Use of breed-specific ranges for the vertebral heart scale as an aid to the radiographic diagnosis of cardiac disease in dogs

The vertebral heart scale was measured on right lateral recumbent thoracic radiographs of 320 dogs of six popular breeds, including for each breed at least 20 dogs with no clinical signs of cardiovascular or respiratory disea se and at least 19 dogs with cardiac or respiratory disease. There were sig nificant differences between the mean values of the scale for the different breeds; the normal boxer dogs had a significantly higher mean value than t he normal dogs of all the other breeds, and the labrador retrievers had a s ignificantly higher mean value than all the other breeds except the boxer a nd the cavalier King Charles spaniel. For all the breeds except the boxer, there was a trend for dogs with cardiac disease (but not respiratory diseas e) to have higher mean values on the scale than normal dogs of the same bre ed; however, at the optimal value of the scale for distinguishing between d ogs of each breed with and without cardiac disease, the sensitivity and spe cificity were relatively low, in the range 58 to 83 per cent. The scale was most accurate for the diagnosis of cardiac disease in the Yorkshire terrie r and the cavalier King Charles spaniel, breeds affected by predominantly d ilative forms of cardiac disease. In contrast, it was very inaccurate in th e boxer, a breed that has a higher incidence of cardiac diseases associated with concentric hypertrophy.