Measurement of Heart Size in the Rabbit (Oryctolagus cuniculus) by Vertebral Scale System

Aim: Cardiac and pericardial diseases are frequently associated with a change in the size of the heart. Therefore, the radiographic evaluation of the heart size is invaluable in the determination of the extent and severity of the cardiac or pericardial disorder. This research was aimed at establishing reference values of vertebral heart size (VHS) of normal New Zealand White (NZW) rabbit.

Materials and Methods: Heart sizes of ten (5 females, 5 males) clinically normal NZW rabbits were studied. A right lateral thoracic radiograph was obtained from each research animal. In each of the radiographs, the cardiac long axis (LA) was measured in centimeters, transposed onto the thoracic vertebrae from T4, and the result read in vertebral lengths. The cardiac short axis (SA) was similarly converted to lengths of thoracic vertebrae. The VHS was then obtained from the addition of the LA and SA thoracic vertebral lengths.

Results: Mean plus or minus standard error of mean (M±SEM) VHS was 8.5±0.3 vertebrae, and the difference between male and female VHSs was insignificant.

Conclusion: Clinically, VHS is objective and easily applicable in radiographic determination of heart size.