Developmental Differences in Platelet Inhibition Response to Prostaglandin E1.

BACKGROUND: The mechanisms underlying neonatal platelets hyporesponsiveness are not fully understood. While previous studies have demonstrated developmental impairment of agonist-induced platelet activation, differences in inhibitory signaling pathways have been scarcely investigated. OBJECTIVE: To compare neonatal and adult platelets with regard to inhibition of platelet reactivity by prostaglandin E1 (PGE1). METHODS: Platelet-rich plasma from umbilical cord (CB) or adult blood was incubated with PGE1 (0-1 µM). We assessed aggregation in response to adenosine diphosphate (ADP), collagen, and thrombin receptor activating peptide as well as cyclic adenosine 3'5'-monophosphate (cAMP) levels (ELISA). Gαs, Gαi2, and total- and phospho-protein kinase A (PKA) were evaluated in adult and CB ultrapure and washed platelets, respectively, by immunoblotting. RESULTS: Neonatal (vs. adult) platelets display hypersensitivity to inhibition by PGE1 of platelet aggregation induced by ADP and collagen (PGE1 IC50: 14 and 117 nM for ADP and collagen, respectively, vs. 149 and 491 nM in adults). They also show increased basal and PGE1-induced cAMP levels. Mechanistically, PGE1 acts by binding to the prostanoid receptor IP (prostacyclin receptor), which couples to the Gαs protein-adenylate cyclase axis and increases intracellular levels of cAMP. cAMP activates PKA, which phosphorylates different target inhibitor proteins. Neonatal platelets showed higher basal and PGE1-induced cAMP levels, higher Gαs protein expression, and a trend to increased PKA-dependent protein phosphorylation compared to adult platelets. CONCLUSION: Neonatal platelets have a functionally increased PGE1-cAMP-PKA axis. This finding supports a downregulation of inhibitory when going from neonate to adult contributing to neonatal platelet hyporesponsiveness.

Neoplasias mieloproliferativas crónicas con cromosoma Filadelfia negativo y neoplasias linfoides concurrentes / Concurrent lymphoid and Philadelphia chromosome-negative myeloproliferative neoplasms

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Relation of the HAS-BLED bleeding risk score to major bleeding, cardiovascular events, and mortality in anticoagulated patients with atrial fibrillation.

BACKGROUND: Stroke risk in atrial fibrillation (AF) using oral vitamin K antagonists is closely related to bleeding risk. The HAS-BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile INR [international normalized ratio], elderly, drugs/alcohol concomitantly) bleeding score has demonstrated usefulness in assessing major bleeding risk in patients with AF. However, risk factors for warfarin-associated bleeding also predict stroke risk in patients with AF. We tested the usefulness of the HAS-BLED score for predicting both major bleeding and cardiovascular events in a cohort of anticoagulated patients with AF. METHODS AND RESULTS: We recruited 965 consecutive anticoagulated outpatients with permanent or paroxysmal AF who were stabilized for at least 6 months on oral anticoagulation (international normalized ratio, 2.0-3.0). Medical history and HAS-BLED score were assessed. Cox regression models were used to determine the association between clinical risk factors and bleeding episodes, adverse cardiovascular events, and mortality. The median HAS-BLED score was 2 (range, 0-6; 29% with a score ≥3 [ie, high risk]). Median follow-up was 861 days (range, 718-1016 days). Independent predictors for major bleeding were age ≥75 years (hazard ratio [HR], 1.74; 95% CI, 1.05-2.87; P=0.030), male sex (HR, 1.70; 95% CI, 1.03-2.80; P=0.036), renal impairment (HR, 2.12; 95% CI, 1.20-3.73; P=0.010), previous bleeding episode (HR, 6.00; 95% CI, 3.73-9.67; P<0.001), current alcohol consumption (HR, 2.28; 95% CI, 1.03-5.06; P=0.043), and concomitant malignant disease (HR, 2.17; 95% CI, 1.13-4.18; P=0.020). Independent predictors for adverse cardiovascular events were age >75 years (HR, 2.20; 95% CI, 1.40-3.46; P=0.001), heart failure (HR, 1.78; 95% CI, 1.20-2.86; P=0.001), and previous stroke (HR, 1.85; 95% CI, 1.20-2.86; P<0.001). The HAS-BLED score was highly predictive for major bleeding events (HR, 2.04; 95% CI, 1.68-2.49; P<0.001) and adverse cardiovascular events (HR, 1.51; 95% CI, 1.27-1.81; P<0.001). The incidence of both bleeding and adverse cardiovascular events was higher as HAS-BLED score increased, and crude bleeding rates only exceeded thrombotic events at a HAS-BLED score >3. The HAS-BLED score also predicted all-cause mortality (HR, 1.68; 95% CI, 1.40-2.01; P<0.001). CONCLUSIONS: The HAS-BLED score not only is useful in the assessment of bleeding risk, but also shows some predictive value for cardiovascular events and mortality in anticoagulated patients with AF, consistent with the relationship between thrombosis and bleeding. Nonetheless, the HAS-BLED score has been designed for predicting bleeding risk rather than thrombotic events per se, and specific risk scores for cardiovascular events and mortality should be applied for these events.

Plasma von Willebrand factor levels are an independent risk factor for adverse events including mortality and major bleeding in anticoagulated atrial fibrillation patients.

OBJECTIVES: The purpose of this study was to evaluate the prognostic value of plasma von Willebrand factor (vWF) levels and fibrin d-dimer in a large cohort of anticoagulated permanent atrial fibrillation (AF) patients. BACKGROUND: In nonanticoagulated AF patients, plasma vWF levels have been related to stroke and vascular events. There are limited data on the prognostic role of biomarkers in anticoagulated AF patients in relation to adverse events (including thromboembolism), mortality, and major bleeding. METHODS: We studied 829 patients (50% male; median age 76 years) with permanent AF who were stabilized (for at least 6 months) on oral anticoagulation therapy (international normalized ratio: 2.0 to 3.0). Plasma d-dimer and vWF levels were quantified by enzyme-linked immunosorbent assay. Patients were followed for 2 years, and adverse events (thrombotic and vascular events, mortality, and major bleeding) were recorded. RESULTS: Patients were followed for a median of 828 days (range 18 to 1,085 days). On multivariate analysis, age 75 years and older, previous stroke, heart failure, and high plasma vWF levels (≥ 221 IU/dl) were associated with future adverse cardiovascular events (all p values <0.05). High plasma vWF levels, elderly patients, diabetes, hypercholesterolemia, and current smoking were associated with mortality (all p values <0.05). High plasma vWF levels were also an independent predictor of major bleeding (hazard ratio: 4.47, 95% confidence interval: 1.86 to 10.75; p < 0.001). High plasma vWF levels were able to refine clinical risk stratification schema for stroke (CHADS2 [Congestive heart failure, Hypertension, Age ≥ 75, Diabetes mellitus, and prior Stroke or transient ischemic attack (doubled)], CHA2DS2-VASc [Congestive heart failure, Hypertension, Age ≥ 75 years, Diabetes mellitus, Stroke, Vascular disease, Age 65 to 74 years, Sex category]) and bleeding (HAS-BLED [Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile International Normalized Ratio, Elderly, Drugs/alcohol concomitantly]). d-dimer did not show any significant impact on adverse events. CONCLUSIONS: High plasma vWF levels (≥221 IU/dl) are an independent risk factor for adverse events in anticoagulated permanent AF patients. This biomarker may potentially be used to refine stroke and bleeding clinical risk stratification in AF.