Vertebral Heart Scale Measurements Methods (Human Operator)

The VHS was independently calculated by two experienced operators: a board-certified cardiologist (ACVIM-Cardiology) and a board-certified radiologist [American College of Veterinary Radiology (ACVR)]. Measurements were performed using Picoxia proprietary software for simplicity of measurements and to avoid calculation errors. In the corresponding interface, keypoints were automatically pre-positioned. However, to limit the influence of AI-suggested dimensions on human measurements [unconscious bias to attain a similar (or dissimilar) result], each operator had to manually center the measurements cursors before beginning his/her own measurements.

Two measurements methods were applied sequentially on each canine radiograph to evaluate the influence of chosen landmarks on the VHS. The operator had to first use the original approach published by Buchanan (8); the long axis was positioned from the carina to the most distant ventral contour of the cardiac apex and the short axis perpendicular to the long axis, for maximal width (Figure 1A). Then the operator applied the slightly modified approach proposed in the EPIC trial; for the positioning of the short axis, the given consigns were perpendicular to long axis, at the ventral border of the CVC, as illustrated in Figure 1B (9).

Lateral projection of skeletally mature canine patient demonstrating the cardiac landmarks for vertebral heart scale (VHS) measurements as described by Buchanan (A) and Poad (B).

In case of an enlarged left atrium, the convention proposed by Buchanan was applied: the long axis was measured from the elevated left bronchus and short axis at the widest level of the heart (8).

For feline radiographs, the method proposed by Buchanan was applied (22): the long axis was measured from the intersection of the ventral edge of the trachea and the most ventral apical pulmonary vein to the ventral contour of the cardiac apex, and the short axis was measured perpendicular to the long axis, at the ventral border of the CVC (Figure 2).

Lateral projection of skeletally mature feline patient demonstrating the cardiac landmarks for vertebral heart scale (VHS) measurements as described by Buchanan.