Cardiac Troponin I in Racing Standardbreds

Twenty-four hour continuous transvenous temporary right ventricular pacing in healthy horses

BACKGROUND

The ability to perform transvenous temporary cardiac pacing (TV-TP) is critical to stabilize horses with symptomatic bradyarrhythmias. Reports of successful TV-TP in horses are limited, and only briefly describe short-term pacing.

OBJECTIVE

To describe temporary, medium-term (24 h) transvenous right ventricular pacing in awake horses using a bipolar torque-directed pacing catheter.

ANIMALS

Six healthy adult institutional teaching horses.

METHODS

Prospective experimental study with 2 immediately successive TV-TP lead placements in each horse with a target location of the RV apex. One placement was performed primarily with echocardiographic guidance and 1 primarily with fluoroscopic guidance. In all placements, corresponding images were obtained with both imaging modalities. Horses were then paced for 24 h, unrestricted in a stall with continuous telemetric ECG monitoring. Echocardiographically determined lead position, episodes of pacing failure in the preceding 6 h, and pacing thresholds were recorded every 6 h. Pacing failure was defined as a period of loss of capture longer than 20 s.

RESULTS

Pacing leads were placed with both guidance methods and maintained for 24 h with no complications. Two horses with leads angled caudally in the right ventricular apex had no pacing failure, the remaining 4 horses had varying degrees of loss of capture. Leads located in the right ventricular apex had longer time to pacing failure and lower capture thresholds P < 0.05.

CONCLUSIONS AND CLINICAL IMPORTANCE

Medium-term TV-TP is feasible and has potential for stabilization of horses with symptomatic bradyarrhythmias. Lead position in the right ventricular apex appears optimal. Continuous ECG monitoring is recommended to detect pacing failure.

Comparison of Hemodynamic Effects of Dobutamine and Ephedrine Infusions in Isoflurane-Anesthetized Horses

The objective of this study was to compare the hemodynamic effects of dobutamine and ephedrine during the management of anesthesia-related hypotension in healthy horses. Thirteen horses underwent general anesthesia with isoflurane and were randomly divided into two different groups, one of which received a dobutamine constant rate infusion (CRI) (1 µg/kg bwt/min) and the other received an ephedrine CRI (20 µg/kg bwt/min) when hypotension (<60 mmHg) was identified, following up to 15 min after the blood pressure reached 70 mmHg. All horses were equipped with a pulmonary artery catheter and a peripheral artery catheter, and multiparameter monitoring commenced as soon as they were under mechanical ventilation. Hemodynamic parameters were recorded, while tissue perfusion markers (peripheral oxygen saturation, arterial oxygen partial pressure, arterial carbon dioxide partial pressure, arterial pH, arterial plasma bicarbonate concentration, arterial oxygen saturation, mixed venous oxygen saturation, mixed venous oxygen content, arterial oxygen content, arteriovenous oxygen difference, oxygen delivery index, oxygen consumption index, and oxygen extraction ratio), serum lactate concentration, and troponin I concentrations were analyzed before the start of infusions (T0), when the blood pressure reached 70 mmHg (T1), and 15 min after T1 (T2). The time to restore the arterial pressure was similar in both groups (p > 0.05); however, the heart rate was higher in the ephedrine group (p = 0.0098), and sinus bradyarrhythmia occurred in the dobutamine group. Furthermore, both experimental protocols increased cardiac output (p = 0.0012), cardiac index (p = 0.0013), systemic vascular resistance (p = 0.008), systemic vascular resistance index (p < 0.001), and ameliorated perfusion markers. In the dobutamine group, the pulmonary artery wedge pressure (p < 0.001) and systolic index (p = 0.003) were elevated, while the arteriovenous oxygen difference was reduced in the ephedrine group (p = 0.02). Troponin I was used as a myocardial injury indicator, and did not differ between moments or between groups (p > 0.05). We concluded that both drugs were effective and safe to treat anesthetic hypotension under the conditions of this study.

Inflammatory Response and Electrocardiographic Examination in Horses Vaccinated against Equine Herpesvirus (Ehv-1)

Simple Summary

Equine herpesvirus 1 (EHV-1) is an alphaherpesvirus that infects horses, causing respiratory, neurologic, and abortion syndromes in pregnant mares. Vaccination induces an immune response that reduces the risk of infection, the severity of clinical signs, and viral excretion. This study aimed to evaluate and describe the clinical and electrocardiographic findings, and changes in cardiac troponin I (cTnI) and inflammatory biomarkers (serum amyloid A (SAA) and C-reactive protein (CRP)) occurring after vaccination against herpesvirus in healthy horses.

Abstract

This study aimed to evaluate possible abnormalities in electrocardiographic findings, and changes in cardiac troponin I (cTnI) and inflammatory biomarkers (serum amyloid A (SAA) and C-reactive protein (CRP)) after inactivated herpesvirus vaccine administration. Eighteen healthy horses were included. All animals were vaccinated with Pneumoequine^® (Merial, France) according to the protocol provided by the manufacturer. They were evaluated 1 day before the first dose of vaccination (D0), and 7 days (D1) and 14 days (D2) afterwards. At D0, D1, and D2, a blood sample was taken for the evaluation of SAA, cTnI, and CRP. An electrocardiographic examination was also performed. The data obtained suggested the possible involvement of the myocardium following vaccination against herpesvirus 1, mostly related to an inflammatory response.

Racing-associated fatalities in Norwegian and Swedish harness racehorses: Incidence rates, risk factors, and principal postmortem findings

Background

There are no reports on the number of fatalities or causes of death in the Norwegian and Swedish harness racehorses.

Objectives

The incidence rates (IRs), risk factors, and postmortem findings in horses that died or were euthanized associated with racing between 2014 and 2019 were investigated.

Animals

Thirty‐eight Standardbreds and 10 Norwegian‐Swedish Coldblooded Trotters died or were euthanized associated with racing. A total of 816 085 race‐starts were recorded.

Methods

Incidence rates were calculated for both countries and horse breeds. Risk factors for sudden death were identified using a case‐control logistic model. Postmortem examinations were performed in 43 horses.

Results

The overall fatality IR was 0.059/1000 race‐starts. Traumatic injuries accounted for 14.5%, while sudden death for 85.5% of fatalities. Only minor differences between countries and breeds were recorded. The number of starts within the last 30 days increased the risk of sudden death (5 starts odds ratio (OR) 228.80, confidence interval (CI) 10.9‐4793). An opposite non‐linear effect was observed in number of starts the last 180 days (>10 starts OR 0.12, CI 0.02‐0.68). Seven horses were euthanized because of catastrophic injury. Acute circulatory collapse because of suspected cardiac or pulmonary failure or both was recorded in 30 horses, while major hemorrhage after vessel rupture was the primary cause of death in 10 cases. One horse collapsed and died but was not submitted for autopsy.

Conclusions and Clinical Importance

Comparatively low rates of catastrophic orthopedic fatalities were reported, while causes and IR of sudden death were similar to previous studies.

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.

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

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.

Prospective pre- and post-race evaluation of biochemical, electrophysiologic, and echocardiographic indices in 30 racing thoroughbred horses that received furosemide

Background

Exercise induced cardiac fatigue (EICF) and cardiac dysrhythmias are well described conditions identified in high-level human athletes that increase in frequency with intensity and duration of exercise. Identification of these conditions requires an understanding of normal pre- and post-race cardiac assessment values. The objectives of this study were to (1) characterize selected indices of cardiac function, electrophysiologic parameters, and biochemical markers of heart dysfunction prior to and immediately after high level racing in Thoroughbred horses receiving furosemide; and (2) create pre- and post-race reference values in order to make recommendations on possible screening practices for this population in the future.

Results

Thirty Thoroughbred horses were enrolled in the study with an age range of 3–6 years. All horses received furosemide prior to racing. Physical exams, ECGs, and echocardiograms were performed prior to racing (T0) and within 30–60 min following the race (T1). Blood samples were obtained at T0, T1, 4 h post-race (T4) and 24 h after the race (T24). Electrolytes, hematocrit, cardiac troponin I, and partial pressure CO2 values were obtained at all time points. Heart rate was significantly increased post-race compared to baseline value with a median difference of 49 bpm, 95% CI [31,58],(P < 0.0001). No dysrhythmias were noted during ECG assessment. Following the race, an increase in number of horses demonstrating regurgitation through the aorta and AV valves was noted. Systolic function measured by fractional shortening increased significantly with a mean difference of 7.9%, 95% CI [4.8, 10.9], (P < 0.0001). Cardiac troponin I was not different at pre- and immediately post-race time points, but was significantly increased at T4 (P < 0.001). Troponin returned to baseline value by T24.

Conclusions

This study utilized a before and after study design where each horse served as its own control, as such the possible effect of regression to the mean cannot be ruled out. The reference intervals generated in this study may be used to identify selected echocardiographic and electrocardiographic abnormalities in racing horses receiving furosemide.

Analytical validation of cardiac troponin I assays in horses

Human cardiac troponin I (cTnI) assays have been used in equine medicine, often without prior analytical validation for equine use. In the absence of appropriate validation, the clinical significance of assay results is uncertain and can lead to misdiagnosis. We followed the American Society for Veterinary Clinical Pathology guidelines and investigated linearity, precision, limit of quantification (LoQ), and comparative recovery for 6 commercial cTnI assays developed for use in human medicine. Clinically acceptable linearity was observed in assays A-D, whereas assay E did not detect equine cTnI in any sample. Comparative recovery revealed 1-3-fold differences between assay results, and low analyte recoveries (2.2-3.4%) were observed in assay F. Precision was investigated in assays A and B, and found to be within acceptable limits. The LoQ was 1.53 ng/L for assay A, and 0.031 µg/L for assay B. Assays A and B performed within clinically acceptable limits and were deemed suitable for use in equine medicine. Assays C and D did not undergo full validation but had acceptable linearity, which demonstrates their potential for use in equine medicine. Assays E and F are unsuitable for use in horses given issues with detection of equine cTnI. The variability in results between assays indicates that reference intervals and cutoffs for diagnostic decision-making are assay specific and should be established prior to adoption by diagnostic laboratories.

24-Hour Kinetics of Cardiac Troponin-T Using a "High-Sensitivity" Assay in Thoroughbred Chuckwagon Racing Geldings after Race and Associated Clinical Sampling Guidelines

Background

A “high‐sensitivity” cardiac troponin‐T (hscTnT) assay recently has been validated for use in horses and is a specific biomarker of myocardial damage. Postexercise release kinetics of cTnT utilizing the hscTnT assay have yet to be established in horses.

Objectives

To determine: (1) cTnT release kinetics in racing Thoroughbreds after a high‐intensity 5/8th mile Chuckwagon race; (2) the effects of age on pre‐ and postrace cTnT concentrations; and (3) sampling guidelines for clinicians evaluating horses presenting after exercise.

Animals

Samples were obtained from 38 Thoroughbred geldings aged 5–16 years before racing and immediately, 2, 3, 4, 6, 12, and 24 hour postrace.

Methods

Prospective, observational study with convenience sampling. A fifth‐generation hscTnT assay was used for plasma sample analysis, and concentrations were compared at all time‐points. Correlations were determined between cTnT concentrations and age. Biochemistry analysis was performed to assess rhabdomyolysis, renal failure, and exercise‐induced dehydration.

Results

All horses with measureable cTnT concentrations had significant postexercise increases in cTnT with a median peak (8.0 ng/L) at 3‐hour postrace. All horses had peak postexercise cTnT concentrations 2‐ to 6‐hour postrace ≤ the 99th percentile upper reference limit of 23.2 ng/L, after which all cTnT concentrations decreased until returning to baseline by 12–24 hours. There was no correlation over time between cTnT concentrations and age.

Conclusions and Clinical Importance

In racing Thoroughbreds completing short‐duration, high‐intensity Chuckwagon races, cTnT concentrations are expected to be increased 2‐ to 6‐hour postrace and to decrease by 12–24 hours while remaining ≤23.2 ng/L throughout. This study contributes to establishing guidelines for clinical use of the hscTnT assay in exercising horses.

The heart remains the core: cardiac causes of poor performance in horses compared to human athletes

Cardiac remodelling occurs in response to exercise and is generally beneficial for athletic performance due to the increase in cardiac output. However, this remodelling also may lead to an increased prevalence of cardiac murmurs and arrhythmias. In most cases, these are not considered to be significant. However, in some cases, there may be potentially deleterious consequences. Whilst sudden cardiac death (SCD) is a rare occurrence, the consequences are catastrophic for both the horse and potentially the rider or driver. Furthermore, the sudden death of a horse in the public arena has negative connotations in regards to public perception of welfare during equestrian sports. Prediction of which individuals might be susceptible to potential deleterious effects of exercise is a focus of interest in both human and equine athletes but remains a challenge because many athletes experience cardiac murmurs and exercise-induced arrhythmias that are clinically irrelevant. This review summarises the effects of exercise on cardiac remodelling in the horse and the potential effects on athletic performance and SCD. The use of biomarkers and their future potential in the management of athletic horses is also reviewed.

Analytical validation and establishment of reference intervals for a 'high-sensitivity' cardiac troponin-T assay in horses

BACKGROUND

Cardiac troponin-I assays have been validated in horses.'High-sensitivity' cardiac troponin assays are now the standard in human cardiology.

OBJECTIVE

Appropriately validate the'high-sensitivity' cardiac Troponin-T (hscTnT) assay for clinical use in horses, establish reference intervals, determine the biological variation, and demonstrate assay utility in selected clinical cases.

METHODS

Analytical validation of the Roche hscTnT assay included within- and between-run precision, linear dose response, limit of quantitation (LoQ), stability, and comparison with cTn-I (iSTAT). Reference intervals and biological variation were determined using adult, healthy, Non-Competition Horses (N = 125) and Racing-Thoroughbreds (N = 178). HscTnT levels were measured in two horses with cardiac pathology.

RESULTS

The hscTnT demonstrates acceptable within-run (L1 = 6.5 ng/L, CV 14.9 %, L2 = 10.1 ng/L, CV 8.7 %, L3 = 15.3 ng/L, CV 5.4 %) and between-run precision (L1 = 12.2 ng/L, CV 8.4 %, L2 = 57.0 ng/L, CV 8.4 %, L3 = 256.0 ng/L, CV 9.0 %). The assay was linear from 3 to 391 ng/L. The LoQ was validated at 3 ng/L. Samples demonstrated insignificant decay over freeze-thaw cycle. Comparison with cTnI assay showed excellent correlation (range: 8.0-3535.0 ng/L, R(2) = 0.9996). Reference intervals: The upper 95(th) and 99(th) percentile of the hscTnT population distribution were 6.8 and 16.2 ng/L in Non-Competition Horses, and 14.0 and 23.2 ng/L in Racing-Thoroughbreds. Between-breed, diurnal effect, and between-day variation was below LoQ. Two clinical cases with presumed cardiac pathology had hscTnT levels of 220.9 ng/L and 5723.0 ng/L.

CONCLUSIONS

This benchmark study is the first to comply with CLSI guidelines, thus further establishing the performance characteristics of the hscTnT assay, and reference intervals in healthy horses. Two clinical cases demonstrated further the clinical utility of the assay.

Cardiac troponin I as compared to troponin T for the detection of myocardial damage in horses

BACKGROUND

Different cardiac troponin I (cTnI) assays give different results. Only 1 manufacturer has marketed troponin T (cTnT) assays. Therefore, cTnT often is preferred for detection of myocardial infarction in human patients. Studies of cTnT in horses are limited.

OBJECTIVES

To compare a cTnI and a high-sensitive cTnT assay (hs-cTnT) in horses.

ANIMALS

Cardiac troponin I and cTnT were determined in 35 healthy horses (group 1), 23 horses suspected to have primary myocardial damage (group 2a), and 41 horses with secondary myocardial damage caused by structural heart disease (group 2b).

METHODS

All cTnI samples were analyzed at laboratory A (limit of detection [LOD]: 0.03 ng/mL), whereas cTnT samples were analyzed at 2 laboratories with the same hs-cTnT assay (laboratory B, LOD: 10.0 pg/mL; laboratory C, LOD: 4.0 pg/mL).

RESULTS

The median cTnI concentration in group 2a (0.90 ng/mL; range, 0.03-58.27 ng/mL) was significantly higher (P < .001) than in group 1 (0.03 ng/mL; range, 0.03-0.09 ng/mL) or group 2b (0.05 ng/mL; range, 0.03-30.92 ng/mL), and the optimal cut-off for detection of primary myocardial damage was 0.095 ng/mL (sensitivity: 90.5%, specificity: 100%). Using an LOD of 10.0 pg/mL for all cTnT samples, a cut-off value of 10.5 pg/mL was found, but sensitivity was low (42.9%). When only samples analyzed at laboratory C (n = 58) were included, a cut-off of 6.6 pg/mL was found (sensitivity: 81%, specificity: 100%).

CONCLUSIONS AND CLINICAL IMPORTANCE

Despite large quantitative differences, cTnI and cTnT are both useful for detection of myocardial damage in horses.

Analytical validation of a high-sensitivity cardiac troponin T assay in horses

Although cardiac troponin T (cTnT) assays have been used to detect myocardial damage in horses, a cTnT assay has not been analytically validated, to our knowledge. The aims of this study were to estimate the precision of a high-sensitivity cTnT assay in horses and determine the effect of hemolysis on the measured cTnT concentration. Serum samples from horses were mixed in 3 different pools. Pool 1 consisted of samples from 3 healthy horses, pool 2 from 6 horses with heart failure or atypical myopathy, and pool 3 from 10 horses with atypical myopathy. The within- and between-run coefficients of variation were determined for each pool. Pools 2 and 3 were diluted to estimate linearity. To study the influence of sample hemolysis, serum was collected from 4 horses with a high cTnT concentration, in which hemolysis was mechanically induced. In addition, ethylenediamine tetra-acetic acid blood tubes were collected from 3 other horses, from which hemolysate was prepared and added to plasma at different concentrations. The within- and between-run coefficients of variation of all pools were <10%, and a good linearity was found. Three out of 4 hemolyzed serum samples had a decreased serum cTnT concentration. Plasma samples with a high hemolysis index showed a negative interference, resulting in a lower cTnT concentration. Results of the high-sensitivity cTnT assay were highly reproducible. Because samples from horses with musculoskeletal damage were included, further studies should test the possible cross-reactivity between troponin T of musculoskeletal and cardiac origin before the assay can be used in equine clinical practice.

Myocardial insult and arrhythmias after acute hemorrhage in horses

OBJECTIVE

The objectives of this investigation were to: (1) Determine if acute hemorrhage is associated with increased plasma cardiac troponin I (cTnI) concentration or cardiac arrhythmias, (2) to describe the types of arrhythmias and their clinical course in horses following acute hemorrhage, (3) to determine the ability of clinical or clinicopathological variables to predict an increase in cTnI concentration and the presence of arrhythmias, and (4) to determine the associations of cTnI and cardiac arrhythmias with outcome.

DESIGN

Prospective observational study.

SETTING

Large animal veterinary teaching hospital.

ANIMALS

Eleven client-owned adult horses admitted for treatment of acute hemorrhage (HG) and 4 adult horses undergoing controlled blood collection (BDG).

METHODS

Serial cTnI concentrations were measured and continuous ECGs were obtained from the HG and BDG groups. Statistical tests were used to determine associations among acute hemorrhage and plasma cTnI concentrations, the presence of cardiac arrhythmias, clinicopathologic data (heart rate [HR], packed cell volume [PCV], total plasma protein [TPP], plasma lactate, and plasma creatinine concentrations), and outcome.

RESULTS

Plasma cTnI concentration and ECG were within reference intervals at all time points in the BDG. All horses in the HG had increased cTnI (ranging from 0.1-29.9 ng/mL). Arrhythmias were detected in 8 of these horses. There was an association between acute hemorrhage and increased cTnI (P = 0.004, ρ = 0.77), and the presence of arrhythmias (P = 0.026, ρ = 0.64). There were associations among plasma cTnI concentration and the presence of arrhythmias (P = 0.005), arrhythmias requiring treatment (P = 0.036), and poor outcome (P = 0.024).

CONCLUSIONS

Acute hemorrhage results in myocardial injury that can be detected by measuring cTnI concentration. Arrhythmias were frequent in hospitalized horses following acute hemorrhage.

Sudden death of a horse with supraventricular tachycardia following oral administration of flecainide acetate

OBJECTIVE

To describe a case of supraventricular tachycardia and sudden death in a horse following administration of flecainide acetate.

CASE SUMMARY

An 8-year-old Hanoverian warmblood gelding was treated for chronic, naturally occurring, supraventricular tachycardia with digoxin, procainamide hydrochloride, quinidine sulfate, and flecainide acetate. After oral administration of flecainide, polymorphic ventricular tachycardia (torsades de pointes) and ventricular fibrillation developed, leading to cardiovascular collapse and death.

NEW OR UNIQUE INFORMATION PROVIDED

Atrial fibrillation is the most commonly diagnosed dysrhythmia associated with poor performance in horses, while atrial tachycardia is rarely documented. Here, we describe a case of sudden death in a horse with atrial tachycardia following the oral administration of flecainide acetate, after the lack of response to other antiarrhythmic drugs. Information provided in this case report is new and will make clinicians aware of the potential complications of flecainide alone or in combination with other drugs, in horses with cardiac dysrhythmias.

Troponin assays in the assessment of the equine myocardium

In 2000, troponin assays were adopted as the test of choice for detection of myocardial injury in man. This decision was made after extensive testing and followed a 60 year search for a biomarker of myocardial damage with sufficient analytical sensitivity and specificity. This has led to proliferation of assays for use in human medicine, each requiring extensive testing and validation before it could be made available on the open market for human use. The search for ever-more analytically sensitive assays and for a standard reference material continues. The adoption of troponin testing in veterinary medicine followed shortly after its development for use in man, providing a much-needed means of detecting and monitoring myocardial damage in horses. However, application of these tests in veterinary medicine has exclusively involved use of assays designed for and clinically validated in human patients. There is no mandated requirement for test validation in veterinary medicine and, while many of these assays have been shown to be capable of detecting equine troponin, the wide diversity of available tests, lack of validation, absence of protocols for their use and lack of standardisation make their application problematic. The objective of this review article is to address this issue, offering guidance where data are available and encouraging caution where there are none. Ultimately, the overall goal of this review is to examine critically the use of troponin assays in the horse and to promote the accurate and appropriate interpretation of valid results.