Frequency and Patterns of Brain Infarction in Patients With Embolic Stroke of Undetermined Source: NAVIGATE ESUS Trial

Importance of infarct topography in determination of stroke mechanism and recurrence risk: a post-hoc analysis of the dabigatran acute treatment of stroke trial

OBJECTIVE

To evaluate the relationship between infarct pattern, inferred stroke mechanism and risk of recurrence in patients with ischaemic stroke. The question is clinically relevant to optimise secondary stroke prevention investigations and treatment.

DESIGN

We conducted a retrospective analysis of the dabigatran treatment of acute stroke II (DATAS II) trial (ClinicalTrials.gove NCT NCT02295826), in which patients underwent diffusion-weighted imaging (DWI) at baseline and 30 days after randomisation to one of two antithrombotic therapies. Patients were classified as embolic, isolated small subcortical infarcts or transient ischaemic attack TIA (no infarct) at baseline and day 30. Stroke mechanism was determined by traditional and modified (based on DWI lesion findings) Trial of Org 10 172 in Acute Stroke Treatment (TOAST) criteria (DWI-TOAST).

SETTING

Multicentre (6) tertiary acute stroke treatment hospitals.

PARTICIPANTS

305 adults with minor ischaemic stroke (National Institutes of Health Stroke Scale (NIHSS) score≤9).

RESULTS

Of 305 patients, 148 had embolic pattern infarcts, 93 were isolated small subcortical infarcts and 64 had no infarct on baseline MRI (TIA). In the absence of DWI, TOAST classification indicated the mechanism was cryptogenic in 147 patients (48.2%), and small-vessel occlusion in 127 (41.6%). Using, DWI-TOAST, the number of cryptogenic strokes decreased to 123 (40.3%), and the number of small-vessel occlusion strokes increased to 151 (49.5%). Recurrent infarcts were seen in 13% of patients with an MRI-defined embolic infarct pattern and cryptogenic mechanism on DWI-TOAST. The relative risk of recurrent infarction in patients with undetermined aetiology was increased compared with other categories (standardised coefficient=1.0 (0.1, 1.9), p=0.029). The topography of recurrent infarcts was most often embolic (60.9%), but in 39.1% an isolated small subcortical infarct was seen.

CONCLUSIONS

Definitive identification of infarct topography with DWI has a significant impact on infarct mechanism classification. The variable relationship between baseline infarct patterns, clinical presentation and recurrent infarct distribution is a challenge to both the lacunar and embolic stroke of uncertain source (ESUS) concepts. Irrespective of aetiological classification, patients with MRI-defined cryptogenic embolic pattern infarcts are at high risk for recurrent events.

TRIAL REGISTRATION NUMBER

Linked to the DATAS II trial.

CLINICALTRIALS

gov ID NCT02295826.

Association of high-sensitivity cardiac troponin T with territorial middle cerebral artery brain infarctions and dynamic cerebral autoregulation

Background

Cardiac high-sensitivity troponin T (hs-cTnT) is linked to the cardioembolic origin, severity, and outcome of acute ischemic stroke. Furthermore, larger brain infarctions are often accompanied by impaired dynamic cerebral autoregulation (dCA), which is also indicative of a poor prognosis.

Objectives

This study aimed to investigate whether hs-cTnT levels can serve as a predictor of dCA impairment.

Design

Retrospective cohort study.

Methods

In 330 consecutive patients with stroke (age 71 years [IQR 59-78]; 100 women; 229 territorial and 111 non-territorial brain infarcts) with successful dCA assessment, hs-cTnT levels were measured within 24 hours of stroke onset. These measurements were analyzed in relation to cerebrovascular risk factors, stroke origin, stroke severity (National Institute of Health Stroke Scale, NIHSS at entry), modified Rankin scale (mRs) at 3 months, and stroke volume determined by cranial computed tomography perfusion (CTP). dCA was assessed using transfer function analysis, which assessed the relationship between middle cerebral artery blood flow velocity and blood pressure. Coherence, gain, and phase were estimated across 3 frequency ranges: very low (0.02-0.07 Hz), low (0.07-0.15 Hz), and high (0.15-0.5 Hz).

Results

In univariate analysis, hs-cTnT was associated with cardioembolism and territorial infarction. In the multinomial logistic regression analysis, independent risk factors for the presence of a territorial infarction included atrial fibrillation, the NIHSS score, the infarct core on CTP, cardioembolism, and large vessel disease, but not hs-cTnT levels. Risk factors for a poor outcome (mRs >2) included age, hs-cTnT, and NIHSS score. Overall, the coherence, gain, and phase were not predicted by hs-cTnT levels.

Conclusions

Hs-cTnT levels are associated with poor stroke outcomes. However, they do not predict dCA impairment.

Registration

ClinicalTrials.gov NCT04611672, 11.10.2020.

MRI in the Evaluation of Cryptogenic Stroke and Embolic Stroke of Undetermined Source

Cryptogenic stroke refers to a stroke of undetermined etiology. It accounts for approximately one-fifth of ischemic strokes and has a higher prevalence in younger patients. Embolic stroke of undetermined source (ESUS) refers to a subgroup of patients with nonlacunar cryptogenic strokes in whom embolism is the suspected stroke mechanism. Under the classifications of cryptogenic stroke or ESUS, there is wide heterogeneity in possible stroke mechanisms. In the absence of a confirmed stroke etiology, there is no established treatment for secondary prevention of stroke in patients experiencing cryptogenic stroke or ESUS, despite several clinical trials, leaving physicians with a clinical dilemma. Both conventional and advanced MRI techniques are available in clinical practice to identify differentiating features and stroke patterns and to determine or infer the underlying etiologic cause, such as atherosclerotic plaques and cardiogenic or paradoxical embolism due to occult pelvic venous thrombi. The aim of this review is to highlight the diagnostic utility of various MRI techniques in patients with cryptogenic stroke or ESUS. Future trends in technological advancement for promoting the adoption of MRI in such a special clinical application are also discussed.

Effect of pre-stroke antiplatelet use on stroke outcomes in acute small vessel occlusion stroke with moderate to severe white matter burden

BACKGROUND

Cerebral small vessel disease is characterized by white matter hyperintensities (WMH) and acute small vessel occlusion (SVO) stroke. We investigated the effect of prior antiplatelet use (APU) on stroke outcome in 1151 patients with acute SVO stroke patients and moderate to severe WMH.

METHODS

Using a multicenter database, this retrospective study used quantitative WMH volume measurements and propensity score matching (PSM) for comparisons between patients with prior APU and without APU. Primary outcomes were stroke progression and poor functional outcome (modified Rankin Scale>2) at 3 months. Logistic regression analyses assessed associations between prior APU, WMH burden, and stroke outcomes.

RESULTS

Stroke progression was lower in the prior APU group in both the total cohort (14.8% vs. 6.9%, p < 0.001) and the PSM cohort (16.3% vs. 6.9%, p < 0.001). The proportion of poor functional outcomes at 3 months was not significantly different in the total cohort, but the PSM cohort showed a lower proportion in the prior APU group (30.8% vs. 20.2%, p = 0.002). Logistic regression analysis confirmed that prior APU was associated with a reduced risk of stroke progression (OR, 0.39; 95% CI, 0.22-0.70; p = 0.001) and poor functional outcome at 3 months (OR, 0.37; 95% CI, 0.23-0.59; p < 0.001).

CONCLUSION

Prior APU is associated with reduced stroke progression and improved functional outcome at 3 months in acute SVO stroke patients with moderate to severe WMH. Early treatment of WMH and acute SVO stroke may have potential benefits in improving stroke outcomes.

Subcortical infarcts in patients with nonstenotic cervical atherosclerotic disease

BACKGROUND

Prior studies have elucidated a relationship between nonstenotic plaque in patients with cryptogenic embolic infarcts with a largely cortical topology, however, it is unclear if nonstenotic cervical internal carotid artery (ICA) plaque is relevant in subcortical cryptogenic infarct patterns.

METHODS

A nested cohort of consecutive patients with anterior, unilateral, and subcortical infarcts without an identifiable embolic source were identified from a prospective stroke registry (September 2019 - June 2021). Patients with extracranial stenosis >50% or cardiac sources of embolism were excluded. Patients with computed tomography angiography were included and comparisons were made according to the infarct pattern being lacunar versus non-lacunar. Prevalence estimates for cervical internal carotid artery (ICA) plaque presence were estimated with 95% confidence intervals (CI), and differences in plaque thickness and features were compared between sides.

RESULTS

Of the 1684 who were screened, 141 met inclusion criteria (n=80 due to small vessel disease, n=61 cryptogenic). The median age was 66y (interquartile range, IQR 58-73) and the National Institutes of Health Stroke Scale score was 3 (IQR 1-5). There was a higher probability of finding excess plaque ipsilateral to the stroke (41.1%, 95% CI 33.3-49.3%) than finding excess contralateral plaque (29.1%, 95% CI 22.2-37.1%; p=0.03), but this was driven by patients with non-lacunar infarcts (excess ipsilateral vs. contralateral plaque frequency of 49.2% vs. 14.8%, p<0.001) rather than lacunar infarcts (35.0% vs. 40.0%, p=0.51).

CONCLUSIONS

The probability of finding ipsilateral, nonstenotic carotid plaque in patients with subcortical cryptogenic strokes exceeds the probability of contralateral plaque and is driven by larger subcortical infarcts, classically defined as being cryptogenic. Approximately 1 in 3 unilateral anterior subcortical infarcts may be due to nonstenotic ICA plaque.

ECG Smart Monitoring versus Implantable Loop Recorders for Atrial Fibrillation Detection after Cryptogenic Stroke-An Overview for Decision Making

Up to 20% of patients with ischemic stroke or transient ischemic attack have a prior history of known atrial fibrillation (AF). Additionally, unknown AF can be detected by different monitoring strategies in up to 23% of patients with cryptogenic or non-cardioembolic stroke. However, most studies had substantial gaps in monitoring time, especially early after the index event. Following this, AF rates would be higher if patients underwent continuous monitoring early after stroke, avoiding any gaps in monitoring. The few existing randomized studies focused on patients with cryptogenic stroke but did not focus otherwise specifically on prevention strategies in patients at high risk for AF (patients at higher age or with high CHA2DS2-VASC scores). Besides invasive implantable loop recorders (ILRs), external loop recorders (ELRs) and mobile cardiac outpatient telemetry (MCOT) are non-invasive tools that are commonly used for long-term ECG monitoring in cryptogenic-stroke patients in the ambulatory setting. The role of MCOT and hand-held devices within ECG smart monitoring in the detection of AF for the prevention of and after cryptogenic stroke is currently unclear. This intense review provides an overview of current evidence, techniques, and gaps in knowledge and aims to advise which patients benefit most from the current available devices.

Is improved access to magnetic resonance imaging imperative for optimal ischemic stroke care?

Neuroimaging, including CT and MRI, is integral to ischemic stroke (IS) treatment, management, and prevention. However, the use of MRI for IS patients is limited despite its potential to provide high-quality images that yield definitive information related to the management of IS. MRI is beneficial when the information provided by CT is insufficient for decisions related to the diagnosis, etiology, or treatment of IS. In the emergency setting, MRI can improve the diagnostic accuracy of CT-negative acute ischemic strokes (AIS) and ensure a better selection of patients for reperfusion therapies with thrombolysis and/or thrombectomy. Moreover, MR imaging may help avoid hospital admissions for patients with stroke mimics, facilitate earlier discharge, and reduce overall hospital costs. MRI in the in-patient setting can help determine stroke etiology to aid in stroke prevention management upon discharge. Furthermore, early access to MRI in IS out-patients can aid in diagnosing, risk stratifying, and determining optimal management strategies for patients with a TIA or a minor stroke. Recent technological advances, particularly low-to-mid-field MR scanners, can improve access to MRI. These MR scanners provide faster protocols, cost-effectiveness, smaller footprints, safety, and lower power requirements. In conclusion, MRI use for IS treatment, management, and prevention is imperative and justifiable, and the latest technological advancements in MR scanners hold the potential to enhance access.

Factor XIa inhibition with asundexian after acute non-cardioembolic ischaemic stroke (PACIFIC-Stroke): an international, randomised, double-blind, placebo-controlled, phase 2b trial

BACKGROUND

Asundexian (Bayer AG, Leverkusen, Germany), an oral small molecule factor XIa (FXIa) inhibitor, might prevent thrombosis without increasing bleeding. Asundexian's effect for secondary prevention of recurrent stroke is unknown.

METHODS

In this randomised, double-blind, placebo-controlled, phase 2b dose-finding trial (PACIFIC-Stroke), patients with acute (within 48 h) non-cardioembolic ischaemic stroke were recruited from 196 hospitals in 23 countries. Patients were eligible if they were aged 45 years or older, to be treated with antiplatelet therapy, and able to have a baseline MRI (either before or within 72 h of randomisation). Eligible participants were randomly assigned (1:1:1:1), using an interactive web-based response system and stratified according to anticipated antiplatelet therapy (single vs dual), to once daily oral asundexian (BAY 2433334) 10 mg, 20 mg, or 50 mg, or placebo in addition to usual antiplatelet therapy, and were followed up during treatment for 26-52 weeks. Brain MRIs were obtained at study entry and at 26 weeks or as soon as possible after treatment discontinuation. The primary efficacy outcome was the dose-response effect on the composite of incident MRI-detected covert brain infarcts and recurrent symptomatic ischaemic stroke at or before 26 weeks after randomisation. The primary safety outcome was major or clinically relevant non-major bleeding as defined by International Society on Thrombosis and Haemostasis criteria. The efficacy outcome was assessed in all participants assigned to treatment, and the safety outcome was assessed in all participants who received at least one dose of study treatment. This study is registered with ClinicalTrials.gov, NCT04304508, and is now complete.

FINDINGS

Between June 15, 2020, and July 22, 2021, 1880 patients were screened and 1808 participants were randomly assigned to asundexian 10 mg (n=455), 20 mg (n=450), or 50 mg (n=447), or placebo (n=456). Mean age was 67 years (SD 10) and 615 (34%) participants were women, 1193 (66%) were men, 1505 (83%) were White, and 268 (15%) were Asian. The mean time from index stroke to randomisation was 36 h (SD 10) and median baseline National Institutes of Health Stroke Scale score was 2·0 (IQR 1·0-4·0). 783 (43%) participants received dual antiplatelet treatment for a mean duration of 70·1 days (SD 113·4) after randomisation. At 26 weeks, the primary efficacy outcome was observed in 87 (19%) of 456 participants in the placebo group versus 86 (19%) of 455 in the asundexian 10 mg group (crude incidence ratio 0·99 [90% CI 0·79-1·24]), 99 (22%) of 450 in the asundexian 20 mg group (1·15 [0·93-1·43]), and 90 (20%) of 447 in the asundexian 50 mg group (1·06 [0·85-1·32]; t statistic -0·68; p=0·80). The primary safety outcome was observed in 11 (2%) of 452 participants in the placebo group versus 19 (4%) of 445 in the asundexian 10 mg group, 14 (3%) of 446 in the asundexian 20 mg group, and 19 (4%) of 443 in the asundexian 50 mg group (all asundexian doses pooled vs placebo hazard ratio 1·57 [90% CI 0·91-2·71]).

INTERPRETATION

In this phase 2b trial, FXIa inhibition with asundexian did not reduce the composite of covert brain infarction or ischaemic stroke and did not increase the composite of major or clinically relevant non-major bleeding compared with placebo in patients with acute, non-cardioembolic ischaemic stroke.

FUNDING

Bayer AG.

Embolic infarct topology differs between atrial fibrillation subtypes and embolic stroke of undetermined source

BACKGROUND

The lack of superiority of anticoagulation over antiplatelet therapy in embolic stroke of undetermined source (ESUS) may be in part due to the misclassification of radiographic ESUS patterns as cardioembolic. In this imaging analysis, we sought to differentiate clinical and radiographic patterns of ESUS patients from patterns in patients with a highly probable cardioembolic source.

MATERIALS & METHODS

A prospective registry of consecutive adults with acute infarction on diffusion-weighted magnetic resonance imaging was queried. Patients with infarctions due to small vessel disease, large vessel disease, and other causes were excluded. Multivariable logistic regression was used to identify independent predictors of two potentially embolic patterns: (1) multifocal and (2) cortical lesions, comparing patients with ESUS against those with atrial fibrillation (AF).

RESULTS

Among 1243 screened patients, 343 (27.6%) experienced strokes due to ESUS or AF. Prior to the index stroke, patients with AF as compared to ESUS were older (median 75 vs. 65, p<0.01) and had more heart failure (25.9% vs. 8.4%, p<0.01). The odds of multifocal infarction were the same between patients with ESUS and both AF subtypes (p>0.05), however, cortical involvement was more associated with both AF versus ESUS (77.7% vs. 65.7%, P=0.02). A higher Fazekas grade of white matter disease was inversely associated with cortical infarction among included patients (aOR 0.77, 95% CI 0.62-0.96).

CONCLUSION

Cortical infarctions were twice as common among patients with AF versus ESUS. Subcortical infarct topography was strongly associated with chronic microvascular ischemic changes and therefore may not represent embolic phenomena. Larger-scale investigations are warranted to discern whether large or multifocal subcortical infarcts ought to be excluded from the ESUS designation.

Impact of Neuroimaging Patterns for the Detection of a Trial Fibrillation by Implantable Loop Recorders in Patients With Embolic Stroke of Undetermined Source

Objectives

Atrial fibrillation (AF) is a well-known etiology of embolic stroke of undetermined source (ESUS), although the optimal detection strategy of AF was not been fully evaluated yet. We assessed AF detection rate by implantable loop recorder (ILR) in patients with ESUS and compared the clinical characteristics and neuroimaging patterns between the patients with AF and AF-free patients.

Methods

We reviewed clinical characteristics and neuroimaging patterns of consecutive patients with who were admitted to our comprehensive stroke center for ESUS and underwent ILR insertion between August 1, 2019, and January 31, 202. The inclusion criteria were (1) 18 years of age or older; (2) classified as having cryptogenic stroke extracted from the group with undetermined stroke according to ESUS International Working Group; and (3) underwent ILR insertion during or after admission due to index ischemic events. Ischemic stroke pattern was classified as (1) tiny-scattered infarction, (2) whole-territorial infarction, (3) lobar infarction and (4) multiple-territorial infarction. Interrogations of data retrieved from the ILR were performed by cardiologists in every month after the implantation.

Results

In this study, 41 ESUS patients who received an ILR implantation were enrolled (mean age, 64 years; male sex, 65.9%). The rate of AF detection at 6 months was 34% (14 patients), and the mean time from ILR insertion to AF detection was 52.5 days [interquartile range (IQR), 45.0–69.5]. The median initial NIH stroke scale scores were significantly greater in patients with AF than those without AF (6.5 vs. 3.0, p = 0.019). Whole-territorial infarction pattern was significantly more frequent in patients with AF than in those without AF (64.3% vs.11.1%, p = 0.002).

Conclusions

Higher covert AF detection rates within the ESUS patients were most often associated with higher NIHSS and whole-territorial infarction patterns on brain imaging.