[Clinical and Diagnostic Value of Cardiac Markers in Human Biological Fluids]

Advances in research on biomarkers associated with acute myocardial infarction: A review

Acute myocardial infarction (AMI), the most severe cardiovascular event in clinical settings, imposes a significant burden with its annual increase in morbidity and mortality rates. However, it is noteworthy that mortality due to AMI in developed countries has experienced a decline, largely attributable to the advancements in medical interventions such as percutaneous coronary intervention. This trend highlights the importance of accurate diagnosis and effective treatment to preserve the myocardium at risk and improve patient outcomes. Conventional biomarkers such as myoglobin, creatine kinase isoenzymes, and troponin have been instrumental in the diagnosis of AMI. However, recent years have witnessed the emergence of new biomarkers demonstrating the potential to further enhance the accuracy of AMI diagnosis. This literature review focuses on the recent advancements in biomarker research in the context of AMI diagnosis.

Cardiospecific Troponins as Laboratory Biomarkers of Myocardial Cell Injury in Hypertension: A Mini-Review

To date, it is well known that a significant number of diseases of cardiovascular genesis (coronary heart disease, myocardial infarction, cardiomyopathy, Takotsubo syndrome, heart failure, etc.) and extra-cardiac genesis (renal failure, chronic obstructive pulmonary disease, sepsis, diabetes mellitus, etc.) cause injury to contractile cells of the heart muscle (myocardial cells). The most sensitive and specific criteria for proving myocardial cell injury are cardiospecific troponins (CSTns) - CSTnI and CSTnT. According to the current clinical recommendations of the European, American, and Russian Cardiological Communities, CSTnI and CSTnT are the main biomarkers for early diagnosis of myocardial infarction. Hypertension is one of the most dangerous and common risk factors for the development of cardiovascular pathologies and is associated with a high risk of dangerous cardiovascular complications. Therefore, there is an urgent need to search for new biomarkers for the timely assessment of the prognosis of patients with hypertension. This mini-review aims to substantiate the possibilities of using the cardiomarkers (CSTnI and CSTnT) to assess the prognosis of patients suffering from hypertension and to discuss potential mechanisms that cause injury to myocardial cells and increase serum levels of CSTnI and CSTnT. This is a narrative mini-review, which was prepared using the following databases: Pubmed/Medline, PubMed Central, Embase, Scopus, and Web of Science. The following keywords were used in the literature search: "myocardial cells", "injury", "damage", and "hypertension" in combination with the terms "mechanisms of injury" "predictive significance", "cardiac troponins", or "cardiospecific troponins".

Modern View on the Role of Sex-Specific Levels of High-Sensitive Cardiospecific Troponins T and I in the Diagnosis of Myocardial Infarction

It is well known that the molecules of cardiospecific troponins T and I are localized in the troponin-tropomyosin complex of the cytoplasm of cardiac myocytes and, due to the specific localization, these cardiospecific troponins are widely used as diagnostic biomarkers of myocardial infarction. Cardiospecific troponins are released from the cytoplasm of cardiac myocytes as a result of irreversible cell damage (for example, ischemic necrosis of cardiomyocytes in myocardial infarction or apoptosis of cardiac myocytes in cardiomyopathies and heart failure) or reversible damage (for example, intense physical exertion, hypertension, the influence of stress factors, etc.). Current immunochemical methods for determining cardiospecific troponins T and I have extremely high sensitivity to subclinical (minor) damage to myocardial cells and, thanks to modern high-sensitive methods, it is possible to detect damage to cardiac myocytes in the early (subclinical) stages of a number of cardiovascular pathologies, including myocardial infarction. So, recently, leading cardiological communities (the European Society of Cardiology, the American Heart Association, the American College of Cardiology, etc.) have approved algorithms for early diagnosis of myocardial infarction based on the assessment of serum levels of cardiospecific troponins in the first 1 - 3 h after the onset of pain syndrome. An important factor that may affect early diagnostic algorithms of myocardial infarction are sex-specific features of serum levels of cardiospecific troponins T and I. This manuscript presents a modern view on the role of sex-specific serum levels of cardiospecific troponins T and I in the diagnosis of myocardial infarction and the mechanisms of formation of sex-specific serum levels of troponins.

Gender Specificities of Cardiac Troponin Serum Levels: From Formation Mechanisms to the Diagnostic Role in Case of Acute Coronary Syndrome

Cardiac troponins T and I are the main (most sensitive and specific) laboratory indicators of myocardial cell damage. A combination of laboratory signs of myocardial cell damage (elevated levels of cardiac troponins T and I) with clinical (severe chest pain spreading to the left side of the human body) and functional (rise or depression of the ST segment, negative T wave or emergence of the Q wave according to electrocardiography and/or decrease in the contractility of myocardial areas exposed to ischemia according to echocardiography) signs of myocardial ischemia is indicative of the ischemic damage to cardiomyocytes, which is characteristic of the development of acute coronary syndrome (ACS). Today, with early diagnostic algorithms for ACS, doctors rely on the threshold levels of cardiac troponins (99th percentile) and on the dynamic changes in the serum levels over several hours (one, two, or three) from the moment of admission to the emergency department. That said, some recently approved highly sensitive methods for determining troponins T and I show variations in 99th percentile reference levels, depending on gender. To date, there are conflicting data on the role of gender specificities in the serum levels of cardiac troponins T and I in the diagnostics of ACS, and the specific mechanisms for the formation of gender differences in the serum levels of cardiac troponins T and I are unknown. The purpose of this article is to analyze the role of gender specificities in cardiac troponins T and I in the diagnostics of ACS, and to suggest the most likely mechanisms for the formation of differences in the serum levels of cardiac troponins in men and women.

Diagnostic Role and Methods of Detection of Cardiac Troponins: An Opinion from Historical and Current Points of View

The laboratory methods for the determination of cardiac troponins (cTnI, cTnT) used nowadays are extremely diverse, which has a significant impact on our understanding of the biology and diagnostic the value of cTnI and cTnT as biomarkers. The main classification of methods for the determination of cTnI and cTnT is based on the sensitivity of the immunoassay. Low- and moderately sensitive detection methods are known to be relatively less sensitive, which leads to a relatively late confirmation of cardiomyocyte death. Due to the new highly sensitive methods used to determine cTnI and cTnT, designated as a highly or ultrasensitive immunoassays (hs-TnT and hs-TnT), we received new, revised data about the biology of cardiac troponin molecules. In particular, it became clear that they can be considered products of normal myocardium metabolism since hs-TnT and hs-TnT are detected in almost all healthy patients. It also turned out that hs-TnT and hs-TnT differ by gender (in men, troponin concentration in the blood is higher than in women), age (in elderly patients, the levels of troponins are higher than in young ones) and circadian cycles (morning concentrations of troponins are higher than in the evening). A large variety of methods for determining cTnI and cTnT, differing in their diagnostic capabilities, creates the need for tests to perform an unbiased assessment of the analytical characteristics of each method. This review focuses on the most pressing issues related to the discussion of the biological characteristics of cardiac troponin and the analytical characteristics of troponin immunoassays from a historical and contemporary point of view.

Acute Cholecystitis Leading to Elevated High-Sensitive Cardiac Troponin I in a Young Female Without Any Cardiac Ailment: A Rare Case Presentation

Cardiac troponin I (cTnI) is regarded as a gold standard investigation for the diagnosis of acute myocardial infarction (AMI). However, cTnI may be elevated in certain non-AMI cardiac conditions and even in certain noncardiac conditions. We report a case of a young female presenting with symptoms suggestive of acute cholecystitis with elevated high-sensitive cardiac troponin I (hs-cTnI). The patient developed acute chest pain during the hospital stay. On evaluation, quantitative assay for hs-cTnI was found to be elevated; however, other markers of cardiac damage such as creatinine kinase-MB (CK-MB), qualitative cTnI by card test, and even echocardiogram (ECG) were found to be negative. As the patient was a young female with no significant history of coronary diseases, the spurious elevation of hs-TnI due to a noncardiac ailment was suspected. The patient was managed with minimal cardiological management till AMI was excluded. The hs-cTnI levels returned to normal post-cholecystectomy. A patient presenting with symptoms suggestive of cholecystitis and elevated hs-cTnI must be carefully evaluated before resorting to any invasive management for AMI. In most cases, hs-cTnI will return to normal post-cholecystectomy.

Review of Recent Laboratory and Experimental Data on Cardiotoxicity of Statins

Due to the fact that statins are among the most high-demand therapeutic agents used for the treatment and prevention of the most common cardiovascular diseases, a significant amount of research is focused on these drugs. As a result, the study and discovery of new effects in statin drugs continues. Research methods are constantly being improved in terms of their sensitivity and specificity, which leads to a change in ideas. In addition to the main lipid-lowering effect, statins have a number of additional effects, which can be conditionally divided into positive (pleiotropic) and negative (side effects). Moreover, information about many of the pleiotropic effects of statins is controversial and may subsequently change as new data become available. To a large extent, this is due to the introduction of new and the improvement of old methods of study: clinical, laboratory and morphological ones. Recent studies report the possibility of statins having potential cardiotoxic properties, which is expressed by an increase in the concentration of highly sensitive cardiac troponins, as well as various adverse changes in cardiac myocytes at the ultrastructural and molecular levels. This paper discusses possible mechanisms of statin cardiotoxicity. This narrative review is based on an analysis of publications in the Medline, PubMed, PubMed Central and Embase databases. The terms “statins”, “troponin”, “troponin I”, “troponin T” in combination with “cardiotoxicity”, “false positive”, “mechanisms of increase”, “pathophysiological mechanisms”, “oxidative stress” and “cardiomyocyte apoptosis” were used to search publications.

Hypertension as One of the Main Non-Myocardial Infarction-Related Causes of Increased Cardiospecific Troponins: From Mechanisms to Significance in Current Medical Practice

It is well known that many pathological conditions of both cardiovascular diseases (CVDs) (coronary heart disease, myocardial infarction, arrhythmias, myocarditis, cardiomyopathy, etc.) and non-cardiac (sepsis, anemia, kidney diseases, diabetes mellitus, etc.) origin in the course of their development cause injury to contractile cardiac muscle cells - myocardial cells (MCs). One of the most sensitive and specific criteria for detecting MC injury are cardiospecific troponins (CTs), which are regulatory protein molecules that are released into the blood serum from MC upon their death or injury. Current methods for determining CTs are called high-sensitive ones, and their main advantage is a very low minimum detectable concentration (limit of detection) (average 1 - 10 ng/L or less), which allows early detection of minor MC injury at the earliest stages of CVDs, and therefore they can change the understanding of disease development mechanisms and open up new diagnostic possibilities. One of the most common and dangerous early diseases of the cardiovascular system is hypertension (HT). The novelty of this article lies in the discussion of a new diagnostic direction - predicting the risk of developing CVDs and their dangerous complications in patients with HT by determining the concentration of CTs. In addition, pathophysiological mechanisms underlying MC injury and the release of CTs into the bloodstream and the elimination of CTs into the urine are proposed. This information will contribute to additional fundamental and clinical research to verify the new diagnostic possibility of using CTs in clinical practice (for the management of patients with HT).

Significance of Markers of Transient Myocardial Ischemia and Hemodynamic Overload in Critically Ill Neonates

Monitoring of cardiospecific markers is significant during intensive care.

The objective: to compare the diagnostic and prognostic significance of cardiac markers in newborns with somatic and surgical pathology.

Subjects and Methods. The study included 76 newborns aged 1 to 14 days with somatic or surgical disorders. The changes in the concentration of cardiomarkers in newborns and their relationship with echocardiography data and non-invasive hemodynamic parameters are presented, their prognostic ability is assessed.

Results. Rigidity of non-invasive hemodynamic parameters, and echocardiography data was revealed. In the somatic group, regression of NT-proBNP from 8,307 ng/ml (3,600; 9,000) to 1,717 ng/ml (1,041; 5,011) was regarded as a marker of resolution of hypervolemia against the background of cardiovascular maladaptation. The increase in NT-proBNP from 4,710 ng/ml (3,400; 6,989) to 7,987 ng/ml (3,397; 9,000) in the postoperative period requires a revision of the infusion therapy program with the priority of volume restriction.

Conclusions. Stabilization of the condition of patients in the groups is accompanied by a decrease in the concentration of markers of myocardial tension (MB-fraction of creatine phosphokinase, troponin T).

Measurement of NT-proBNP concentration allows assessment of fluid overload in critically ill neonates.

Analysis of new calculated echocardiographic indicators on a clinical example of a typical patient with pulmonary embolism of moderate-high risk of early death

The article presents an analysis of the developed calculated echocardiographic indicators: the final diastolic pressure in the pulmonary artery, the pressure gradient on the pulmonary artery valve, the volume of tricuspid regurgitation, as well as the work of the heart on the pulmonary artery valve.

The Role of Fine Particles (PM 2.5) in the Genesis of Atherosclerosis and Myocardial Damage: Emphasis on Clinical and Epidemiological Data, and Pathophysiological Mechanisms

Due to the fact that atherosclerotic cardiovascular diseases (CVDs) dominate in the structure of morbidity, disability and mortality of the population, the study of the risk factors for the development of atherosclerotic CVDs, as well as the study of the underlying pathogenetic mechanisms thereof, is the most important area of scientific research in modern medicine. Understanding these aspects will allow to improve the set of treatment and preventive measures and activities. One of the important risk factors for the development of atherosclerosis, which has been actively studied recently, is air pollution with fine particulate matter (PM 2.5). According to clinical and epidemiological data, the level of air pollution with PM 2.5 exceeds the normative indicators in most regions of the world and is associated with subclinical markers of atherosclerosis and mortality from atherosclerotic CVDs. The aim of this article is to systematize and discuss in detail the role of PM 2.5 in the development of atherosclerosis and myocardial damage.

Cardiac Troponins as Biomarkers of Cardiac Myocytes Damage in Case of Arterial Hypertension: From Pathological Mechanisms to Predictive Significance

Background. Many pathological conditions of both cardiovascular and non-cardiac origin in the course of their development cause damage to contractile cardiac muscle cells—cardiac myocytes (CMCs). One of the most sensitive and specific criteria for detecting CMCs are cardiac troponins (CTs), which are regulatory protein molecules that are released into the blood serum from CMCs upon their death or damage. New (high-sensitive) methods for detecting CTs allow the detection of minor CMCs damages at the earliest stages of cardiovascular diseases and can therefore change the understanding of disease development mechanisms and open up new diagnostic possibilities. One of the most common and dangerous early diseases of the cardiovascular system is arterial hypertension. The purpose of this paper is to summarize the pathophysiological mechanisms underlying CMCs damage and CTs release into the bloodstream in the case of arterial hypertension and to state the clinical significance of increased CTs levels in patients with arterial hypertension. Materials and methods. This is a descriptive review, which was prepared using the following databases: Embase, Pubmed/Medline and Web of Science. The following key words were used in the literature search: “myocardial injury” and “arterial hypertension” in combination with the terms “cardiac troponins” and “mechanisms of increase”. Conclusions. According to a literature analysis, CMCs damage and CTs release in the case of arterial hypertension occur according to the following pathophysiological mechanisms: myocardial hypertrophy, CMCs apoptosis, damage to the CMC cell membrane and increase in its permeability for CTs molecules, as well as changes in the glomerular filtration rate. Most often, increased CTs serum levels in case of arterial hypertension indicate an unfavorable prognosis. Data on the CTs predictive significance in case of arterial hypertension open the prospects for the use of these biomarkers in the choice of patient management plans.

On the Effect of Heterophilic Antibodies on Serum Levels of Cardiac Troponins: A Brief Descriptive Review

Serum levels of cardiac troponins can be increased both with myocardial damage and in the absence of myocardial damage. In the second case, this is due to the influence of false-positive factors, among which heterophilic antibodies play a significant role. Understanding the causes of the formation of heterophilic antibodies, the features and mechanisms of their effect on serum levels of cardiac troponins, is an important condition for interpreting a false-positive result due to the influence of heterophilic antibodies. This brief, descriptive review presents the causes of heterophilic-antibodies formation and discusses their effect on serum levels of cardiac troponins.

Metabolic Pathway of Cardiospecific Troponins: From Fundamental Aspects to Diagnostic Role (Comprehensive Review)

Many molecules of the human body perform key regulatory functions and are widely used as targets for the development of therapeutic drugs or as specific diagnostic markers. These molecules undergo a significant metabolic pathway, during which they are influenced by a number of factors (biological characteristics, hormones, enzymes, etc.) that can affect molecular metabolism and, as a consequence, the serum concentration or activity of these molecules. Among the most important molecules in the field of cardiology are the molecules of cardiospecific troponins (Tns), which regulate the processes of myocardial contraction/relaxation and are used as markers for the early diagnosis of ischemic necrosis of cardiomyocytes (CMC) in myocardial infarction (MI). The diagnostic value and diagnostic capabilities of cardiospecific Tns have changed significantly after the advent of new (highly sensitive (HS)) detection methods. Thus, early diagnostic algorithms of MI were approved for clinical practice, thanks to which the possibility of rapid diagnosis and determination of optimal tactics for managing patients with MI was opened. Relatively recently, promising directions have also been opened for the use of cardiospecific Tns as prognostic markers both at the early stages of the development of cardiovascular diseases (CVD) (arterial hypertension (AH), heart failure (HF), coronary heart disease (CHD), etc.), and in non-ischemic extra-cardiac pathologies that can negatively affect CMC (for example, sepsis, chronic kidney disease (CKD), chronic obstructive pulmonary disease (COPD), etc.). Recent studies have also shown that cardiospecific Tns are present not only in blood serum, but also in other biological fluids (urine, oral fluid, pericardial fluid, amniotic fluid). Thus, cardiospecific Tns have additional diagnostic capabilities. However, the fundamental aspects of the metabolic pathway of cardiospecific Tns are definitively unknown, in particular, specific mechanisms of release of Tns from CMC in non-ischemic extra-cardiac pathologies, mechanisms of circulation and elimination of Tns from the human body, mechanisms of transport of Tns to other biological fluids and factors that may affect these processes have not been established. In this comprehensive manuscript, all stages of the metabolic pathway are consistently and in detail considered, starting from release from CMC and ending with excretion (removal) from the human body. In addition, the possible diagnostic role of individual stages and mechanisms, influencing factors is analyzed and directions for further research in this area are noted.

Aptamers Targeting Cardiac Biomarkers as an Analytical Tool for the Diagnostics of Cardiovascular Diseases: A Review

The detection of cardiac biomarkers is used for diagnostics, prognostics, and the risk assessment of cardiovascular diseases. The analysis of cardiac biomarkers is routinely performed with high-sensitivity immunological assays. Aptamers offer an attractive alternative to antibodies for analytical applications but, to date, are not widely practically implemented in diagnostics and medicinal research. This review summarizes the information on the most common cardiac biomarkers and the current state of aptamer research regarding these biomarkers. Aptamers as an analytical tool are well established for troponin I, troponin T, myoglobin, and C-reactive protein. For the rest of the considered cardiac biomarkers, the isolation of novel aptamers or more detailed characterization of the known aptamers are required. More attention should be addressed to the development of dual-aptamer sandwich detection assays and to the studies of aptamer sensing in alternative biological fluids. The universalization of aptamer-based biomarker detection platforms and the integration of aptamer-based sensing to clinical studies are demanded for the practical implementation of aptamers to routine diagnostics. Nevertheless, the wide usage of aptamers for the diagnostics of cardiovascular diseases is promising for the future, with respect to both point-of-care and laboratory testing.

The Importance of Cardiac Troponin Metabolism in the Laboratory Diagnosis of Myocardial Infarction (Comprehensive Review)

The study of the metabolism of endogenous molecules is not only of great fundamental significance but also of high practical importance, since many molecules serve as drug targets and/or biomarkers for laboratory diagnostics of diseases. Thus, cardiac troponin molecules have long been used as the main biomarkers for confirmation of diagnosis of myocardial infarction, and with the introduction of high-sensitivity test methods, many of our ideas about metabolism of these cardiac markers have changed significantly. In clinical practice, there are opening new promising diagnostic capabilities of cardiac troponins, the understanding and justification of which are closely connected with the fundamental principles of the metabolism of these molecules. Our current knowledge about the metabolism of cardiac troponins is insufficient and extremely disconnected from various literary sources. Thus, many researchers do not sufficiently understand the potential importance of cardiac troponin metabolism in the laboratory diagnosis of myocardial infarction. The purpose of this comprehensive review is to systematize information about the metabolism of cardiac troponins and during the discussion to focus on the potential impact of cTns metabolism on the laboratory diagnosis of myocardial infarction. The format of this comprehensive review includes a sequential consideration and analysis of the stages of the metabolic pathway, starting from possible release mechanisms and ending with elimination mechanisms. This will allow doctors and researchers to understand the significant importance of cTns metabolism and its impact on the laboratory diagnosis of myocardial infarction.

Features of the Metabolisms of Cardiac Troponin Molecules—Part 1: The Main Stages of Metabolism, Release Stage

Cardiac troponins (cTns) have long been the most valuable and specific biomarkers for detecting ischemic myocardial cells (MCs) injury, which is one of the key signs of myocardial infarction (MI). Modern methods (highly sensitive and ultra-sensitive immunoassays (hs-cTns)) of detection are an important and indispensable tool for the early diagnosis of MI and the choice of patient management protocols. Timely diagnosis of MI can significantly improve the prognosis of patients. However, in real clinical practice, doctors often face a significant problem when using cTns—the difficulty of differential diagnosis due to frequent and unexplained increases in the concentration of cTns in blood serum. In addition, there is conflicting information that may potentially affect the diagnostic capabilities and value of cTns: the influence of certain biological factors (diurnal rhythm, gender and age) on serum cTns levels; extra-cardiac expression of cTns; the possibilities of non-invasive diagnosis of MI; and other pathological conditions that cause non-ischemic injury to MCs. To solve these problems, it is necessary to concentrate on studying the metabolism of cTns. The review of our current knowledge about cTns metabolism consists of two parts. In this (first) part of the manuscript, the main stages of cTns metabolism are briefly described and the mechanisms of cTns release from MCs are considered in detail.

Biology of Cardiac Troponins: Emphasis on Metabolism

Simple Summary

Cardiovascular diseases, including myocardial infarction, are among the most common diseases worldwide. Markers associated with the diagnosis of myocardial infarction have been in the spotlight for many years. The most commonly used markers of myocardial infarction are cardiac troponins. However, insufficient understanding of the biology and metabolism of cardiac troponins does not allow us to fully unlock the full diagnostic potential of these cardiomarkers. In this article, I summarized and discussed in detail the features of the metabolism of cardiac troponins. I conducted a comprehensive review of current literary sources and presented my point of view. The format of the manuscript includes a consistent description of the biology and stages of the metabolism of cardiac troponins, starting from the release and circulation, and ending with the features of elimination of cardiac troponins. The possible influence of the biology of cardiac troponins on the diagnostic value of cardiac troponins is analyzed. Based on the analysis of the literature, I found a close relationship between the diagnostic value of cardiac troponins and their biology/metabolism. Further research is needed to increase the diagnostic value of cardiac troponins, and to fully unlock their diagnostic potential.

Abstract

Understanding of the biology of endo- and exogenous molecules, in particular their metabolism, is not only of great theoretical importance, but also of high practical significance, since many molecules serve as drug targets or markers for the laboratory diagnostics of many human diseases. Thus, cardiac troponin (cTns) molecules have long been used as key markers for the confirmation of diagnosis of myocardial infarction (MI), and with the introduction of contemporary (high sensitivity) test methods, many of our concepts related to the biology of these cardiac markers have changed significantly. In current clinical practice, there are opening new promising diagnostic capabilities of cTns, the understanding and justification of which is closely connected with the theoretical principles of the metabolism of these molecules. However, today, the biology and metabolism of cTns have not been properly investigated; in particular, we do not know the precise mechanisms of release of these molecules from the myocardial cells (MCs) of healthy people and the mechanisms of circulation, and the elimination of cTns from the bloodstream. The main purpose of this manuscript is to systematize information about the biology of cTns, with an emphasis on the metabolism of cTns. The format of this paper, starting with the release of cTns in the blood and concluding with the metabolism/filtration of troponins, provides a comprehensive yet logically easy way for the readers to approach our current knowledge in the framework of understanding the basic mechanisms by which cTns are produced and processed. Conclusions. Based on the analysis of the current literature, the important role of biology and all stages of metabolism (release, circulation, removal) of cTns in laboratory diagnostics should be noted. It is necessary to continue studying the biology and metabolism of cTns, because this will improve the differential diagnosis of MI and i a new application of cTns immunoassays in current clinical practice.

Cardioprotective Strategies for Doxorubicin-induced Cardiotoxicity: Present and Future

The improvement of drugs and protocols of chemotherapeutic treatment has led to improved outcomes and survival in patients with cancer. But along with this, at first glance a positive point, there was another interdisciplinary problem, which is the need for early detection and treatment of developing cardiotoxicity when taking chemotherapy drugs. The study of cardioprotective strategies has recently become increasingly relevant, due to the fact that many patients who have successfully undergone treatment for cancer have a high risk of developing or are at high risk of death from cardiovascular diseases. One of the main drugs for the treatment of a number of oncological diseases is an anthracycline – type antibiotic-doxorubicin. This review briefly examines the risk factors and pathophysiological mechanisms underlying anthracycline cardiotoxicity. The current possibilities of cardioprotection of anthracycline cardiotoxicity are considered in detail, and some promising targets and drugs for improving cardioprotective strategies are discussed.

Interpretation of Cardiac and Non-Cardiac Causes of Elevated Troponin T Levels in Non-Acute Coronary Syndrome Patients in the Emergency Department

The definition of myocardial infarction was updated in 2000 to include an elevation of cardiac troponin T or I (cTnT or xTnI) alongside clinical evidence of myocardial infarction. The redefinition was jointly done by the American College of Cardiology Committee and the European Society of Cardiology. Since then, cardiac troponin T and I have assumed the position as the primary biochemical markers for diagnosing myocardial infarction. The high sensitivity of cardiac troponin for myocardial necrosis influenced the decision to include cardiac troponins (cTn) in the diagnostic pathway. An elevated cTn level indicates the presence of myocardial injury. However, it does not give the underlying reason for the damage. Apart from acute myocardial infarction (AMI), a range of potential diseases feature troponin release, including heart failure, acute pulmonary embolism, end-stage renal disease, and myocarditis. However, regardless of the mechanism that triggers the release from cardiac myocytes, elevated cTnI and cTnT typically implies a poor prognosis. This review attempts to explain both the cardiac and non-cardiac causes of increased cTnT in emergency department patients.

Some Common Causes of False Positive Increases in Serum Levels of Cardiac Troponins

Cardiac troponin molecules (cTnI and cTnT) are the most valuable and in-demand biomarkers for detecting various types of myocardial damage (reversible and irreversible, ischemic, inflammatory, toxic, etc.) in current clinical practice. These biomarkers are widely used for early diagnosis of acute myocardial infarction (AMI) and risk stratification of patients suffering from a number of cardiac (such as myocarditis, heart failure, cardiomyopathy, etc.) and extra-cardiac diseases (such as sepsis, renal failure, pulmonary embolism, neurological pathologies, etc.) that negatively affect the cells of cardiac muscle tissue. However, in daily routine clinical activities, internists and cardiologists often encounter cases of false increases in the concentrations of cardiospecific troponins. A false increase in the concentration of troponins contributes to an incorrect diagnosis and incorrect therapy, which can harm the patient. A false increase in the concentration of troponins contributes to an incorrect diagnosis and incorrect therapy, which can harm the patient, therefore, internists and cardiologists should be well aware of the main reasons and mechanisms for false-positive results cTnI and cTnT. This review article mainly focuses on the causes of falsepositive increases in serum levels of cTnI and cTnT, which provide helpful clues for the accurate diagnosis of AMI and evidence for the differential diagnosis.

Cardiac troponins: current information on the main analytical characteristics of determination methods and new diagnostic possibilities

The methods used to diagnose cardiovascular diseases are constantly being improved, leading to an expanded perception of the diagnostic value of biomarkers and their new diagnostic possibilities. One striking example are the main biomarkers used to diagnose acute myocardial infarction: cardiac troponins. The first methods for determining cardiac troponins (proposed 30 years ago) were characterized by extremely low sensitivity. Therefore, they could only detect large acute myocardial infarctions. These methods were also characterized by low specificity, expressed as a high probability of cross-reactivity with skeletal troponin isoforms, which generated false-positive results in the presence of skeletal myopathies and skeletal muscle lesions. With the introduction of high-sensitivity cardiac troponins into clinical practice, the possibility of early diagnosis and exclusion of acute myocardial infarction by assessing troponin concentrations in the first few hours (from admission to the first hour, second hour, or third hour) has become more specific. Our knowledge about cardiac troponins has changed over the years and promising new medical uses have emerged. This paper reviews current data on the diagnostic value of cardiac troponins, the main methods used for their determination, and their analytical characteristics from historical and modern insights.

[Mechanisms of increase and diagnostic role of highly sensitive troponins in arterial hypertension]

Improvement in immunochemical methods for the determination of key biomarkers of acute myocardial infarction has led not only to an improvement in the early diagnosis of acute myocardial infarction, but also to a change in many of our ideas about the biology and diagnostic role of cardiac troponins. Modern (highly and ultrasensitive) laboratory methods for the determination of cardiac troponin molecules in human biological fluids are highly sensitive, which makes it possible to detect even the smallest damage to cardiomyocytes that occur at the early stages of many pathologies of cardiac (coronary heart disease, arterial hypertension, etc.) and extracardiac etiology (renal failure, sepsis, chronic obstructive pulmonary disease and others), as well as under the influence of a number of physiological conditions, including the influence of physical exercises, psychoemotional stress, gender characteristics (higher levels of cardiac troponins in men, compared with women), age characteristics (an increase in the concentration of cardiac troponins with age) and circadian characterisics (prevalence of morning values of cardiac troponins concentration over evening ones). In this regard, the diagnostic capabilities of the use of highly sensitive cardiac troponins have been significantly expanded. One of the promising areas for the use of highly sensitive cardiac troponins includes the assessment of the risk of adverse cardiovascular events both in healthy patients and in patients with various risk factors for their development, one of which can be considered arterial hypertension. This article systematizes the results of clinical studies evaluating the diagnostic role of highly sensitive cardiac troponins in biological fluids (blood serum and urine) in hypertension and discusses in detail the mechanisms of increasing the levels of highly sensitive troponins in this pathological condition.

Elevation Mechanisms and Diagnostic Consideration of Cardiac Troponins under Conditions Not Associated with Myocardial Infarction. Part 2

This article proceeds with a discussion of the causes and mechanisms of an elevation in cardiac troponins in pathological conditions not associated with acute myocardial infarction. The second part of the article discusses the causes and mechanisms of cardiac troponins elevation in diabetes mellitus, arterial hypertension, hereditary cardiomyopathies, cardiac arrhythmias (atrial fibrillation, supraventricular tachycardia), acute aortic dissection, and diseases of the central nervous system (strokes, subarachnoidal hemorrhage). The final chapter of this article discusses in detail the false-positive causes and mechanisms of elevated cardiac troponins.

Microrna: the role in the pathophysiology of atrial fibrillation and potential use as a biomarker

The aim of the study was to analyze medical literature on the role of microRNA in the pathophysiology of atrial fibrillation and the possibilities of using microRNAs as biomarkers.The analysis of modern medical literature was carried out using the PubMed – NCBI database.

Atrial fibrillation (AF) is a common and serious cardiovascular disease. The pathophysiological mechanisms underlying the development of atrial fibrillation are not entirely clear. In addition, there are no optimal biomarkers for early detection and assessment of the prognosis for patients with atrial fibrillation. Recently, the attention of researchers has been directed to the molecules of microRNA. There is a lot of evidence that they are involved in the pathogenesis of neurological, oncological, and cardiovascular diseases. This review examines the role of microRNAs in the pathophysiology of atrial fibrillation. The possibility of using microRNA as a biomarker for the diagnosis and prediction of atrial fibrillation is also discussed.MicroRNAs play a crucial role in the pathophysiology of atrial fibrillation, regulating the mechanisms of atrial remodeling, such as electrical remodeling, structural remodeling, remodeling of the autonomic nervous system, and impaired regulation of calcium levels. The stability of microRNAs and the possibility to study them in various biological fluids and tissues, including blood, make these molecules a promising diagnostic biomarker for various cardiovascular diseases. The presented data clearly indicate that AF is associated with changes in the expression level of various microRNAs, which can be quantified using a polymerase chain reaction. Further research is required to assess the role of microRNAs as biomarkers for atrial fibrillation, in particular to establish precise reference limits.

Cardiac Troponins Metabolism: From Biochemical Mechanisms to Clinical Practice (Literature Review)

The metabolic processes of endo- and exogenous compounds play an important role in diagnosing and treating patients since many metabolites are laboratory biomarkers and/or targets for therapeutic agents. Cardiac troponins are one of the most critical biomarkers to diagnose cardiovascular diseases, including acute myocardial infarction. The study of troponin metabolism is of great interest as it opens up new possibilities for optimizing laboratory diagnostics. This article discusses in detail the key stages of the cardiac troponins metabolism, in particular the mechanisms of release from a healthy myocardium, mechanisms of circulation in the bloodstream, possible mechanisms of troponin penetration into other biological fluids (oral fluid, cerebrospinal fluid, pericardial and amniotic fluids), mechanisms of elimination of cardiac troponins from the blood, and daily changes in the levels of troponins in the blood. Considering these aspects of cardiac troponin metabolism, attention is focused on the potential value for clinical practice.

The Main Causes and Mechanisms of Increase in Cardiac Troponin Concentrations Other Than Acute Myocardial Infarction (Part 1): Physical Exertion, Inflammatory Heart Disease, Pulmonary Embolism, Renal Failure, Sepsis

The causes and mechanisms of increased cardiac troponin T and I (cTnT and cTnI) concentrations are numerous and are not limited to acute myocardial infarction (AMI) (ischemic necrosis of cardiac myocytes). Any type of reversible or irreversible cardiomyocyte injury can result in elevated serum cTnT and cTnI levels. Researchers and practitioners involved in the diagnosis and treatment of cardiovascular disease, including AMI, should know the key causes and mechanisms of elevated serum cTnT and cTnI levels. This will allow to reduce or completely avoid diagnostic errors and help to choose the most correct tactics for further patient management. The purpose of this article is to discuss the main causes and mechanisms of increase in cardiac troponins concentrations in frequently occurring physiological (physical exertion, psycho-emotional stress) and pathological conditions (inflammatory heart disease, pulmonary embolism, chronic renal failure and sepsis (systemic inflammatory response)) not related to myocardial infarction.

Experimental Modeling Of Hypothyroidism: Principles, Methods, Several Advanced Research Directions In Cardiology

Hypothyroidism is one of the most common pathological conditions in modern clinical practice. Due to the fact that the targets of thyroid hormones are virtually all organs and tissues, the morphological and clinical manifestations arising with a deficiency of thyroid hormones are quite diverse. Experimental models of hypothyroidism in laboratory animals are widely used for preclinical study of the fundamental pathophysiological mechanisms underlying hypothyroidism, as well as for assessing the effectiveness of treatment-and-prophylactic effects. Currently, several groups of effective models of hypothyroidism have been developed: dietary, surgical, medicamentous, genetic, radioactive and immunological. Each of the specified models is based on different principles, has advantages and disadvantages, and can be used depending on the goals and objectives of the experiment. In this review, we will consistently consider hypothyroidism modeling methods and indicate some promising areas of their use in cardiology.

Elevation Mechanisms and Diagnostic Consideration of Cardiac Troponins under Conditions Not Associated with Myocardial Infarction. Part 1

Although cardiac troponins are considered the most specific biomarkers for the diagnosis of acute myocardial infarction (AMI), their diagnostic consideration goes far beyond the detection of this dangerous disease. The mechanisms of cardiac troponin elevation are extremely numerous and not limited to ischemic necrosis of cardiac myocytes. Practitioners should be well aware of the underlying pathological and physiological conditions that can lead to elevated serum levels of cardiac troponins to avoid differential diagnostic errors, which will be greatly increased if clinicians rely on laboratory data alone. This article presents a classification of the main causes of an elevation in cardiac troponins and discusses in detail the mechanisms of such elevation and the diagnostic consideration of cardiac troponins in some conditions not associated with AMI, such as physical exertion, inflammatory heart diseases (myocarditis and endocarditis), pulmonary embolism (PE), renal failure, and systemic inflammation (sepsis).

Clinical and Diagnostic Value of Highly Sensitive Cardiac Troponins in Arterial Hypertension

In modern laboratory diagnostics of cardiovascular diseases (CVD), there is a clear tendency toward an increase in the sensitivity of methods for determining key CVD biomarkers, among which highly sensitive cardiac troponins (hs-Tn) deserve special attention. The introduction of the latter into clinical practice made it possible not only to improve the early diagnosis of acute myocardial infarction but also to open up a number of additional valuable opportunities for the use of hs-Tn, including the assessment of the risk of developing CVD in a healthy population, detection and monitoring of early myocardial injuries in the early stages of CVD development (for example, with ischemic heart disease and arterial hypertension), with noncardiac pathologies (for example, sepsis, chronic obstructive pulmonary disease, chronic renal failure, stroke, cancer, etc), and diagnostics of CVD by using biological fluids that can be obtained by noninvasive methods. This article discusses in detail the diagnostic value of hs-Tn in serum and urine in cases of arterial hypertension. Also, the paper pays considerable attention to the consideration of the mechanisms underlying the increase in hs-Tn in serum and urine in cases of arterial hypertension.

Cardiac Troponins: Contemporary Biological Data and New Methods of Determination

Laboratory diagnosis plays one of the key roles in the diagnosis of many diseases, including cardiovascular diseases (CVD). The methods underlying the in vitro study of many CVD biomarkers, including cardiac troponins (cTnI and cTnT), are imperfect and are continually being improved to enhance their analytical performance, with sensitivity and specificity being the most important. Recently developed improved cTnI and cTnT detection methods, referred to as highly sensitive methods (hs-cTnI, hs-cTnT), have changed many of our ideas about the biology of cardiac troponins and opened up a number of additional diagnostic capabilities for practical healthcare. This article systematizes some relevant data on the biology of cardiac troponins as well as on methods for determining cTnI and cTnT with an analysis of the diagnostic value of their analytical characteristics (limit of blank, limit of detection, 99th percentile, coefficient of variation, and others). Data on extracardiac expression of cTnI and cTnT, mechanisms of formation and potential clinical significance of gender, age, and circadian characteristics of hs-cTnI and hs-cTnT content in serum are discussed. Considerable attention is paid to the discussion of new diagnostic capabilities of hs-cTnI, hs-cTnT, including consideration of promising possibilities for their study in biological fluids that can be obtained by non-invasive methods. Also, some possibilities of using hs-cTnI and hs-cTnT as prognostic laboratory biomarkers in healthy people (for example, to assess the risk of developing CVD) and in patients suffering from a number of pathological conditions that cause damage to cardiomyocytes are examined, and the potential mechanisms underlying the increase in hs-cTnI and hs-cTnT are discussed.

Comorbidity in chronic obstructive pulmonary disease and cardiovascular disease

Comorbidity is one of the most significant problems of modern healthcare. Numerous studies have analyzed the possible pathogenetic mechanisms and relationships between a wide variety of diseases. Cardiovascular (CVD) and pulmonary diseases, in particular chronic obstructive pulmonary disease (COPD), have a number of the same risk factors and pathogenetic links, which aggravate each other's course. Moreover, CVD and COPD are among the most common diseases in the world. This review provides up-to-date information on the prevalence, risk factors and pathophysiological mechanisms underlying this unfavorable combination of diseases. Some problems of diagnosis and treatment of patients with COPD and CVD are also discussed.

High-sensitivity cardiac troponins: detection and central analytical characteristics

Recently, there have been some important changes in the laboratory diagnosis of patients with acute coronary syndrome, due to the introduction into routine practice of new high- and ultra-sensitive techniques for detection of myocardial damage biomarkers — cardiac troponins. Each method for cardiac troponins’ detection, among the existing wide variety of troponin immunoassays, has different analytical characteristics and allows the detection of different concentrations of troponins in the same patient. With an increasing number of companies developing high-sensitivity troponin immunoassays receiving regulatory approval, there is an urgent need for independent analytical and clinical evaluation of each method. This article discusses high- and ultrasensitive techniques for detection of cardiac troponins. The modern data on biochemical and metabolic characteristics of troponins, obtained using high- and ultra-sensitive techniques, are described: sex, age, circadian features and potential for detecting troponins in other biological fluids. Considerable attention is paid to the analytical characteristics of troponin immunoassays: limit of blank, limit of detection and limit of quantitation, coefficient of variation, as well as the 99th percentile and factors influencing it.

High-sensitivity cardiac troponins: circadian rhythms

High-sensitivity cardiac troponins (hs-cTnI and hs-cTnT) contribute to a progression in the diagnosis and treatment of cardiovascular diseases: acceleration of diagnosis of acute myocardial infarction (early diagnostic algorithms: 0-1 h, 0-3 h), and earlier initiation of optimal treatment, expansion of diagnostic and prognostic potential (earlier detection of myocardial damage during chemotherapy, endocarditis, myocarditis and other diseases). However, increased sensitivity slightly reduced the specificity and created the need for a more thorough interpretation of elevated levels of hs-cTnI and hs-cTnT in a number of pathologies that damage cardiomyocytes. In addition, there was a need to introduce reference levels of hs-cTnI and hs-cTnT (99 percentile), taking into account sex. Recently, there has also been information about circadian (diurnal) variations in hs-cTnT and hs-cTnI levels. We analyze in detail the results of clinical studies that found circadian changes in hs-cTnI and hs-cTnT. Possible mechanisms underlying these changes in hs-cTnT and hs-cTnI concentrations are discussed.

Biomarkers of acute myocardial infarction: diagnostic and prognostic value. Part 2 (Literature review)

In the second part of the review, we continue the discussion of biomarkers that have a diagnostic and prognostic significance in acute myocardial infarction (AMI). The study of the AMI pathophysiology through the experimental and clinical research contributes to the discovery of new regulatory molecules and pathogenetic mechanisms underlying AMI. At the same time, many molecules involved in the pathogenesis of AMI can be used as effective biomarkers for the diagnosis and prediction of AMI. This article discusses in detail the diagnostic and prognostic value of inflammatory biomarkers of AMI (C-reactive protein, interleukin-6, tumor necrosis factor-alpha, myeloperoxidase, matrix metalloproteinases, soluble form of CD40 ligand, procalcitonin, placental growth factor) and a number of recently discovered new biomarkers of AMI (microribonucleic acids, galectin-3, stimulating growth factor expressed by gene 2, growth differentiation factor 15, proprotein convertase of subtilisin-kexin type 9).

Pathophysiological mechanisms of cardiotoxicity in chemotherapeutic agents

Certain success has been achieved in the treatment of cancer due to the development of various effective chemotherapeutic drugs. However, an increase in their effectiveness (aggressiveness) was associated with a growth of undesirable effects on the entire human body, in particular, on the cardiovascular system. The damage to the cardiovascular system from chemotherapy in many cases is more significant than from the underlying disease. In recent years, a new direction of medicine has been formed - cardio-oncology. The major groups of cardiotoxic chemotherapeutic agents are anthracyclines, inhibitors of epidermal growth factor receptor type 2 (anti-HER2), antimetabolites, microtubule inhibitors, proteasome inhibitors, platinum-based chemotherapeutic drugs, and angiogenesis inhibitors (inhibitors of vascular endothelial growth factor). This review discusses principal pathophysiological mechanisms of the cardiotoxicity of these chemotherapeutic drugs.

Biomarkers of acute myocardial infarction: diagnostic and prognostic value. Part 1 (literature review)

Morbidity and mortality rates from acute myocardial infarction (AMI) have been growing rapidly in recent years, causing significant socio-economic damage. Cardiac biomarkers play an important role in the diagnosis and prediction of AMI. In our review article, we will summarize information about the main existing cardiac biomarkers and focus on their diagnostic and prognostic value for patients with AMI. In the first part of the review, we consider the diagnostic and prognostic value of biomarkers of necrosis and myocardial ischemia (aspartate aminotransferase; creatine phosphokinase; cardiac troponins; myoglobin, ischemia-modified albumin, fatty acid binding protein) and neuroendocrine AMI biomarkers (natriuretic peptides, adrenomedullin, catestatin, components of the renin-angiotensin-aldosterone system). In the second part of the review, we discuss the diagnostic and prognostic value of inflammatory AMI biomarkers (C-reactive protein, interleukin-6, tumor necrosis factor, myeloperoxidase, matrix metalloproteinases, soluble CD40 ligand form (sCD40L), procalcitonin, placental growth factor (PGF), procalcitonin) and recently discovered new biomarkers (microRNA, stimulating growth factor, expressed by genome 2 (ST2), growth differentiation factor 15 (GDF-15), galectin-3).

Non-coronarogenic causes of increased cardiac troponins in clinical practice

Cardiospecific isoforms of troponins are the most sensitive and specific biomarkers for the diagnosis of myocardial infarction. However, though elevated troponin levels indicate myocardial damage, they do not determine the cause and mechanism of the damage. With the new highly sensitive methods, very minor damages of the heart muscle can be detected. Myocardial damage can occur in many non-coronarogenic diseases. In this review, we discuss the mechanisms of elevation, the diagnostic value of cardiac troponins in the renal failure, tachyarrhythmias, endocarditis, myocarditis, pericarditis, sepsis, neurogenic pathologies (stroke), pulmonary embolism. In addition, we pay attention to the main reasons for a false-positive increase of the concentration of cardiac troponins: heterophilic antibodies, rheumatoid factor, alkaline phosphatase, cross-reactions with skeletal muscle troponins.