Persistent perfusion abnormalities at day 1 correspond to different clinical trajectories after stroke

Chronic hypertension and perfusion deficits conjointly affect disease outcome after tPA treatment in a rodent model of thromboembolic stroke

Futile recanalization hampers prognoses for ischemic stroke patients despite successful recanalization therapy. Allegedly, hypertension and reperfusion deficits contribute, but a better understanding is needed of how they interact and mediate disease outcome. We reassessed data from spontaneously hypertensive and normotensive Wistar-Kyoto rats (male, n = 6-7/group) that were subjected to two-hour embolic middle cerebral artery occlusion and thrombolysis in preclinical trials. Serial MRI allowed lesion monitoring and parcellation of regions-of-interest that represented infarcted (core) or recovered (perilesional) tissue. Imaging markers of hemodynamics and blood-brain barrier (BBB) status were related to tissue fate and neurological outcome. Despite comparable ischemic severity during occlusion between groups, hypertensive rats temporarily developed larger lesions after recanalization, with permanently aggravated vasogenic edema and BBB permeability. One day post-stroke, cerebral blood flow (CBF) was variably restored, but blood transit times were consistently prolonged in hypertensives. Compared to the core, perilesional CBF was normo-to-hyperperfused in both groups, yet this pattern reversed after seven days. Volumes of hypo- and hyperperfusion developed irrespective of strain, differentially associating with final infarct volume and behavioral outcome. Incomplete reperfusion and cerebral injury after thrombolysis were augmented in hypertensive rats. One day after thrombolysis, fractional volumes of hypoperfusion associated with worsened outcomes, while fractional volumes of hyperperfusion appeared beneficial or benign.

Incomplete reperfusion and the presence of distal emboli in predicting clinical outcome after endovascular thrombectomy

Objectives

To explore the relationship between final expanded treatment in cerebral infarction (eTICI) score and the presence or absence of distal emboli on final angiography on clinical outcome after endovascular thrombectomy (EVT) for acute ischaemic stroke (AIS). Persistent distal emboli on angiography are commonly noted, yet not all patients with intermediate eTICI scores demonstrate clear angiographic emboli, raising the possibility that these angiographic differences may correlate with distinct mechanisms of 'no-reflow'. Therefore, we sought to better understand the potential clinical impact of such angiographic markers in cases of incomplete reperfusion.

Design

We performed an exploratory retrospective analysis of a prospectively collected group of AIS patients who underwent EVT for M1 occlusions using the ASSIST Registry.

Setting

71 sites in 11 countries participated in the registry.

Participants

A total of 650 patients with M1 occlusions were included.

Main outcome measures

We compared 90-day modified Rankin scale (mRS) scores based on eTICI score as well as the presence or absence of distal emboli on final angiography.

Results

Clinical outcome based only on eTICI score revealed a shift in 90-day mRS, with a significant difference across eTICI scores in predicting 90-day mRS 0-2. In the intermediate eTICI grades 2b67 and 2c, there was a trend towards better 90-day mRS when emboli were present on final angiography than when emboli were absent. However, pairwise comparisons between these levels were non-significant.

Conclusion

In patients with final eTICI 2b67 or 2c, those with persistent emboli trended towards better clinical outcomes. With intermediate eTICI reperfusion, identifying the presence or absence of distal emboli on final angiography may be useful in distinguishing patterns of incomplete reperfusion. These findings should be followed by investigations on correlation between angiography and other markers of microcirculatory 'no-reflow'.

Trial registration number

NCT03845491.

Pericytes in the brain and heart: functional roles and response to ischaemia and reperfusion

In the last 20 years, there has been a revolution in our understanding of how blood flow is regulated in many tissues. Whereas it used to be thought that essentially all blood flow control occurred at the arteriole level, it is now recognized that control of capillary blood flow by contractile pericytes plays a key role both in regulating blood flow physiologically and in reducing it in clinically relevant pathological conditions. In this article, we compare and contrast how brain and cardiac pericytes regulate cerebral and coronary blood flow, focusing mainly on the pathological events of cerebral and cardiac ischaemia. The cerebral and coronary capillary beds differ dramatically in morphology, yet in both cases, pericyte-mediated capillary constriction plays a key role in restricting blood flow after ischaemia and possibly in other pathological conditions. We conclude with suggestions for therapeutic approaches to relaxing pericytes, which may prove useful in the long-term for reducing pericyte-induced ischaemia.

Cognitive impairment after intravenous thrombolysis in mild stroke: assessment of cerebral blood flow covariance network

Background

Mild stroke may lead to cognitive impairment, and it remains unclear whether intravenous thrombolysis (IVT) can mitigate cognitive deficits. This study investigates whether IVT can help alleviate cognitive function impairment in patients and further explores changes in the topological properties of cerebral blood flow (CBF) networks.

Methods

This observational study prospectively enrolled 94 patients with acute mild ischemic stroke (44 IVT vs. 50 non-IVT) from two hospitals. A battery of neuropsychological tests and arterial spin labeling were performed to evaluate their cognitive functioning and CBF in 116 brain regions. Voxel-wise CBF was compared between patients and health controls. The CBF covariance network of patients was constructed by calculating across-subject CBF covariance among 116 brain regions. Network properties were calculated and compared between IVT and no-IVT groups.

Results

The mild stroke group demonstrated significantly lower Montreal Cognitive Assessment (MoCA) scores compared to healthy controls (p < 0.001). Patients receiving IVT showed superior performance on the Trail Making Test-B (p = 0.043), Clock Drawing Test (p = 0.001), and Verbal Fluency Test (p = 0.033). Multivariate regression analysis adjusted for covariates demonstrated significant associations between IVT and cognitive outcomes: Montreal Cognitive Assessment (β = 2.85; 95% CI, 0.64-5.13), Trail Making Test-A (β = -16.90; 95% CI, -32.89--0.90), Trail Making Test-B (β = -43.27; 95% CI, -78.78--7.76), Hopkins Verbal Learning Test-Revised total recall (β = 3.57; 95% CI, 1.36-5.78), HVLT-R delayed recall (β = 1.53; 95% CI, 0.43-2.63), Clock Drawing Test (β = 7.09; 95% CI, 2.40-11.79), and Verbal Fluency Test (β = 3.00; 95% CI, 1.33-4.68). IVT patients exhibited higher small-worldness, clustering coefficient, and global efficiency of the network compared to non-IVT patients.

Conclusion

Intravenous thrombolysis demonstrated early cognitive benefits across multiple domains in patients with mild stroke. Improvement in the brain CBF covariance network properties may be the underlying mechanism.

Acute Ischemic Stroke in the Clinic and the Laboratory: Targets for Translational Research

Ischemic stroke research has enabled significant advancements in diagnosis, treatment, and management of this debilitating disease, yet challenges remain standing in the way of better patient prognoses. In this narrative review, a fictional case illustrates challenges and uncertainties that medical professionals still face - penumbra identification, lack of neuroprotective agents, side-effects of tissue plasminogen activator, dearth of molecular biomarkers, incomplete microvascular reperfusion or no-reflow, post-recanalization hyperperfusion, blood pressure management and procedural anesthetic effects. The current state of the field is broadly reviewed per topic, with the aim to introduce a broad audience (scientist and clinician alike) to recent successes in translational stroke research and pending scientific queries that are tractable for preclinical assessment. Opportunities for co-operation between clinical and experimental stroke experts are highlighted to increase the size and frequency of strides the field makes to improve our understanding of this disease and ways of treating it.

Implications of Post-recanalization Perfusion Deficit After Acute Ischemic Stroke: a Scoping Review of Clinical and Preclinical Imaging Studies

The goal of reperfusion therapy for acute ischemic stroke (AIS) is to restore cerebral blood flow through recanalization of the occluded vessel. Unfortunately, successful recanalization does not always result in favorable clinical outcome. Post-recanalization perfusion deficits (PRPDs), constituted by cerebral hypo- or hyperperfusion, may contribute to lagging patient recovery rates, but its clinical significance remains unclear. This scoping review provides an overview of clinical and preclinical findings on post-ischemic reperfusion, aiming to elucidate the pattern and consequences of PRPD from a translational perspective. The MEDLINE database was searched for quantitative clinical and preclinical studies of AIS reporting PRPD based on cerebral circulation parameters acquired by translational tomographic imaging methods. PRPD and stroke outcome were mapped on a charting table, creating an overview of PRPD after AIS. Twenty-two clinical and twenty-two preclinical studies were included. Post-recanalization hypoperfusion is rarely reported in clinical studies (4/22) but unequivocally associated with detrimental outcome. Post-recanalization hyperperfusion is more commonly reported (18/22 clinical studies) and may be associated with positive or negative outcome. PRPD has been replicated in animal studies, offering mechanistic insights into causes and consequences of PRPD and allowing delineation of possible courses of PRPD. Complex relationships exist between PRPD and stroke outcome. Diversity in methods and lack of standardized definitions in reperfusion studies complicate the characterization of reperfusion patterns. Recommendations are made to advance the understanding of PRPD mechanisms and to further disentangle the relation between PRPD and disease outcome.

Incidence, severity and impact on functional outcome of persistent hypoperfusion despite large-vessel recanalization, a potential marker of impaired microvascular reperfusion: Systematic review of the clinical literature

The reported incidence of persistent hypoperfusion despite complete recanalization as surrogate for impaired microvascular reperfusion (IMR) has varied widely among clinical studies, possibly due to differences in i) definition of complete recanalization, with only recent Thrombolysis in Cerebral Infarction (TICI) grading schemes allowing distinction between complete (TICI3) and partial recanalization with distal occlusions (TICI2c); ii) operational definition of IMR; and iii) consideration of potential alternative causes for hypoperfusion, notably carotid stenosis, re-occlusion and post-thrombectomy hemorrhage. We performed a systematic review to identify clinical studies that carried out brain perfusion imaging within 72 hrs post-thrombectomy for anterior circulation stroke and reported hypoperfusion rates separately for TICI3 and TICI2c grades. Authors were contacted if this data was missing. We identified eight eligible articles, altogether reporting 636 patients. The incidence of IMR after complete recanalization (i.e., TICI3) tended to decrease with the number of considered alternative causes of hypoperfusion: range 12.5-42.9%, 0-31.6% and 0-9.1% in articles that considered none, two or all three causes, respectively. No study reported the impact of IMR on functional outcome separately for TICI-3 patients. Based on this systematic review, IMR in true complete recanalization appears relatively rare, and reported incidence highly depends on definition used and consideration of confounding factors.