Enhanced neutrophil extracellular traps formation in AF patients with dilated left atrium

NET burden in left atrial blood is associated with biomarkers of thrombosis and cardiac injury in patients with enlarged left atria

BACKGROUND

Emerging data suggest an association between left atrial (LA) enlargement, thrombus formation, and ischemic stroke. However, it is unknown what may mediate such clot formation in LA dysfunction. Neutrophils promote large vessel occlusion and microthrombosis via neutrophil extracellular trap (NET) release, thus lying at the interface of inflammation, thrombosis, and fibrosis.

APPROACH

We conducted a prospective all-comers cohort study in patients undergoing catheterization procedures with atrial transseptal access (MitraClip, MC; left atrial appendage closure, LAAC; pulmonary vein ablation, PVA; patent foramen ovale closure, PFO). We measured NETs, cytokines, thrombotic factors, and cardiac injury markers in paired blood samples collected from peripheral blood and within the left atrium. We correlated these biomarkers with echocardiographic measures of LA structure and function (including left atrial volume index, LAVI). Data were analyzed by procedure type, and stratified by LAVI or atrial fibrillation (AF) status.

RESULTS

We enrolled 70 patients (mean age 64 years, 53% women). NETs, but not other markers, were elevated in LA compared to peripheral blood samples. Most thrombotic, inflammatory, and cardiac damage markers were elevated in LAs from MC or LAAC compared to PFO patients. Overall, NET biomarkers positively correlated with VWF, LAVI, and markers of cardiac injury and negatively with ADAMTS13 activity. LA enlargement and the presence of AF similarly stratified patients based on thromboinflammation measurements, but this was not limited to AF at the time of sample collection.

CONCLUSION

Elevated NETs and VWF in patients with enlarged LA or AF suggest enhanced thromboinflammation within the LA.

White blood cell subtypes and neutrophil extracellular traps content as biomarkers for stroke etiology in acute ischemic stroke clots retrieved by mechanical thrombectomy

BACKGROUND

Lymphocytes, macrophages, neutrophils, and neutrophil extracellular traps (NETs) associate with stroke risk factors and form a thrombus through different mechanisms. We investigated the total WBCs, WBC subtypes and NETs composition in acute ischemic stroke (AIS) clots to identify possible etiological differences that could help us further understand the process of thrombosis that leads to AIS.

METHODS

AIS clots from 100 cases each of atherothrombotic (AT), cardioembolic (CE) and cryptogenic stroke etiology were collected per-pass as part of the CÚRAM RESTORE registry of AIS clots. Martius Scarlet Blue stain was used to identify the main histological components of the clots. Immunohistochemical staining was used to identify neutrophils, lymphocytes, macrophages, and NETs patterns. The cellular and histological components were quantified using Orbit Image Analysis software.

RESULTS

AT clots were larger, with more red blood cells and fewer WBCs than CE clots. AT clots had more lymphocytes and cryptogenic clots had fewer macrophages than other etiologies. Most significantly, CE clots showed higher expression of neutrophils and extracellular web-like NETs compared to AT and cryptogenic clots. There was also a significantly higher distribution of web-like NETs around the periphery of the CE clots while a mixed distribution was observed in AT clots.

CONCLUSION

The difference in neutrophil and NETs expression in clots from different etiologies may provide insight into the mechanism of clot formation.

Soluble PILRα: A novel plasma biomarker for atrial fibrillation progression and recurrence after catheter ablation

BACKGROUND

We aimed to identify plasma biomarkers of atrial fibrillation (AF) progression and recurrence after catheter ablation.

METHODS

Using AF gene profiling data from GEO database, a weighted gene co-expression network analysis (WGCNA) was conducted to determine the most significant module and hub genes associated with AF. Subsequently, 318 consecutively admitted patients who had undergone radiofrequency catheter ablation were enrolled in this study.

RESULTS

WGCNA results revealed that paired immunoglobulin-like type 2 receptor alpha (PILRA) was the only black module gene highly correlated with clinical traits. Plasma soluble PILRα (sPILRα) levels were elevated in patients with AF and significantly elevated in patients with persistent versus paroxysmal AF (4.64 ± 2.74 vs. 3.04 ± 1.56 ng/mL, p < 0.001). Elevated sPILRα level was an independent risk factor for AF progression even after adjusting for traditional factors (adjusted odds ratio: 3.06, 95 % confidence interval [CI]: 1.88-5.27, p < 0.001) and AF recurrence after catheter ablation in patients with persistent AF (adjusted hazards ratio: 4.41, 95 % CI: 1.22-15.92, p = 0.023).

CONCLUSIONS

WGCNA screening of GEO microarray gene profiling data showed PILRA expression levels to be correlated with AF progression and recurrence after catheter ablation in patients with persistent AF.