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.

Post-exercise cardiac troponin I release and clearance in normal Standardbred racehorses.

BACKGROUND: There are currently no studies detailing cardiac troponin I (cTnI) release 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 injury. OBJECTIVE: To plot the magnitude and time course of cTnI release after maximal effort, using validated cTnI assays. STUDY DESIGN: Descriptive longitudinal study. METHODS: Five clinically normal Standardbred racehorses in race training were included in the study. Horses were exercised in harness at near-race intensity. Blood samples were taken immediately pre- and post-exercise and then hourly for 24 h. Samples were analysed using the validated high-sensitivity cTnI assay and a contemporary sensitivity cTnI assay. RESULTS: Mean resting cTnI was 1.33 ± 0.6 s.d. ng/L (range, 0.82-2.33 ng/L) using assay A. All horses were below the detection limit at rest using assay B. Peak elevation occurred 2-6 h post-exercise with both assays (mean, 4.6 ± 1.7 and 4.0 ± 2 h, respectively). Mean peak increase in cTnI was 11.96 ± 9.41 ng/L (range, 1.72-23.76 ng/L) using assay A. Peak concentrations were detectable in three of the horses using assay B and were between 0.039 and 0.051 µg/L (mean: 0.043 ± 0.006 µg/L). All horses returned to baseline within 24 h. MAIN LIMITATIONS: A small (n = 5) convenience sample was used as random sampling was not logistically possible. CONCLUSIONS: All horses experienced an increase in cTnI post-exercise, with peak occurring 2-6 h post-exercise. Cardiac troponin I elevation was detected earlier using the high-sensitivity assay, which may convey a diagnostic advantage. Targeted studies are needed to determine the significance of these increases.

Use of an interferon-gamma based assay to assess bladder cancer patients treated with intravesical BCG and exposed to tuberculosis.

OBJECTIVE: Compare the QuantiFERON-TB Gold In-Tube (QFT) assay and the tuberculin skin test (TST) in bladder cancer patients receiving high dose BCG therapy (BCG patients). DESIGN AND METHODS: BCG patients and healthy visitors, both exposed to tuberculosis, were screened with a TST and QFT. RESULTS: QFT-TST correlation was excellent in visitors, but poor in BCG patients. BCG therapy predicted a positive TST (p<0.001) but not a positive QFT (p=0.35). DISCUSSION: The management of BCG patients was impacted, by measuring the QFT.