JPEMS 2015
BIOMARKERS IN CARDIAC DISEASES
FAINELLI Manon, University of Nantes
BOGÓ Ákos, University of Szeged
Supervisor: SZAKÁCS Julia, M.D., Department of Pathophysiology
2015.10.06
Abbreviations
ACS Acute Coronary Syndrome
AF Arterial fibrillation
ATS Atherosclerosis
BBB Bundle-Branch Block
BNP B-type natriuretic peptide
CK-MB Creatine kinase - MB
CRP C-reactive protein
cTnI Cardiac-type troponin I
cTnT Cardiac-type troponin T
CTproET1 C-terminal pro-endothelin-1
ECG Electrocardiogram
ET-1 Endothelin-1
H-FABP Heart-type fatty-acid-binding protein
IL Interleukine
IMA Ischemia-modified albumin
MI Myocardial infarction
HF Heart failure
HF-PEF Heart failure with Preserved Ejection Fraction
HF-REF Heart Failure with Reduced Ejection Fraction
hs-CRP high-sensitivity C-reactive protein
IGF-1 Insulin-like growth factor 1
LDL Low Density Lipoprotein
LVEJ Left Ventricular Ejection Fraction
LVH Left Ventricular Hypertrophy
MMP Metalloproteinase
MPO Myeloperoxidase
MR-proANP Mid-regional pro-atrial natriuretic peptide
NPV Negative predictive value
NSTEMI Non- ST-segment Elevation Myocardial Infarction
NT-proBNP N-terminal pro-B-type natriuretic peptide
Biomarkers in cardiac diseases
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PMH Past medical history
STEMI ST-segment Elevation Myocardial Infarction
TNF-α Tumor Necrotizing Factor- α
PaPPA Pregnancy-associated plasma protein A
Tables of contents
Abbreviations .................................................................................................................................................... 1
Introduction ....................................................................................................................................................... 3
Cardiac diseases ............................................................................................................................................... 3
Biomarkers......................................................................................................................................................... 6
Inflammation ................................................................................................................................................ 6
Oxidative stress ........................................................................................................................................... 7
Neurohormones .......................................................................................................................................... 8
Myocyte injury ............................................................................................................................................. 9
Myocyte stress .......................................................................................................................................... 11
Conclusion ....................................................................................................................................................... 12
Appendix .......................................................................................................................................................... 13
References ....................................................................................................................................................... 18
Biomarkers in cardiac diseases
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Introduction
Cardiovascular diseases are the leading cause of death in the world. They are
responsible of 7.5 millions of death per year, representing the half of the worldwide
mortality.¹ Diagnosis, prognosis, treatment or even more prevention of these disorders appear
as one of the most important concerns of ours societies.¹
In the the 21th
century, the new scientific breakthroughs related to the pathomechanism of
certain cardiac disease, have allowed to identify some measurable and quantifiable biological
parameters suitable for the early diagnosis, prognosis, follow up and risk stratification of
these conditions.
This concept is not brand-new but nowadays, multiple researches are about to find the
ideal marker. As a matter of fact, this one must be easily measurable (quick and adapted to
emergency situations), cardiospecific with sufficiently released concentration levels, accurate,
reproducible and cost-effective.
However, since the 1st founded biomarker (in the 60’s), many studies have been led and
have permitted to improve, or to find more efficient biomarkers.¹
In this thesis, we will discuss the pathophysiology of some cardiac diseases and the role of
certain biomarkers in these conditions, their benefits and disadvantages, based upon data from
relevant scientific publications.¹
Cardiac diseases
Two major cardiac diseases are highlighted in this work: ischemic heart diseases, which
includes stable angina, unstable angina, myocardial infarction (MI) cf Figure 1 and heart
failure (HF). Unstable angina and MI are part of Acute Coronary Syndrome (ACS), which
occur due to a rupture of an atherosclerotic plaque leading to partial or complete thrombosis
and occlusion of the affected coronary artery.² cf Figure 2
ACS includes the following conditions: unstable angina, NSTEMI (Non ST segment
Elevation Myocardial Infarction), STEMI (ST segment Elevation Myocardial Infarction) and
sudden cardiac death.² cf Figure 3
Biomarkers in cardiac diseases
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Ischemic heart diseases are characterized by a decrease (relative ischemia) or an arrest
(complete ischemia) of the blood supply and oxygen delivery to the myocardium due to
atherosclerosis of the coronary arteries.²
Atherosclerosis (ATS) is a chronic progressive inflammatory disease, which involves the
accumulation of lipids, and inflammatory cells leading to plaque formation, calcification and
fibrosis, which modifies the intima of large and medium arteries².cf Figure 2
The known complications of ATS are: stable angina (effort angina, provoked by effort or
stress) appears as chest pain, because of coronary stenosis, unstable angina (at rest, de novo or
crescendo), and MI, as mentioned previously. ²
The term acute myocardial infarction (AMI) should be used in presence of necrosis of the
myocardium and may be characterized by some criteria.3;4!cf Figure 4
STEMI incidence decreases, whereas NSTEMI incidence increases. The mortality
depends on many facts as the age, the delay before the beginning of the treatment and the type
of treatment, the past medical history (PMH), (previous cardiac or renal issues, diabetes,
drugs...).³
With the view to diagnose it, some features are reliable and have to be noticed.
The patient has to complain about a chest pain (for at least 20 min and not affected by
position changing), which is not relieved by nitroglycerine, added to radiation of pain to the
lower jaw or the left-arm, even gastric pain.³ Symptoms could be less specific and described
as nausea or vomiting, short breathlessness (dyspnea), tiredness, palpitations, sweating or
fainting; which explains that some patients would not be treated as soon as possible impacting
the evolution of the acute ischemia.3;4
In less than ten minutes, after this complains, lethal arrhythmias are diagnosed by ECG
monitoring, leading to indication of defibrillation. The interpretation of ECG may show
STEMI in two successive leads, but some precautions should be considered in specific cases:
e.g. NSTEMI, when another ECG should be performed fifteen to thirty min later, or
permanent ECG monitoring is required.³ Often ECG manifestations of myocardial infarction
are ST segment depression associated to T waves changes.⁴ ACS occlusion and its
consequences are usually considered if there are ST-segment elevations associated with ST-
segment depression in opposite leads. Moreover ECG is not sufficient to get the diagnosis,
because in some cases (bundle branch block (BBB), ventricular pacing, previous myocardial
Biomarkers in cardiac diseases
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infarction, left ventricular hypertrophy (LVH) and other cardiac diseases...) there is also ST
segment elevation. So that, taking blood samples to detect biomarkers levels (elevation of
cardiac troponin I or T in response of muscle cell death) have to be associated, and starting
the treatment before getting the results is fully recommended.³ Many techniques of imaging
are very useful to detect the outcomes of the myocardial ischemia, namely loss of function,
myocardiocytes necrosis and fibrosis; some parameters are examined as perfusion, damage of
the cardiac muscle cell and permits to rapidly start the treatment. ³
To provide a better evolution and treatment, clinic classification has been described, in
addition of STEMI or NSTEMI and Q waves MI and non-Q MI.³ cf Figure 5
Furthermore, other clinical conditions can also induce myocardial injury and elevation of
troponin levels.³ cf Figure 6
Heart failure is described as an abnormality of the structure or the function of
myocardium, which prevents enough oxygen delivery to satisfy the metabolic needs of the
tissues, at a normal filling blood pressure. This syndrome gives rise to specific clinical
symptoms and signs. Its manifestation is progressive and leads to adaptive and maladaptive
compensatory mechanisms. The prevalence in developed countries is about 1-2% and the
main causes in developed countries are CAD in 66% of cases, but also arterial hypertension
and diabetes mellitus.⁵
The condition is divided in two entities: with preserved left ventricular ejection fraction
(or systolic heart failure) and with impaired left ventricular ejection fraction (LVEF). In
systolic HF there is a reduced contraction and emptying of the left ventricule present.⁵ There
are also more rare etiologies: valvular pathologies, abnormalities of heart rhythm, and
conduction, infectious, congenital causes, specific cardiomyopathies systemic diseases
(amyloidosis, sarcoidosis...), alcohol abuse, chemoterapy.⁵
HF de novo can be acute consecutive to acute MI. A patient having a heart failure for a
long time is suffering from a chronic HF. Congestive HF refers to acute or chronic HF with
congestion's proof.⁵
Some typical clinical symptoms and signs of HF are summarized in Figure 7 5
The NYHA classification describes classes according to severity and prognosis, it can
evolve if the disease deteriorates or ameliorates.⁵ cf Figure 8
Biomarkers in cardiac diseases
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European Society of Cardiology’s guidelines also indicate the algorithm of diagnosing
heart failure.⁵ cf Figure 9
Biomarkers
Biomarkers found in different secretions and the bloodstream are considered very useful
tools in everyday medical practice to identify high risk patients, to improve and speed the
diagnosis, to provide effective treatment, screening and follow-up to the patient or even more
to estimate the prognosis of a certain disease.⁶ The criteria for a good biomarker are accuracy,
cost-effectiveness, reproducibility and rapidity.⁷
To evaluate this chapter, different biomarkers will be described according to their
function or their involvement in the pathomechanisms of MI or HF.
Inflammation
The inflammation is a non-specific process, whose the goal is to eradicate the cause of
tissue injury, its consequences (necrosis) and to repair tissues so as to re-establish the
homeostasis. Some mechanisms however can be very harmful for the organism. When cardiac
tissue is injured, it implies the presence of inflammatory mediators.⁸
C-reactive protein (CRP) is produced by the liver after being stimulated by IL-6 during
the acute inflammation, and is localized in adipocytes and atheromatous plaques. It is easily
measured. The peak comes 2-4 days after the events, so the measurements don't have to occur
before 12-24h after the event. The level returns to the baseline only 8-12 weeks later, so it
won't be able to predict additional events (as recurrent MI).⁹
The level increases after ACS event because of myocardial necrosis, correlating to the
severity of MI. It can help to stratify, to screen ischemic heart disease and seems to be a
prognostic factor of acute or chronic HF, which evaluates the detrimental consequences.
There is a correlation with risk of death and future events for chronic HF. High CRP levels
are also associated with class III/IV (NYHA), demonstrating a low quality of life and a
dysfunctional neurohormonal profile.6 CRP however it’s not enough specific and increases in
all inflammatory processes (smoking, acute and chronic infections, atherosclerosis), so it is
not considered the first-choice biomarker .⁷ Some tests are improving the accuracy and can
detect very low levels of so called high-sensitivity CRP (hs-CRP), which can predict death in
Biomarkers in cardiac diseases
7
patients suffering from acute MI. Its level is correlated to the ST-segment elevation and can
predict the risk of ventricular remodelling six months after MI. While even low levels are
detectable, it could also help to evaluate the risk of early complications.¹⁰
To overcome this lack of specificity an isoform of this protein, the pentraxin-3 is
examined, which is only localized in the vascular endothelium so it could be more specific for
the inflammatory activity of the atherosclerotic plaque ⁹.
Some other inflammatory proteins are increased during HF because of the death of
myocardial cells.⁷
TNF-α (a cytokine produced by many immune cells during acute inflammation) levels
increase and so do IL-1 and IL-6, respectively because of the hypertrophy of the ventricles,
and the maladaptive neurohormonal pathways present in HF. Therefore, IL-6 and TNF-α can
screen a potential HF without symptoms.⁷
Fas (APO-1) molecule, which is involved in the cellular apoptosis, similarly increases in
in patients suffering from HF, so the inhibition of soluble Fas ligand appears a new
perspective treatment in animal studies, because it may decrease the ventricular remodelling
following MI.⁷
To identify asymptomatic patients and to evaluate the risk of HF, CRP and Fas appear as
great tools.⁷
The Pregnancy-associated plasma protein A (PaPPA) is a proatherosclerotic
metalloproteinase, it cleaves the insulin-like growth factor 1 (IGF-1) and plays a role in
suppression of inflammation.⁷ In unstable angina and AMI levels are much more higher, in
correlation with CRP. It is used to predict the risk of cardiovascular death and future MI.
More assays are needed however to investigate this option.⁷
Oxidative stress
Another response of the myocardium to ischemia is oxidative stress, which is described as
an imbalance between reactive oxygen species (ROS) and the internal antioxidant
mechanisms. It can lead to cell damage and to myocytes apoptosis or necrosis.⁷
Biomarkers in cardiac diseases
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Oxidative stress indicates the dysfunction of the endothelium, which decreases the
production of nitric oxide (NO) and stimulates the production of peroxynitrite which impairs
myoardial function.⁷
Some indirect markers of this phenomenon are measurable as plasma-oxidized low-
density lipoproteins (LDL). This particle passes through the endothelium, is deposited in the
intima, where it can be oxidized by biochemical reactions, and is taken up by the foam cells.
They can be indirectly detected with antibodies to oxidized LDL, whose plasma levels are
correlated to conditions such atheromatous plaque formation and angina pectoris¹¹.
The isoprostanes are markers of the lipid peroxydation (plasmatic levels are in
correlation with the development of the atheromatous plaque). The urinary levels of 8-
isoprostane correlate with matrix metalloproteinases levels, predicting the risk of ventricular
remodeling and more severe HF.⁷
Myeloperoxidase (MPO) produces hypochlorous acid and injures cardiac tissues. It can
predict death caused by HF, or high levels of MPO after ACS can anticipate the predictions of
death and MI after one year (even if N-terminal pro-B-type natriuretic peptide (NT-proBNP)
level is below or above the average). Isoprostane and MPO levels correlate with the severity
of HF and can also predict the mortality.⁷
The levels of urinary biopyrrins are elevated in patients with HF, and correlated
to the severity of this disorder.12
Xanthine oxidase catalyses the production of hypoxanthine in xanthine, and xanthine in
uric acid. Involved in the pathophysiology of the HF. High levels of uric acid indicate
detrimental prognosis in HF.⁷
Neurohormones
Even in the early 1960s it was observed that during heart failure the sympathetic nervous
system becomes activated thus the plasma and urine levels of norepinephrine of the patients
are increased. Therefore, it is a marker of it and according to Cohn et al, it might be a
predictor of mortality. Further observations by Swedberg et al found that in case of heart
failure the renin-angiotensin-aldosterone system also becomes activated, making the
components possible biomarkers.7
Biomarkers in cardiac diseases
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Later the attention focused on the big endothelin-1, which is, according to Braunwald et
al, the most powerful predictor of hospitalization and death for heart failure, right after BNP,
and followed by norepinephrine7 It seems so that the level of endothelin-1 (ET1) increases
post-MI, further reducing the diameter of coronary vessels. This peptide is very unstable and
difficult to measure; however, the C-Terminal portion of pro-Endothelin-1 (CTproET1) is
much more stable, therefore easier to measure. The elevation is proportional to severity of
MI.9
The neuropeptide, arginine vasopressin, also carries a great prognostic and diagnostic
value in conditions like shock, sepsis, stroke, or cardiovascular diseases.13
However,
vasopressin itself is not stable enough for measurement, so the more stable substitute of it is
in use, namely copeptin.9 Studies regarding it claimed that in patients with AMI the plasma
copeptin was the highest on admission, and in case of continuously elevated levels it is clearly
associated with high risk for heart failure or mortality. In combination with cTns it showed a
great sensitivity and even better negative predictive value (NPV).13
These previously mentioned biomarkers are part of the pathomechanism of heart failure,
and the blockage of their receptors might be a promising therapeutic approach.7
Myocyte injury
It is exceptionally important and useful to know the biomarkers of myocyte injury,
because most cardiac diseases will impair the function of the myocardium. Therefore, these
markers have a high prognostic value. Cardiac myocyte injury often occurs as a result of
severe ischemia (like AMI), or other stresses, such as inflammation or oxidative stress, as
mentioned before.7
The most commonly used biomarkers of myocardial injury and therefore necrosis, are the
troponins. More specifically the cardiac type of Troponin I and T (cTnI, cTnT), which have
emerged as a specific and sensitive marker of the damaged myocardium, making it useful in
diagnostics and also risk stratification in patients suffering from diseases like acute coronary
syndrome or heart failure.7
Troponin itself is a complex of three regulatory proteins: Troponin C, Troponin T and
Troponin I.14
Troponin T and Troponin I are only present in the heart muscle, therefore these
are very specific markers of the injury or necrosis of this tissue. Futhermore, out of all the
biomarkers cTnT might have the widest diagnostic window, that is four times longer than for
Biomarkers in cardiac diseases
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the formerly used biomarker, creatine kinase (CK-MB). The elevation is also higher than in
case of CK.MB, and it also correlates with the size of infarction.14
However the fact that it
needs 12 hours to peak is still a disadvantage of this technique.9
For the previously mentioned reasons the measurement of cTns became a very commonly
used method in clinical tests. Furthermore, with the application of this test we are able to
predict what possible consequences have the diseases, like acute coronary syndrome or severe
heart failure. Therefore, this method has a great prognostic value too.9
As mentioned before, cTns are specific markers of cardiac muscle necrosis like in acute
myocardial infarction (AMI). However, in the absence of AMI, even the mildly elevated level
of cTroponins might indicate a poor prognosis. In diagnostics and prognostics cTns are
commonly used in addition to BNP measurements. Especially to detect deterioration of heart
failure. In addition, the application of serial measurements and high sensitivity assays can
help us to detect 92% of these patients.7 According to a study from 2010 the cardiac troponins
are currently the only biomarkers, which can influence the treatment of patients.9
Although the troponins are nowadays the most commonly used biomarkers for
myocardial cell necrosis, there are other cardiac proteins as well, which might give additional
informations in case of AMI and HF as well.
One of these proteins is the formerly used creatine kinase-MB (CK-MB). The “MB”
stands for the gene M and gene B, the product of which is two enzymes. The dimer of these
two enzymes is the isotype most frequently found in myocardial cells, but is also present in
skeletal muscle in smaller quantity (1%). Following myocardial necrosis the serum creatine
kinase levels rapidly increase, reaching the measurable level after 4 hours and its peak after 6
hours, returning to the normal after 24 hours.14
For many years this biomarker was the “gold
standard” in AMI diagnostics, and if measured by mass assays, it was in use for evaluation of
patients with acute coronary syndrome. Similarly to cardiac troponin T, the presence of CK in
severe heart failure is a predictor of hospitalization or death.7;13
Despite its usefulness, it is
still not as sensitive or specific as cTns, therefore, in 2000, it was replaced by cardiac
troponins.9
Another possible biomarker for myocyte injury is myoglobin, which is a small heme
protein in the cytoplasm of all types of myocytes, therefore not as specific for myocardial
injuries as the previously mentioned biomarkers. This is the earliest measurable marker partly
because of its small size and partly because it is not bound to any myofibrillar structure.13;14
Biomarkers in cardiac diseases
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The elevated serum level is already detectable 2 hours after the injury. This is the reason why
it is used in the early detection of AMI, and together with cTns might detect patients with
ACS as well.13
It takes 12-24 hours for the elevated serum level to return to normal.14
There are lot of recent studies suggesting promising candidate biomarkers, when
combined with cTns.15
One of these molecules is the heart-type fatty-acid-binding protein
(H-FABP). Similarly to myoglobin, it has a small size, therefore in case of myocardial
necrosis, after it is released into the extracellular space, it quickly reaches the circulation,
making it one of the earliest biomarkers.9;15
There are several studies concerning H-FABP
with mixed results, but this protein seems to be associated with MI, HF and death. Other
studies state that the combination of H-FABP and cTnI measurements has higher sensitivity
and negative predictive value (NPV) than separately measured.9;13
Another molecule that is useful for acute myocardial ischemia detection is ischemia-
modified albumin (IMA). Under ischemic circumstances it loses its ability to bind divalent
ions and becomes measurable and remains elevated for 6-12 hours. The results regarding the
usefulness of IMA are very contradictory, so additional research must be done regarding this
biomarker.13;15
Choline is one of the phospholipids and is an important component of the cell membrane.
It might have potential to become a useful biomarker in diagnosis and prognosis of ischemia,
necrosis and ACS. According to Kehl et al, it is also a strong predictor of cardiac arrest or
death. But, it should be combined with other biomarkers for more precise results.9;13
Myocyte stress
Nowadays there are three biomarkers that are thought to be related to cardiac muscle
stretch, therefore reflecting to ventricular stress, and probably also having a great prognostic
value in risk stratification. These three markers are NT-proBNP, MR-pro-adrenomedullin and
ST2.7
B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-
proBNP) are recently emerged as useful biomarkers for HF and myocardial dysfunction. BNP
and NT-proBNP is cleaved from pro-BNP, which is cleaved from pre-pro-BNP. The latter
cleavage is performed in the ventricular myocardium, where the pre-pro-hormone BNP is
synthetized.13
From there the pro-hormone is released as a consequence of myocyte stress and
gets cleaved by a circulating endoprotease. The two products are the inactive NT-proBNP and
Biomarkers in cardiac diseases
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the active BNP, that acts as a protective hormone and causes vasodilation, natriuresis,
diuresis, and reduces the activity of the sympathetic nervous system and the renin-
angiotensin-aldosterone system.7 It has marked prognostic and diagnostic utility for MI and in
HF. In addition, it also shows great potential in the assessment and management of patients
with ACS.13
BNP has similar effects as ANP and also has a similar secretory profile post-MI. Recently
the more stable mid-regional pro-atrial natriuretic peptide (MRproANP) was found to be
as useful at death and heart failure prediction as NTproBNP.9
Adrenomedullin is a peptide that causes vasodilation and has inotropic and natriuretic
effects. Its production is stimulated by cardiac pressure and volume overload; therefore, the
serum level is increased in patients with heart failure, and is proportionate to severity.
Although adrenomedullin is unstable, mid-regional pro-adrenomedullin is much more stable,
thus it can be used for measurements. According to Khan et al, mid-regional pro-
adrenomedullin and NT-proBNP are equally strong predictors of heart failure and death.7
ST2 is an IL-1-receptor-like protein that is secreted by monocytes due to mechanical
stretch. The ligand of this receptor is IL-33, which antagonize angiotensin II and cardiac
hypertrophy, thus having a cardioprotective role. Similarly to the previously mentioned ones,
the elevated serum level in patients with MI predicts heart failure or death. Therefore, it
correlates with NT-proBNP changes too.7;9
Conclusion
Heart failure and MI are major causes of morbidity and mortality worldwide. A relevant
biormarker profile might improve the early diagnosis, prognosis and treatment of the patients.
At present, natriuretic peptides and troponins are considered as the most promising tools.
According to the literature data the combination of different biomarkers (troponin I, NT-
proBNP, C-reactive protein and cystatin C) would highly improve their usefulness in clinical
practice.
Biomarkers in cardiac diseases
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Appendix
Figure 1-Essentials of Pathophysiology: Concepts of Altered Health State; C. MATTSON
PORTH and G.MATFIN
Figure 2- Essentials of Pathophysiology: Concepts of Altered Health State; C. MATTSON
PORTH and G.MATFIN
Biomarkers in cardiac diseases
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Figure 3-Robbins Basic Pathology (9th
Edition); KUMAR, ABBAS, ASTER
Figure 4- Universal definition of myocardial infarction. European Heart Journal (2012) 33,
2569–2619
Biomarkers in cardiac diseases
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Figure 5- European Heart Journal (2012) 33, 2551–2567
Figure 6- European Heart Journal (2012) 33, 2551–2567
Biomarkers in cardiac diseases
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Figure 7- European Heart Journal (2012) 33, 1787–1847
Figure 8- European
Heart Journal
(2012) 33, 1787–
1847
Biomarkers in cardiac diseases
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Figure 9- European Heart Journal (2012) 33, 1787–1847
Biomarkers in cardiac diseases
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