Two-dimensional and M-mode echocardiographic findings in healthy Thoroughbred foals

Objective: The aim of this study was to establish reference values for a series of conventional two-dimensional (2-D) and M-mode echocardiographic variables in Thoroughbred foals at increasing age intervals.

Design: Nineteen healthy Thoroughbred foals (11 males, 8 females) were examined at 1, 2, 4, 8, 12 and 16 weeks of life. Auscultatory findings were recorded and echocardiographic examinations (2-D and M-mode) were performed. Descriptive statistical analyses, including mean, standard deviation and 95% confidence interval for the means, were used to summarise the data. The relationships between selected echocardiographic variables and age, body weight and heart rate were analysed.

Results: Reference values were determined for 12 routinely used 2-D and M-mode echocardiographic variables in healthy Thoroughbred foals at increasing age intervals. Linear relationships between echocardiographic variables and age (P < 0.001) and body weight (P < 0.001) were found, with the linear relationships between echocardiographic variables and body weight being stronger than those with age. Weak (R(2) ≤ 0.37) but significant (P < 0.001) correlations between the echocardiographic variables and heart rate were identified.

Conclusions: Reference values for 2-D and M-mode echocardiographic variables in clinically normal Thoroughbred foals up to 4 months of age and approximately 190 kg body weight may assist in the interpretation of echocardiograms of Thoroughbred foals of similar age and body weight with suspected congenital or acquired cardiac disease.