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of accuracy. Concentrations of natriuretic peptides
have been shown to increase with increasing disease severity in dogs with myxomatous mitral valve disease (MMVD), and NT-proBNP concentration has been shown predicative of outcome. Furthermore, higher NT-proBNP concentrations have been found in dogs affected by the clinical stage of dilated cardiomyopathy (DCM) compared to dogs affected by pre-clinical DCM. Various studies indicate that NT-proBNP has a potential in distinguishing healthy cats from cats with pre-clinical cardiomyopathy, but the capacity of NT-proBNP for this purpose in a screening situation need to be further evaluated.
Although the use of NT-proBNP in dogs and cats seem promising, further studies need to be conducted in order to optimize the clinical use of this biomarker.
Cardiac troponins
Cardiac troponins are myofibril proteins, which by regulating the calcium-mediated action between actin and myosin filaments in the myocytes are crucial for muscle contraction. The cardiac troponin complex is composed of three subunits, troponin C, T and I, of which cardiac troponin I (cTnI) is the only one uniquely expressed in the myocardium. Myocyte injury causes
a release of troponins into the circulation. If the rate of release exceeds the rate of synthesis, the myocardium may become partially depleted of troponins, affecting the contractile function. In the veterinary community, several studies have convincingly shown the ability of cTnI to detect myocardial lesions where other conventional diagnostic methods fail. The value of cTnI as a cardiac biomarker in dogs and cats is supported by studies demonstrating increased circulating cTnI concentrations in animals with a variety of etiologies of cardiac injuries.
Several studies have been conducted in order to investigate the utility of cTnI in dogs and cats with primary heart disease, such as DCM (dogs), MMVD (dogs), hypertrophic cardiomyopathy (HCM, cats) and different congenital heart diseases. Studies in dogs affected by MMVD show that cTnI concentration, assessed by high-sensitivity tests, is associated with disease severity. However, although circulating cTnI concentration increase with increasing MMVD disease severity, a considerable overlap exist between different severity groups. Accordingly, cTnI concentration alone cannot effectively be used for cardiac disease severity assessment. Establishing prognosis in a single individual with a chronic cardiac disease is difficult. Increased
cTnI concentrations have been shown linked to a worse outcome in dogs with primary cardiac diseases; however, the value of the test for prognostication of the individual patient need to be further evaluated.
Detection of secondary cardiac injury caused by extracardiac disease processes can be challenging. Extracardiac diseases, such as gastric torsion, pyometra
An Urban Experience
and snake bite, causing secondary myocardial damage, have been shown to be associated with increased cTnI concentrations. cTnI concentration has, furthermore, been shown to be a predictor of short-term death in dogs with systemic inflammation (and without a primary cardiac disease). In order to reduce the risk of sudden death, or marked influence on long-time survival, dogs with evidence of myocardial injury may benefit from restricted exercise until the acute myocardial injury has healed.
Summary
Measurement of cTnI concentrations can be valuable both for detecting and monitoring myocardial injury. Asssessment of circulating biomarkers are unlikely
to perform well to establish a specific cardiac diagnosis, but altered biomarker concentrations can provide the impetus to pursue additional and more definitive diagnostics, and contribute to optimal case management.
Suggested reading
1. Hamacher L, Dorfelt R, Muller M, Wess G. Serum cardiac troponin I concentrations in dogs with systemic inflammatory response syndrome. J Vet Intern Med. 2015;29(1):164-70.
2. Langhorn R, Oyama MA, King LG, Machen MC, Trafny DJ, Thawley V, et al. Prognostic importance of myocardial injury in critically ill dogs with systemic inflammation. J Vet Intern Med. 2013;27(4):895-903.
3. Wess G, Simak J, Mahling M, Hartmann K. Cardiac troponin I in Doberman Pinschers with cardiomyopathy. J Vet Intern Med. 2010;24(4):843-9.
4. Ljungvall I, Hoglund K, Tidholm A, Olsen LH, Borgarelli M, Venge P, et al. Cardiac Troponin I Is Associated with Severity of Myxomatous Mitral Valve Disease, Age, and C-Reactive Protein in Dogs. J Vet Intern Med. 2010;24:153-9.
5. Oyama MA, Sisson DD. Cardiac troponin-I concentration in dogs with cardiac disease. J Vet Intern Med. 2004;18(6):831-9.
6. Singletary GE, Rush JE, Fox PR, Stepien RL, Oyama MA. Effect of NT-pro- BNP assay on accuracy and confidence of general practitioners in diagnosing heart failure or respiratory disease in cats with respiratory signs. J Vet Intern Med. 2012;26(3):542-6.
7. Hezzell MJ, Boswood A, Chang YM, Moonarmart W, Souttar K, Elliott J. The combined prognostic potential of serum high-sensitivity cardiac troponin I and N-terminal pro-B-type natriuretic peptide concentrations in dogs with degenerative mitral valve disease. J Vet Intern Med. 2012;26(2):302-11.
8. Pelander L, Ljungvall I, Haggstrom J. Myocardial cell damage in 24 dogs bitten by the common European viper (Vipera berus). Vet Rec. 2010;166(22):687-90.
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