Ischemic Stroke Phenotype in Patients With Nonsustained Atrial Fibrillation

Imaging features for the identification of atrial fibrillation in cryptogenic stroke patients

BACKGROUND

Whether specific imaging aspects can be used to identify cryptogenic stroke (CS) patients with high risk of underlying atrial fibrillation (AF) remains unclear. The purpose of this study was to evaluate brain-imaging features in CS patients and their utility as AF predictors.

METHODS

The Nordic Atrial Fibrillation and Stroke study was a prospective observational study of CS and transient ischemic attack patients undergoing 12-month cardiac-rhythm monitoring, biomarker and clinical assessments. In this imaging sub-study, brain magnetic resonance imaging and computed tomography scans from 106 patients were assessed for acute and chronic ischemic lesions in relation to AF occurrence and included in a score to predict AF. Receiver operating characteristics (ROC) curve was used to evaluate the discriminative ability of the score and for its dichotomization for predictive model.

RESULTS

Age, periventricular white-matter hyperintensities (PVWMH), acute lesion size, and vessel occlusion were significantly associated with AF. Acute and chronic cortical infarcts as well as chronic cerebellar infarcts were numerically more frequent in the AF group than the non-AF group. A score consisting of six features (0-6 points) was proposed (age ≥ 65 years, chronic cortical or cerebellar lesions, acute cortical lesions, PVWMH ≥ 2 in Fazekas scale, vessel occlusion, and acute lesion size ≥ 10 mm). Area under ROC curve was 0.735 and a score of ≥ 3 points was a predictor of AF.

CONCLUSIONS

The suggested score was shown to identify CS patients with an increased risk of underlying AF.

Detection of Non-Sustained Supraventricular Tachycardia in Atrial Fibrillation Screening

OBJECTIVE

Non-sustained supraventricular tachycardia (nsSVT) is associated with a higher risk of developing atrial fibrillation (AF), and, therefore, detection of nsSVT can improve AF screening efficiency. However, the detection is challenged by the lower signal quality of ECGs recorded using handheld devices and the presence of ectopic beats which may mimic the rhythm characteristics of nsSVT.

METHODS

The present study introduces a new nsSVT detector for use in single-lead, 30-s ECGs, based on the assumption that beats in an nsSVT episode exhibits similar morphology, implying that episodes with beats of deviating morphology, either due to ectopic beats or noise/artifacts, are excluded. A support vector machine is used to classify successive 5-beat sequences in a sliding window with respect to similar morphology. Due to the lack of adequate training data, the classifier is trained using simulated ECGs with varying signal-to-noise ratio. In a subsequent step, a set of rhythm criteria is applied to similar beat sequences to ensure that episode duration and heart rate is acceptable.

RESULTS

The performance of the proposed detector is evaluated using the StrokeStop II database, resulting in sensitivity, specificity, and positive predictive value of 84.6%, 99.4%, and 18.5%, respectively.

CONCLUSION

The results show that a significant reduction in expert review burden (factor of 6) can be achieved using the proposed detector.Clinical and Translational Impact: The reduction in the expert review burden shows that nsSVT detection in AF screening can be made considerably more efficiently.

Atrial fibrillation and stroke: State-of-the-art and future directions

Atrial fibrillation (AF) and stroke remain a major cause of morbidity and mortality. The two conditions shared common co-morbidities and risk factors. AF-related strokes are associated with worse clinical outcomes and higher mortality compared to non-AF-related. Early detection of AF is vital for prevention. While various scores have been developed to predict AF in such a high-risk group, they are yet to incorporated into clinical guidelines. Novel markers and predictors of AF including coronary and intracranial arterial calcification have also been studied. There are also ongoing debates on the management of acute stroke in patients with AF, and those who experienced breakthrough stroke while on oral anticoagulants. We provided an overview of the complex interplay between AF and stroke, as well as the treatment and secondary prevention of stroke in AF. We also comprehensively discussed the current evidence and the ongoing conundrums, and highlighted the future directions on the topic.

Decreased longitudinal systolic strain rate of the left atrial myocardium as one of the earliest markers of atrial cardiomyopathy in subjects with brief paroxysmal atrial fibrillation

PURPOSE

Brief paroxysmal atrial fibrillation (BPAF) is defined as episodes of atrial fibrillation (AF) lasting less than 30 seconds and can be a sign of atrial cardiomyopathy. We aimed to evaluate left atrial (LA) function in patients with BPAF.

METHODS

This cross-sectional prospective study consecutively recruited 42 patients with BPAF on 24 to 48 hour electrocardiography Holter monitoring. We selected 50 volunteers as the control group after 24 hours electrocardiography Holter monitoring. Two-dimensional speckle-tracking echocardiography was performed to evaluate the longitudinal deformation variables of LA function.

RESULTS

Strain rate during LA reservoir phase was lower (P = .018) in patients with BPAF (2.0 ± 0.4 second^-1 ) than in controls (2.2 ± 0.5 second^-1 ). This difference remained significant after adjustments for left ventricular ejection fraction, LA maximal volume, and diabetes (β = 0.222, P = .036). Strain during LA reservoir, conduit, and contraction phases and strain rate during the conduit and contraction phases were not significantly different between the two groups.

CONCLUSIONS

The reservoir function of the LA evaluated by two-dimensional speckle-tracking echocardiography was lower in subjects than that without BPAF.

Ischemic Stroke in a Patient With Atrial Tachycardia, Methylenetetrahydrofolate Reductase Mutation and New-Onset Atrial Fibrillation: Is Early Initiation of Anticoagulation Therapy Indicated?

Atrial fibrillation is the most common dysrhythmia, affecting about 6 million people in the United States. Atrial fibrillation has been shown to be an independent risk factor for stroke. Atrial tachycardia are common findings on Holter monitoring in the general population and may be associated with the development of atrial remodeling and atrial fibrillation inducibility. Studies have shown that atrial tachycardia is associated with the development of atrial fibrillation and subsequent stroke. The American Heart Association current guidelines recommend the use of oral anticoagulants in patients with atrial fibrillation and an elevated CHA2DS2-VASc ≥2 in men or ≥3 in women. However, anticoagulant therapy is not currently recommended in patients with atrial tachycardia despite increasing evidence of its association with the development of stroke. We report the case of a 68-year-old woman with a past medical history significant for repetitive atrial tachycardia and methylenetetrahydrofolate reductase mutation who presented to an outside emergency department following a fall, weakness and associated aphasia while in atrial fibrillation. Thrombolysis and control of the patient's rhythm resulted in an initial improvement in the patient symptoms and reversal to normal sinus rhythm. She was subsequently referred to a tertiary stroke center for further management.

Diagnostic accuracy of acute infarcts in multiple cerebral circulations for cardioembolic stroke: Literature review and meta-analysis

OBJECTIVE

To determine the diagnostic value of acute infarcts in multiple cerebral circulations (AIMCC) on MRI diffusion-weighted imaging (DWI) for cardioembolism (CE) stroke subtype in adult patients hospitalized with acute ischemic stroke, we conducted a systematic literature review and meta-analysis.

METHODS

MEDLINE was searched via PubMed for articles reporting patients hospitalized with acute ischemic stroke with MRI DWI categorized as AIMCC vs other and use of Trial of Org 10172 in Acute Stroke Treatment (TOAST) Criteria for cardioembolism subtype. Measures of diagnostic accuracy were calculated from the retrieved studies.

RESULTS

Seven eligible articles comprised 5813 patients. Bivariate random effects models estimated sensitivity 0.19 (95% CI, 0.13 to 0.27), specificity 0.89 (0.86 to 0.91), positive predictive value 0.37 (0.30 to 0.45), negative predictive value 0.76 (0.7 to 0.82), positive likelihood ratio 1.70 (1.13 to 2.57) and negative likelihood ratio 0.91 (0.83 to 1).

INTERPRETATION

The pattern of AIMCC on DWI is of limited diagnostic value. It is not sufficiently accurate to exclude cardiac pathology by a negative test nor does a positive test indicate a major increase in the probability of identifying a potential cardioembolic source.

The Relationship between Diffusion-Weighted Magnetic Resonance Imaging Lesions and 24-Hour Rhythm Holter Findings in Patients with Cryptogenic Stroke

BACKGROUND AND OBJECTIVES

Cranial magnetic resonance imaging findings of patients considered to be cryptogenic stroke may be useful in determining the clinical and prognostic significance of arrhythmias, such as atrial premature beats and atrial run attacks, that are frequently encountered in rhythm Holter analysis. This study was conducted to investigate the relationship between short atrial runs and frequent premature atrial contractions detected in Holter monitors and infarct distributions in cranial magnetic resonance imaging of patients diagnosed with cryptogenic stroke.

MATERIALS AND METHODS

We enrolled the patients with acute ischemic stroke whose etiology were undetermined. We divided the patients in two groups according to diffusion-weighted magnetic resonance imaging as single or multiple vascular territory acute infarcts. The demographic, clinical, laboratory, echocardiographic, and rhythm Holter analyses were compared.

RESULTS

The study investigated 106 patients diagnosed with cryptogenic stroke. Acute cerebral infarctions were detected in 31% of the investigated patients in multiple territories and in 69% in a single territory. In multivariate logistic regression analysis, the total premature atrial contraction count (OR = 1.002, 95% CI: 1.001⁻1.004, p = 0.001) and short atrial run count (OR = 1.086, 95% CI: 1.021⁻1.155, p = 0.008) were found as independent variables that could distinguish between infarctions in a single or in multiple vascular territories.

CONCLUSIONS

Rhythm Holter monitoring of patients with infarcts detected in multiple vascular territories showed significantly higher premature atrial contractions and short atrial run attacks. More effort should be devoted to the identification of cardioembolic etiology in cryptogenic stroke patients with concurrent acute infarcts in the multiple vascular territories of the brain.

Frequency and features of embolic stroke of undetermined source in young adults

INTRODUCTION

The sources of emboli in those with embolic stroke of undetermined source may differ in old and young. We assessed the frequency, features and potential embolic sources of younger vs. older embolic stroke of undetermined source patients in the embolic stroke of undetermined source Global Registry.

PATIENTS AND METHODS

Cross-sectional study of consecutive patients over age 18 years, with recent ischaemic strokes at 19 centres conducted in 2013-2014. Characteristics of embolic stroke of undetermined source patients who aged ≤50 years were analysed and compared with embolic stroke of undetermined source patients who aged >50 years.

RESULTS

Among 2144 patients with ischaemic stroke, 323 (15.1%, 95% confidence interval: 13.6-16.7%) were ≤50 years old and, 1821 >50 years. 24% (n = 78) of young vs. 15% (n = 273) of older patients met embolic stroke of undetermined source criteria. The mean age of young embolic stroke of undetermined source patients was 40 years (standard deviation +/-9), 33% were women and the most prevalent vascular risk factor was hypertension (38%). Conventional vascular risk factors were less frequent in younger embolic stroke of undetermined source patients. Fewer young embolic stroke of undetermined source patients (63%) had potential minor risk embolic sources identified vs. older embolic stroke of undetermined source patients (77%) (p = 0.02). Stroke severity on admission was similar in younger vs. older patients (National Institute of Health Stroke Scale (NIHSS) 3 vs. 4, p = 0.06).

DISCUSSION

Young embolic stroke of undetermined source patients comprise an important subset of ischaemic stroke patients around the world. Severity of stroke on admission and 30-day mortality rates are similar among young and older patients. However, there are important differences between younger vs. older embolic stroke of undetermined source patients with respect to risk factors, and potential embolic sources that could affect response to anticoagulants vs. antiplatelet therapies.

CONCLUSION

This study provides a benchmark for the global frequency and characteristics of young embolic stroke of undetermined source patients and shows consistent high frequency of embolic stroke of undetermined source in young adults.

Towards phenotyping stroke: Leveraging data from a large-scale epidemiological study to detect stroke diagnosis

Objective

1) To develop a machine learning approach for detecting stroke cases and subtypes from hospitalization data, 2) to assess algorithm performance and predictors on real-world data collected by a large-scale epidemiology study in the US; and 3) to identify directions for future development of high-precision stroke phenotypic signatures.

Materials and methods

We utilized 8,131 hospitalization events (ICD-9 codes 430–438) collected from the Greater Cincinnati/Northern Kentucky Stroke Study in 2005 and 2010. Detailed information from patients’ medical records was abstracted for each event by trained research nurses. By analyzing the broad list of demographic and clinical variables, the machine learning algorithms predicted whether an event was a stroke case and, if so, the stroke subtype. The performance was validated on gold-standard labels adjudicated by stroke physicians, and results were compared with stroke classifications based on ICD-9 discharge codes, as well as labels determined by study nurses.

Results

The best performing machine learning algorithm achieved a performance of 88.57%/93.81%/92.80%/93.30%/89.84%/98.01% (accuracy/precision/recall/F-measure/area under ROC curve/area under precision-recall curve) on stroke case detection. For detecting stroke subtypes, the algorithm yielded an overall accuracy of 87.39% and greater than 85% precision on individual subtypes. The machine learning algorithms significantly outperformed the ICD-9 method on all measures (P value<0.001). Their performance was comparable to that of study nurses, with better tradeoff between precision and recall. The feature selection uncovered a subset of predictive variables that could facilitate future development of effective stroke phenotyping algorithms.

Discussion and conclusions

By analyzing a broad array of patient data, the machine learning technologies held promise for improving detection of stroke diagnosis, thus unlocking high statistical power for subsequent genetic and genomic studies.

Holter Monitorisation Results in Early Period of Acute Ischemic Stroke

Introduction

Paroxysmal atrial fibrillation (PAF) has a similar risk with persistent AF for ischemic stroke. Holter monitorization (HM) and other long-term monitorization methods increased the detection of PAF and short-lasting runs of tachyarrhythmias. Their classification as PAF and roles in the etiology of ischemic stroke is controversial. In this study, we aimed to investigate the frequency of any duration of PAF and clinical characteristics of the patients with acute ischemic stroke who have undergone 24-hrs HM.

Methods

Patients with acute ischemic stroke and transient ischemic attack (TIA) hospitalized in the Neurology ward and undergone 24-hrs of HM during their hospital stay were included in the study. HM reports, clinical, and laboratory characteristics were analyzed, retrospectively. Patients were grouped into three based on HM: 1st group, without PAF; 2nd group, PAF >30 seconds (s) and 3rd group, PAF<30s.

Results

PAF of any duration was detected in 18.8% (n=49) of 261 patients. The duration of PAF was <30s in 16.1% (n=42) and >30s in 2.7% (n=7) of the patients. The mean age, left atrium diameter and CHA2DS2-VASc scores of the second group were significantly higher than the first group (p<0.001, p<0.001 and p=0.007; respectively). The mean age, left atrium diameter, modified Rankin Scores (mRS), and CHA2DS2-VASc scores of the third group were significantly higher than the first group (p<0.001; for all). There was no difference between the second and the third groups in means of mean age, left atrial diameter, MRS, and CHA2DS2-VASc scores (p<0.017, for all).

Conclusion

In this study, 24-hrs HM in the early period of acute ischemic stroke results yielded a high frequency of PAF<30s and predictive features were in parallel with the literature.

Premature atrial complexes in an ischemic stroke population and risk of recurrent stroke: a systematic review

INTRODUCTION

Premature atrial complexes (PACs) have been proposed as a possible mediator between normal sinus rhythm and atrial fibrillation (AF). The aim of this study was to summarize the available knowledge of association between PACs and recurrent stroke or transient ischemic attack (TIA) in ischemic stroke patients. Areas covered: In this systematic review, we investigated the risk of recurrent events in patients who experienced ischemic stroke or TIA. Occurrence of PACs in electrocardiographic monitoring after index stroke/TIA was required. We identified and included three observational cohort studies, investigating in total 1005 patients. The studies reported that a significant burden of PACs occurred in a high proportion of stroke and TIA patients. More PACs were independently associated with an increased risk of recurrent stroke or TIA or the composite of recurrent stroke/TIA or death. Definition of PACs cut-off as well as patient characteristics differed between groups. Expert Commentary: This review supports an association between higher burden of PACs and recurrent stroke, and stresses the need for studies on PACs in stroke patients. A special awareness of stroke patients with a high PACs load is recommendable particularly for assessing the intensity and duration toward AF progression, and possible future treatment recommendations.

Nonsustained Atrial Fibrillation in Ischemic Stroke Patients and Stroke-Free Controls From the Perspective of Stroke Pathophysiology

BACKGROUND

Short-lasting (<30 s), nonsustained episodes of atrial fibrillation (NS-AF) are considered a risk factor for future development of paroxysmal or persistent AF. Nonetheless, their causal role in stroke pathogenesis is currently unknown. In this study we determined the frequency of NS-AF, together with the associated clinical and imaging features, in stroke-free controls and ischemic stroke patients.

METHODS AND RESULTS

A total of 332 controls, ≥50 years of age and no prior history of stroke or AF, were evaluated with 24-hour Holter monitoring for the presence of <30-s-long AF episodes. The demographic and cardiovascular features of this cohort, together with imaging finding on magnetic resonance imaging, were compared to a consecutive series of ≥50-year-old ischemic stroke patients without AF (n=498). The prevalence of NS-AF was significantly higher among ischemic stroke patients in comparison to controls (37% versus 27%; P=0.002). In multivariable analyses, after adjustment for demographic and cardiovascular risk factors, patients with ischemic stroke were more likely to harbor NS-AF episodes (odds ratio 1.43; 95% CI 1.01-2.02; P=0.041). The association between ischemic stroke and NS-AF weakened when the analyses were restricted to cryptogenic stroke patients (odds ratio 1.31; 95% CI 0.82-2.08). No significant association was observed between the presence of chronic cortical infarcts and NS-AF.

CONCLUSIONS

Our study shows a higher prevalence of NS-AF episodes in ischemic stroke patients in comparison to controls. Nonetheless, the lack of a stronger association with cryptogenic strokes and absence of a relationship with chronic cortical infarcts brings into question the causal influence of NS-AF in the ischemic stroke setting.

Global Survey of the Frequency of Atrial Fibrillation–Associated Stroke

Background and Purpose—

Atrial fibrillation (AF) is increasingly recognized as the single most important cause of disabling ischemic stroke in the elderly. We undertook an international survey to characterize the frequency of AF-associated stroke, methods of AF detection, and patient features.

Methods—

Consecutive patients hospitalized for ischemic stroke in 2013 to 2014 were surveyed from 19 stroke research centers in 19 different countries. Data were analyzed by global regions and World Bank income levels.

Results—

Of 2144 patients with ischemic stroke, 590 (28%; 95% confidence interval, 25.6–29.5) had AF-associated stroke, with highest frequencies in North America (35%) and Europe (33%) and lowest in Latin America (17%). Most had a history of AF before stroke (15%) or newly detected AF on electrocardiography (10%); only 2% of patients with ischemic stroke had unsuspected AF detected by poststroke cardiac rhythm monitoring. The mean age and 30-day mortality rate of patients with AF-associated stroke (75 years; SD, 11.5 years; 10%; 95% confidence interval, 7.6–12.6, respectively) were substantially higher than those of patients without AF (64 years; SD, 15.58 years; 4%; 95% confidence interval, 3.3–5.4; P <0.001 for both comparisons). There was a strong positive correlation between the mean age and the frequency of AF ( r =0.76; P =0.0002).

Conclusions—

This cross-sectional global sample of patients with recent ischemic stroke shows a substantial frequency of AF-associated stroke throughout the world in proportion to the mean age of the stroke population. Most AF is identified by history or electrocardiography; the yield of conventional short-duration cardiac rhythm monitoring is relatively low. Patients with AF-associated stroke were typically elderly (>75 years old) and more often women.

Embolic strokes of undetermined source: Prevalence and patient features in the ESUS Global Registry

Background

Recent evidence supports that most non-lacunar cryptogenic strokes are embolic. Accordingly, these strokes have been designated as embolic strokes of undetermined source (ESUS).

Aims

We undertook an international survey to characterize the frequency and clinical features of ESUS patients across global regions.

Methods

Consecutive patients hospitalized for ischemic stroke were retrospectively surveyed from 19 stroke research centers in 19 different countries to collect patients meeting criteria for ESUS.

Results

Of 2144 patients with recent ischemic stroke, 351 (16%, 95% CI 15% to 18%) met ESUS criteria, similar across global regions (range 16% to 21%), and an additional 308 (14%) patients had incomplete evaluation required for ESUS diagnosis. The mean age of ESUS patients (62 years; SD = 15) was significantly lower than the 1793 non-ESUS ischemic stroke patients (68 years, p ≤ 0.001). Excluding patients with atrial fibrillation ( n = 590, mean age = 75 years), the mean age of the remaining 1203 non-ESUS ischemic stroke patients was 64 years ( p = 0.02 vs. ESUS patients). Among ESUS patients, hypertension, diabetes, and prior stroke were present in 64%, 25%, and 17%, respectively. Median NIHSS score was 4 (interquartile range 2–8). At discharge, 90% of ESUS patients received antiplatelet therapy and 7% received anticoagulation.

Conclusions

This cross-sectional global sample of patients with recent ischemic stroke shows that one-sixth met criteria for ESUS, with additional ESUS patients likely among those with incomplete diagnostic investigation. ESUS patients were relatively young with mild strokes. Antiplatelet therapy was the standard antithrombotic therapy for secondary stroke prevention in all global regions.

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.

Silent Atrial Fibrillation: Definition, Clarification, and Unanswered Issues

Silent or subclinical asymptomatic atrial fibrillation has currently gained wide interest in the epidemiologic, neurologic and cardiovascular communities. The association of brief episodes of paroxysmal atrial fibrillation or surrogate atrial arrhythmias which predict future clinical adverse events have been established. Nevertheless there exists a confounding array of definitions to indicate its presence without discrete indication of which populations should be examined. Moreover the term "atrial fibrillation burden" (AFB) has emerged from such studies with a plethora of descriptions to prognosticate both arrhythmic and clinical adverse events. This presentation suggests clarification of diagnostic definitions associated with silent atrial fibrillation, and a more precise description of AFB. It examines the populations across the current disease and cardiovascular invasive therapeutic spectrum that lead to both silent atrial fibrillation and AFB. It describes the diagnostic methods of arrhythmia detection utilizing the surface ECG, subcutaneous ECG or intra-cardiac devices and their relationship in seeking meaningful arrhythmic markers of silent atrial fibrillation. Whereas a wide range of clinical risk factors of silent atrial fibrillation have been validated in the literature, there is an ongoing search for those arrhythmic risk factors that precisely identify and prognosticate outcome events in diverse populations at risk of atrial fibrillation and its complications. This presentation identifies this chaos, and focuses attention on the issues to be addressed to facilitate descriptive and comparative scientific studies in the future. It is a call to action specifically to the medical arrhythmic community and its specialty societies (i.e., ISHNE, HRS, EHRA) to begin a quest to unravel the arrhythmic quagmire associated with "silent atrial fibrillation."