High levels of platelet-monocyte aggregates after valve replacement for aortic stenosis: Relation to soluble P-selectin and P-selectin glycoprotein ligand-1 genes

Platelets reprogram monocyte functions by secreting MMP-9 to benefit postoperative outcomes following acute aortic dissection

Platelets have a great ability to modulate immune responses. Monocyte-platelet aggregates (MPAs) are associated with the pathogenesis of cardiac disease. Notably, a low preoperative platelet count often indicates poor postoperative recovery following acute aortic dissection (AAD). The functions of platelets and MPAs in AAD, however, remain poorly understood. We found that, despite decreased platelet counts, platelets were also activated in AAD patients, with significant alterations in immune-modulating mediators. Of interest, monocytes in AAD patients had a suppressed immune status, which was correlated with poor outcomes following surgery. Interestingly, platelets preferentially aggregated with monocytes, and the levels of MPAs were related to recovery after surgical repair in AAD patients. Platelets restored suppressed monocyte functions in AAD patients by forming aggregates and partly by secreting matrix metalloproteinase-9 (MMP-9). Thus, the results point to a previously unknown mechanism for platelets involving monocyte reprogramming, which may improve postoperative outcomes following complex cardiovascular surgery.

Peri-procedural hemostasis disorders in surgical and transcatheter aortic valve implantation

Introduction

Despite their high effectiveness, surgical aortic valve replacement (AVR) and transcatheter aortic valve implantation (TAVI) are associated with substantial risk of bleeding. Although procedure-related hemostasis disorders might be crucial for safety of both procedures, the amount of data on the peri-procedural status of hemostasis in patients with aortic valve stenosis (AS) subjected to AVR and TAVI is negligible.

Aim

To investigate the profile of peri-procedural hemostasis in elderly patients with AS, subjected to aortic valve prosthesis implantation.

Material and methods

We performed a prospective analysis of global hemostasis using ROTEM thromboelastometry and platelet reactivity assessment using impedance aggregometry in 30 consecutive patients ≥ 70 years old subjected to AVR and TAVI. All tests were performed within 24 h before, directly and 24 h after the procedures.

Results

Surgical aortic valve replacement was characterized by transient hypofibrinogenemia and von Willebrand factor (vWF) depletion, which quickly recovered within 24 h after AVR. Transcatheter aortic valve implantation was characterized by substantial alteration of platelet function and vWF depletion with significant platelet reactivity impairment and increase in platelet sensitivity to antiplatelet agent, early after the procedure. TAVI-related hemostasis alterations were not recovered at 24 h after the procedure.

Conclusions

Surgical and transcatheter aortic valve replacement procedures are associated with substantial and diverse peri-procedural hemostasis disorders. Since hemostasis disorders related to TAVI are mainly characterized by impaired platelet function, early dual antiplatelet prophylaxis after TAVI requires careful consideration.

Circulating monocyte-platelet aggregates are a robust marker of platelet activity in cardiovascular disease

BACKGROUND AND AIMS

Platelets are a major culprit in the pathogenesis of cardiovascular disease (CVD). Circulating monocyte-platelet aggregates (MPA) represent the crossroads between atherothrombosis and inflammation. However, there is little understanding of the platelets and monocytes that comprise MPA and the prevalence of MPA in different CVD phenotypes. We aimed to establish (1) the reproducibility of MPA over time in circulating blood samples from healthy controls, (2) the effect of aspirin, (3) the relationship between MPA and platelet activity and monocyte subtype, and (4) the association between MPA and CVD phenotype (coronary artery disease, peripheral artery disease [PAD], abdominal aortic aneurysm, and carotid artery stenosis).

METHODS AND RESULTS

MPA were identified by CD14⁺ monocytes positive for CD61⁺ platelets in healthy subjects and in patients with CVD. We found that MPA did not significantly differ over time in healthy controls, nor altered by aspirin use. Compared with healthy controls, MPA were significantly higher in CVD (9.4% [8.2, 11.1] vs. 21.8% [11.5, 44.1], p < 0.001) which remained significant after multivariable adjustment (β = 9.1 [SER = 3.9], p = 0.02). We found PAD to be associated with a higher MPA in circulation (β = 19.3 [SER = 6.0], p = 0.001), and among PAD subjects, MPA was higher in subjects with critical limb ischemia (34.9% [21.9, 51.15] vs. 21.6% [15.1, 40.6], p = 0.0015), and significance remained following multivariable adjustment (β = 14.77 (SE = 4.35), p = 0.001).

CONCLUSIONS

Circulating MPA are a robust marker of platelet activity and monocyte inflammation, unaffected by low-dose aspirin, and are significantly elevated in subjects with CVD, particularly those with PAD.

Association of platelet activation markers with recurrence of atrial fibrillation after pulmonary vein isolation

Atrial fibrillation (AF) is known to cause platelet activation. AF and its degree of thrombogenesis could be associated with monocyte-platelet aggregates (MPAs). We investigated on whether the content of MPAs or other platelet activation markers is associated with the recurrence of AF after pulmonary vein isolation (PVI). A total of 73 patients with symptomatic AF underwent PVI. After 6 months, all patients were evaluated for episodes of AF recurrence. At the same time, flow-cytometric quantification analyses were performed to determine the content of MPAs. Further platelet activation parameters were detected by using either cytometric bead arrays or quantitative immunological determination. Patients with recurrent AF (n = 20) compared to individuals without AF relapse (n = 53) were associated with an increased content of MPAs (43 ± 3% vs. 33 ± 2%, p = 0.004), as well as an increased CD41 expression on monocytes (191 ± 20 vs. 113 ± 6, p = 0.001). The level of the soluble platelet activation markers such as D-dimer, sCD40L, and sP-selectin did not differ between these groups. The content of MPAs correlated weakly with the level of sCD40L (r = 0.26, p = 0.03), but not with sP-selectin and D-dimer, whereas sP-selectin and sCD40L correlated with each other (r = 0.38, p = 0.001). Only the cellular marker of platelet activation, the content of MPAs, was increased in patients with recurrent AF after PVI. In contrast, soluble markers remained unaltered. These data indicate a distinct mechanism and level of platelet activation in AF. The clinical relevance of MPAs in identifying AF recurrence or in guiding the therapy with anticoagulants remains to be elucidated.

Increased Smad2/3 phosphorylation in circulating leukocytes and platelet-leukocyte aggregates in a mouse model of aortic valve stenosis: Evidence of systemic activation of platelet-derived TGF-β1 and correlation with cardiac dysfunction

BACKGROUND

Transforming growth factor-β1 (TGF-β1) has been implicated in the pathogenesis of aortic valve stenosis (AS). There is, however, little direct evidence for a role of active TGF-β1 in AS due to the sensitivity of current assays. We searched for evidence of plasma TGF-β1 activation by assaying Smad2/3 phosphorylation in circulating leukocytes and platelet-leukocyte aggregates (PLAs) in a mouse model of AS (Reversa).

METHODS

Echocardiography was used to measure AS and cardiac function. Intracellular phospho-flow cytometry in combination with optical fluorescence microscopy was used to detect PLAs and p-Smad2/3 levels.

RESULTS

Reversa mice on a western diet developed AS, had significantly increased numbers of PLAs and more intense staining for p-Smad2/3 in both PLAs and single leukocytes (all p<0.05). p-Smad2/3 staining was more intense in PLAs than in single leukocytes in both diet groups (p<0.05) and correlated with plasma total TGF-β1 levels (r=0.38, p=0.05 for PLAs and r=0.37, p=0.06 for single leukocytes) and reductions in ejection fraction (r=-0.42, p=0.03 for PLAs and r=-0.37, p=0.06 for single leukocytes).

CONCLUSIONS

p-Smad2/3 staining is more intense in leukocytes of hypercholesterolemic mice that developed AS, suggesting increased circulating active TGF-β1 levels. Leukocyte p-Smad2/3 may be a valuable surrogate indicator of circulating active TGF-β1.

Coronary neutrophil extracellular trap burden and deoxyribonuclease activity in ST-elevation acute coronary syndrome are predictors of ST-segment resolution and infarct size

RATIONALE

Mechanisms of coronary occlusion in ST-elevation acute coronary syndrome are poorly understood. We have previously reported that neutrophil (polymorphonuclear cells [PMNs]) accumulation in culprit lesion site (CLS) thrombus is a predictor of cardiovascular outcomes.

OBJECTIVE

The goal of this study was to characterize PMN activation at the CLS. We examined the relationships between CLS neutrophil extracellular traps (NETs), bacterial components as triggers of NETosis, activity of endogenous deoxyribonuclease, ST-segment resolution, and infarct size.

METHODS AND RESULTS

We analyzed coronary thrombectomies from 111 patients with ST-elevation acute coronary syndrome undergoing primary percutaneous coronary intervention. Thrombi were characterized by immunostaining, flow cytometry, bacterial profiling, and immunometric and enzymatic assays. Compared with femoral PMNs, CLS PMNs were highly activated and formed aggregates with platelets. Nucleosomes, double-stranded DNA, neutrophil elastase, myeloperoxidase, and myeloid-related protein 8/14 were increased in CLS plasma, and NETs contributed to the scaffolds of particulate coronary thrombi. Copy numbers of Streptococcus species correlated positively with dsDNA. Thrombus NET burden correlated positively with infarct size and negatively with ST-segment resolution, whereas CLS deoxyribonuclease activity correlated negatively with infarct size and positively with ST-segment resolution. Recombinant deoxyribonuclease accelerated the lysis of coronary thrombi ex vivo.

CONCLUSIONS

PMNs are highly activated in ST-elevation acute coronary syndrome and undergo NETosis at the CLS. Coronary NET burden and deoxyribonuclease activity are predictors of ST-segment resolution and myocardial infarct size.

Preserved thrombin-inducible platelet activation in thienopyridine-treated patients

BACKGROUND

Abundant thrombin generation may be a major reason for subsequent thromboembolic events in patients with cardiovascular disease receiving dual antiplatelet therapy. We therefore investigated the susceptibility of thienopyridine responders and nonresponders to thrombin receptor-activating peptide (TRAP)-6- and adenosine diphosphate (ADP)-inducible platelet activation.

MATERIALS AND METHODS

Response to clopidogrel or prasugrel was determined by the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay and multiple electrode aggregometry (MEA) in 317 patients undergoing angioplasty and stenting for cardiovascular disease. Baseline, TRAP-6-, and ADP-inducible P-selectin expression, activated glycoprotein IIb/IIIa (GPIIb/IIIa) and monocyte-platelet aggregate (MPA) formation were measured as sensitive parameters of platelet activation.

RESULTS

In patients with high on-treatment residual ADP-inducible platelet reactivity (HRPR), baseline P-selectin expression, GPIIb/IIIa and MPA formation were similar to those in patients without HRPR (all P > 0.05). After platelet activation with TRAP-6 or ADP, patients with HRPR by both assays exhibited significantly higher levels of P-selectin expression, GPIIb/IIIa and MPA formation than patients with an adequate thienopyridine-mediated platelet inhibition (all P ≤ 0.02). However, high levels of TRAP-6-inducible P-selectin, GPIIb/IIIa and MPA formation also occurred in 20.4%, 19.1% and 20.1% of the good responders by the VASP assay, and in 19.6%, 16.6% and 20.6% of the good responders by MEA, respectively.

CONCLUSIONS

Thienopyridine nonresponders are more susceptible to thrombin- and ADP-inducible platelet activation than patients with good platelet inhibition. However, even patients with adequate thienopyridine-mediated platelet inhibition often show a preserved responsiveness to thrombin. These patients may benefit from additional thrombin receptor blockage or inhibition of thrombin generation.

Effect of transcatheter (via femoral artery) aortic valve implantation on the platelet count and its consequences

Decrease in blood platelet count has been described after percutaneous coronary intervention and surgical valve replacement, although no study has been performed in the setting of transcatheter aortic valve implantation (TAVI). The aim of this study was to address the incidence, mechanism, and impact of blood platelet count decrease after TAVI. One hundred forty-four consecutive patients (mean age 84 ± 7 years, 64 men) with severe symptomatic aortic stenosis who underwent TAVI from December 2007 to July 2011 were enrolled. Blood platelet count was recorded before and after aortic valve implantation. Decrease in blood platelet count was compared with in-hospital major adverse cardiovascular events (death, stroke, and major or life-threatening bleeding). Blood platelet count decreases occurred in all but 1 patient. The percentage of platelet count decrease averaged 34 ± 15% and was 24% greater than blood protein decrease. Decrease in platelet count was associated with a higher rate of prosthesis migration, longer x-ray and procedural times, and larger contrast amounts (230 ± 128 ml for the third tertile vs 170 ± 77 ml for the second and first tertiles, p = 0.0006), but no association was observed with regard to changes in bilirubin. In-hospital major adverse cardiovascular events (n = 50 [35%]) were observed more frequently in patients with severe platelet count decreases (21% for the first tertile, 35% for the second tertile, and 48% for the third tertile, p = 0.02). Finally, the percentage of blood platelet count decrease was the only predictor of in-hospital major adverse cardiovascular events (odds ratio 1.67, 95% confidence interval 1.05 to 2.67, p = 0.03). In conclusion, a decrease in platelet count is a common phenomenon after TAVI, and its severity is associated with poor outcomes.