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Keywords:

  • horse;
  • maximum oxygen uptake;
  • echocardiography;
  • heart size

Summary

  1. Top of page
  2. Summary
  3. References

Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (V̇O2max) and cardiac size measured by echocardiography, guided M-mode and 2-dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of V̇O2max from 126 to 217 ml/min/kg STPD (mean ± s.d. 158 ± 28 ml/min/kg). Horses were age 2–10 years and weighed 430–510 kg. Echocardiography was performed using a Vingmed System V echocardiograph with a 2.25 MHz phased array ultrasound transducer. All images were obtained from the right hemithorax using a short axis view of the left ventricle (LV) at the level of the chordae tendinae. All horses were free from significant regurgitation at the aortic or mitral valves. Maximal oxygen uptake was measured during a standardised incremental treadmill exercise test to fatigue. Maximal oxygen uptake was correlated significantly with LVIDd (r = 0.71; P = 0.001), MWT (r = 0.72; P = 0.001), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). When indices of heart size were indexed to bodyweight, the correlation between V̇O2max and indices of heart size were LVIDd (r = 0.57; P = 0.01), MWT (r = 0.44; P = 0.07), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). The current study suggests there is a strong relationship between V̇O2max and measurements of left ventricular size in Thoroughbred horses when individuals with a range of V̇O2max are compared.

Abbreviations
2-D

Two-dimensional

M-mode

Motion mode

LVIDd

Left ventricular internal diameter at end-diastole

LVIDs

Left ventricular internal diameter in systole

IVSd

Interventricular septal thickness at end-diastole

IVSs

Interventricular septal thickness in systole

LVFWd

Left ventricular free wall thickness at end-diastole

MWT

Mean left ventricular free wall thickness at end-diastole

VO2max

Maximum oxygen uptake

LV mass

Calculated left ventricular muscle mass

STPD

Standard temperature and pressure, dry

References

  1. Top of page
  2. Summary
  3. References
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