Radiographic quantification of left atrial size in dogs with myxomatous mitral valve disease

FIGURE 1. Measurements of M‐VLAS, VLAS, VHS, and RLAD demonstrated on the same right lateral inspiratory radiograph of a dog with stage B2 MMVD. All methods take their respective measurements from the cranial edge of the T4 vertebral body extending caudally, parallel to the vertebral column, rounded to the nearest 0.1 vertebrae. A. MVLAS—an initial line (yellow)—is drawn from the centre of the most ventral aspect of the carina to the intersection between the most caudal aspect of the left atrium and the dorsal border of the caudal vena cava. A second additional line (red) is then drawn from the most distal border of the left atrium towards the first line, intersecting it perpendicularly. Two separate straight lines corresponding to the lengths of the first 2 lines (yellow + red) were then drawn from the cranial edge of the T4 vertebral body extending in a caudal direction, ventral and parallel to the vertebral canal. The M‐VLAS for this dog is 2.2 + 1.4 = 3.6 vertebrae (v). (Note: the first value being the VLAS.) B. Vertebral left atrial size (VLAS = 2.2v)—yellow line C. Vertebral heart score (VHS = 5.7 + 4.6 = 10.3v), vertical axis—thick white line; horizontal axis—thin white line. D.…

FIGURE 2. Receiver operating characteristic (ROC) curves of M‐VLAS, VLAS, VHS, and RLAD measured in 29 dogs with LA/Ao < 1.6, and 41 dogs with LA/Ao ≥1.6. Significant difference in AUC was observed between M‐VLAS (AUC 0.97, 95% CI 0.90‐1.00) and VHS (AUC 0.90, 95% CI 0.80‐0.96) (P = .03). Blue solid—M‐VLAS, green dashed—VLAS, orange dotted—VHS, and black dot‐dashed—RLAD