Use of color Doppler echocardiography to assess the development of valvular regurgitation in Standardbred trotters.

Objective: To evaluate the incidence and development of valvular regurgitation and its effect on racing performance in Standardbred trotters from 2 to 3.5 years of age.

Design: Longitudinal observational study.

Animals: 103 horses.

Procedure: Horses were examined via echocardiographic imaging 4 times at 6-month intervals. Two-dimensional and M-mode echocardiographic examinations were performed in each horse, and color Doppler imaging was used to detect and evaluate regurgitant blood flow at each valve.

Results: For all cardiac valves, the frequency of valvular regurgitation increased significantly during the 18-month study period. Regurgitation was mild in all valves in which it was detected, and no progression in severity was observed at any valve. Tricuspid regurgitation was more prevalent in horses that raced regularly and was diagnosed more frequently in males and horses with larger left ventricular mass and left ventricular internal diameter during diastole. No relationship between racing performance and valvular regurgitation was observed.

Conclusions And Clinical Relevance: The incidence of valvular regurgitation increased during the study period, and it was common at 3.5 years of age. It was not possible to determine whether the increase was a result of maturity or training. The study revealed that there is a high prevalence of mild valvular regurgitation at this age, but apparently, the regurgitation had no effect on racing performance in this age group. Whether regurgitation will progress or influence future performance is not known.