Echocardiographic measurements of cardiac dimensions in normal Standardbred racehorses

Objectives: The aim of this study was to obtain echocardiographic measurements and establish reference ranges for 14 parameters in Standardbred racehorses in training. Background: Several studies have been published about cardiac measurements in Thoroughbreds, Standardbreds, National Hunt horses, Warmbloods and ponies; however, not all parameters have been published for the Standardbred trotter in training. Animals, materials and methods: Thirty normal Standardbred racehorses in training were assessed by two-dimensional echocardiography (2-D) and M-mode echocardiography using standardized imaging planes. Mean values, standard deviations, 95% confidence interval for the means and 95% confidence interval for the cardiac parameters measured in the population were calculated. Furthermore, a general linear model was constructed using sex, age and body weight (bwt) of the horses as independent variables and the echocardiographic measurements as dependent variables. Multivariate linear regression analysis was performed with the level of significance at p < 0.05 for all the null hypotheses. Results: Reference ranges were established for 14 echocardiographic parameters in Standardbred racehorses. Weak linear relationships between echocardiographic measurements and body weight were observed for LVIDd, LVIDs, LVFWs, and AOD. Linear regressions on these parameters were used to calculate the 95% confidence intervals for the predicted values. Conclusions: The data collected in this study provide reference values for the evaluation of Standardbred racehorses in training. Body weight has a negligible affect on most echocardiographic parameters in this homogeneous population, but did mildly influence the results of left ventricular and aortic measurements.