Summary: There is growing recognition of the critical role of platelets in inflammation and immune responses. Recent studies have indicated that antiplatelet medications may reduce mortality from infections and sepsis, which suggests possible clinical relevance of modifying platelet responses to inflammation. Platelets release numerous inflammatory mediators that have no known role in haemostasis. Many of these mediators modify leukocyte and endothelial responses to a range of different inflammatory stimuli. Additionally, platelets form aggregates with leukocytes and form bridges between leukocytes and endothelium, largely mediated by platelet P-selectin. Through their interactions with monocytes, neutrophils, lymphocytes and the endothelium, platelets are therefore important coordinators of inflammation and both innate and adaptive immune responses.

Thrombosis is a common consequence of infection that is associated with poor patient outcome. Nevertheless, the mechanisms by which infection-associated thrombosis is induced, maintained and resolved are poorly understood, as is the contribution thrombosis makes to host control of infection and pathogen spread. The key difference between infection-associated thrombosis and thrombosis in other circumstances is a stronger inflammation-mediated component caused by the presence of the pathogen and its products. This inflammation triggers the activation of platelets, which may accompany damage to the endothelium, resulting in fibrin deposition and thrombus formation. This process is often referred to as thrombo-inflammation. Strikingly, despite its clinical importance and despite thrombi being induced to many different pathogens, it is still unclear whether the mechanisms underlying this process are conserved and how we can best understand this process. This review summarizes thrombosis in a variety of models, including single antigen models such as LPS, and infection models using viruses and bacteria. We provide a specific focus on Salmonella Typhimurium infection as a useful model to address all stages of thrombosis during infection. We highlight how this model has helped us identify how thrombosis can appear in different organs at different times and thrombi be detected for weeks after infection in one site, yet largely be resolved within 24 h in another. Furthermore, we discuss the observation that thrombi induced to Salmonella Typhimurium are largely devoid of bacteria. Finally, we discuss the value of different therapeutic approaches to target thrombosis, the potential importance of timing in their administration and the necessity to maintain normal hemostasis after treatment. Improvements in our understanding of these processes can be used to better target infection-mediated mechanisms of thrombosis.

Undetected atrial fibrillation (AF) is a major health concern. Blood biomarkers associated with AF could simplify patient selection for screening and further inform ongoing research towards stratified prevention and treatment of AF. Forty common cardiovascular biomarkers were quantified in 638 consecutive patients referred to hospital [mean ± standard deviation age 70 ± 12 years, 398 (62%) male, 294 (46%) with AF] with known AF or ≥2 CHA₂DS₂-VASc risk factors. Paroxysmal or silent AF was ruled out by 7-day ECG monitoring. Logistic regression with forward selection and machine learning algorithms were used to determine clinical risk factors, imaging parameters, and biomarkers associated with AF. Atrial fibrillation was significantly associated with age [bootstrapped odds ratio (OR) per year = 1.060, 95% confidence interval (1.04–1.10); P = 0.001], male sex [OR = 2.022 (1.28–3.56); P = 0.008], body mass index [BMI, OR per unit = 1.060 (1.02–1.12); P = 0.003], elevated brain natriuretic peptide [BNP, OR per fold change = 1.293 (1.11–1.63); P = 0.002], elevated fibroblast growth factor-23 [FGF-23, OR = 1.667 (1.36–2.34); P = 0.001], and reduced TNF-related apoptosis-induced ligand-receptor 2 [TRAIL-R2, OR = 0.242 (0.14–0.32); P = 0.001], but not other biomarkers. Biomarkers improved the prediction of AF compared with clinical risk factors alone (net reclassification improvement = 0.178; P < 0.001). Both logistic regression and machine learning predicted AF well during validation [area under the receiver-operator curve = 0.684 (0.62–0.75) and 0.697 (0.63–0.76), respectively]. Three simple clinical risk factors (age, sex, and BMI) and two biomarkers (elevated BNP and elevated FGF-23) identify patients with AF. Further research is warranted to elucidate FGF-23 dependent mechanisms of AF.

Objective—: Clinical studies suggest that platelet P2Y ₁₂ inhibitors reduce mortality from sepsis, although the underlying mechanisms have not been clearly defined in vivo. We hypothesized that P2Y ₁₂ inhibitors may improve survival from sepsis by suppressing systemic inflammation and its prothrombotic effects. We therefore determined whether clopidogrel and the novel, more potent P2Y ₁₂ inhibitor, ticagrelor, modify these responses in an experimental human model. Approach and Results—: We randomized 30 healthy volunteers to ticagrelor (n=10), clopidogrel (n=10), or no antiplatelet medication (controls; n=10). We examined the effect of P2Y ₁₂ inhibition on systemic inflammation, which was induced by intravenous injection of Escherichia coli endotoxin. Both P2Y ₁₂ inhibitors significantly reduced platelet–monocyte aggregate formation and peak levels of major proinflammatory cytokines, including tumor necrosis factor α, interleukin-6, and chemokine (C–C motif) ligand 2. In contrast to clopidogrel, ticagrelor also significantly reduced peak levels of IL-8 and growth colony-stimulating factor and increased peak levels of the anti-inflammatory cytokine IL-10. In addition, ticagrelor altered leukocyte trafficking. Both P2Y ₁₂ inhibitors suppressed D-dimer generation and scanning electron microscopy revealed that ticagrelor also suppressed prothrombotic changes in fibrin clot ultrastructure. Conclusions—: Potent inhibition of multiple inflammatory and prothrombotic mechanisms by P2Y ₁₂ inhibitors demonstrates critical importance of platelets as central orchestrators of systemic inflammation induced by bacterial endotoxin. This provides novel mechanistic insight into the lower mortality associated with P2Y ₁₂ inhibitors in patients with sepsis in clinical studies.

The use of risk markers has transformed cardiovascular medicine, exemplified by the routine assessment of troponin, for both diagnosis and assessment of prognosis in patients with chest pain. Clinical risk factors form the basis for risk assessment of cardiovascular disease and the addition of biochemical, cellular, and imaging parameters offers further refinement. Identifying novel risk factors may allow greater risk stratification and a steady, but gradual progression toward precision medicine. Indeed, the generation of data in this area of research is explosive and when combined with new technologies and techniques provides the potential for more refined, targeted approaches to cardiovascular medicine. Although discussing the most recent developments in this field, this review article aims to strike a balance between novelty and validity by focusing on recent large sample-size studies that have been validated in a separate cohort in most cases. Risk markers related to atherosclerosis, thrombosis, inflammation, cardiac injury, and fibrosis are introduced in the context of their pathophysiology. Rapidly developing new areas, such as assessment of micro-RNA, are also explored. Subsequently the prognostic ability of these risk markers in coronary artery disease, heart failure, and atrial fibrillation is discussed in detail.

The PEGASUS-TIMI 54 (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin-Thrombolysis In Myocardial Infarction 54) trial studied 2 doses of ticagrelor, 90 mg twice a day (bid) and 60 mg bid, for long-term prevention of ischemic events in patients with prior myocardial infarction. Both doses similarly reduced the rate of ischemic events versus placebo. The pharmacokinetics and pharmacodynamics of ticagrelor 60 mg bid have not been studied. In this study, the authors sought to study the pharmacokinetics and pharmacodynamics for ticagrelor 60 mg compared with 90 mg bid. A total of 180 patients who received >4 weeks of study medication had blood sampling in the morning pre-maintenance dose and again 2 h post-dose. All patients received aspirin. Plasma levels of ticagrelor and its active metabolite AR-C124910XX were determined. P2Y12 inhibition was assessed by the VerifyNow P2Y12 assay (Accumetrics, Inc., San Diego, California) (P2Y12 reaction units [PRU]), light transmittance aggregometry (adenosine diphosphate 5 and 20 μmol/l and arachidonic acid), and vasodilator-stimulated phosphoprotein phosphorylation assays. VerifyNow Aspirin assays and serum thromboxane B2 measurements were performed. Mean pre- and post-dose plasma levels of ticagrelor were 35% and 38% lower, respectively, with 60 mg versus 90 mg. Both doses achieved high levels of platelet inhibition pre- and post-dose, with numerically slightly more variability with 60 mg: mean (SD) pre-dose PRU values were 59 ± 63 and 47 ± 43 for ticagrelor 60 and 90 mg, respectively (p = 0.34). High platelet reactivity, determined as PRU >208, was rare with the 60-mg pre-dose and was absent post-dose. Platelet reactivity pre- and post-dose, as measured by light transmittance aggregometry or vasodilator-stimulated phosphoprotein assays, was numerically but not significantly lower with 90 mg than with 60 mg. Aspirin response was not affected by either dose. Ticagrelor 60 mg bid achieved high levels of peak and trough platelet inhibition in nearly all patients, similar to that with 90 mg bid, helping to explain the efficacy of the lower ticagrelor dose in PEGASUS-TIMI 54.