Interobserver Variability of Vertebral Heart Size Measurements in Dogs With Normal and Enlarged Hearts

Abstract

The vertebral heart size (VHS) method by Buchanan is based on anatomic landmarks. A potential source of variation among observers is differences in the selection of measurement points. The objective was to test variability between observers with different levels of training in thoracic radiology and small animal clinical practice. Fifty sets of thoracic radiographs of cavalier King Charles spaniels, were divided into five groups; (Normal) normal cardiopulmonary structures, (I) slight cardiomegaly, (II) moderate cardiomegaly, (II +) moderate cardiomegaly with congestive heart failure, and (III +) severe cardiomegaly with congestive heart failure. Cardiomegaly was confirmed by echocardiography to be caused by mitral regurgitation because of myxomatous mitral valve disease. Sixteen observers representing four levels of experience (four observers/level) evaluated the radiographs; (1) European Diplomates in Veterinary Diagnostic Imaging, (2) Experienced small animal clinicians, (3) Trainees in small animal clinical practice (4) Veterinary students. Almost identical mean VHS values were found among the four experience levels for each of the five groups of radiographs with a low coefficient of variation, range 1.5-3.2%. Mean difference among the 16 observers was 1.05 +/- 0.32 vertebrae (v). Mean difference among individuals in each observer group was approximately 0.5 v for all but the groups of trainees were the difference was 0.6-0.9 v. The conclusion is that VHS method for heart size is independent of observer experience but dependent of individual observers selection of reference points and transformation of long and short axis dimensions into VHS units.

Avaliação radiográfica da silhueta cardíaca, pelo método VHS (Vertebral Heart Size), de quatis (Nasua nasua, Linnaeus 1766) jovens e adultos mantidos em cativeiro

“…(HANSSON et al, 2005) e que os resultados obtidos com número pequeno de animais desse estudo, provavelmente não refletem com precisão os valores de VHS da espécie, contudo são bastante úteis como índices iniciais de referência.…”

Establishment of Vertebral Heart Scale in the Growth Period of the Japanese Macaque (Macaca fuscata)

“…VHS is used as an indicator of heart enlargement in canine and feline veterinary clinical fields. VHS is known to increase in cardiac disease [3,4]. Mean VHS is 9.7  0.5v in the normal dog and 7.5  0.3v in the normal cat [5,9].…”

“…VHS has proven useful as an easily measured and relatively objective value [3]. In dogs, studies of VHS in puppies, adult dogs and different breeds have been performed [2][3][4][5]9].…”

“…Various methods have been used to measure heart size, including planimetry and various cardio-thoracic ratios [3]. VHS has proven useful as an easily measured and relatively objective value [3].…”

“…This method was derived from the correlation between heart weight and body length in cats [5]. Values used in this method are relatively objective, with little room for interpretation by the operator [3]. The method is based on the relationship between vertebral length and heart size [9].…”