VERTEBRAL SCALE SYSTEM TO MEASURE CANINE HEART SIZE IN RADIOGRAPHS

A method for measuring canine heart size in radiographs was developed on the basis that there is a good correlation between heart size and b ody length regardless of the conformation of the thorax. The lengths o f the long and short axes of the heart of 100 clinically normal dogs w ere determined with calipers, and the dimensions were scaled against t he length of vertebrae dorsal to the heart beginning with T4. The sum of the long and shout axes of the heart expressed as vertebral heart s ize war 9.7 +/- 0.5 vertebrae. The differences between dogs with a wid e or deep thorax, males and females, and right or left lateral recumbe ncy were not significant. The caudal vena cava was 0.75 vertebrae +/- 0.13 in comparison to the length of the vertebra over the tracheal bif urcation.