BC98 Biomedical Sciences : Pathophysiology of Troponin

Discuss the application of laboratory diagnosis for two marker Troponin and (NT-pro BNP) that used in laboratory. 

What to include essay introduction:
1.What cardiac marker? 
2.What biomarker are good for?
3.Why do we use cardiac marker?
4.History of cardiac marker 

Use
Prognostic 
Risk stratification 
Advantages 
Types of cardiac marker 

5.Why two cardiac marker (Troponin and NT-pro BNP) in relative detail are important?
6.Why we do troponin test and NT-pro BNP?
7.When cardiac troponin and NT-pro BNP release and use diagram with it .
8.How troponin and and NT-pro BNP influence on prognosis 
9.Lab detail for troponin : Immunoassay method how it work with diagram 
10.Lab detail for NT-proBNP : not sure which method used  
11.Troponin and NT-pro BNP levels what mean by that for patient. 
12.What troponin and NT-pro BNP indicate?
13.What is the pathophysiology of troponin and NT-pro BNP?
14.What advantage of doing troponin and NT-pro BNP  test to the patient?
15.Pathophysiology of condition Troponin and NT-pro BNP and why they are important? For example if there is heart injury this marker can go up In relative detail discussion Not we use this marker it  tell us about heart injury it allows it to treat quicker but we need it in relative detail For example we use this marker because it released in response to this point of injury Which can be detected by using this system And turn around result this quickly then we can give this treatment 
16.Tables to show the scope of other cardiac marker ?
17.What happened in the damage that cause release of troponin and NT-pro BNP?
18.Principle method of measurement Troponin (ElISA) method with figure.
19.Synthesis  and function of NT-proBNP and Troponin
20.Pathophysiology of NT-proBNP and Troponin

Cardiac markers are defined as biomarkers that allow the evaluation of heart function, specifically in case of myocardial infarction. However, in case of other conditions elevation of the level of biomarker also observed. Research indicates that cardiac biomarkers show up in the blood as a result of severe stress since there is a lack of oxygen. The underlying reason is that the cardiovascular system suffers certain negative impact as a result of stress. Therefore, application of biomarkers in diagnosis and treatment of certain disease are useful in medical research.

The first cardiac marker that discovered in 1978 was myoglobin which detected in Serum in patients suffering cardiac stress during myocardial infraction and reflects the severity of myocardial infarction. Myoglobin is a oxygen-binding cytoplasmic protein, small in size which is present in skeletal and cardiac muscle. Its release into the serum takes place early, almost 1 h after the onset of myocardial injury (Clericoet al. 2015).

Previously, for many years’ serologic markers such as lactate dehydrogenase, creatinine kinase, ischemic modified albumins were used as potential marker in the diagnosis of patients with cardiovascular disease (Acosta and Nilsson 2012). However, the current research prefers the assistance of protein marker like troponin and N-terminal pro b-type natriuretic peptide since these markers are more sensitive and specific than enzyme biomarkers. Moreover, these biomarkers facilitate the risk stratification for patient with angina. Researchers can carry out simple visualization of protein separation and then transfer of the same is possible through when prestained markers are used. Previously medical research blindly relies on serological marker since protein markers were not in use due to unclear advantages of the same. However, current medical research relies on more sensitive protein marker such as troponin and N-terminal pro b-type natriuretic peptide. The underlying cause is that generally, proteins are easier to be assessed through immunohistochemistry. The researchers can therefore easily apply the technique in all routine diagnostics (Jarolim 2015). 

Three regulatory proteins (Troponin C, I and T) form a complex which give rise to potential cardiac marker troponin and found in integral part of skeletal muscle (Feheret al. 2014). Specifically, troponin I and T are important because they are very sensitive; they measured the accurate difference between angina and myocardial infarction (Nagele et al. 2014). In specific heart injury, the level of troponin may elevate within three and four hours and it remain elevated for approximately 10 to 14 days (Limkakenget al. 2015). However, in individuals who experience angina, elevated level of troponin observed due to myocyte necrosis and it indicate the higher risk of heart attack (Bonaca et al. 2016). Troponin T are highly specific, elevation observed in case of chronic heart failure and it also identified in those with latent myocardial damage along with individual who might experience severe cardiac events.

Pathophysiology of troponin release is quite complex procedure. Cardiac troponin is complex of regulatory protein that controls the interaction of actin and myosin. However, I and T subtype of troponin are specific to cardiac muscle (Dedic et al. 2016). Troponin lies within the specific groove of actin filaments in muscle tissue by attaching with another protein tropomysin (Zahranet al. 2018).In that case, accumulation of metabolites observed in blood. However, these protein circulation in blood predominately detected after permanent injury observed in myocytes. Troponin distribution can be structural and cytosol so it follows biphasic pattern for indication of cardiovascular diseases. In initial stages of myocardial injury, blebs produced in heart which contains cytoplasmic protein. The blebs are formed in a complex process. The initial stage involves a release from the cytoplasmic pool. The second step relates to the slow degradation of the sarcomere and release of complexed troponin. After bleb ruptures due to necrosis in heart, these troponin releases into blood (fig 3). In order to get the estimation of elevated level of troponin, cardiac Troponin rapid test and dipstick tests are used. Generally, Troponin is bound to myofibril but when myocardial damages occurred then all of the bound troponin released in serum (Dedic et al 2016). There is high levels 1-2hrs post MI with the levels decreasing but still detectable until 14 days post myocardial infarction (Balaney and Bowman 2016).

A troponin test primarily measures the levels troponin T and I protein in blood when there is an indication or chance that a patient is suffering from heart attack. Greater amount of troponin in blood observed if high amount of cardiac damages occurred since myocardial muscle cells dies. At the time of stretch of ventricular wall, secretion of Natriuretic peptides occurs from cardiac myocytes. The precursor protein is cleaved into the biologically active troponin which can be used to detect abnormal ventricular function. Sometimes, the test used to distinguish between the angina and other heart injury and conditions such as endocarditis, myocarditis, pericarditis and cardiomyopathy (Jarolim 2015).

At this juncture it would be desirable to describe the advantages and disadvantages of using troponin biomarkers. There are three distinct advantages of the test. Firstly, troponin is released only after cardiac damage. Secondly, troponin is present for, and is elevated for a considerable time frame. Lastly, the test is highly sensitive. The two most noted disadvantage is that elevation of troponin is absolutely indicative of cardiac damage; however it can take place due to other reasons such as trauma due to surgery. Further, failure to detect a rise in troponin does not exclude the absolute chances of diagnosing ischemic heart disease (Maisel and Jaffe 2016).

Cardiac troponin is very sensitive marker for all heart muscles damages. However, it can be distinguishable between the amount of troponin released in heart attack and moderate to severe chest pain (Dedic et al . 2016). Recently, World health organization has set an indicative value of troponin for heart attack which is 2ug higher than any other heart damages (Hijazi et al.  2014). Release of NT-pro BNP is a response to increased pressure in the heart as a result of physiological changes. This is what is detected and the level of risk to a patient is ascertained (Stiell et al. 2016).

 Cardiac troponins are highly sensitive in nature, provide indication for myocardial necrosis, and predict the gradual increase of the death rate. Moreover, it also indicates the chances of re-infarction in-patient with already existing disease (Grinstein et al. 2015). The assays with troponin are precise, and small CV levels are present even at the 99% in reference populations. Further, they have specificity for myocardial necrosis (Sherwood and Newby 2014). 

When there is no other marker for indication of cardiac disease, cardiologist solely depends on biomarker at the time of diagnosis but in non-surgical patient with coronary syndrome minute changes of troponin associated with severe outcome. Immunoassay for troponin is gold standard to measure the elevation of troponin because it is more rapid method than western blot (Singal, Srivastava and Gahtori 2016). For performing immuno assay,  first, acquire antibody against troponin collected and appropriate reagent used to quantify the troponin. Secondly, absorption of monoclonal antibody (M7) to the solid surface and attachment of troponin to the antibody was conducted( Zverevaet al. 2015). Third, the washing of unbound troponin was done and blocking non-specific attachment was done to reduce noise. Attachment of secondary antibody to troponin was done and then washing of the unbound antibody was done. Then signal created by secondary antibody detected in UV spectrometry to get the estimation of elevation level of troponin in severe cardiovascular diseases ( fig 1.).

Cardiac troponin level is generally low (5.3 ng/ml) in blood for normal individuals (Diez et al 2016). Cardiac Troponin is used as the primary marker in myocardial necrosis of heart in cardiac patient (Body et al. 2016). 

NT- pro BNP (N terminal pro btype natriuretic peptide) is hormone secreted by cardiomyocytes in heart ventricles due to increases of ventricular blood volume in heart and helps to differentiate between heart failure and other diseases. It is a sensitive marker for heart failure and provides a risk prediction to cardiovascular diseases in adults with coronary syndrome. In people who do not have baseline cardiovascular disease, NT-proBNP concentration assessment is a strong prediction of first-onset heart failure and augmented coronary heart disease along with stroke prediction (Jones et al. 2016). However, medical experts use this peptide as promising marker for cardiac heart failure since in heart failure, increased wall stretch, neurohormonal activation and hypoxia stimulate secretion of NT-proBNP (Hall 2005).

It can be commented that NT- pro BNP is a gold standard in routine diagnosis that indicates the heart failure in emergency department since it releases immediately after pressure in heart (Stiellet al. 2017). At this juncture it would be desirable to describe the advantages and disadvantages of using NT- pro BNP biomarker. The primary advantage is that the long half-life of NT-proBNP allows for better measurement of steady-state ventricular function. Further, the level of the marker is not affected by neprilysin which is a neutral endopeptidase whose inhibition is responsible for increasing the bioavailability of natriuretic peptides. The disadvantage is related to stability in room temperature (Maisel and Jaffe 2016).

It is difficult to distinguish between sign and symptoms of chronic obstructive pulmonary disease and heart failure by using diagnosis as they show similar kinds of symptoms. The signs and symptoms of COPD include wheezing, shortness of breath, chest tightness, swelling in ankle and feet. The symptoms of heart failure include fatigue and weakness, shortness of breath, irregular heartbeat and swelling in legs and feet (Theander et al. 2014). Therefore, NT- pro BNP is used as promising marker for detecting heart failure. Elevated level of NT pro BNP indicates long-term prognosis is poor and has negative effect on mortality rate of cardiac patients (Hezzell et al. 2016). Evidences show that these peptides are predictor of sudden heart failure without prior symptoms (Hezzell et al. 2016).

NT pro BNP test follows the principle of immunofluroscent ELISA method. ELISA (enzyme-linked immunosorbent assay) is a notable plate-based assay technique for detection and quantification of substances like hormore, protein and pepetides. In such a test, immobilisation of an antigen is done on a solid surface and then it is complexed with an antibody that is linked to an enzyme. Detection can be done through assessment of the conjugated enzyme activity when incubation is done with a substrate for producing a certain measureable product (Lundblad and Macdonald 2018). Depending on the attachment of flourophore it is named as direct process or indirect process. In the direct immunofluoroscene process, a single antibody is used directed against the target of interest. Further, there is direct conjugation between the primary antibody and flurophore. In case of indirect immunofluoroscene process, to antibodies are used and the primary antibody is unconjugated. Further, a fluorophore-conjugated secondary antibody is used against the primary antibody.

In primary process, primary antibody directly conjugated to the target site where as in case of indirect process a secondary antibody used for detection (Fig 2). NT pro BNP values below 300pg/ml consider as least probability for developing acute cardiovascular disease as pressure is less in heart where as a patient with approx. 1000 pg/ml of cardiac marker in blood has greater chances of acute congestive heart failure (Ponikowski et al. et al. 2016).

In case of NT pro BNP it is normally approximately 369.5 pg/ml is consider as normal in individual whereas elevated level of this marker such as 2584pg/ml indicate heart failure (Ponikowskiet al. 2016). Moreover, it has half-life of approximately 60 min in body, which indicate the stability of this marker in blood and its contribution in detection of heart failure (Yehet al. 2015).

On the other hand, Brain natriuretic peptide secreted from cardiac myocetes in response to stretch because of increase of heart ventricle. During the incidence of heart failure, stretching of wall resulted in activation of hormone and hypoxia stimulate the secretion of NT pro BNP.  Since, it has longer half life, gives the confirmation for heart failure as stays longer period of time in blood. Therefore, detection in lab become easier due to longer period of time.

It can be concluded that cardiac markers are most promising marker for addressing cardio vascular disease. Two most noteworthy markers are troponin and NT pro BNP which are essential components in the diagnosis and determining prognosis. While the advantages of the markers are multiple, the disadvantages mainly relate to the fact that failure to detect a rise in the markers does not exclude the absolute chances of diagnosing ischemic heart disease. As highlighted, majority of the value related to the novice biomarkers in case of cardiac condition detection have association with prognostication. It has been argued that the true value of a biomarker can be useful when specific changes in clinical conditions are distinct. There is a need of further research to understand the extensive applicability of the biomarkers in clinical practice. A robust strategy of a more personalized and precise approach to clinical care using biomarkers is gaining momentum in cardiology field.

Cardiac marker	Peak time	Description
Creatine kinase	10-24 hours	Specific when skeletal muscle remain intact
Lactate dehydrogenase	72 hours	Not that specific as trroponin
Ischemic modified albumin	Not specific	Not that specific
Myoglobin	2 hours	Low specificity during myocardial infraction
Glycogen phosphorylaseisoenzyme	7 hours	Low specificity

Table 1: table of other cardiac marker

Source: Created by author

References:

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