Reference Values and Association of Body Weight, Age, and Sex With Echocardiographic Measurements in Non-Athletic Quarter Horses.
Authors: Selecky Madeline E, Louie Elizabeth Williams, Donnelly Callum, Finno Carrie J, Morgan Jessica M
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Echocardiographic Reference Values in Quarter Horses Whilst echocardiographic standards exist for many equine populations, Quarter Horses—particularly sedentary individuals—have been notably under-represented in the literature. This cross-sectional study examined 41 clinically normal, non-athletic Quarter Horses from a university research herd between 2020 and 2022 to establish baseline cardiac measurements and determine how body weight, age, and sex influence key echocardiographic variables. Body weight emerged as a significant driver of cardiac dimensions: each 100 kg increment was associated with a 3 mm thicker left ventricular free wall in systole, an 8 mm larger left atrial diameter, and a 4 mm larger pulmonary artery diameter. Age also played a role, with each additional year correlating to modest but measurable increases in left atrial, aortic, and pulmonary artery diameters, whilst geldings demonstrated a smaller left atrial-to-left ventricular ratio compared to mares. These reference intervals are particularly valuable for practitioners conducting pre-purchase examinations, monitoring suspected cardiac disease, or establishing baseline measurements in this breed, as applying generic equine standards may lead to misinterpretation of normal anatomical variation related to individual conformation, maturity, and sex.
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Practical Takeaways
- •Heavier Quarter Horses will have naturally larger cardiac chamber dimensions and wall thickness; use body weight-adjusted reference intervals when interpreting echocardiograms rather than absolute values alone
- •Age and sex influence cardiac measurements; establish age- and sex-specific reference ranges when screening Quarter Horses for cardiac disease to avoid over-diagnosis in older or heavier animals
- •These reference intervals apply only to sedentary Quarter Horses; athletic or performance horses will have different measurements and should not be compared to these values
Key Findings
- •Every 100 kg of body weight was associated with 3 mm thicker left ventricular free wall in systole, 8 mm larger left atrial diameter, and 4 mm larger pulmonary artery diameter
- •Every year of age was associated with increases in left atrial diameter, aortic diameter, and pulmonary artery diameter (0-1 mm each)
- •Geldings had 1 mm smaller left atrial to left ventricular ratio compared to mares
- •Study provides first echocardiographic reference intervals for sedentary Quarter Horses free of cardiac disease