Thoracic Vertebral Length-to-Height Ratio, a Promising Parameter to Predict the Vertebral Heart Score in Normal Welsh Corgi Pembroke Dogs

SIMPLE SUMMARY: The vertebral heart score (VHS) is the most frequent technique for evaluating the canine cardiac size on thoracic radiographs. However, VHS values are varied among dog breeds, possibly due to the characteristics of the thoracic vertebrae. The characteristics of the thoracic vertebrae and the range of the VHS value of the healthy Welsh Corgi Pembroke (Corgis) have never been reported. Therefore, the current study aimed to explore the characteristics of the thoracic vertebrae of the Corgi in comparison with other small-to-medium breed dogs. Among the dog breeds, the characteristics observed through the ratio between the vertebral length and height were different, and the rank of these ratios among the breeds was correlated to the rank of the previously published VHS values. Comparing among the dog breeds, the characteristics of the Corgi’s thoracic vertebrae were more elongated in shape, and the Corgi-specific VHS was significantly lower than the original reported value. Therefore, the characteristics of the thoracic vertebrae might be one of the main factors affecting the normal VHS values among different dog breeds. ABSTRACT: The vertebral heart score (VHS) is the sum of the ratio of the cardiac dimensions to the number of thoracic vertebrae, starting from the fourth thoracic vertebra (T4) to the intervertebral disk space (IVS). Breed-specific VHSs, in most cases, were different from the original reference value. Characteristics of the thoracic vertebrae and IVS may influence this variation. This study was conducted to investigate the characteristics of the T4 and IVS on the thoracic radiographs of Corgis in comparison with other small-to-medium breed dogs to evaluate the Corgi-specific VHSs in healthy dogs. The ratio of the T4’s length/height (T4L/H) was significantly different among dog breeds but not the IVS between the T4 and T5. The T4L/H was highest in the Shih Tzu and lowest in Beagle dogs. The Corgi-specific VHS obtained from the ventrodorsal radiograph was significantly higher than that from the dorsoventral radiograph, but a significant difference was not observed between the right and left lateral radiographs. In contrast, the Corgi-specific VHS derived from the right lateral thoracic radiograph was significantly lower than the reference value. This may be correlated with the characteristics of the thoracic vertebrae of Corgis, which were slightly higher than those of the other breeds.