Reference Values and Association of Body Weight, Age, and Sex With Echocardiographic Measurements in Non‐Athletic Quarter Horses

Echocardiographic reference intervals for Quarter Horses are infrequently reported. To provide standard echocardiographic measurements for sedentary Quarter Horses and evaluate the relationship between physical characteristics (body weight, age, sex) and echocardiographic measurements. Forty-one sedentary Quarter Horses, free of cardiac disease, from a university research herd. A cross-sectional study evaluating standardized echocardiograms performed on sedentary Quarter Horses (41) between 2020 and 2022. Reference intervals were calculated for raw and weight-corrected values. Multiple linear regression was performed to evaluate the relationship between the physical characteristics (body weight, age, sex) and echocardiographic variables. Multiple linear regression showed that every 100 kg of body weight was associated with a 3 (95% CI 1-6) mm thicker left ventricular free wall in systole (p = 0.02), an 8 (95% CI 2-13) mm larger left atrial diameter (p < 0.01), and a 4 (95% CI 0-9) mm larger pulmonary artery diameter (p = 0.04). Every year in age was associated with a 0 (95% CI 0-1) mm larger left atrial diameter (p = 0.02), a 0 (95% CI 0-1) mm larger aortic diameter (p = 0.01), and a 0 (95% CI 0-1) mm larger pulmonary artery diameter (p = 0.01). Left atrial to left ventricular ratio was 1 (95% CI -1 to 0) mm smaller in geldings compared to mares (p = 0.03). This study provides echocardiographic reference intervals for a cohort of sedentary Quarter Horses and clarifies the association with body weight, age, and sex with these variables.