Breed‐specific vertebral heart score, vertebral left atrial size, and radiographic left atrial dimension in Cavalier King Charles Spaniels: Reference interval study

Cavalier King Charles Spaniels (CKCS) are predisposed to developing myxomatous mitral valve disease (MMVD), with radiographs frequently used to screen for evidence of left‐sided cardiomegaly secondary to MMVD. Vertebral heart size (VHS), vertebral left atrial size (VLAS), modified VLAS (M‐VLAS), and radiographic left atrial dimension (RLAD) are reported as objective measurements of global heart size and left atrial size. Normal VHS in CKCS (10.6 ± 0.5) is reportedly higher than the non‐breed‐specific value (9.7±0.5). Breed‐specific VLAS, M‐VLAS, and RLAD cut‐offs have not been reported in CKCS. The aim of this prospective reference interval study was to describe the VHS, VLAS, M‐VLAS, and RLAD values for 30 clinically healthy adult CKCS. Inclusion criteria were unremarkable physical examination, normal echocardiography, and thoracic radiographs without malposition/abnormalities. There were 22 female and eight male dogs. Ages ranged from 1 to 6 years. The VHS mean value in our sample was 10.08 ± 0.56 (95% range, 9.87‐10.29). This was significantly greater than a previously published general canine reference value of 9.7 ± 0.5 and significantly less than a previously published CKCS breed‐specific value of 10.6 ± 0.5 (P < 0.01). Mean VLAS, M‐VLAS, and the RLAD values in our study were 1.79 ± 0.3 (95% range, 1.68‐1.9), 2.23 ± 0.44 (95% range, 2.06‐2.39), and 1.2 ± 0.34 (95% range, 1.07‐1.33), respectively. These were significantly less than previously published reference interval values (P < 0.001). The VHS, M‐VLAS, and the RLAD were not affected by sex, body weight, or BCS; whereas the VLAS was moderately affected by body weight. Findings from this study can be used as background for future thoracic radiographic assessments in CKCS.