Cardiac Biomarker Responses to Dobutamine Stress Echocardiography in Healthy Volunteers and Patients with Coronary Artery Disease

The current paradigm of cardiac troponin increase among athletes

Although it is known that exercise improves cardiovascular health and extends life expectancy, a significant number of people may also experience an elevation in cardiac troponin levels as a result of exercise. For many years, researchers have argued whether exercise-induced cardiac troponin rises are a consequence of a physiological or pathological reaction and whether they are clinically significant. Differences in cardiac troponin elevation and cardiac remodeling can be seen between athletes participating in different types of sports. When forecasting the exercise-induced cardiac troponin rise, there are many additional parameters to consider, as there is a large amount of interindividual heterogeneity in the degree of cardiac troponin elevation. Although it was previously believed that cardiac troponin increases in athletes represented a benign phenomenon, numerous recent studies disproved this notion by demonstrating that, in specific individuals, cardiac troponin increases may have clinical and prognostic repercussions. This review aims to examine the role of cardiac troponin in athletes and its role in various sporting contexts. This review also discusses potential prognostic and clinical implications, as well as future research methods, and provides a straightforward step-by-step algorithm to help clinicians interpret cardiac troponin rise in athletes in both ischemic and non-ischemic circumstances.

Myocardial injury in stress echocardiography: Comparison of dobutamine, dipyridamole and dynamic stressors-single center study

OBJECTIVES

In stress echocardiography (SE), dipyridamole (DIP) and dynamic stress (ExSE) are reported as being safer than dobutamine stress echocardiography (DSE). We investigated whether these commonly used stressors cause myocardial injury, measured by high sensitivity troponin T (hsTnT).

METHODS

One hundred and thirty five patients (DSE n = 46, ExsE n = 46, DIP n = 43) with negative result of SE were studied. The exclusion criteria were known ischaemic heart disease (IHD), baseline wall motion abnormalities, left ventricle systolic dysfunction/regional wall motion abnormalities, septum/posterior wall ≥13 mm, diabetes/pre-diabetes, baseline hsTnT level ≥14 ng/L, baseline blood pressure ≥160/100 mmHg, peak pulmonary pressure ≥45mmHg, eGFR <1ml/s/1.73m² , more than mild to moderate valvular disease and dobutamine side effects. HsTnT was measured before and 180 minutes after the test.

RESULTS

All patients had low pre-test probabilities of having obstructive IHD. HsTnT increased in DSE, less so in ExSE, and was unchanged in the DIP group (∆hsTnT 9.4 [1.5-58.6], 1.1 [-0.9-15.7], -0.1 [-1.4-2.1] ng/L, respectively, p<0.001). In DSE, the ∆hsTnT was associated with peak dobutamine dose (r = 0.30, p = 0.045), test length (r = 0.43, p = 0.003) and atropine use (p<0.001). In ExSE, the hsTnT increase was more likely in females (p = 0.012) and the elderly (>65 years) (r = 0.32, p = 0.03); no association was found between atropine use (p = 0.786) or test length and ∆hsTnT (r = 0.10, p = 0.530).

CONCLUSIONS

DSE is associated with myocardial injury in patients with negative SE, no injury was observed in DIP and only mild case in ExSE. Whether myocardial injury is causative of the higher reported adverse event rates in DSE remains to be determined.

Myocardial injury after major noncardiac surgery: A secondary analysis of a randomized controlled trial

BACKGROUND

Myocardial injury after noncardiac surgery frequently occurs and may influence survival. The aims of this study were to examine the association between myocardial injury after noncardiac surgery and patient and procedural factors as well as its impact on postoperative clinical outcome.

METHODS

A retrospective analysis was conducted from data collected in adults enrolled in a randomized trial in elective major open abdominal surgery. Preoperative patient characteristics, intraoperative hemodynamic changes, and postoperative adverse events were analyzed, and Kaplan-Meier curves were built for postoperative survival probability. After adjustment for baseline patient and procedural characteristics, the effect of myocardial injury after noncardiac surgery on postoperative outcomes was analyzed in a propensity score matched cohort.

RESULTS

Among 394 patients, myocardial injury after noncardiac surgery was reported in 109 (27.7%) and was associated with a higher cardiovascular risk profile, prolonged surgery (333 ± 111 min vs 295 ± 134 min, P = .010), greater need for transfusions (41.3% vs 19.3%, P < .001), higher incidence of major adverse cardiac events (22.9% vs 6.7%, P < .001), pulmonary complications (31.2% vs 17.9%, P = .004) , acute kidney injury (30.3% vs 18.2%, P = .009), and systemic inflammatory syndrome (28.4% vs 13.0%, P < .001). After propensity score matching, the operative time and the need for blood transfusion remained higher among myocardial injury after noncardiac surgery patients who experienced more frequent major adverse cardiac events and acute kidney injury. In both the entire and matched cohorts, survival up to 30 months after surgery was determined mainly by the presence of cancer.

CONCLUSION

The burden of cardiovascular disease and operative stress surgery is predictive of myocardial injury after noncardiac surgery and, in turn, with a higher incidence of cardiac adverse events, whereas the presence of cancer is associated with poor survival in patients undergoing major open abdominal surgery. Further studies are needed to determine whether myocardial injury after noncardiac surgery can be prevented by better control of the patient's cardiovascular condition and implementation of less invasive of surgical procedures.

Cardioprotective shock management: monitoring and supportive therapies

Cardiogenic shock is a highly lethal syndrome, leading to rapid death or secondary multiorgan damage, but current shock therapies, including mechanical support devices, also have a significant side effect profile. The overarching goal of shock therapy is ensuring long-term survival with good quality of life. This implies averting death, modifying the disease course by promoting heart recovery and avoiding additional cardiac damage, protecting other organs, and circumventing complications. Monitoring and supportive therapies are subordinate to these goals. Rather than merely following preconceived notions, the rapid evolution in mechanical support technology requires iterative and critical review of the benefits of current procedures, protocols and drugs in view of their overall contribution to the therapeutic goals. This article discusses various monitoring and supportive pharmaceutical modalities typically used in patients with cardiogenic shock requiring mechanical support.

Cardiac troponin and defining myocardial infarction

The 4th Universal Definition of Myocardial Infarction has stimulated considerable debate since its publication in 2018. The intention was to define the types of myocardial injury through the lens of their underpinning pathophysiology. In this review, we discuss how the 4th Universal Definition of Myocardial Infarction defines infarction and injury and the necessary pragmatic adjustments that appear in clinical guidelines to maximize triage of real-world patients.

Coronavirus Disease 2019 (COVID-19) and its implications for cardiovascular care: expert document from the German Cardiac Society and the World Heart Federation

Coronavirus diseases 2019 (COVID-19) has become a worldwide pandemic affecting people at high risk and particularly at advanced age, cardiovascular and pulmonary disease. As cardiovascular patients are at high risk but also have dyspnea and fatigue as leading symptoms, prevention, diagnostics and treatment in these patients are important to provide adequate care for those with or without COVID-19 but most importantly when comorbid cardiovascular conditions are present. Severe COVID-19 with acute respiratory distress (ARDS) is challenging as patients with elevated myocardial markers such as troponin are at enhanced high risk for fatal outcomes. As angiotensin-converting enzyme 2 (ACE2) is regarded as the viral receptor for cell entry and as the Coronavirus is downregulating this enzyme, which provides cardiovascular and pulmonary protection, there is ongoing discussions on whether treatment with cardiovascular drugs, which upregulate the viral receptor ACE2 should be modified. As most of the COVID-19 patients have cardiovascular comorbidities like hypertension, diabetes, coronary artery disease and heart failure, which imposes a high risk on these patients, cardiovascular therapy should not be modified or even withdrawn. As cardiac injury is a common feature of COVID-19 associated ARDS and is linked with poor outcomes, swift diagnostic management and specialist care of cardiovascular patients in the area of COVID-19 is of particular importance and deserves special attention.

Predicting cardiac risk in noncardiac surgery: a narrative review

Risk stratification endeavors to categorize patients into groups based on the level of risk for each group. Improved perioperative screening tests using more sensitive cardiac biomarkers have revealed that about 68% of perioperative myocardial infarctions (MI) are asymptomatic and may only be detected by routine postoperative screening with troponin measurements. This is important since myocardial injury not meeting criteria for myocardial infarction is associated with increased risk of 30-day mortality (Botto et al. in Anesthesiology 120:564-578, 2014). Traditional risk indices including the revised cardiac risk index (RCRI) and the myocardial infarction cardiac arrest (MICA) index were developed based on overt clinical signs of myocardial infarction and significantly underestimate adverse cardiac events. Recently, brain type natriuretic peptides (BNP) and its precursor n- terminal pro-brain type natriuretic peptide (nt-proBNP) have been shown to be powerful prognostic markers. Incorporating serum biomarkers into updated clinical risk indices is likely to improve their performance. Further studies are needed to determine appropriate clinical interventions to treat isolated elevations in cardiac troponin levels and further mitigate the increased risk of morbidity and mortality. The objective of this review is to summarize the current literature on the clinical diagnoses of perioperative myocardial injury in the setting of noncardiac surgery.

Implications of the complex biology and micro-environment of cardiac sarcomeres in the use of high affinity troponin antibodies as serum biomarkers for cardiac disorders

Cardiac troponin I (cTnI), the inhibitory-unit, and cardiac troponin T (cTnT), the tropomyosin-binding unit together with the Ca-binding unit (cTnC) of the hetero-trimeric troponin complex signal activation of the sarcomeres of the adult cardiac myocyte. The unique structure and heart myocyte restricted expression of cTnI and cTnT led to their worldwide use as biomarkers for acute myocardial infarction (AMI) beginning more than 30 years ago. Over these years, high sensitivity antibodies (hs-cTnI and hs-cTnT) have been developed. Together with careful determination of history, physical examination, and EKG, determination of serum levels using hs-cTnI and hs-cTnT permits risk stratification of patients presenting in the Emergency Department (ED) with chest pain. With the ability to determine serum levels of these troponins with high sensitivity came the question of whether such measurements may be of diagnostic and prognostic value in conditions beyond AMI. Moreover, the finding of elevated serum troponins in physiological states such as exercise and pathological states where cardiac myocytes may be affected requires understanding of how troponins may be released into the blood and whether such release may be benign. We consider these questions by relating membrane stability to the complex biology of troponin with emphasis on its sensitivity to the chemo-mechanical and micro-environment of the cardiac myocyte. We also consider the role determinations of serum troponins play in the precise phenotyping in personalized and precision medicine approaches to promote cardiac health.

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Serum levels of cardiac TnI and cardiac TnT permit stratification of patients with chest pain.

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Release of troponins into blood involves not only frank necrosis but also programmed necroptosis.

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Genome wide analysis of serum troponin levels in the general population may be prognostic about cardiovascular health.

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Significant levels of serum troponins with exhaustive exercise may not be benign.

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Troponin in serum can lead to important data related to personalized and precision medicine.

Development of mutant human immunoreactive trypsinogen 1 (IRT1) and mutant human immunoreactive trypsinogen 2 (IRT2) for use in immunoassays

Immunoreactive Trypsinogen (IRT) is a protein-based pancreatic proenzyme that has an important role in protein digestion in humans. In human body, once IRT present in the small intestine, the proteolytic cleavage activates trypsinogen into trypsin. When IRT is in the active form, it is capable to cleave antibodies, other proteins and even itself while it is desired to use in immunoassays. According to the literature, there are three important IRT isoforms called Immunoreactive Trypsinogen 1 (IRT1), Immunoreactive Trypsinogen 2 (IRT2), and Immunoreactive Trypsinogen 3 (IRT3). However, trypsinogen 1 (cationic trypsinogen, IRT1) and trypsinogen 2 (anionic trypsinogen, IRT2) are the major isoforms in human pancreatic juice and used in the diagnosis of cystic fibrosis (CF). In this study, it is aimed to restrain its proteolytic activity with K23D mutation, which changes lysine (K) residue at the 23rd position to aspartic acid (D). Because we wanted to produce a hassle-free human recombinant immune reactive trypsinogen proenzyme which has similar antigenic properties with the native form. It is also aimed that the mutant IRTs do not exhibit proteolytic activity for the development of durable detection kits with a longer shelf life for both two isoforms. The innovation was actualized in order to use IRTs as a standard antigen in Immunoassays such as ELISA kits. The gene was synthesized as mutated and expressed in P. pastoris X-33 strain. The loss of proteolytic activity has been proven with the BAEE test. Antigenic properties of K23D IRTs and the effect of proteolytic inactivation on their performance in immunoassays were assessed with ELISA and Western Blot. In ELISA results K23D mutated IRTs showed higher signals than Wild-Type forms.

Troponin Release and Reversible Left Ventricular Dysfunction After Transient Pressure Overload

BACKGROUND

The authors previously demonstrated that brief ischemia elicits cardiac troponin I (cTnI) release and myocyte apoptosis in the absence of necrosis. It remains uncertain whether other pathophysiological stresses can produce apoptosis and transient cTnI release without ischemia.

OBJECTIVES

This study sought to determine whether a transient increase in left ventricular (LV) preload elicits cTnI release in the absence of ischemia.

METHODS

Propofol-anesthetized swine (N = 13) received intravenous phenylephrine (PE) (300 μg/min) for 1 h to increase left ventricular end-diastolic pressure (LVEDP) to ∼30 mm Hg. Serial cTnI and echocardiographic function were assessed for 24 h, and myocardial tissue was analyzed for apoptosis and necrosis.

RESULTS

PE infusion increased systolic blood pressure from 137 ± 14 mm Hg to 192 ± 11 mm Hg (mean ± SD; p < 0.001) and increased LVEDP from 17 ± 2 mm Hg to 30 ± 5 mm Hg (p < 0.001). Myocardial flow measurements demonstrated no evidence of ischemia. Hemodynamics normalized rapidly after PE, but LV ejection fraction remained depressed (32 ± 21% vs. 58 ± 7%; p < 0.01) with normalization after 24 h (51 ± 16%; p = 0.31). Baseline transcoronary cTnI release was low (16 ± 20 ng/l) but increased to 856 ± 956 ng/l (p = 0.01) 1 h after LVEDP elevation. Circulating cTnI rose above the 99th percentile within 30 min and remained elevated at 24 h (1,462 ± 1,691 ng/l). Pathological analysis demonstrated myocyte apoptosis at 3 h (31.3 ± 11.9 myocytes/cm² vs. 4.6 ± 3.7 myocytes/cm²; p < 0.01), that normalized after 24 h (6.2 ± 5.6 myocytes/cm²; p = 0.46) without histological necrosis.

CONCLUSIONS

Transient elevations of LVEDP lead to cTnI release, apoptosis, and reversible stretch-induced stunning in the absence of ischemia. Thus, preload-induced myocyte injury may explain many cTnI elevations seen in the absence of clinical signs or symptoms of myocardial ischemia.

Relation of Isolated Systolic Hypertension and Pulse Pressure to High-Sensitivity Cardiac Troponin-T and N-Terminal pro-B-Type Natriuretic Peptide in Older Adults (from the Atherosclerosis Risk in Communities Study)

Isolated systolic hypertension (ISH) and elevated pulse pressure (PP) are common blood pressure (BP) abnormalities in older adults, reflect poor vascular compliance, and can signify risk for cardiovascular outcomes. We sought to characterize the associations of ISH and widened PP with high-sensitivity Troponin-T (hs-cTnT; a marker of myocardial damage) and N-terminal pro-B-type natriuretic peptide (NT-proBNP; a marker of hemodynamic stress) levels in older adults. We performed a cross-sectional analysis of 5,251 Atherosclerosis Risk in Communities (ARIC) study participants without heart failure who attended visit 5 (2011 to 2013). We used logistic regression to evaluate the association of ISH (systolic BP ≥140 mm Hg and diastolic BP < 90 mm Hg) and quartiles of PP with detectable (≥5 ng/L) and elevated hs-cTnT (≥14 ng/L); as well as elevated NT-proBNP (≥100 pg/mL). The mean age was 75 years, 58% were women, and 78% were white. ISH was present in 24.7% and PP ≥ 70 mm Hg in 30.3% of this cohort. Compared to participants with nonhypertensive BP (<140/90 mm Hg), ISH was independently associated with hs-cTnT and NT-proBNP; adjusted odds ratio of 1.5 (95% confidence interval: 1.1 to 1.9) for detectable hs-cTnT; 1.3 (1.1 to 1.5) for elevated hs-cTnT; and 1.8 (1.6 to 2.1) for elevated NT-proBNP. Increasing quartiles of PP were also significantly associated with both elevated hs-cTnT (p-for-trend <0.0001) and NT-proBNP (p-for-trend <0.0001). These associations were not modified by BP treatment status. In conclusion, ISH and wide PP are relatively common in older adults despite contemporary BP treatment and are associated with abnormalities in hs-cTnT and NT-pro BNP, findings that could guide personalized treatment of older patients with these BP aberrations.

Revisiting the Biological Variability of Cardiac Troponin: Implications for Clinical Practice

The diagnosis of acute myocardial injury requires a rise and/or fall of cardiac troponin (cTn) on serial testing, with at least one concentration above the 99^th percentile value of a normal reference population according to the recently published Fourth Universal Definition of Myocardial Infarction.1 However, the magnitude of change in cTn that constitutes a significant rise and/or fall was again not specified in detail. High-sensitivity cardiac troponin (hs-cTn) assays can measure ten-fold lower concentrations of cTn with more precision than older assays, and can accurately quantify cTn in more than 50% of healthy individuals with a coefficient of variation of less than 10% at the 99^th percentile. These hs-cTn assays are also able to detect the normal variations in cTn results that are due to biological variability. Understanding and quantifying the normal variations in cTn is important as this would allow significant changes to be better defined. Numerous studies have sought to investigate the biological variability of cTn over the last ten years. Such studies are usually conducted in healthy individuals, however individuals with chronic cardiac disease or chronic renal failure have also been examined. These studies have yielded varying results in regards to significant change values for cTn. In light of the recent redefinition for myocardial infarction, the purpose of this mini-review is to revisit the biological variability of cTn. In particular, we outline concepts for determining a significant change value, review the results of previous studies on the biological variation of cTn and discuss potential considerations for clinical practice.

Clinical use of cardiac troponin for acute cardiac care and emerging opportunities in the outpatient setting

Cardiac troponin (cTn) testing has evolved significantly in recent times. Because of increased sensitivity, its use has shifted from a marker used to help diagnose acute myocardial infarction (MI) to a marker than can be used in the outpatient setting, as well as for both detection of myocardial injury and risk-stratification. Its main role remains in the diagnosis of acute MI and the risk-stratification of patients presenting with suspected acute coronary syndrome. The analytical improvements in assays leading to precise high-sensitivity cTn assays have contributed to the development of numerous strategies to identify patients at both low- and high-risk for acute MI within a few hours. These approaches should reduce overcrowding in the emergency room and expedite triaging. The ability of measuring cTn in most patients using high-sensitivity (hs) assays has allowed for the opportunity to examine its use in the detection of cardiotoxicity in patients undergoing chemotherapy, as well as exploring the application in both primary and secondary prevention of coronary artery disease. This particular field of research has become increasingly complex, partly due to the numerous cTn assays available (I and T; point-of-care, contemporary, hs) and an array of approaches in which one can use the test. The purpose of this document is to summarize the analytical and clinical information relevant to cTn assays, in particular, hs-cTn assays, and describe present and future opportunities for use of cTn in acute cardiac care and in the outpatient setting.

High-sensitivity cardiac troponin T in young, healthy adults undergoing non-cardiac surgery

BACKGROUND

It is unclear if isolated postoperative cardiac-troponin elevation, often referred to as myocardial injury, represents a pathological event, as control studies in otherwise healthy adults are lacking.

METHODS

In this single-centre prospective observational cohort study, serial high-sensitivity cardiac troponin T (hscTnT) plasma concentrations were obtained from young, healthy adults undergoing elective orthopaedic surgery at three time points: before operation, 2-6 h, and 18-30 h after surgery. End points were hscTnT increases after surgery: ≥20% (exceeding analytical variability), ≥50% (exceeding short-term biological variability), and ≥85% (exceeding long-term biological variability). The secondary end point was myocardial injury, defined as new postoperative hscTnT elevation >99th % upper reference limit (URL) (women >10 ng litre^-1; men >15 ng litre^-1).

RESULTS

Amongst the study population (n=95), no hscTnT increase ≥20% was detected in 68 patients (73%). A hscTnT increase between 20% and 49% was observed in 17 patients (18%), 50-84% in seven patients (7%), and ≥85% in three patients (3%). Twenty patients (21%) had an absolute ΔhscTnT between 0 and 2 ng litre^-1, 12 patients (13%) between 2 and 4 ng litre^-1, three patients between 4 and 6 ng litre^-1, and one patient (1%) between 6 and 8 ng litre^-1. Myocardial injury (new hscTnT elevation >99th%) was diagnosed in one patient (1%). The median hscTnT concentrations did not increase after operation, and were 4 (3.9-5, inter-quartile range) ng litre^-1 at baseline, 4 (3.9-5) ng litre^-1 at 2-6 h after surgery, and 4 (3.9-5) ng litre^-1 on postoperative day 1.

CONCLUSIONS

One in four young adult patients without known cardiovascular disease developed a postoperative hscTnT increase, but without exceeding the 99th% URL and without evidence of myocardial ischaemia. These results may have important ramifications for the concept of postoperative myocardial injury, as they suggest that, in some patients, postoperative cardiac-troponin increases may be the result of a normal physiological process in the surgical setting.

CLINICAL TRIAL REGISTRATION

NCT 02394288.

Reference Values and Release Kinetics of B-Type Natriuretic Peptide Signal Peptide in Patients with Acute Myocardial Infarction

BACKGROUND

The signal peptide for human B-type natriuretic peptide preprohormone (BNPsp), which is released from cardiomyocytes, is increased in plasma of patients with acute myocardial infarction (AMI); however, its exact release kinetics have not been defined.

METHODS

We measured BNPsp and high-sensitivity cardiac troponin T (hs-cTnT) in a reference group of individuals without structural heart disease (n = 285) and determined the release kinetics of these biomarkers in patients (n = 29) with hypertrophic obstructive cardiomyopathy undergoing transcoronary ablation of septal hypertrophy (TASH), a procedure allowing exact timing of onset of iatrogenic AMI. Blood samples were collected before TASH and at numerous preselected time points after TASH.

RESULTS

The reference median BNPsp concentration was 53.4 pmol/L [interquartile range (IQR) 47.0–61.0; 95th percentile 85.9 pmol/L; 99th percentile 116.3 pmol/L]. Baseline concentrations in patients undergoing TASH were higher than in the reference group [91.9 pmol/L (IQR 62.9–116.4); P &lt; 0.0001]. BNPsp increased significantly, peaking at 15 min after induction of AMI [149.6 pmol/L (109.5–204.9) vs baseline; P = 0.004] and declining slowly thereafter, falling below the preprocedural value after 8 h (P = 0.014). hs-cTnT increased significantly 15 min after induction of AMI [26 ng/L (19–39) vs 18 ng/L (11–29); P = 0.001] and remained high at all later time points.

CONCLUSIONS

BNPsp concentrations increased immediately after AMI induction, providing early evidence of myocardial injury. The release kinetics of BNPsp differed from those of hs-cTnT. These findings provide information that should help in establishing the diagnostic value of BNPsp in the setting of early AMI.

Making sense of high sensitivity troponin assays and their role in clinical care

Cardiac troponin assays have an established and undisputed role in the diagnosis and risk stratification of patients with acute myocardial infarction. As troponin assays gets more sensitive and more precise, the number of potential uses has rapidly expanded, but the use of this test has also become more complicated and controversial. Highly sensitive troponin assays can now detect troponin levels in most individuals, but accurate interpretation of these levels requires a clear understanding of the assay in the context of the clinical scenario. This paper provides a practical and up-to-date overview of the uses of highly sensitive troponin assays for diagnosis, prognosis, and risk stratification in clinical practice.

Signal peptides: new markers in cardiovascular disease?

Proteins and peptides are well-documented as useful marker adjuncts to cardiovascular clinical decision-making. Most markers measured derive from a defined, stable proprotein region of their respective gene. However, a neglected portion of preproproteins known as the signal peptide (SP) is also present in the circulation and may also present as a measurable marker. SPs were assumed to be degraded intracellularly after directing secretion, but a small, growing body of evidence is identifying SPs as not being degraded within and without cells. In this article, evidence for the persistence of SPs after translation is presented and their role as potential cardiovascular biomarkers is discussed.