Identification of Hub Genes Associated with Immune Infiltration in Cardioembolic Stroke by Whole Blood Transcriptome Analysis

Cardioembolic stroke (CS) is the most common type of ischemic stroke in the clinic, leading to high morbidity and mortality worldwide. Although many studies have been conducted, the molecular mechanism underlying CS has not been fully grasped. This study was aimed at exploring the molecular mechanism of CS using comprehensive bioinformatics analysis and providing new insights into the pathophysiology of CS. We downloaded the public datasets GSE58294 and GSE16561. Differentially expressed genes (DEGs) were screened via the limma package using R software. CIBERSORT was used to estimate the proportions of 22 immune cells based on the gene expression profiling of CS patients. Using weighted gene correlation network analysis (WGCNA) to cluster the genes into different modules and detect relationships between modules and immune cell types, hub genes were identified based on the intersection of the protein-protein interaction (PPI) network analysis and WGCNA, and their clinical significance was then verified using another independent dataset GSE16561. Totally, 319 genes were identified as DEGs and 5413 genes were clustered into nine modules using WGCNA. The blue module, with the highest correlation coefficient, was identified as the key module associated with stroke, neutrophils, and B cells naïve. Based on the PPI analysis and WGCNA, five genes (MCEMP1, CLEC4D, GPR97, TSPAN14, and FPR2) were identified as hub genes. Correlation analysis indicated that hub genes had general association with infiltration-related immune cells. ROC analysis also showed they had potential clinical significance. The results were verified using another dataset, which were consistent with our analysis. Five crucial genes determined using integrative bioinformatics analysis might play significant roles in the pathophysiological mechanism in CS and be potential targets for pharmaceutic therapies.

Hemorrhagic Transformation Following Childhood Cardioembolic Stroke Is Not Increased in Anticoagulated Patients

Objective: To characterize the risk of hemorrhagic transformation following cardioembolic stroke in childhood, and whether anticoagulation impacts that risk. Methods: Ninety-five children (1 month-18 years) with cardioembolic arterial ischemic stroke between January 1, 2009, and December 31, 2019, at 2 institutions were identified for retrospective chart review. Neuroimaging was reviewed to assess for hemorrhagic transformation. Results: There were 11 cases of hemorrhagic transformation; 8 occurred within 2 days of stroke diagnosis. Risk of hemorrhagic transformation did not differ in patients with and without anticoagulation use (15% vs 9%, estimated risk difference 5%; CI –9%, 19%). Stroke size did not predict hemorrhagic transformation (OR 1.004, 95% CI 0.997, 1.010). Risk of hemorrhagic transformation was higher in strokes that occurred in the inpatient compared with the outpatient setting (16% vs 6%). Conclusion: Hemorrhagic transformation occurred in 11% of pediatric cardioembolic ischemic stroke, usually within 2 days of stroke diagnosis, and was not associated with anticoagulation or stroke size.

MULTITRAIT ANALYSIS EXPANDS GENETIC RISK FACTORS IN CARDIOEMBOLIC STROKE

Background and Purpose: The genetic architecture of cardioembolic stroke (CES) is still poorly understood. Atrial fibrillation (AF) is the main cause of CES, with which it shares heritability. We aimed to discover novel loci associated with CES by performing a Multitrait Analysis of the GWAS (MTAG) with atrial fibrillation genetic data. Methods: For the MTAG analysis we used the MEGASTROKE cohort, which comprises European patients with CES and controls (n=362,661) and an AF cohort composed of 1,030,836 subjects. Regional genetic pleiotropy of the significant results was explored using an alternative Bayesian approach with GWAS-pairwise method. A replication was performed in an independent European cohort comprising 9,105 subjects using a Genome Wide Association Study (GWAS). Results: MTAG-CES analysis revealed 40 novel and significant loci (p-value<5x10-8) associated with CES, four of which had not previously been associated with AF. A significant replication was assessed for eight novel loci: CAV1, IGF1R, KIAA1755, NEURL1, PRRX1, SYNE2, TEX41 and WIPF1, showing a p-value<0.05 in the CES vs controls independent analysis. KIAA1755, a locus not previously described associated with AF. Interestingly, 51 AF risk loci were not associated with CES according to GWAS-pairwise analysis. Gene Ontology (GO) analysis revealed that these exclusive AF genes from the 51 loci participate in processes related mainly to cardiac development, whereas genes associated with AF and CES participate mainly in muscle contraction and the conduction of electrical impulses. Conclusions: We found eight new loci associated with CES. In addition, this study provides novel insights into the pathogenesis of CES, highlighting multiple candidate genes for future functional experiments.

Cardioembolic stroke: classification of causes and prevention strategies

This literature review covers the diversity of cardioembolic stroke (CES), the heterogeneity of the embolism sources and the morphological characteristics of the embolic substrate. It is emphasized that the determination of the individual tactics of secondary prevention is based on the verification of specific cardiac causes of stroke, for convenience, stratified as pathology of chambers, heart valves and variants of paradoxical embolism (PE). It has been shown that the leading pathology of the heart chambers associated with CES is nonvalvular atrial fibrillation and left ventricular thrombosis, and the main basis for the prevention of stroke in this pathology is oral anticoagulant therapy with direct oral anticoagulants or vitamin K antagonists (warfarin). The main types of heart valve pathology are prosthetic valves and rheumatic mitral stenosis. In this case, oral anticoagulant therapy also serves as the basis for secondary prevention. In the absence of the need to prescribe anticoagulants (mainly in the pathology of natural heart valves) acetylsalicylic acid is the drug of choice. In infective endocarditis (IE), the basic prevention strategies are antibiotic therapy and surgery. Surgical tactics also remain the main one for the prevention of CES in tumors of the left heart. Transcatheter closure of the patent foramen ovale and occlusion of the left atrial appendage are being introduced into the daily practice of interventional medicine in order to prevent ischemic stroke. A balanced individual approach to the patient, a targeted cardiological examination, a comprehensive analysis of clinical and instrumental data and the reasonable use of funds that have proven their effectiveness and safety in the main strategies for stroke prevention, are essential in effective prevention of CES.

Heart–Brain Relationship in Stroke

The patient presenting with stroke often has cardiac-related risk factors which may be involved in the mechanism of the stroke. The diagnostic assessment is predicated on recognition of this potential relationship. Naturally, an accurate history is of utmost importance in discerning a possible cause and effect relationship. The EKG is obviously an important clue as well as it allows immediate assessment for possible cardiac arrhythmia, such as atrial fibrillation, for possible acute ischemic changes reflective of myocardial ischemia, or there may be indirect factors such as the presence of left ventricular hypertrophy, typically seen with longstanding hypertension, which could be indicative of a hypertensive mechanism for a patient presenting with intracerebral hemorrhage. For all presentations in the emergency room, the vital signs are important. An elevated body temperature in a patient presenting with acute stroke raises concern about possible infective endocarditis. An irregular–irregular pulse is an indicator of atrial fibrillation. A markedly elevated blood pressure is not uncommon in both the acute ischemic and acute hemorrhagic stroke setting. One tends to focus on possible cardioembolic stroke if there is the sudden onset of maximum neurological deficit versus the stepwise progression more characteristic of thrombotic stroke. Because of the more sudden loss of vascular supply with embolic occlusion, seizure or syncope at onset tends to be supportive of this mechanism. Different vascular territory involvement on neuroimaging is also a potential indicator of cardioembolic stroke. Identification of a cardiogenic source of embolus in such a setting certainly elevates this mechanism in the differential. There have been major advances in management of acute cerebrovascular disease in recent decades, such as thrombolytic therapy and endovascular thrombectomy, which have somewhat paralleled the advances made in cardiovascular disease. Unfortunately, the successful limitation of myocardial damage in acute coronary syndrome, with intervention, does not necessarily mirror a similar salutary effect on functional outcome with cerebral infarction. The heart can also affect the brain from a cerebral perfusion standpoint. Transient arrhythmias can result in syncope, while cardiac arrest can result in hypoxic–ischemic encephalopathy. Cardiogenic dementia has been identified as a mechanism of cognitive impairment associated with severe cardiac failure. Structural cardiac abnormalities can also play a role in brain insult, and this can include tumors, such as atrial myxoma, patent foramen ovale, with the potential for paradoxical cerebral embolism, and cardiomyopathies, such as Takotsubo, can be associated with precipitous cardioembolic events.