Canine mitral valve size as measured by computed tomography.

Objective: To measure the mitral annulus in dogs. Our hypothesis was that mitral measurement would be possible and consistent among observers using CT.

Sample: Thoracic CT scans of dogs without known heart disease.

Procedures: Five trained investigators measured 4 aspects of the mitral valve and the fourth thoracic vertebrae (T4) length using multiplanar reformatting tools. Ten randomly chosen animals were measured by all investigators to determine interobserver reliability.

Results: There were 233 CT scans eligible for inclusion. Dogs weighed 2 to 96 kg (mean, 28.1 kg), with a variety of breeds represented. Golden Retrievers (n = 28) and Labrador Retrievers (n = 37) were overrepresented. The intraclass correlations were all greater than 0.9, showing excellent agreement between observers. The means and SDs of each measurement were as follows: trigone-to-trigone distance, 17.2 ± 4.7 mm; the remaining circumference, 79.0 ± 17.5 mm; commissure-to-commissure distance, 30.8 ± 6.5 mm; septal leaflet-to-lateral leaflet distance, 26.3 ± 6.0 mm; T4 length, 16.9 ± 3.1 mm; and the total circumference normalized by T4, 5.7 ± 0.7 mm.

Clinical Relevance: This study provides information that may help in the development of future treatment for mitral valve dysfunction and subsequent annular enlargement.