In various species including human beings and small animals, it has been shown that echocardiographic parameters are affected by physiological factors such as sex, age, breed, training or body size. The objective of this study was to evaluate the effect of body size on morphological echocardiographic parameters in the equine species.

Bidimensional and M-mode echocardiographic measurements (systolic and diastolic right and left ventricular and left atrial internal diameter, interventricular and left ventricular free wall thickness, and aortic and pulmonary internal diameter) were performed in 163 healthy horses. The correlation between those measurements and body weight, body surface area, body volume, height at withers, body length and thoracic circumference of the horses were studied using a simple linear regression test.

All echocardiographic parameters showed a strong (r² : 0.62-0.92) and significant (p < 0.05) correlation with all body size parameters, and the correlation obtained with each body size parameter was quite comparable. However, for most echocardiographic parameters, the correlation was stronger with the thoracic circumference than with the other body size parameters.

In conclusion, this study suggests that (1) whatever the parameter used to evaluate the body size, it significantly affects morphological echocardiographic parameters in the equine species, and (2) the thoracic circumference could be superior to evaluate the body size effect on echocardiographic parameters in this species.