Increased plasma cardiac troponin I concentration in lambs with myocarditis.

ABSTRACT

BACKGROUND: Cardiac troponin I (cTnI) is a blood biomarker of myocardial injury. A human cTnI assay may be useful for measuring cTnI concentrations in lambs with naturally occurring myocarditis. OBJECTIVE: The aims of this study were to evaluate the utility of a commercially available human chemiluminescent microparticle cTnI immunoassay for measuring plasma cTnI concentrations in lambs with naturally occurring myocarditis from infection with foot and mouth disease virus (FMDV), and to determine cTnI expression in cardiac muscle of affected lambs. METHODS: Ten lambs with myocarditis and 10 clinically healthy lambs (control group) were included. Clinical signs, gross and histologic necropsy findings, and immunoreactivity for cTnI in cardiac tissue were evaluated. Plasma cTnI concentration was determined using the commercial human immunoassay system. RESULTS: All lambs with myocarditis died within 1 day of clinical signs. Infection with FMDV was confirmed by PCR analysis. Gross cardiac lesions were evident and histologic examination revealed myocarditis. Immunoreactivity for cTnI was absent in cardiac myocytes that were degenerative or necrotic, but was strong in cardiac myocytes from unaffected areas of the myocardium and in all cardiac myocytes of healthy lambs. The geometric mean plasma concentrations of cTnI for lambs in the myocarditis and control groups were 146.78 µg/L (95% confidence interval [CI], 61.90-348.06) and 0.013 µg/L (95% CI, 0.010-0.017), respectively (t-value 19.27; P < .0001). CONCLUSIONS: A commercial human cTnI assay may be used to detect plasma cTnI concentrations in sheep, and cTnI may be used as a blood-based biomarker of myocarditis in this species.