Post Exercise Cardiac Troponin I Release and Clearance in Normal Standardbred Racehorses

Reasons for performing study There are currently no studies detailing cardiac troponin I (cTnI) release and clearance in normal horses post exercise using an analytically validated assay. These data are essential for selecting appropriate sampling times in equine athletes with suspected myocardial damage. Objective To plot the magnitude and time course of cTnI release and clearance, using a validated cTnI assay, after maximal effort. Study design Descriptive longitudinal study. Methods Five clinically normal Standardbred racehorses in full race training were included in the study. Physical examinations were performed on subjects and blood samples were taken via jugular venipuncture pre‐exercise. Horses were exercised in harness at race intensity in groups on a training track. A second blood sample was taken immediately post exercise and an intravenous catheter was then placed in a jugular vein. Hourly blood samples were taken for 24 h. All samples were collected in red top serum Vacutainer® tubes and allowed to clot for 30 min before being centrifuged and serum harvested. Serum samples were stored at −80° C until analysis. All samples were analysed using the Abbott ARCHITECT STAT High Sensitivity cTnI® assay. Results Mean resting cTnI level was 1.33 ± 0.6 ng/l (range, 0.82–2.33 ng/l). All horses exhibited an increase in cTnI level after exercise with peak elevation occurring 2–6 h post exercise (mean, 4.6 ± 1.7 h). Mean peak increase in cTnI level was 11.96 ± 9.41 ng/l (range, 1.72–23.76 ng/l). All horses returned to baseline levels within 24 h. Conclusions All horses experienced an increase in cTnI post exercise, with the peak occurring 2–6 h post exercise. Further studies are needed to determine the significance of these increases. Ethical animal research: The study protocol was approved by the University's Animal Care Committee. Explicit informed consent was obtained in writing for all client‐owned animals. Source of funding: Equine Guelph. Competing interests: Dr Kavsak has received grants/honoraria/consultant/advisor fees from Abbott Laboratories, Abbott Point of Care, Beckman Coulter, Ortho Clinical Diagnostics, Randox Laboratories, Roche Diagnostics, and the Canadian Agency for Drugs and Technologies in Health. He is listed as an inventor on patents filed by McMaster University related to laboratory testing in acute cardiac care. No funding was received from the manufacturer of the assay evaluated in this study.