Abstract
In order to determine if training efficacy or racing performance of Thoroughbred horses could be assessed by measurements of left ventricular function, echocardiographic examinations were conducted on 45 horses aged 2 to 6 years old, which belonged to the Ritto Training Center, Japan Racing Association. The following results were obtained.
1) The morphological and functional findings of the left ventricle were determined by a probe, the approarch of which was made a restricted area in the left third intercostal space, the cardiac-window. This approarch was simple and sufficiently acculate for examination of left ventricular function.
2) Correlation coefficiency (r=0.956) based on the stroke volume of 15 Thoroughbred horses (3 to 5 years old) was obtained by echocardiography and dye-dilution method. So that stroke volume as measured by echocardiography was considered reasonable.
3) Stroke index as shown by the stroke volume per kg increased with age and or progress of training. Relatively stable values were obtained ranging from 2.42ml/kg to 3.37ml/kg in horses over 3 years old. Comparing these values for 5 horses (4 years old) with excellent racing performance and 10 horses (4 to 6 years old) of ordinary performance, significantly higher values (p<0.001) were obtained in the former (3.55ml/kg in average) than in the latter (2.85ml/kg).
4) End-systolic internal dimensions in this study did not differ significantly. End-diastolic dimensions did, however, differ significantly in the above two groups of horses. The usefullness of echocardiography assessing left ventricular function of Thoroughbred horses is thus comfirmed. The left ventricular volume at end-diastolic stage in horses with excellent racing performance had much greater than that in horses of ordinary performance.
