Microbleeds and the Effect of Anticoagulation in Patients With Embolic Stroke of Undetermined Source: An Exploratory Analysis of the NAVIGATE ESUS Randomized Clinical Trial

Importance

The reported associations of cerebral microbleeds with recurrent stroke and intracerebral hemorrhage have raised concerns regarding antithrombotic treatment in patients with a history of stroke and microbleeds on magnetic resonance imaging.

Objective

To characterize microbleeds in embolic strokes of undetermined source (ESUS) and report interactions between microbleeds and the effects of random assignment to anticoagulant vs antiplatelet therapy.

Design, Setting, and Participants

Subgroup analyses of the New Approach Rivaroxaban Inhibition of Factor Xa in a Global Trial vs Aspirin to Prevent Embolism in ESUS (NAVIGATE ESUS) international, double-blind, randomized, event-driven phase 3 clinical trial. Participants were enrolled between December 2014 and September 2017 and followed up for a median of 11 months. The study setting included 459 stroke recruitment centers in 31 countries. Patients aged 50 years or older who had neuroimaging-confirmed ESUS between 7 days and 6 months before screening were eligible. Of these 7213 NAVIGATE ESUS participants, 3699 (51%) had information on cerebral microbleeds reported on their baseline clinical magnetic resonance imaging and were eligible for these analyses. Patients with a prior history of symptomatic intracerebral hemorrhage were excluded from the NAVIGATE ESUS trial.

Interventions

Rivaroxaban, 15 mg, compared with aspirin, 100 mg, daily.

Main Outcomes and Measures

The primary outcome was recurrent stroke. Secondary outcomes were ischemic stroke, intracerebral hemorrhage, and all-cause mortality.

Results

Microbleeds were present in 395 of 3699 participants (11%). Of patients with cerebral microbleeds, mean (SD) age was 69.5 (9.4) years, 241 were men (61%), and 201 were White (51%). Advancing age (odds ratio [OR] per year, 1.03; 95% CI, 1.01-1.04), East Asian race/ethnicity (OR, 1.57; 95% CI, 1.04-2.37), hypertension (OR, 2.20; 95% CI, 1.54-3.15), multiterritorial infarcts (OR, 1.95; 95% CI, 1.42-2.67), chronic infarcts (OR, 1.78; 95% CI, 1.42-2.23), and occult intracerebral hemorrhage (OR, 5.23; 95% CI, 2.76-9.90) were independently associated with microbleeds. The presence of microbleeds was associated with a 1.5-fold increased risk of recurrent stroke (hazard ratio [HR], 1.5; 95% CI, 1.0-2.3), a 4-fold risk of intracerebral hemorrhage (HR, 4.2; 95% CI, 1.3-13.9), a 2-fold risk of all-cause mortality (HR, 2.1; 95% CI, 1.1-4.3), and strictly lobar microbleeds with an approximately 2.5-fold risk of ischemic stroke (HR, 2.3; 95% CI, 1.3-4.3). There were no interactions between microbleeds and treatment assignments for recurrent stroke, ischemic stroke, or all-cause mortality. The HR of intracerebral hemorrhage on rivaroxaban was similar between persons with microbleeds (HR, 3.1; 95% CI, 0.3-30.0) and persons without microbleeds (HR, 3.0; 95% CI, 0.6-14.7; interaction P = .97).

Conclusions and Relevance

Microbleeds mark an increased risk of recurrent stroke, ischemic stroke, intracerebral hemorrhage, and mortality in ESUS but do not appear to influence effects of rivaroxaban on clinical outcomes.

Trial Registration

ClinicalTrials.gov Identifier: NCT02313909.

Abstract 41: Cerebral Microbleeds and the Effect of Anticoagulation on Outcomes in 3699 Patients With Embolic Strokes of Undetermined Source: An Exploratory Analysis of the NAVIGATE ESUS Trial

Background: Cerebral microbleeds (CMBs) are reported to predict recurrent stroke and antithrombotic-related intracerebral hemorrhage (ICH). We characterize CMBs in a well-defined population of embolic strokes of undetermined source (ESUS). Notably, we report for the first time interactions between CMBs and effects of random assignment to anticoagulant therapy.

Methods: Subgroup analyses of the NAVIGATE ESUS randomized trial comparing rivaroxaban 15 mg vs. aspirin 100 mg daily were performed. CMBs were rated on T2*-GRE sequences obtained at baseline MRI in 3699 participants (mean age 67y). Multivariable regression analyses were used to identify variables independently associated with CMBs. Cox proportional hazards models were used to estimate the contribution of CMBs to risk of recurrent stroke, ischemic stroke, ICH and all-cause mortality. Analyses followed the intent-to-treat paradigm.

Results: CMBs were present in 11% of participants. CMBs were strictly deep in 55%, lobar in 26%, and mixed in 19% of cases. Most (68%) had 1-2 CMBs, 27% had 3-10, and 5% >10. Advancing age (OR per yr 1.0, 95% CI 1.01-1.04), East Asian ethnicity (1.6, 1.0-2.4), hypertension (2.2, 1.5-3.2), multi-territorial ESUS (2.0, 1.4-2.7), chronic infarcts (1.8, 1.4-2.2), and occult ICH (5.2, 2.8-9.9) were independently associated with CMBs. During a median follow-up of 11 months, 5.1% of participants had recurrent stroke (4.8% ischemic stroke; 0.3% ICH) and 1.3% died. The presence of CMBs was associated with a 50% increased risk of recurrent stroke (HR 1.5, 95% CI 1.0-2.3), four-fold risk of ICH (4.2, 1.3-13.9), and two-fold risk of all-cause mortality (2.1, 1.1-4.3), and strictly lobar CMBs with a ~2.5-fold risk of ischemic stroke (2.3, 1.3-4.3). There were no interactions between CMBs and treatment assignments for recurrent stroke (p-value for interaction=0.2), ischemic stroke (p=0.3), or all-cause mortality (p=0.6). The hazard ratio (HR) of ICH on rivaroxaban was similar between persons with CMBs (HR 3.1, 95% CI 0.3 - 30.0) and persons without CMBs (HR 3.0, 95% CI 0.6 - 14.7; interaction p=1.0).

Conclusions: CMBs mark an increased risk of recurrent ischemic stroke, ICH and mortality in ESUS, but do not appear to influence effects of rivaroxaban, particularly on the outcome of ICH.

Rivaroxaban or aspirin for patent foramen ovale and embolic stroke of undetermined source: a prespecified subgroup analysis from the NAVIGATE ESUS trial

BACKGROUND

Patent foramen ovale (PFO) is a contributor to embolic stroke of undetermined source (ESUS). Subgroup analyses from previous studies suggest that anticoagulation could reduce recurrent stroke compared with antiplatelet therapy. We hypothesised that anticoagulant treatment with rivaroxaban, an oral factor Xa inhibitor, would reduce the risk of recurrent ischaemic stroke compared with aspirin among patients with PFO enrolled in the NAVIGATE ESUS trial.

METHODS

NAVIGATE ESUS was a double-blinded, randomised, phase 3 trial done at 459 centres in 31 countries that assessed the efficacy and safety of rivaroxaban versus aspirin for secondary stroke prevention in patients with ESUS. For this prespecified subgroup analysis, cohorts with and without PFO were defined on the basis of transthoracic echocardiography (TTE) and transoesophageal echocardiography (TOE). The primary efficacy outcome was time to recurrent ischaemic stroke between treatment groups. The primary safety outcome was major bleeding, according to the criteria of the International Society of Thrombosis and Haemostasis. The primary analyses were based on the intention-to-treat population. Additionally, we did a systematic review and random-effects meta-analysis of studies in which patients with cryptogenic stroke and PFO were randomly assigned to receive anticoagulant or antiplatelet therapy.

FINDINGS

Between Dec 23, 2014, and Sept 20, 2017, 7213 participants were enrolled and assigned to receive rivaroxaban (n=3609) or aspirin (n=3604). Patients were followed up for a mean of 11 months because of early trial termination. PFO was reported as present in 534 (7·4%) patients on the basis of either TTE or TOE. Patients with PFO assigned to receive aspirin had a recurrent ischaemic stroke rate of 4·8 events per 100 person-years compared with 2·6 events per 100 person-years in those treated with rivaroxaban. Among patients with known PFO, there was insufficient evidence to support a difference in risk of recurrent ischaemic stroke between rivaroxaban and aspirin (hazard ratio [HR] 0·54; 95% CI 0·22-1·36), and the risk was similar for those without known PFO (1·06; 0·84-1·33; p_interaction=0·18). The risks of major bleeding with rivaroxaban versus aspirin were similar in patients with PFO detected (HR 2·05; 95% CI 0·51-8·18) and in those without PFO detected (HR 2·82; 95% CI 1·69-4·70; p_interaction=0·68). The random-effects meta-analysis combined data from NAVIGATE ESUS with data from two previous trials (PICSS and CLOSE) and yielded a summary odds ratio of 0·48 (95% CI 0·24-0·96; p=0·04) for ischaemic stroke in favour of anticoagulation, without evidence of heterogeneity.

INTERPRETATION

Among patients with ESUS who have PFO, anticoagulation might reduce the risk of recurrent stroke by about half, although substantial imprecision remains. Dedicated trials of anticoagulation versus antiplatelet therapy or PFO closure, or both, are warranted.

FUNDING

Bayer and Janssen.

Cellular distribution of exogenous aprotinin in the rat kidney

Aprotinin, an inhibitor of the enzymatic activity of kallikrein in vitro, has been used to study the possible contributions of the kallikrein-kinin systems to physiological and pathological conditions. Pharmacokinetic studies indicate that aprotinin is concentrated in the kidney; however, there is little information with regard to its cellular distribution. The purpose of the present work was to study the cellular distribution of aprotinin, which would be valuable for a better understanding of its intrarenal effects. Sprague-Dawley rats (200-250g, n = 36) received aprotinin (50000 KIU/rat) and were killed at different intervals after its administration. The kidneys were examined histologically and the cellular distribution of aprotinin was studied by immunohistochemistry. Aprotinin was localized at 30 min concentrated within vesicles in the apical border of the proximal tubule cells. Later (2 h) it was observed distributed over the cytoplasm, where it remained for the 24 h studied. Aprotinin was also detected in connecting tubule cells colocalized with kallikrein, and in the basal portion of collecting tubule cells. No evidence of endogenous aprotinin was observed. The binding of aprotinin to the connecting tubule cells and collecting ducts offers a partial explanation of its renal effects.