What is the clinical evidence from this study?

Study design: Observational. Population: Healthy young Standardbred racehorses (n=103). Intervention: Training and racing vs. Baseline (first examination) and unraced horses. Primary outcome: Change in left ventricular muscle mass (LV mass) from baseline to fourth examination (p=<0.001).

June 1, 2005Journal of the American Veterinary Medical Association107 citationsOpen Access

Changes over time in echocardiographic measurements in young Standardbred racehorses undergoing training and racing and association with racing performance

Q: What are the key findings of this study?

In young Standardbred racehorses, training and racing over 1.5 years resulted in significant cardiac enlargement, including a 40.3% increase in left ventricular mass which correlated with performance.

RBRikke BuhlElectrophysiology AEAnnette Kjær ErsbøllUniversity of Southern Denmark LEL. EriksenUniversity of Copenhagen

Key Result

In young Standardbred racehorses, training and racing over 1.5 years resulted in significant cardiac enlargement, including a 40.3% increase in left ventricular mass which correlated with performance.

Study Design

Type

Observational (n=103)

Multicenter

Yes

Structured PICO

Does training and racing affect echocardiographic measurements and correlate with racing performance in young Standardbred racehorses?

Population

103 young Standardbred racehorses followed for 1.5 years to evaluate echocardiographic changes during training and racing.

Exposure

Training and racing over time

Comparator

Unraced horses

Outcome

Changes in echocardiographic measurements (LVIDd, LV mass, mean wall thickness) and relationship with racing performancesurrogate

In young Standardbred racehorses, cardiac dimensions increase significantly with age and training, and larger left ventricular size correlates with better racing performance.

Main Result

p-value: p=<0.001

Limitations

Lack of an untrained, age-matched control group to separate training effects from normal physiologic growth
Body weight was estimated from chest girth rather than measured directly or as lean body mass
Exact quantification of exercise was difficult to achieve in a field study
Examiner was not blinded to the horses' performance ability at later examinations
High dropout rate and relatively low fraction of horses that managed to race regularly

Abstract

OBJECTIVE: To evaluate changes over time in echocardiographic measurements in young Standardbred racehorses undergoing training and racing and determine whether there was any relationship between cardiac dimensions and racing performance. DESIGN: Longitudinal observational study. ANIMALS: 103 horses. PROCEDURE: 2-dimensional and M-mode echocardiography was performed 4 times at 6-month intervals. RESULTS: Significant cardiac enlargement took place during the study period as indicated by increases in left ventricular internal diameter in diastole (LVIDd), estimated left ventricular muscle mass (LV mass), and mean wall thickness attributable to eccentric left ventricular hypertrophy. Estimated body weight was positively correlated with left ventricular size, and males had significantly larger LVIDd and LV mass than did females. Horses that were racing regularly had larger LVIDd and LV mass than did unraced horses. A significant relationship between left ventricular size and racing performance was observed. The relationship was strongest at the time of the fourth examination. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that age must be taken into account when interpreting results of echocardiography in young Standardbred racehorses because significant cardiac enlargement takes place with age and training. A larger heart was found in horses that were racing, and size of the heart was correlated with athletic performance of the horse.

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