Evaluation of Cryptogenic Stroke With Advanced Diagnostic Techniques

High CD3+ Cells in Intracranial Thrombi Represent a Biomarker of Atherothrombotic Stroke

Background and Purpose

Approximately 30% of strokes are cryptogenic despite an exhaustive in-hospital work-up. Analysis of clot composition following endovascular treatment could provide insight into stroke etiology. T-cells already have been shown to be a major component of vulnerable atherosclerotic carotid lesions. We therefore hypothesize that T-cell content in intracranial thrombi may also be a biomarker of atherothrombotic origin.

Materials and Methods

We histopathologically investigated 54 consecutive thrombi retrieved after mechanical thrombectomy in acute stroke patients. First, thrombi were classified as fibrin-dominant, erythrocyte-dominant or mixed pattern. We then performed quantitative analysis of CD3+ cells on immunohistochemically-stained thrombi and compared T-cell content between “atherothrombotic”, “cardioembolism” and “other causes” stroke subtypes.

Results

Fourteen (26%) thrombi were defined as fibrin-dominant, 15 (28%) as erythrocyte-dominant, 25 (46%) as mixed. The stroke cause was defined as “atherothrombotic” in 10 (18.5%), “cardioembolism” in 25 (46.3%), and “other causes” in 19 (35.2%). Number of T-cells was significantly higher in thrombi from the “atherothrombotic” group (53.60 ± 28.78) than in the other causes (21.77 ± 18.31; p<0.0005) or the “cardioembolism” group (20.08 ± 15.66; p<0.0003).

Conclusions

The CD3+ T-cell count in intracranial thrombi was significantly higher in “atherothrombotic” origin strokes compared to all other causes. Thrombi with high content of CD3+ cells are more likely to originate from an atherosclerotic plaque.

An Approach to Working Up Cases of Embolic Stroke of Undetermined Source

Background

From a therapeutic viewpoint, it is important to differentiate the underlying causes of embolism in patients with cryptogenic stroke, such as aortic arch atheroma, patent foramen ovale, and paroxysmal atrial fibrillation. We investigated the clinical and radiological characteristics of these 3 common causes of cryptogenic embolism to develop models for decision making in etiologic workups.

Methods and Results

A total of 321 consecutive patients with acute infarcts from cryptogenic embolism were included. Patients were divided into 3 groups—aortic arch atheroma (n=40), patent foramen ovale (n=153), and paroxysmal atrial fibrillation (n=128)—based on extensive cardiologic workups. We used a multinomial logistic regression analysis to detect the clinical and diffusion‐weighted imaging factors associated with the probability of aortic arch atheroma, patent foramen ovale, and paroxysmal atrial fibrillation. Clinical and radiological features differed among the groups. The patent foramen ovale group had a healthy vascular risk factor profile and showed posterior circulation involvement compared with other groups (P<0.01). In contrast, paroxysmal atrial fibrillation–related strokes had higher initial National Institutes of Health Stroke Scale (NIHSS) scores and larger lesions than the other groups (P<0.001). The aortic arch atheroma group had clinical features similar to those of the paroxysmal atrial fibrillation group but showed small lesions scattered in multiple vascular territories (P<0.001). Multivariate regression analysis revealed that age, initial NIHSS score, lesion size (≥20 mm), multiple (≥3) lesions, and involvement of posterior circulation or multiple vascular territories differentiated the 3 groups (pseudo, R²=0.656). The prediction ability of this model was validated in the external validation cohort (n=117, area under the curve 0.78).

Conclusions

Our data indicate that patients with cryptogenic embolic stroke show distinct clinical and radiological features depending on the underlying causes.

Ischemic stroke in the young: Current perspectives on incidence, risk factors, and cardiovascular prognosis

About one-fourth of ischemic strokes occur in working-aged individuals in the high-income countries, with worldwide increasing incidence in this age group from 1980s to present. Recent evidence suggests that traditional vascular risk factors are more prevalent than previously suggested in young adult stroke patients and they accumulate with age particularly in men. Accordingly, relatively high rates of atherosclerotic changes have been detected in these patients. The strength of association of vascular risk factors has gone poorly studied, however. Many young patients with ischemic stroke have, in turn, no traditional risk factors, while they may harbor other conditions with weak or uncertain association with the stroke alone. These individual conditions often represent a risk factor that may be strictly young-age specific, more prevalent in younger than older stroke patients (e.g. patent foramen ovale), or more prevalent among the young in the population. Despite high rates of vascular risk factors and atherosclerotic changes, these findings do not translate to higher frequencies of identified classical stroke mechanisms. In fact, cryptogenic causes are markedly common and even more frequent among the very young patients. Limited randomized trial evidence exists to support secondary prevention decision-making in patients, yet they face an increased risk of death and future vascular events for years to come-dependent on risk factor profile and cause of the stroke. This review provides an overview of recent data on epidemiology, risk factors, and their strength of association in ischemic stroke in the young. Furthermore, the relationship between with the risk factors and cardiovascular outcomes and key features on the evidence related to secondary prevention will be discussed.

Considerations When Subtyping Ischemic Stroke in Asian Patients

Both the incidence and prevalence of stroke in Asia are steadily increasing, and the burden of stroke is particularly high in Asian countries. Although strokes in Asians and Caucasians share many common features, there are some differences that are probably due to differences in lifestyle and genetic background. While there have been advances in the stroke classification system, the assignment of Asian stroke patients to etiological categories has received little attention. The current classification system may not be well suited to Asian patients with ischemic stroke because the proportions and relative importance of stroke subtypes may differ with race and ethnicity. This review addresses concerns about the use of the current stroke classification system in Asian patients with ischemic stroke, and proposes a classification system that is more specific to the Asian population, in conjunction with discussing advances in diagnostic techniques.

Cost-effectiveness of an insertable cardiac monitor to detect atrial fibrillation in patients with cryptogenic stroke

Background and aims

Documentation of atrial fibrillation is required to initiate oral anticoagulation therapy for recurrent stroke prevention. Atrial fibrillation often goes undetected with traditional electrocardiogram monitoring techniques. We evaluated whether atrial fibrillation detection using continuous long-term monitoring with an insertable cardiac monitor is cost-effective for preventing recurrent stroke in patients with cryptogenic stroke, in comparison to the standard of care.

Methods

A lifetime Markov model was developed to estimate the cost-effectiveness of insertable cardiac monitors from a UK National Health Service perspective using data from the randomized CRYSTAL-AF trial and other published literature. We also conducted scenario analyses (CHADS2 score) and probabilistic sensitivity analyses. All costs and benefits were discounted at 3.5%.

Results

Monitoring cryptogenic stroke patients with an insertable cardiac monitor was associated with fewer recurrent strokes and increased quality-adjusted life years compared to the standard of care (7.37 vs 7.22). Stroke-related costs were reduced in insertable cardiac monitor patients, but overall costs remained higher than the standard of care (£19,631 vs £17,045). The incremental cost-effectiveness ratio was £17,175 per quality-adjusted life years gained, compared to standard of care in the base-case scenario, which is below established quality-adjusted life years willingness-to-pay thresholds. When warfarin replaced non-vitamin-K oral anticoagulants as the main anticoagulation therapy, the incremental cost-effectiveness ratio was £13,296 per quality-adjusted life years gained.

Conclusion

Insertable cardiac monitors are a cost-effective diagnostic tool for the prevention of recurrent stroke in patients with cryptogenic stroke. The cost-effectiveness results have relevance for the UK and across value-based healthcare systems that assess costs relative to outcomes.

Atrial Fibrillation Monitoring in Cryptogenic Stroke: the Gaps Between Evidence and Practice

Identifying occult paroxysmal atrial fibrillation as the etiology of cryptogenic stroke has been a top research priority in the past decade. This is because prompt initiation of anticoagulation has significantly decreased subsequent stroke risk. Available evidence suggests that prolonged cardiac monitoring after stroke increases the likelihood of detecting atrial fibrillation. However, further research is required to fill in the gaps in regard to the optimal period of monitoring, candidates for monitoring, etc. Here, we review the current evidence supporting the use of prolonged monitoring for cryptogenic stroke patients and discuss the directions of future research.

Patent Foramen Ovale and Stroke-Current Status

Patent foramen ovale (PFO) is growing in clinical interest because of a renewed focus on embolic stroke of undetermined source (ESUS), the PFO attributable fraction (the 10-point Risk of Paradoxical Embolism score), technical advances in PFO diagnosis, and the emergence of endovascular device closure as a treatment option. However, recent randomized controlled trials of the management of patients with ESUS and PFO failed to demonstrate the superiority of closure over medical treatment. The mechanisms of stroke other than paradoxical embolism may be important in patients with ESUS and PFO. This paper reviews the current understanding of the pathophysiology of stroke and therapeutic options in patients with PFO and ESUS.

Differential Vascular Pathophysiologic Types of Intracranial Atherosclerotic Stroke: A High-Resolution Wall Magnetic Resonance Imaging Study

BACKGROUND AND PURPOSE

Intracranial atherosclerotic stroke (ICAS) has various stroke mechanisms, including branch occlusive disease (BOD), subcortical infarcts caused by parent arterial disease occluding the perforator's orifice, and non-BOD, infarcts beyond the subcortical area caused by artery-to-artery embolism. To test whether these 2 types of ICAS had different vascular pathophysiologies, we compared the high-resolution magnetic resonance imaging characteristics between BOD and non-BOD ICAS.

METHODS

Eighty patients with acute infarcts caused by ICAS of proximal middle cerebral artery or basilar artery without carotid/cardiac embolic sources or nonatherosclerotic causes were enrolled (36 BOD and 44 non-BOD patients). The steno-occlusive intracranial artery at the maximal stenosis was analyzed for vascular remodeling and wall enhancement.

RESULTS

BOD had distinct radiological features in terms of vascular morphology and enhancement. BOD showed a milder stenosis than non-BOD (P<0.001). Positive remodeling was more frequently observed in non-BOD than in BOD (P=0.005). Wall area index was also lower in BOD. Plaque enhancement was observed in all but one non-BOD patient and in one fourth of BOD patients (P=0.003). Although both types showed an eccentric enhancement, this enhancement was more frequently distributed in the BOD group on the side where the perforators arose. As the number of asymptomatic intracranial stenosis increased, the degree of stenosis (rho=0.513, P=0.003) increased in the BOD group, whereas enhanced plaque area (rho=0.343, P=0.030) increased in the non-BOD group.

CONCLUSIONS

Our data indicate that BOD is a common and unique form of ICAS, distinct from non-BOD. These 2 types of ICAS have different vascular pathophysiologies in terms of vascular remodeling and plaque characteristics.

Incidence and mortality of ischemic stroke subtypes in Joinville, Brazil: a population-based study

Aims To measure the incidence and mortality rates of ischemic stroke (IS) subtypes in Joinville, Brazil. Methods All first-ever IS patients that occurred in Joinville from January 2005 to December 2006 were identified. The IS subtypes were classified by the TOAST criteria, and the patients were followed-up for one year after IS onset. Results The age-adjusted incidence per 100,000 inhabitants was 26 (17-39) for large-artery atherosclerosis (LAA), 17 (11-27) for cardioembolic (CE), 29 (20-41) for small vessel occlusion (SVO), 2 (0.6-7) for stroke of other determined etiology (OTH) and 30 (20-43) for stroke of undetermined etiology (UND). The 1-year mortality rate per 100,000 inhabitants was 5 (2-11) for LAA, 6 (3-13) for CE, 1 (0.1-6) for SVO, 0.2 (0-0.9) for OTH and 9 (4-17) for UND. Conclusion In the population of Joinville, the incidences of IS subtypes were similar to those found in other populations. These findings highlight the importance of better detection and control of atherosclerotic risk factors.

Risk factors, aetiology and outcome of ischaemic stroke in young adults: the Swiss Young Stroke Study (SYSS)

Ischaemic stroke (IS) in young adults has been increasingly recognized as a serious health condition. Stroke aetiology is different in young adults than in the older population. This study aimed to investigate aetiology and risk factors, and to search for predictors of outcome and recurrence in young IS patients. We conducted a prospective multicentre study of consecutive IS patients aged 16-55 years. Baseline demographic data, risk factors, stroke aetiology including systematic genetic screening for Fabry disease and severity were assessed and related to functional neurological outcome (modified Rankin Scale, mRS), case fatality, employment status, place of residence, and recurrent cerebrovascular events at 3 months. In 624 IS patients (60% men), median age was 46 (IQR 39-51) years and median NIHSS on admission 3 (IQR 1-8). Modifiable vascular risk factors were found in 73%. Stroke aetiology was mostly cardioembolism (32%) and of other defined origin (24%), including cervicocerebral artery dissection (17%). Fabry disease was diagnosed in 2 patients (0.3%). Aetiology remained unknown in 20%. Outcome at 3 months was favourable (mRS 0-1) in 61% and fatal in 2.9%. Stroke severity (p < 0.001) and diabetes mellitus (p = 0.023) predicted unfavourable outcome. Stroke recurrence rate at 3 months was 2.7%. Previous stroke or TIA predicted recurrent cerebrovascular events (p = 0.012). In conclusion, most young adults with IS had modifiable vascular risk factors, emphasizing the importance of prevention strategies. Outcome was unfavourable in more than a third of patients and was associated with initial stroke severity and diabetes mellitus. Previous cerebrovascular events predicted recurrent ones.

Global Survey of the Diagnostic Evaluation and Management of Cryptogenic Ischemic Stroke

Background

About 25% of ischemic strokes are categorized as cryptogenic (i.e. of unknown cause), but few data exist about the extent of diagnostic testing or treatment. We undertook an international survey to characterize current diagnostic evaluation and antithrombotic management of patients with cryptogenic ischemic stroke in 2014.

Aims/Hypothesis

To determine the type of diagnostic evaluation undertaken for cryptogenic ischemic stroke and antithrombotic management and to compare across global regions.

Methods

An 18-question online survey was sent to 995 physicians involved in stroke care in 61 countries. Countries were separated into World Bank global regions and income groups. Diagnostic tests were considered routine if performed in >75% of patients at a center.

Results

Three hundred one completed surveys were received from 48 countries (response rate ∼30%). The majority (82%) of hospitals were from high-income countries and mainly from Europe and Central Asia (56%) and North America (19%). For ischemic stroke patients, magnetic resonance imaging is routinely obtained at 36% of hospitals (highest in North America, 58%). Among cryptogenic stroke patients, transesophageal echocardiography is routinely performed in 17% of hospitals. More than 24 hour cardiac rhythm monitoring is done routinely at relatively few (17%) hospitals (highest in North America, 33%). Intracranial arterial imaging is done routinely at 70% of hospitals, with no significant regional differences. Antiplatelet therapies are routinely prescribed for secondary prevention at 94% of hospitals.

Conclusions

Based on self-selected respondents from a large number of international stroke centers, transesophageal echocardiography and prolonged (>24 h) cardiac rhythm monitoring are not routinely performed in cryptogenic stroke patients, even in high-income countries. Antiplatelet therapy is the global standard for secondary prevention of cryptogenic stroke.

Undetermined stroke with an embolic pattern--a common phenotype with high early recurrence risk

INTRODUCTION

Undetermined strokes with an embolic pattern (USEP) represent a common phenotype. We assessed their frequency and compared USEP with cardioembolic stroke with a known source and non-cardioembolic stroke etiology.

METHODS

Study patients were 540 consecutive ischemic stroke patients admitted to Helsinki University Hospital with primary end-point of recurrent stroke in a 21-month follow-up. Cox regression adjusting for CHA2DS2-VASc and anticoagulation estimated the risk of USEP on recurrent stroke.

RESULTS

A total of 229 (42.4%) patients had a non-cardioembolic stroke etiology, 184 (34.1%) had a cardioembolic stroke with a known source, and 127 (23.5%) were classified as USEP. USEP patients had less diabetes and prior TIA, with more severe symptoms than the non-cardioembolic stroke cases. They were younger, had fewer comorbidities, and less severe symptoms than the cardioembolic stroke patients. Cumulative risk of recurrent stroke was 10.0% (95% CI 4.1%-15.9%) for USEP, 5.0% (1.1%-8.9%) for cardioembolic strokes, and 5.0% (3.0%-7.0%) for non- cardioembolic strokes (P = 0.089). USEP associated with a higher risk of recurrent stroke compared to non-cardioembolic strokes (hazard ratio 2.36, 95% CI 1.02-5.47; P = 0.046) and cardioembolic stroke with a known source (1.83, 1.07-3.14; P = 0.028).

CONCLUSIONS

Despite their younger age and more favorable risk factor profile compared with other phenotypes, USEP exhibited a high risk of stroke recurrence.

MRI-based Algorithm for Acute Ischemic Stroke Subtype Classification

Background and Purpose

In order to improve inter-rater reliability and minimize diagnosis of undetermined etiology for stroke subtype classification, using a stroke registry, we developed and implemented a magnetic resonance imaging (MRI)-based algorithm for acute ischemic stroke subtype classification (MAGIC).

Methods

We enrolled patients who experienced an acute ischemic stroke, were hospitalized in the 14 participating centers within 7 days of onset, and had relevant lesions on MR-diffusion weighted imaging (DWI). MAGIC was designed to reflect recent advances in stroke imaging and thrombolytic therapy. The inter-rater reliability was compared with and without MAGIC to classify the Trial of Org 10172 in Acute Stroke Treatment (TOAST) of each stroke patient. MAGIC was then applied to all stroke patients hospitalized since July 2011, and information about stroke subtypes, other clinical characteristics, and stroke recurrence was collected via a web-based registry database.

Results

The overall intra-class correlation coefficient (ICC) value was 0.43 (95% CI, 0.31-0.57) for MAGIC and 0.28 (95% CI, 0.18-0.42) for TOAST. Large artery atherosclerosis (LAA) was the most common cause of acute ischemic stroke (38.3%), followed by cardioembolism (CE, 22.8%), undetermined cause (UD, 22.2%), and small-vessel occlusion (SVO, 14.6%). One-year stroke recurrence rates were the highest for two or more UDs (11.80%), followed by LAA (7.30%), CE (5.60%), and SVO (2.50%).

Conclusions

Despite several limitations, this study shows that the MAGIC system is feasible and may be helpful to classify stroke subtype in the clinic.

How predictors and patterns of stroke recurrence after a TIA differ during the first year of follow-up

The highest risk of subsequent stroke after a TIA occurs within the first week after the index event. However, the risk of stroke recurrence (SR) remains high during the first year of follow-up. We studied the temporal pattern and predictors of SR (at 7 days and from 7 days to 1-year follow-up). Between April 2008 and December 2009, we included 1,255 consecutive TIA patients from 30 Spanish stroke centers (PROMAPA study). We determined the short-term (at 7 days) and long-term (from 8 days to 1 year) risk of SR. Patients who underwent short-term recurrence and long-term recurrence were compared with regard to clinical findings, vascular territories, and etiology. Enough information (clinical variables and extracranial vascular imaging) was assessed in 1,137 (90.6 %) patients. The 7-day stroke risk was 2.6 %. 32 (3.0 %) patients had an SR after 7-day follow-up. Multiple TIA (HR 3.50, 1.67-7.35, p = 0.001) and large artery atherosclerosis (HR 2.51, 1.17-5.37, p = 0.018) were independent predictors of early SR, whereas previous stroke (HR 1.40, 1.03-1.92, p = 0.034) and coronary heart disease (2.65, 1.28-5.50, p = 0.009) were independent predictors of late SR. Notoriously, 80 % of SR happened in the same territory of the index TIA at 7-day follow-up, whereas only 38 % during the long-term follow-up (p < 0.001). Different predictors of SR were identified throughout the follow-up period. Moreover, the ischemic mechanism differed in early and late stroke recurrences.