Reference intervals and allometric scaling of echocardiographic measurements in small size growing dogs

In growing dogs, echocardiographic studies are scarce and carried out in large and medium breeds. In echocardiography, the most frequently used allometric reference ranges included adult dogs. Therefore, puppy reference values are required to identify normal and abnormal echocardiographic measurements. The aims of this study were 1) to analyse morphological and functional echocardiographic changes in small size dogs during the first 1.5 years of life; 2) to determine the effect of body weight (BW) and breed on these echocardiographic variables; 3) to compare echocardiographic reference intervals (RI) with allometric-scaled RI; 4) to estimate the proportionality constant (a) and the scaling exponent (b) in a specific allometric equation for these pure and cross-bred dogs. Thirteen, 2 months of age, 1.3-2.55kg, client-owned, healthy puppies were included. The animals were evaluated every two months during the first year of life and then at the age of 18 months. At each time point, a physical examination, BW recording and echocardiographic evaluations were performed. BW had an effect on all echocardiographic morphological variables, while SV was the only functional variable modified. Conversely, no breed effect was shown in any echocardiographic variable. It was demonstrated that the previously reported constants were not accurate to predict echocardiographic variables in these small size growing dogs. Specific allometric equations for small size puppies were provided.