Influence of Signalment Variables on Body Weight-Normalized Echocardiographic Measurements of Heart Size in 56 169 Adult Unsedated Normal Pure-Bred Cats.

BACKGROUND

Echocardiography is widely used to breed-screen cats for the presence of heart disease. Left-sided cardiac dimensions are non-linearly related to body weight (BW), but the association with signalment variables is incompletely evaluated.

OBJECTIVE

To validate previously published prediction equations (PE) and 95% prediction intervals (PI) and study the effects of breed, age, sex, and neutering on BW-normalized aortic (Ao), left atrial (LA) and ventricular (LV) dimensions.

ANIMALS

56 169 pure-bred adult cats.

METHODS

Data from heart screens conducted between 1999 and 2023 were included. Body-weight-(BW)-based PE and 95% PIs were obtained by allometric scaling including only cats considered normal. The effects of signalment variables on BW-normalized cardiac dimensions were examined using group-wise comparisons and uni- and multivariable analyses.

RESULTS

The PE and PI changed marginally from those previously reported. The BW-normalized measurements showed greater variation for LV systolic than diastolic measurements (p < 0.001), and LA showed greater variation than Ao measurements. All signalment variables had small but significant effects on BW-normalized variables (p < 0.001), where the effect of breed was most prominent. None of the breeds had a variable median measurement > 10% above or below the PE, or > 10% of cats outside the PI. Signalment main effects persisted after adjusting for examiner and year of examination.

CONCLUSIONS AND CLINICAL RELEVANCE

Breed, age, sex, and neutering status had small and mostly clinically irrelevant effects on BW-normalized Ao, LA, and LV linear dimensions. The PE and PI intervals are valid in adult pure-bred cats across many breeds, different ages, sexes, and neutering status.