Hypoperfusion Intensity Ratio Predicts Infarct Growth After Successful Thrombectomy for Distal Medium Vessel Occlusion

Pretreatment CTP Collateral Parameters Predict Good Outcomes in Successfully Recanalized Middle Cerebral Artery Distal Medium Vessel Occlusions

BACKGROUND/PURPOSE

Distal medium vessel occlusions (DMVOs) account for a large percentage of vessel occlusions resulting in acute ischemic stroke (AIS) with disabling symptoms. We aim to assess whether pretreatment quantitative CTP collateral status (CS) parameters can serve as imaging biomarkers for good clinical outcomes prediction in successfully recanalized middle cerebral artery (MCA) DMVOs.

METHODS

We performed a retrospective analysis of consecutive patients with AIS secondary to primary MCA-DMVOs who were successfully recanalized by mechanical thrombectomy (MT) defined as modified thrombolysis in cerebral infarction (mTICI) 2b, 2c, or 3. We evaluated the association between the CBV index and HIR independently with good clinical outcomes (modified Rankin score 0-2) using Spearman rank correlation, logistic regression, and ROC analyses.

RESULTS

From 22 August 2018 to 18 October 2022 8/22/2018 to 10/18/2022, 60 consecutive patients met our inclusion criteria (mean age 71.2 ± 13.9 years old [mean ± SD], 35 female). The CBV index (r = -0.693, p < 0.001) and HIR (0.687, p < 0.001) strongly correlated with 90-day mRS. A CBV index ≥ 0.7 (odds ratio, OR, 2.27, range 6.94-21.23 [OR] 2.27 [6.94-21.23], p = 0.001)) and lower likelihood of prior stroke (0.13 [0.33-0.86]), p = 0.024)) were independently associated with good outcomes. The ROC analysis demonstrated good performance of the CBV index in predicting good 90-day mRS (AUC 0.73, p = 0.003) with a threshold of 0.7 for optimal sensitivity (71% [52.0-85.8%]) and specificity (76% [54.9-90.6%]). The HIR also demonstrated adequate performance in predicting good 90-day mRS (AUC 0.77, p = 0.001) with a threshold of 0.3 for optimal sensitivity (64.5% [45.4-80.8%]) and specificity (76.0% [54.9-90.6%]).

CONCLUSION

A CBV index ≥ 0.7 may be independently associated with good clinical outcomes in our cohort of AIS caused by MCA-DMVOs that were successfully treated with MT. Furthermore, a HIR < 0.3 is also associated with good clinical outcomes. This is the first study of which we are aware to identify a CBV index threshold for MCA-DMVOs.

Hypoperfusion Intensity Ratio is Associated with Early Neurologic Deficit Severity and Deterioration after Mechanical Thrombectomy in Large-Vessel Occlusion Ischemic Stroke

BACKGROUND AND PURPOSE

The hypoperfusion intensity ratio is a surrogate marker for collateral status and a predictor of infarct growth, malignant cerebral edema, and hemorrhagic transformation. Its utility to predict a poor NIHSS score and early neurologic deterioration after mechanical thrombectomy for large vessel (LVO) versus distal and medium vessel occlusions (DMVO) has not been investigated. The objective of this study was to determine whether the higher hypoperfusion intensity ratio is associated with a worse NIHSS score at 24 hours post-mechanical thrombectomy and early neurologic deterioration in LVO versus DMVO acute ischemic stroke.

MATERIALS AND METHODS

This was a retrospective study of 231 patients with acute ischemic stroke with LVO or DMVO amenable for mechanical thrombectomy and available CTP for hypoperfusion intensity ratio assessment pre-mechanical thrombectomy. Clinical and imaging characteristics were abstracted from the medical records. The primary outcome was the NIHSS score at 24 hours post-mechanical thrombectomy. The secondary outcome was early neurologic deterioration, defined as a >4-point increase in the NIHSS score between the initial assessment and 24 hours post-mechanical thrombectomy. All analyses were first conducted in the entire cohort and then separately for the LVO versus DMVO groups.

RESULTS

The optimal hypoperfusion intensity ratio threshold to detect early neurologic deterioration was 0.54. A hypoperfusion intensity ratio ≥ 0.54 was more frequently present in LVO versus DMVO (n = 37 [77.1%] versus n = 11 [22.9%]; P < .001). On multivariable linear regression, the hypoperfusion intensity ratio ≥ 0.54 was independently associated with a worse NIHSS score at 24 hours post-mechanical thrombectomy in the entire cohort (β = 0.163; P = .002) and the LVO group (β = 0.210; P = .005), but not in the DMVO group. The early neurologic deterioration occurred in 26 (11.3%) subjects. On multivariable logistic regression, there was no association of the hypoperfusion intensity ratio ≥ 0.54 with early neurologic deterioration in the entire cohort. However, when analyzed separately, a hypoperfusion intensity ratio ≥ 0.54 significantly increased the odds of early neurologic deterioration in subjects with LVO (OR = 5.263; 95% CI, 1.170-23.674; P = .030) but not in the DMVO group.

CONCLUSIONS

The hypoperfusion intensity ratio ≥ 0.54 was independently associated with a worse 24-hour post-mechanical thrombectomy NIHSS score and early neurologic deterioration in LVO, but not in DMVO acute ischemic stroke. Pending confirmation in future, prospective studies assessing the hypoperfusion intensity ratio may help identify patients at risk of secondary decline to improve peri-thrombectomy care and clinical decision-making.

Lower admission stroke severity is associated with good collateral status in distal medium vessel occlusion stroke

BACKGROUND AND PURPOSE

Distal medium vessel occlusions (DMVOs) are a significant contributor to acute ischemic stroke (AIS), with collateral status (CS) playing a pivotal role in modulating ischemic damage progression. We aimed to explore baseline characteristics associated with CS in AIS-DMVO.

METHODS

This retrospective analysis of a prospectively collected database enrolled 130 AIS-DMVO patients from two comprehensive stroke centers. Baseline characteristics, including patient demographics, admission National Institutes of Health Stroke Scale (NIHSS) score, admission Los Angeles Motor Scale (LAMS) score, and co-morbidities, including hypertension, hyperlipidemia, diabetes, coronary artery disease, atrial fibrillation, and history of transient ischemic attack or stroke, were collected. The analysis was dichotomized to good CS, reflected by hypoperfusion index ratio (HIR) <.3, versus poor CS, reflected by HIR ≥.3.

RESULTS

Good CS was observed in 34% of the patients. As to the occluded location, 43.8% occurred in proximal M2, 16.9% in mid M2, 35.4% in more distal middle cerebral artery, and 3.8% in distal anterior cerebral artery. In multivariate logistic analysis, a lower NIHSS score and a lower LAMS score were both independently associated with a good CS (odds ratio [OR]: 0.88, 95% confidence interval [CI]: 0.82-0.95, p < .001 and OR: 0.77, 95% CI: 0.62-0.96, p = .018, respectively). Patients with poor CS were more likely to manifest as moderate to severe stroke (29.1% vs. 4.5%, p < .001), while patients with good CS had a significantly higher chance of having a minor stroke clinically (40.9% vs. 12.8%, p < .001).

CONCLUSIONS

CS remains an important determinant in the severity of AIS-DMVO. Collateral enhancement strategies may be a worthwhile pursuit in AIS-DMVO patients with more severe initial stroke presentation, which can be swiftly identified by the concise LAMS and serves as a proxy for underlying poor CS.

Pretreatment parameters associated with hemorrhagic transformation among successfully recanalized medium vessel occlusions

Although pretreatment radiographic biomarkers are well established for hemorrhagic transformation (HT) following successful mechanical thrombectomy (MT) in large vessel occlusion (LVO) strokes, they are yet to be explored for medium vessel occlusion (MeVO) acute ischemic strokes. We aim to investigate pretreatment imaging biomarkers representative of collateral status, namely the hypoperfusion intensity ratio (HIR) and cerebral blood volume (CBV) index, and their association with HT in successfully recanalized MeVOs. A prospectively collected registry of acute ischemic stroke patients with MeVOs successfully recanalized with MT between 2019 and 2023 was retrospectively reviewed. A multivariate logistic regression for HT of any subtype was derived by combining significant univariate predictors into a forward stepwise regression with minimization of Akaike information criterion. Of 60 MeVO patients successfully recanalized with MT, HT occurred in 28.3% of patients. Independent factors for HT included: diabetes mellitus history (p = 0.0005), CBV index (p = 0.0071), and proximal versus distal occlusion location (p = 0.0062). A multivariate model with these factors had strong diagnostic performance for predicting HT (area under curve [AUC] 0.93, p < 0.001). Lower CBV indexes, distal occlusion location, and diabetes history are significantly associated with HT in MeVOs successfully recanalized with MT. Of note, HIR was not found to be significantly associated with HT.

CTA and CTP for Detecting Distal Medium Vessel Occlusions: A Systematic Review and Meta-analysis

BACKGROUND

The optimal imaging method for detecting distal medium vessel occlusions (DMVOs) remains undefined.

PURPOSE

The objective of this study is to compare the diagnostic performance of CTA with CTP in detecting DMVOs.

DATA SOURCES

We searched PubMed, EMBASE, Web of Science Core Collection, and Cochrane Central Register of Controlled Trials up to March 31, 2023 (PROSPERO: CRD42022344006).

STUDY SELECTION

A total of 12 studies reporting accuracy values of CTA and/or CTP were included, comprising 2607 patients with 479 cases (18.3%) of DMVOs.

DATA ANALYSIS

Pooled sensitivity and specificity of both imaging methods were compared using a random-effects model. Subgroup analyses were performed based on the technique used in CTA (multi or single-phase) and the subtype of DMVOs (M2-only vs. M2 and other DMVOs). We applied Quality Assessment of Diagnostic Accuracy (QUADAS-2) tool and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) quality assessment criteria.

DATA SYNTHESIS

CTA demonstrated significantly lower sensitivity compared to CTP in detecting DMVOs [0.74, 95%CI (0.63-0.82) vs. 0.89, 95% CI (0.82-0.93), P < 0.01]. When subgrouped into single-phase and multi-phase CTA, multi-phase CTA exhibited higher sensitivity for DMVO detection than single-phase CTA [0.91, 95%CI (0.85-0.94) vs. 0.64, 95%CI (0.56-0.71), P < .01], while reaching similar levels to CTP. The sensitivity of single-phase CTA substantially decreased when extending from M2 to other non-M2 DMVOs [0.74, 95%CI (0.63-0.83) vs. 0.61, 0.95%CI (0.53-0.68), P = .02].

LIMITATIONS

We identified an overall high risk of bias and low quality of evidence, attributable to the design and reference standards of most studies.

CONCLUSIONS

Our findings highlight a significantly lower sensitivity of single-phase CTA compared to multi-phase CTA and CTP in diagnosing DMVOs.

Cerebral blood volume index can predict the long-term prognosis after endovascular thrombectomy in patients with acute ischemic stroke due to large vessel occlusion

Long-term prognosis and factors influencing endovascular therapy (EVT) remain unclear. This study aimed to investigate the association between computed tomography perfusion (CTP) parameters and long-term prognosis of patients with acute ischemic stroke (AIS) treated with EVT. Patients with AIS due to large vessel occlusion treated with EVT were prospectively included for a 1-year follow-up. All patients and their data were grouped based on the hypoperfusion intensity ratio (HIR, ＜0.3 vs. ≥ 0.3) and cerebral blood volume (CBV) index (＞0.7 vs. ≤ 0.7). The primary outcome was favorable prognosis, defined as a modified Rankin Scale (mRS) score of 0-2. Multivariate logistic regression was used to analyze factors influencing long-term favorable prognosis. Of 69 patients included, 35 (50.7 %) achieved mRS 0-2 at one year. A favorable prognosis was observed predominantly in patients with higher CBV index (75.0 % vs. 34.1 %, p= 0.001) and lower HIR (72.0 % vs. 38.6 %, p=0.008). In the multivariate logistic regression, CBV index (odds ratio (OR) = 4.362; 95 % confidence interval (CI): 1.052, 18.082; p = 0.042), baseline National Institutes of Health Stroke Scale (NIHSS) score (OR = 0.913; 95 % CI: 0.836, 0.997; p = 0.044), and symptomatic intracranial hemorrhage (sICH) (OR = 0.089; 95 % CI: 0.009, 0.925; p = 0.043) were independently associated with a long-term favorable prognosis. The CBV index may serve as a predictor of the long-term prognosis of patients treated with EVT. The novel finding is that the baseline NIHSS score and sICH were associated with long-term prognosis.

Elevated Hypoperfusion Intensity Ratio (HIR) observed in patients with a large vessel occlusion (LVO) presenting in the evening

BACKGROUND

Circadian variability has been implicated in timing of stroke onset, yet the full impact of underlying biological rhythms on acute stroke perfusion patterns is not known. We aimed to describe the relationship between time of stroke onset and perfusion profiles in patients with large vessel occlusion (LVO).

METHODS

A retrospective observational study was conducted using prospective registries of four stroke centers across North America and Europe with systematic use of perfusion imaging in clinical care. Included patients had stroke due to ICA, M1 or M2 occlusion and baseline perfusion imaging performed within 24h from last-seen-well (LSW). Stroke onset was divided into eight hour intervals: (1) Night: 23:00-6:59, (2) Day: 7:00-14:59, (3) Evening: 15:00-22:59. Core volume was estimated on CT perfusion (rCBF <30%) or DWI-MRI (ADC <620) and the collateral circulation was estimated with the Hypoperfusion Intensity Ratio (HIR = [Tmax>10s]/[Tmax>6s]). Non-parametric testing was conducted using SPSS to account for the non-normalized dependent variables.

RESULTS

A total of 1506 cases were included (median age 74.9 years, IQR 63.0-84.0). Median NIHSS, core volumes, and HIR were 14.0 (IQR 8.0-20.0), 13.0mL (IQR 0.0-42.0), and 0.4 (IQR 0.2-0.6) respectively. Most strokes occurred during the Day (n = 666, 44.2%), compared to Night (n = 360, 23.9%), and Evening (n = 480, 31.9%). HIR was highest, indicating worse collaterals, in the Evening compared to the other timepoints (p = 0.006). Controlling for age and time to imaging, Evening strokes had significantly higher HIR compared to Day (p = 0.013).

CONCLUSION

Our retrospective analysis suggests that HIR is significantly higher in the evening, indicating poorer collateral activation which may lead to larger core volumes in these patients.