Effect of racing on cardiac troponin I concentration and associations with cardiac rhythm disturbances in Standardbred racehorses

Introduction/Objectives: Accumulating evidence indicates intense exercise can be associated with myocardial damage. Investigating the impact of maximal effort on myocardium and exploring possible association of injury with rhythm disturbance requires a high-sensitivity cardiac troponin assay. The objectives of this study were: (1) to determine the effect of racing on serum cardiac troponin I (cTnI) in Standardbred horses using a high-sensitivity assay; (2) to determine the 99th percentile of cTnI in healthy horses and investigate the effect of demographic variables on cTnI prevailing pre-race in Standardbred horses using a validated high-sensitivity assay and a contemporary assay, and; ( 3) to explore associations between exercise-associated arrhythmia and cTnI concentration. Animals: Racehorses (n = 145). Materials and methods: <= 2 h pre-race, cTnI concentrations were measured in 158 race starts. Electrocardiogram (ECG) monitoring was applied during racing and race recovery and screened for complex ventricular arrhythmia. Associations between cTnI prevailing before racing concentration, age, sex, and gait were investigated. Demographic and performance variables were evaluated for associations with cTnI concentration post-race and rhythm disturbance. Results: Incidence of arrhythmia was 11.6% (16 horses). A significant increase in median (interquartile range) cTnI concentration of 1.36 (0.49-2.81) ng/L was found post-race (p < 0.0001). Serum cardiac troponin I (cTnI) concentration prevailing pre-race was positively associated with increasing age, and gait. Serum cardiac troponin I prevailing post-race was positively associated with concentration prevailing pre-race. Interaction between arrhythmia and finishing distanced revealed horses finishing distanced and experiencing arrhythmia displayed higher cTnI release than with the presence of either alone. Conclusions: Racing increased cTnI concentration. Horses finishing distanced and also exhibiting arrhythmia may be experiencing myocardial compromise. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the effects of racing on serum cardiac troponin I (cTnI) in Standardbred horses, using high-sensitivity assays. Results showed a significant increase in cTnI concentration post-race. Factors such as age, gait, and pre-race cTnI concentration were found to be positively associated with cTnI levels. Horses finishing distanced and experiencing arrhythmia exhibited higher cTnI release, suggesting potential myocardial compromise.