients with GIC (80 vs. 49%, p = 0.01).

Conclusions

CTP CBF < 30% may overestimate infarct core volume, especially in patients imaged in the very early time window and with fast complete reperfusion. Therefore, the CTP CBF technique may exclude patients who would benefit from endovascular treatment.

Admission CT perfusion may overestimate initial infarct core: the ghost infarct core concept

Background

Identifying infarct core on admission is essential to establish the amount of salvageable tissue and indicate reperfusion therapies. Infarct core is established on CT perfusion (CTP) as the severely hypoperfused area, however the correlation between hypoperfusion and infarct core may be time-dependent as it is not a direct indicator of tissue damage. This study aims to characterize those cases in which the admission core lesion on CTP does not reflect an infarct on follow-up imaging.

Methods

We studied patients with cerebral large vessel occlusion who underwent CTP on admission but received endovascular thrombectomy based on a non-contrast CT Alberta Stroke Program Early CT Score (ASPECTS) >6. Admission infarct core was measured on initial cerebral blood volume (CBV) CTP and final infarct on follow-up CT. We defined ghost infarct core (GIC) as initial core minus final infarct >10 mL.

Results

79 patients were studied. Median National Institutes of Health Stroke Scale (NIHSS) score was 17 (11–20), median time from symptoms to CTP was 215 (87–327) min, and recanalization rate (TICI 2b–3) was 77%. Thirty patients (38%) presented with a GIC >10 mL. GIC >10 mL was associated with recanalization (TICI 2b–3: 90% vs 68%; p=0.026), admission glycemia (<185 mg/dL: 42% vs 0%; p=0.028), and time to CTP (<185 min: 51% vs >185 min: 26%; p=0.033). An adjusted logistic regression model identified time from symptom to CTP imaging <185 min as the only predictor of GIC >10 mL (OR 2.89, 95% CI 1.04 to 8.09). At 24 hours, clinical improvement was more frequent in patients with GIC >10 mL (66.6% vs 39%; p=0.017).

Conclusions

CT perfusion may overestimate final infarct core, especially in the early time window. Selecting patients for reperfusion therapies based on the CTP mismatch concept may deny treatment to patients who might still benefit from reperfusion.

Cerebral Blood Volume ASPECTS Is the Best Predictor of Clinical Outcome in Acute Ischemic Stroke: A Retrospective, Combined Semi-Quantitative and Quantitative Assessment

Introduction

The capability of CT perfusion (CTP) Alberta Stroke Program Early CT Score (ASPECTS) to predict outcome and identify ischemia severity in acute ischemic stroke (AIS) patients is still questioned.

Methods

62 patients with AIS were imaged within 8 hours of symptom onset by non-contrast CT, CT angiography and CTP scans at admission and 24 hours. CTP ASPECTS was calculated on the affected hemisphere using cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) maps by subtracting 1 point for any abnormalities visually detected or measured within multiple cortical circular regions of interest according to previously established thresholds. MTT-CBV ASPECTS was considered as CTP ASPECTS mismatch. Hemorrhagic transformation (HT), recanalization status and reperfusion grade at 24 hours, final infarct volume at 7 days and modified Rankin scale (mRS) at 3 months after onset were recorded.

Results

Semi-quantitative and quantitative CTP ASPECTS were highly correlated (p<0.00001). CBF, CBV and MTT ASPECTS were higher in patients with no HT and mRS≤2 and inversely associated with final infarct volume and mRS (p values: from p<0.05 to p<0.00001). CTP ASPECTS mismatch was slightly associated with radiological and clinical outcomes (p values: from p<0.05 to p<0.02) only if evaluated quantitatively. A CBV ASPECTS of 9 was the optimal semi-quantitative value for predicting outcome.

Conclusions

Our findings suggest that visual inspection of CTP ASPECTS recognizes infarct and ischemic absolute values. Semi-quantitative CBV ASPECTS, but not CTP ASPECTS mismatch, represents a strong prognostic indicator, implying that core extent is the main determinant of outcome, irrespective of penumbra size.