Increased platelet reactivity in unstable angina patients is not related to C-reactive protein levels

The Multiple Faces of C-Reactive Protein-Physiological and Pathophysiological Implications in Cardiovascular Disease

C-reactive protein (CRP) is an intriguing protein which plays a variety of roles in either physiological or pathophysiological states. For years it has been regarded merely as a useful biomarker of infection, tissue injury and inflammation, and it was only in the early 80s that the modified isoforms (mCRP) of native CRP (nCRP) appeared. It soon became clear that the roles of native CRP should be clearly discriminated from those of the modified form and so the impacts of both isoforms were divided to a certain degree between physiological and pathophysiological states. For decades, CRP has been regarded only as a hallmark of inflammation; however, it has since been recognised as a significant predictor of future episodes of cardiovascular disease, independent of other risk factors. The existence of modified CRP isoforms and their possible relevance to various pathophysiological conditions, suggested over thirty years ago, has prompted the search for structural and functional dissimilarities between the pentameric nCRP and monomeric mCRP isoforms. New attempts to identify the possible relevance between the diversity of structures and their opposing functions have initiated a new era of research on C-reactive protein. This review discusses the biochemical aspects of CRP physiology, emphasizing the supposed relevance between the structural biology of CRP isoforms and their differentiated physiological and pathophysiological roles.

Correlation of platelet reactivity and C-reactive protein levels to occurrence of peri-procedural myocardial infarction in patients undergoing percutaneous coronary intervention (from the ARMYDA-CRP study)

The incremental predictive value of high inflammatory status and high on-treatment platelet reactivity (HPR) on the occurrence of periprocedural myocardial infarction (PMI) after percutaneous coronary intervention (PCI) has not been characterized. The aim of this study was to evaluate the correlation of elevated C-reactive protein (CRP) level and/or HPR with the incidence of PMI in patients who undergo PCI. Five hundred consecutive patients treated with clopidogrel who underwent PCI had preprocedural measurement of CRP levels and platelet reactivity using the point-of-care VerifyNow P2Y12 assay. Elevated inflammatory status was defined as CRP >3 mg/L and HPR as P2Y12 reactivity units ≥240. The primary end point was the incidence of PMI in relation to platelet reactivity and/or inflammatory status. Rates of PMI were increased in patients with CRP levels >3 mg/L (10.9% vs 4.6% in those with normal levels, odds ratio 2.4, 95% confidence interval 1.2 to 4.5, p = 0.015) and in patients with HPR (11% vs 5.5% in those without HPR, odds ratio 2.2, 95% confidence interval 1.2-4.4, p = 0.018). The occurrence of PMI was highest in the subgroup with HPR and high inflammatory status (16.6% vs 3.6% in patients with CRP ≤3 mg/L and P2Y12 reactivity units <240, odds ratio 4.3, 95% confidence interval 1.5 to 12.6, p = 0.008). HPR in association with elevated CRP levels resulted in a significant increase in the discriminatory power of a model including clinical and procedural variables in predicting PMI (area under the curve 0.811, p = 0.041). In conclusion, in patients who undergo PCI, baseline stratification according to platelet reactivity and inflammatory status may identify those at higher risk for PMI.

Effect of alpha lipoic acid on cardiac autonomic dysfunction and platelet reactivity in type 1 diabetes: rationale and design of the AUTOnomic function and platelet REACTivity trial (AUTO-REACT protocol)

BACKGROUND

The aim of this study is to assess the relationship between cardiac autonomic dysfunction and increased platelet reactivity in patients with type 1 diabetes and whether alpha lipoic acid therapy (ALA) might improve both abnormalities in these patients.

METHODS AND MATERIALS

Cardiac autonomic function will be assessed by heart rate variability (HRV) analysis. Platelet reactivity will be investigated by both measuring the aggregation time on the PFA-100 method and flow cytometry. HRV and platelet reactivity will be re-assessed in the patients with depressed HRV after 4 weeks from randomization to ALA or placebo.

DISCUSSION

The cardiovascular autonomic system might play a role in the modulation of platelet reactivity which is increased in diabetes. Within this framework, ALA might be found to exercise antithrombotic effects in addition to its known antioxidants properties.

TRIAL REGISTRATION

Australian Clinical Trials Registry ACTRN 12610000291088.

Effects of in vitro adult platelet transfusions on neonatal hemostasis

BACKGROUND

Thrombocytopenia is frequent among neonates, and 20-25% of affected infants are treated with platelet transfusions. These are frequently given for mild thrombocytopenia (platelets: 50-100 × 10(9) L(-1)), largely because of the known hyporeactivity of neonatal platelets. In tests of primary hemostasis, however, neonates have shorter bleeding and closure times (CTs) than adults. This has been attributed to their higher hematocrits, higher von Willebrand factor (VWF) concentrations, and predominance of longer VWF polymers.

OBJECTIVE

To determine whether the 'transfusion' of adult (relatively hyperreactive) platelets into neonatal blood results in a hypercoagulable profile.

METHODS

Cord blood (CB) and adult peripheral blood (PB) were separated (with a modified buffy coat method) to generate miniaturized platelet concentrates (PCs) and thrombocytopenic blood. PB-derived and CB-derived PCs (n = 7 per group) were then 'transfused'in vitro into thrombocytopenic CB and PB. The effects of autologous vs. allogeneic (developmentally mismatched) 'transfusions' were evaluated with whole blood aggregometry, a platelet function analyzer (PFA-100), and thromboelastography (TEG).

RESULTS

Adult platelets aggregated significantly better than neonatal platelets in response to thrombin receptor-activating peptide, ADP, and collagen, regardless of the blood into which they were transfused. The 'transfusion' of adult platelets into thrombocytopenic CB resulted in shorter CTs-EPI (PFA-100) and higher clot strength and firmness (TEG) than 'transfusion' of neonatal autologous platelets.

CONCLUSIONS

In vitro'transfusion' of adult platelets into neonatal blood results in shorter CTs than 'transfusion' with neonatal platelets. Our findings should raise awareness of the differences between the neonatal and adult hemostatic system and the potential 'developmental mismatch' associated with platelet transfusions for neonatal hemostasis.

Leukocyte count is associated with increased platelet reactivity and diminished response to aspirin in healthy individuals with a family history of coronary artery disease

BACKGROUND

Markers of systemic inflammation, including blood leukocyte count, are associated with increased cardiovascular risk, but the mechanisms underlying this association are unclear. Leukocytes may promote platelet reactivity and thrombus formation, providing a basis for increased risk, but a relation between leukocyte count and platelet function has not been studied.

METHODS

We evaluated the relation of blood leukocyte count, C-reactive protein (CRP), and interleukin-6 (IL-6) to platelet aggregation to collagen, ADP and arachidonic acid, and to urinary excretion of 11-dehydro thromboxane B2. Studies were conducted in 1600 individuals (45.0+/-12.9 years, 42.7% male) at risk for coronary artery disease (CAD) before and after low dose aspirin.

RESULTS

At baseline, platelet reactivity increased with increasing quartile of leukocyte count (median counts for each quartile were normal) for all measures of platelet function (P<0.0001). These relations were unchanged by aspirin. The relation between leukocyte count and each measure of platelet reactivity remained significant (P<0.05) after multivariable adjustment for CRP, IL-6, cardiac risk factors, hematologic variables, and platelet thromboxane production. CRP and IL-6 were independently associated with few measures of platelet reactivity.

CONCLUSIONS

Increasing quartile of leukocyte count, even within the normal range, is associated with increasing platelet reactivity in individuals at risk for CAD. This relationship is not altered by aspirin and is independent of inflammatory markers and platelet thromboxane production. Additional studies are needed to determine the mechanism(s) for this association and therapies to reduce cardiovascular risk in patients with elevated leukocyte counts.

Lack of early augmentation of platelet reactivity after coronary intervention in patients treated with bivalirudin

To determine whether a regimen of aspirin pretreatment, bivalirudin during the procedure and clopidogrel (600 mg) immediately after percutaneous coronary intervention (PCI) was associated with platelet activation during and shortly after (1 and 2 h) PCI, we characterized platelet function in 10 patients with the use of flow cytometry in the absence of agonist and in response to thrombin (10 nM), ADP (1 microM), the collagen-mimetic convulxin (5 ng/ml), and platelet activating factor (10 nM). Activation of platelets in peripheral blood was rare (<0.5% of platelets) before, during and after PCI. Platelet reactivity in response to each of the agonists was lower after the PCI compared with that in blood taken before the PCI. Accordingly, platelet activation and platelet reactivity were not increased after elective PCI when patients were treated during the procedure with aspirin and bivalirudin and immediately after the procedure with a 600 mg loading dose of clopidogrel.

Platelet reactivity and the identification of acute coronary syndromes in the emergency department

Risk stratifying patients with potential acute coronary syndromes (ACS) in the Emergency Department is an imprecise and resource-consuming process. ACS cannot be ruled in or out efficiently in a majority of patients after initial history, physical exam, and ECG are analyzed. This has led to a reliance on cardiac markers of myocardial necrosis as a key means of making the diagnosis. Commonly used markers, CK-MB and troponin-I, have the drawback of delayed sensitivity. This has led to an ongoing search for one or more marker(s) that would be more sensitive in early ACS. With the central role that platelets play in the pathophysiology of coronary thrombosis, measures of platelet function represent one potential area where an early ACS marker might be identified. This review will focus on selected tests/markers of platelet function that have shown some promise with respect to the risk stratification of patients with potential ACS.