Biomarkers for Prognostication After Acute Coronary Syndromes

Soluble Platelet Release Factors as Biomarkers for Cardiovascular Disease

Platelets are the main players in thrombotic diseases, where activated platelets not only mediate thrombus formation but also are involved in multiple interactions with vascular cells, inflammatory components, and the coagulation system. Although in vitro reactivity of platelets provides information on the function of circulating platelets, it is not a full reflection of the in vivo activation state, which may be relevant for thrombotic risk assessment in various disease conditions. Therefore, studying release markers of activated platelets in plasma is of interest. While this type of study has been done for decades, there are several new discoveries that highlight the need for a critical assessment of the available tests and indications for platelet release products. First, new insights have shown that platelets are not only prominent players in arterial vascular disease, but also in venous thromboembolism and atrial fibrillation. Second, knowledge of the platelet proteome has dramatically expanded over the past years, which contributed to an increasing array of tests for proteins released and shed from platelets upon activation. Identification of changes in the level of plasma biomarkers associated with upcoming thromboembolic events allows timely and individualized adjustment of the treatment strategy to prevent disease aggravation. Therefore, biomarkers of platelet activation may become a valuable instrument for acute event prognosis. In this narrative review based on a systematic search of the literature, we summarize the process of platelet activation and release products, discuss the clinical context in which platelet release products have been measured as well as the potential clinical relevance.

Impact of platelet phenotype on myocardial infarction

In acute myocardial infarction patients the injured vascular wall triggers thrombus formation in the damage site. Fibrin fibers and blood cellular elements are the major components of thrombus formed in acute occlusion of coronary arteries. It has been established that the initial thrombus is primarily composed of activated platelets rapidly stabilized by fibrin fibers. This review highlights the role of platelet membrane phenotype in pathophysiology of myocardial infarction. Here, we regard platelet phenotype as quantitative and qualitative parameters of the plasma membrane outer surface, which are crucial for platelet participation in blood coagulation, development of local inflammation and tissue repair.

Long-term trajectory of two unique cardiac biomarkers and subsequent left ventricular structural pathology and risk of incident heart failure in community-dwelling older adults at low baseline risk

OBJECTIVES

This study sought to determine whether the combined trajectories of cardiac biomarkers identify those older adults with initial low levels who have an increased risk for structural heart disease, incident heart failure (HF), and cardiovascular (CV) death.

BACKGROUND

Initial low levels of high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) identify older adults at lower risk for CV events.

METHODS

We performed an observational study among older adults without prevalent HF in the CHS (Cardiovascular Health Study). NT-proBNP and hs-cTnT were measured at baseline and after 2 to 3 years. In those with low baseline levels, a significant increase was defined as cardiac troponin T (cTnT) >50% and NT-proBNP >25% increase to >190 pg/ml. Left ventricular ejection fraction and left ventricular mass were measured by echocardiography at baseline and 5 years. Cox regression was used to estimate the association of change in biomarkers with HF and CV mortality.

RESULTS

Among 2,008 participants with initially low biomarker concentrations, significant increases occurred in 14.8% for cTnT only, 13.2% for NT-proBNP only, and 6.1% for both. After 10 years, cumulative HF incidence was 50.4% versus 12.2% among those with both biomarkers versus neither biomarker increased. The adjusted relative risk comparing those with increases in both biomarkers versus neither biomarker was 3.56 for incident HF (95% confidence interval: 2.56 to 4.97) and 2.98 for CV mortality (95% confidence interval: 2.98 to 4.26). Among 1,340 participants with serial echocardiography, the frequency of new abnormal left ventricular ejection fraction was 11.8% versus 4% for those with increases in both biomarkers versus neither biomarker (p = 0.007).

CONCLUSIONS

Among older adults without HF with initially low cTnT and NT-proBNP, the long-term trajectory of both biomarkers predicts systolic dysfunction, incident HF, and CV death.

Biomarkers of platelet activation in acute coronary syndromes

The most convincing evidence for the participation of platelets in arterial thrombosis in humans comes from studies of platelet activation in patients with acute coronary syndromes (ACS) and from trials of antiplatelet drugs. Both strongly support the concept that repeated episodes of platelet activation over the thrombogenic surface of a vulnerable plaque may contribute to the risk of death from coronary causes. However, the relation of in vivo platelet activation and adverse clinical events to results of platelet function tests remains largely unknown. A valuable marker of in vivo platelet activation should be specific, unaltered by pre-analytical artefacts and reproducibly measured by easily performed methods. This article describes current biomarkers of platelet activation in ACS, reviews their advantages and disadvantages, discusses their potential pitfalls, and demonstrates emerging data supporting the positive clinical implications of monitoring in vivo platelet activation in the setting of ACS.

Further opportunities for cost reduction of medical care

The already high and still rising cost of health care has become a matter of serious concern and a subject of political dispute. The problem has no magic cures but, as is shown here, there are a number of promising modifications in current practice that promise to reduce the required outlays without impairing appropriate health care. Continual reports of new medicines, new tests, and new procedures have created an urgent need for careful comparison and evaluation of the advantages and beneficial results that these innovations offer. The same is true for the growing knowledge of genetic variations, which affects the course of therapy for some patients. Costs also can be saved, in some instances, by utilization of medical therapy, rather than interventional procedures. Preventive medicine provides still more opportunities for cost savings. This paper provides an overview of promising potential approaches to reduce the cost of health care.

Biomarkers of risk stratification in congestive heart failure: North American view

There is broad adoption of various cardiac and noncardiac biomarkers in clinical practices across North America for the diagnosis and management of heart failure. Like any clinical condition, there are several overall objectives in biomarker testing: to establish or refute a diagnosis of heart failure and/or cardiac dysfunction; to understand the underlying pathophysiologic processes that may warrant specific interventions; to determine the level of disease severity in a manner to triage medical decisions; to detect and potentially avoid adverse consequences as a result of therapeutic interventions; and to monitor responses to treatment. While at present no single biomarker can serve all of these objectives, the growing experience with cardiac-specific biomarkers, such as natriuretic peptide and cardiac troponin testing, has allowed clinicians to better identify those at heightened short- or long-term risk. It is clear that difficulty remains in translating research evidence into clinical practice. While studies demonstrate statistical differences in short- and long-term outcomes, there is still limited information on how such improvements can be achieved solely based on current therapeutic options. Meanwhile, many commonly ordered tests have important prognostic information that can be overlooked, yet their changes may or may not affect prognosis. With healthcare cost on the rise in North America, clinical utility of biomarkers must demonstrate relative safety and potential incremental benefits to standard approaches.