How body weight affects heart size X-ray readings in dogs

Abstract

The vertebral heart scale (VHS) is widely known and used as an objective standard for the evaluation of cardiomegaly on thoracic radiographs. It, therefore, plays an important role in assessing the severity of canine heart disease. The body condition score (BCS) is a nine-scale body condition scoring system used to objectively document the body condition in dogs. Obese animals have widened precardiac and postcardiac mediastinum, fat deposits between the sternum and lungs or heart, as well as increased pericardial fat. These conditions could complicate cardiac silhouette evaluation and could, therefore, result in higher interobserver variability in the assessment of VHS. The purpose of this study was to investigate whether overweight dogs (BCS 6/9, 7/9, 8/9, and 9/9) have more variability in the interobserver VHS measurement compared with dogs with a normal BCS (BCS 4/9 and 5/9). The dogs were admitted to a private referral center for different medical reasons. The VHS was measured by three trained observers in right lateral radiographs of 18 overweight dogs and 33 dogs with a normal BCS. Bland-Altmann plots were constructed, and limits of agreement were calculated to show the variability of VHS measurements. No statistically significant differences in VHS variability were found between BCS categories, observers, sex, or age categories. In conclusion, BCS does not affect the reliability of VHS assessment among trained veterinarians.