Antithrombotic therapy for patients with chronic coronary syndromes

Coagulopathy and acute pancreatitis: pathophysiology and clinical treatment

Coagulopathy is a critical pathophysiological mechanism of acute pancreatitis (AP), arising from the complex interplay between innate immune, endothelial cells and platelets. Although initially beneficial for the host, uncontrolled and systemic activation of coagulation cascade in AP can lead to thrombotic and hemorrhagic complications, ranging from subclinical abnormalities in coagulation tests to severe clinical manifestations, such as disseminated intravascular coagulation. Initiation of coagulation activation and consequent thrombin generation is caused by expression of tissue factor on activated monocytes and is ineffectually offset by tissue factor pathway inhibitor. At the same time, endothelial-associated anticoagulant pathways, in particular the protein C system, is impaired by pro-inflammatory cytokines. Also, fibrin removal is severely obstructed by inactivation of the endogenous fibrinolytic system, mainly as a result of upregulation of its principal inhibitor, plasminogen activator inhibitor type 1. Finally, increased fibrin generation and impaired break down lead to deposition of (micro) vascular clots, which may contribute to tissue ischemia and ensuing organ dysfunction. Despite the high burden of coagulopathy that have a negative impact on AP patients' prognosis, there is no effective treatment yet. Although a variety of anticoagulants drugs have been evaluated in clinical trials, their beneficial effects are inconsistent, and they are also characterized by hemorrhagic complications. Future studies are called to unravel the pathophysiologic mechanisms involved in coagulopathy in AP, and to test novel therapeutics block coagulopathy in AP.

The role of platelet P2Y12 receptors in inflammation

Inflammation is a complex pathophysiological process underlying many clinical conditions. Platelets contribute to the thrombo-inflammatory response. Platelet P2Y12 receptors amplify platelet activation, potentiating platelet aggregation, degranulation and shape change. The contents of platelet alpha granules, in particular, act directly on leucocytes, including mediating platelet-leucocyte aggregation and activation via platelet P-selectin. Much evidence for the role of platelet P2Y12 receptors in inflammation comes from studies using antagonists of these receptors, such as the thienopyridines clopidogrel and prasugrel, and the cyclopentyltriazolopyrimidine ticagrelor, in animal and human experimental models. These suggest that antagonism of P2Y12 receptors decreases markers of inflammation with some evidence that this reduces incidence of adverse clinical sequelae during inflammatory conditions. Interpretation is complicated by pleiotropic effects such as those of the thienopyridines on circulating leucocyte numbers and of ticagrelor on adenosine reuptake. The available evidence suggests that P2Y12 receptors are prominent mediators of inflammation and P2Y12 receptor antagonism as a potentially powerful strategy in a broad range of inflammatory conditions. LINKED ARTICLES: This article is part of a themed issue on Platelet purinergic receptor and non-thrombotic disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.4/issuetoc.

Platelet biology and function: plaque erosion vs. rupture

The leading cause of heart disease in developed countries is coronary atherosclerosis, which is not simply a result of ageing but a chronic inflammatory process that can lead to acute clinical events upon atherosclerotic plaque rupture or erosion and arterial thrombus formation. The composition and location of atherosclerotic plaques determine the phenotype of the lesion and whether it is more likely to rupture or to erode. Although plaque rupture and erosion both initiate platelet activation on the exposed vascular surface, the contribution of platelets to thrombus formation differs between the two phenotypes. In this review, plaque phenotype is discussed in relation to thrombus composition, and an overview of important mediators (haemodynamics, matrix components, and soluble factors) in plaque-induced platelet activation is given. As thrombus formation on disrupted plaques does not necessarily result in complete vessel occlusion, plaque healing can occur. Therefore, the latest findings on plaque healing and the potential role of platelets in this process are summarized. Finally, the clinical need for more effective antithrombotic agents is highlighted.

Influence of body weight and body mass index on the chronic pharmacokinetic and pharmacodynamic responses to clinically available doses of ticagrelor in patients with chronic coronary syndromes

Ticagrelor has multiple indications, including for some patients with chronic coronary syndromes (CCS) at high risk of ischaemic events. Body mass can potentially affect pharmacodynamics (PD) and pharmacokinetics (PK). We investigated the influence of body mass (range 53-172 kg, 20.8-46.9 kg/m²) on PD/PK in 221 CCS patients receiving ticagrelor 60 mg or 90 mg twice-daily (BD) during two randomised-controlled trials. Correlations between body weight (BW) or body mass index (BMI) and PD/PK measurements obtained during maintenance treatment at trough ('pre-dose') and peak effect ('post-dose') were assessed. BW and BMI correlated with P2Y₁₂ reactivity units at pre-dose (e.g. BW:R = 0.26, p = 0.008) but not post-dose timepoints. BW affected ticagrelor active metabolite (TAM) levels (e.g. 60 mg BD, post-dose:R = -0.39, p < 0.0001) and there was evidence of an inverse power law relationship between BW and TAM-to-ticagrelor ratio. PK with ticagrelor 60 mg correlated significantly with BMI. BW and BMI did not affect the chance of high platelet reactivity, which remained very low across the whole cohort. There was no difference in PRU between the two doses of ticagrelor within each weight or BMI group. Body mass has modest effects on the PK/PD response to ticagrelor in patients with CCS but currently-used regimens appear adequate across the range of BW/BMI studied.

Current and novel biomarkers of thrombotic risk in COVID-19: a Consensus Statement from the International COVID-19 Thrombosis Biomarkers Colloquium

Coronavirus disease 2019 (COVID-19) predisposes patients to thrombotic and thromboembolic events, owing to excessive inflammation, endothelial cell activation and injury, platelet activation and hypercoagulability. Patients with COVID-19 have a prothrombotic or thrombophilic state, with elevations in the levels of several biomarkers of thrombosis, which are associated with disease severity and prognosis. Although some biomarkers of COVID-19-associated coagulopathy, including high levels of fibrinogen and D-dimer, were recognized early during the pandemic, many new biomarkers of thrombotic risk in COVID-19 have emerged. In this Consensus Statement, we delineate the thrombotic signature of COVID-19 and present the latest biomarkers and platforms to assess the risk of thrombosis in these patients, including markers of platelet activation, platelet aggregation, endothelial cell activation or injury, coagulation and fibrinolysis as well as biomarkers of the newly recognized post-vaccine thrombosis with thrombocytopenia syndrome. We then make consensus recommendations for the clinical use of these biomarkers to inform prognosis, assess disease acuity, and predict thrombotic risk and in-hospital mortality. A thorough understanding of these biomarkers might aid risk stratification and prognostication, guide interventions and provide a platform for future research.

A randomised controlled trial to assess the antithrombotic effects of aspirin in type 1 diabetes: role of dosing and glycaemic control

Background

The enhanced thrombotic milieu in diabetes contributes to increased risk of vascular events. Aspirin, a key antiplatelet agent, has inconsistent effects on outcomes in diabetes and the best dosing regimen remains unclear. This work investigated effects of aspirin dose and interaction with glycaemia on both the cellular and protein components of thrombosis.

Methods

A total of 48 participants with type 1 diabetes and 48 healthy controls were randomised to receive aspirin 75 or 300 mg once-daily (OD) in an open-label crossover study. Light transmittance aggregometry and fibrin clot studies were performed before and at the end of each treatment period.

Results

Aspirin demonstrated reduced inhibition of collagen-induced platelet aggregation (PA) in participants with diabetes compared with controls, although the higher dose showed better efficacy. Higher aspirin dose facilitated clot lysis in controls but not individuals with diabetes. Collagen-induced PA correlated with glycaemic control, those in the top HbA1c tertile having a lesser inhibitory effect of aspirin. Threshold analysis suggested HbA1c levels of > 65 mmol/mol and > 70 mmol/mol were associated with poor aspirin response to 75 and 300 mg daily doses, respectively. Higher HbA1c was also associated with longer fibrin clot lysis time.

Conclusions

Patients with diabetes respond differently to the antiplatelet and profibrinolytic effects of aspirin compared with controls. In particular, those with elevated HbA1c have reduced inhibition of PA with aspirin. Our findings indicate that reducing glucose levels improves the anti-thrombotic action of aspirin in diabetes, which may have future clinical implications.

Trial registration

EudraCT, 2008-007875-26, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2008-007875-26.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01427-y.