Abstract

Background and Aim: Computed tomographic (CT) images can elucidate the variations of cardiac orientation that this information among dog breeds has never been reported. This study aimed to explore the heart orientations of dogs with different thoracic types and study their effects on vertebral heart score (VHS) measurements using CT images. 

Materials and Methods: Thoracic CT images of 115 mature dogs without thoracic abnormalities were retrospectively examined. The dogs were classified into four groups: Normal Broad, Abnormal Broad, Normal, and Deep. All dogs were also classified based on their heart deviations. The VHSs were evaluated using lateral VHS, dorsal VHS, and adjusted VHS, and all were compared. 

Results: In the normal broad and abnormal broad groups, the lateral VHS and lateral long-axis dimensions were significantly lower than those obtained from the dorsal and adjusted VHSs. In addition, heart deviations were mostly observed in the normal broad and abnormal broad groups. Nevertheless, little evidence was found in the normal and deep groups. The lateral VHS and lateral long-axis dimensions were significantly reduced by heart deviation more than the dorsal and adjusted VHSs. 

Conclusion: Cardiac orientations among dog breeds can affect VHSs of lateral projection, especially in the broad thoracic group. Clinical evaluation of the VHS in the broad thoracic dogs should be performed on the dorsal view for more accurate measurement of heart size. 

Keywords: cardiac dimension, computed tomography, dog, heart orientation, thoracic cage.