Pre- and post-race serum cardiac troponin T concentrations in Standardbred racehorses

I.R Hellings,R Krontveit,M Øverlie,A Kallmyr,T Holm,C Fintl

doi:10.1016/j.tvjl.2020.105433

Abstract

Elevated cardiac troponin T (cTnT) concentrations may provide evidence of myocardial injury but physiological post-exercise release also occurs. Reference intervals are not fully established in horses making interpretation difficult. The aims of this study were to establish an upper reference limit for serum cTnT, compare pre-and post-race serum cTnT concentrations, and to evaluate factors that may influence these in a population of healthy, race-fit Standardbred racehorses. Serum samples were collected pre- (n = 108) and 1–2 h post-racing (n = 101) and analysed using a high sensitivity-cTnT assay. Reference limits with 90% confidence intervals (CI) were calculated by non-parametric methods using the bootstrap method. Effects of sex, age, racing speed, distance, placings and track surface were assessed by fitting generalized linear models with an identity link function and inverse Gaussian distribution.The upper reference limit for serum cTnT concentration was 27.4 ng/L (90% CI 13.1–32.0). The median serum cTnT concentration was significantly higher 1–2 h post-racing compared to pre-racing (P < 0.001). Age and sex did not significantly affect serum cTnT concentrations pre-racing (P = 0.5 and P = 0.11). Cardiac troponin T concentrations were significantly higher post-racing in females (P = 0.018). Racing speed and placings had no effect on serum cTnT concentrations post-race (P = 0.71 and P = 0.66). The study contributed towards establishing an upper reference limit for serum cTnT concentrations in a population of race-fit Standardbreds and evaluated factors that may have influenced the results obtained.

Highlights

Cardiac disease is increasingly recognized as a cause of poor performance as well as of sudden death in horses (Brown et al, 1988; Boden et al, 2006; Lyle et al, 2011; Reef et al, 2014)
Exercise-associated increases in cardiac troponin T (cTnT) typically peak within few hours (2À5 h) (Gresslien and Agewall, 2016) post-exercise and return to baseline within 24 h and differ from the prolonged elevated concentrations typically seen in humans with myocardial injury (Shave et al, 2010; Donnellan and Phelan, 2018)
One horse was defined as an outlier and removed from the statistical analysis because it had a pre-race serum cTnT concentration (76 ng/L) more than twice the maximum value of other samples from the group

Summary

Introduction

Cardiac disease is increasingly recognized as a cause of poor performance as well as of sudden death in horses (Brown et al, 1988; Boden et al, 2006; Lyle et al, 2011; Reef et al, 2014). Cardiac troponins (cTn) are a group of cardiac regulatory proteins unique to the myocardium (Sharma et al, 2004). In humans, both cardiac troponin I (cTnI) and troponin T (cTnT) have been shown to be useful markers in diagnosing myocardial injury (Sharma et al, 2004; Thygesen et al, 2010). Exercise-associated increases in cTnT typically peak within few hours (2À5 h) (Gresslien and Agewall, 2016) post-exercise and return to baseline within 24 h and differ from the prolonged elevated concentrations typically seen in humans with myocardial injury (Shave et al, 2010; Donnellan and Phelan, 2018). 78% of runners had cTnT above 0.01 ug/L (10 ng/L) while 36% had cTnT concentrations above the cut off values for acute myocardial infarct in humans of 5 ng/L (Shave et al, 2007)

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