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

Abstract

BACKGROUND: Echocardiographic reference intervals for Quarter Horses are infrequently reported. OBJECTIVES: To provide standard echocardiographic measurements for sedentary Quarter Horses and evaluate the relationship between physical characteristics (body weight, age, sex) and echocardiographic measurements. ANIMALS: Forty-one sedentary Quarter Horses, free of cardiac disease, from a university research herd. METHODS: 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. RESULTS: Multiple linear regression showed that every 100&#x2009;kg of body weight was associated with a 3 (95% CI 1-6) mm thicker left ventricular free wall in systole (p&#x2009;=&#x2009;0.02), an 8 (95% CI 2-13) mm larger left atrial diameter (p&#x2009;<&#x2009;0.01), and a 4 (95% CI 0-9) mm larger pulmonary artery diameter (p&#x2009;=&#x2009;0.04). Every year in age was associated with a 0 (95% CI 0-1) mm larger left atrial diameter (p&#x2009;=&#x2009;0.02), a 0 (95% CI 0-1) mm larger aortic diameter (p&#x2009;=&#x2009;0.01), and a 0 (95% CI 0-1) mm larger pulmonary artery diameter (p&#x2009;=&#x2009;0.01). Left atrial to left ventricular ratio was 1 (95% CI -1 to 0) mm smaller in geldings compared to mares (p&#x2009;=&#x2009;0.03). CONCLUSIONS AND CLINICAL IMPORTANCE: 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.