**8. Serum cardiac troponin**

Studies across many species have demonstrated the specificity of cardiac troponin to the heart muscle, and elevated levels of cardiac troponin subunits, especially cTnI, which shows a positive correlation with acute myocardial damage [31, 32]. Cardiac biomarkers have therefore been studied in farm practice following the need for an accessible and cheap method of detecting cardiac damage. Analysis of cardiac biomarkers in serum samples of TRP affected cattle could provide information on the prognosis and has the potential to surpass other diagnostic techniques especially in reference to TP [33–35].

There is a significant difference in cTnI levels between healthy cattle and those with cardiac disease. A study found that serum cTnI was higher in 4 out of 5 confirmed pericarditis cases, compared to 34 healthy control animals [36]. In a different study which used a cut off value of 0.08 ng/ml, elevated levels of cTnI was observed in 14/18 pericarditis cases, 12/15 endocarditis cases, 5/10 congenital heart defect cases, 3/7 mediastinal abscesses, 3/5 caudal vena cava thrombosis cases and in 4/13 cattle with chronic suppurative pneumonia [33]. All of these conditions were confirmed at necropsy. By investigating the concentrations of cTnI in 40 perceptively healthy cattle another study concluded that the normal range of cTnI in normal, healthy, lactating (Holstein) dairy cattle was 0.00–0.05 ng/ml (using iSTAT- immunoassay). Although, serum cTnI concentrations are usually increased with cardiac disease in cattle, this parameter cannot be used to differentiate pericarditis from other heart diseases (**Figure 2**), or to differentiate primary cardiac disease from other

#### **Figure 2.**

*Sensitivity and specificity of cTnI as a test for various cardiovascular diseases including two studies on pericarditis. Information adapted from Pericarditis A [37], and Pericarditis B, endocarditis, congenital heart defect, mediastinal abscess, caudal vena cava thrombosis, chronic suppurative pneumonia [34].*

non-cardiac, intrathoracic diseases [33, 36, 37]. Despite the research conducted to date, further studies are also necessary in order to confirm the normal range of cTnI in healthy cattle which can then be used to determine specific cut off values for use in disease assessment. However, standardization of cTnI assays is difficult due to the use of different antibodies in differing assays [38]. Additionally, the assays used in cTnI investigations were designed for use in human medicine, cattle specific assays may be more appropriate.

Whilst comparison of serum cTnI levels between cardiac diseases has not been fully established, an additional complicating factor is non-cardiac disease. Elevated cTnI levels have been demonstrated in non-cardiac intrathoracic and non-intrathoracic diseases in cattle. The concentrations of serum cTnI in cattle with metritis, mastitis, left displaced abomasum, downer cow syndrome and other calving and post-calving complications determined that in 43 of the 53 diseased cattle cTnI values were above the cut off value of 0.02 ng/ml [39]. Cattle with downer cow syndrome showed the highest levels of serum cTnI out of these diseases, with a maximum value of 27 ng/ml. This illustrates the need to consider secondary myocardial involvement as a result of other disease processes [39] and again, it reflects the importance of a thorough clinical exam. The research also found that non-surviving diseased cows (which died or were euthanized) had significantly higher median cTnI than surviving cows and that the cTnI in healthy cows was in the undetectable range (<0.02 ng/ ml). However, it was concluded that further standardization studies are necessary to confirm such claims.

Using cTnI to detect TP and therefore determine the prognosis for cattle with TRP has been investigated [40]. Investigations found that measurement of serum cTnI in cattle with TRP could potentially provide an earlier diagnosis of TP. Making an early diagnosis of TP could save time and money for the vet and farmer and reduce suffering for cattle, since treatment, at present, is generally unrewarding and the prognosis is poor particularly when diagnoses are made further along the disease process [10].

Concentrations of cTnI have been recorded in cattle with confirmed TRP to try and show possible myocardial degeneration [37]. In 55% of confirmed TRP cases, significantly elevated levels (>0.3 ng/ml) of cTnI were observed, with the mean cTnI recorded at 3.26 ng/ml (standard deviation of 2.1 ng/ml). This compares to 0.052 ng/ ml mean serum cTnI (standard deviation 0.001 ng/ml) recorded in 10 healthy control animals that were used in the study.

It should be considered that elevated cTnI levels in the serum of TRP affected cattle may not correlate directly with the severity of myocardial damage. No postmortem examinations, echocardiograms or thorough clinical examinations were described in the report, therefore potential correlations of cTnI concentration and the stage/severity of disease could not be established [37]. A positive correlation between the magnitude of cTnI increase and the severity of myocardial damage on histopathology has been demonstrated in cattle with monesin toxicosis [41] and in calves with Foot and Mouth disease [35]. Another study [36] concluded that increased serum cTnI might be more likely in acute presentations of TP compared to chronic cases, as is seen in human medicine. This emphasizes a need to consider the magnitude of the rise in serum cardiac biomarker levels over a significant timeframe.

A more recent study [42] assessed other cardiac biomarkers including heart-type fatty acid-binding protein (H-FABP), Pentraxin-3 (PTX-3) and thrombomodulin (TM) in cases of TP in cattle. There were significantly elevated H-FABP, TM and PTX-3 levels in the 25 Holstein TP positive cattle compared to 10 healthy control animals. The elevations in these biomarkers positively correlated with elevations

*Evaluation of Current and Future Diagnostic and Prognostic Techniques for Traumatic… DOI: http://dx.doi.org/10.5772/intechopen.106576*

in cTnI. However, it was concluded that there is a need to correlate cTnI levels with other cardiac biomarkers not just in TP but also other cardiac diseases. Additionally the need to correlate H-FABP, PTX-3 and TM to necropsy and histological findings in TP has been highlighted. The use of multiple cardiac biomarkers in such cases could help to further confirm thoughts of pericardial involvement when no cardiac signs are observed clinically and this could assist with determining prognosis before the expense of treatment is pursued [42].
