Thoracic Radiographic Evaluation of Canine Dilated Cardiomyopathy: An Anatomical Perspective

Dilated cardiomyopathy (DCM) is one of the most common acquired myocardial diseases in dogs and a major cause of congestive heart failure. Thoracic radiography remains an essential first-line imaging modality for the rapid assessment of cardiac size, pulmonary vasculature, airways and secondary changes associated with heart failure. This research aims to present a systematic anatomical approach to the radiographic evaluation of dogs with dilated cardiomyopathy. Rather than relying solely on global cardiac enlargement, each thoracic structure-including the cardiac silhouette, individual left cardiac chambers, pulmonary vessels, aorta, lung parenchyma, airways like trachea and pleural space-is assessed in a stepwise manner. For this purpose, a total of 30 dogs with DCM were evaluated in this study. The relationships between parameters related to the cardiac silhouette, size and dimension of the left atrium and data regarding vascular structures, airways, distances and the planar ratios of thoracic cavity were investigated. In particular, it was found that pulmonary veins were more dilated than arteries, and that pulmonary venous dilatation was more pronounced in cases of DCM. Significant correlations were found between Vertebral left atrial size (VLAS) and radiographic left atrial dimension (RLAD); thus, it was demonstrated that using both RLAD and VLAS together is more reliable than using Vertebral heart score (VHS) solely. Furthermore, there was a strong positive correlation between VLAS and ratio of thoracic inlet and left atrial size (TILAS). By adopting an anatomical approach, clinicians may improve the diagnostic utility of thoracic radiographs and enhance early recognition of clinically significant DCM in dogs.