Objective—To determine whether echocardiographic variables differed between successful (elite) and less successful (nonelite) Arabian endurance horses. Animals—34 Arabian horses that competed in endurance racing. Procedures—Horses were assigned to either an elite or nonelite group on the basis of results of a previous competition, and a standardized echocardiographic examination was performed on each horse within 1 to 4 weeks after that competition. Multivariable logistic regression with backward stepwise elimination was used to create a prediction model for the determination of horse status (elite or nonelite) as a function of the measured echocardiographic variables. Results—The elite and nonelite groups consisted of 23 and 11 horses, respectively. One horse in the nonelite group had a frequent ventricular dysrhythmia that could have negatively affected its performance and rider's safety, whereas none of the horses in the elite group had remarkable cardiac abnormalities. The left ventricular internal diameter during systole and diastole and left ventricular mass and stroke volume were significantly greater for horses in the elite group, compared with those for horses in the nonelite group. The final logistic regression model correctly predicted the horse status for all of the horses in the elite group and 8 of 11 horses in the nonelite group. Conclusions and Clinical Relevance—Results indicated that heart size was significantly associated with performance for Arabian endurance horses in a manner similar to findings for Thoroughbred and Standardbred racehorses in active competition.

Objective-To assess the feasibility and reproducibility of longitudinal tissue Doppler ultrasonographic imaging with regard to determination of velocity, strain, and strain rate (SR) of the left atrium (LA) and use those data to characterize LA synchrony (LAS) for a group of healthy dogs. Animals-15 healthy dogs. Procedures-For each dog, apical 4- and 2-chamber echocardiographic views were obtained. Peak velocity, strain, and SR and time to peak value during systole, early diastole, and late diastole were measured for each of the 4 LA walls. To characterize LAS, mean and SD maximal late diastolic time difference (LAD) among the 4 walls were calculated on the basis of time to peak for velocity, strain, and SR; for each, the 95% confidence interval (mean ± 2SD) was calculated. Within-day and between-day intraobserver variability was calculated. Results-For all dogs, tissue velocity and SR had peak positive values during systole and 2 negative peaks during early and late diastole. Atrial strain had a peak positive value during systole, positive values during early diastole, and a negative peak value during late diastole. Reproducibility was acceptable for most variables. Diastolic strain and SR had the highest variability, but times to peak values were always reproducible. For velocity, strain, and SR, the 95% confidence interval for the maximal LAD was < 50 milliseconds and that for the SD of the LAD was < 23 milliseconds. Conclusions and Clinical Relevance-Longitudinal tissue Doppler imaging of LA deformation was feasible in healthy dogs, and its application may be useful for understanding atrial pathophysiologic changes associated with various cardiac diseases in dogs.