Ph.D student University of Minnesota, Equine Genetics and Genomics Lab Minneapolis, Minnesota, United States
Abstract: Background – Echocardiography is a mainstay of cardiac evaluations. Numerous reference ranges have been published for different horse breeds, however, many were published >10 years ago. We are currently performing cardiac evaluations, including echocardiography, on 1,000 healthy Standardbred and Thoroughbred racehorses. In evaluating echocardiographic measurements, interobserver variability can be a significant source of data inaccuracy.
Objectives – Our primary objective is to identify structural cardiac abnormalities in and update reference ranges for healthy racehorses. Our secondary objective is to determine interobserver variability.
Animals – Echocardiography was performed on Thoroughbreds (n=31) and Standardbreds (n=53), comprised of 51 geldings, 24 mares, 4 stallions, and 5 undesignated, aged 2 – 10 years old.
Methods – This was a non-randomized observational case-control study. Echocardiography was performed on non-sedated horses. Standard measurements were obtained.
Results – Mean (standard deviation) values for Thoroughbreds and Standardbreds respectively were obtained: ejection fraction (64.37%, 4.92; 64.0%, 4.18), fractional shortening (37.35%, 3.82; 37.07%, 3.24), left atrial diameter (12.22 cm, 0.72; 12.42 cm, 0.77), interventricular septum (2.61 cm, 0.25; 2.65 cm, 0.33), diastolic left ventricular diameter (11.08 cm, 1.18; 11.25 cm, 1.08), left ventricular free wall (2.58 cm, 0.23; 2.32 cm, 0.25) and systolic left ventricular diameter (6.96 cm, 0.88; 7.08 cm, 0.76). No horses had clinically relevant structural disease.
Conclusions and clinical importance – These measurements will provide updated reference ranges for healthy racehorses and information about the proportion of horses with structural cardiac disease. Interobserver agreement will be evaluated for three observers.
