Vertebral heart size and vertebral left atrial size reference intervals in 8 canine breeds.

Use breed-specific VHS and VLAS reference intervals to accurately diagnose radiographic cardiomegaly in these eight breeds.

This study established breed-specific reference intervals for vertebral heart size (VHS) and vertebral left atrial size (VLAS) in eight canine breeds: Australian Cattle Dogs, Shih Tzus, Maltese, Dachshunds, Greyhounds, French Bulldogs, Norwich Terriers, and Brittany Spaniels. Dogs were included if they had two- or three-view thoracic radiographs and were free of cardiopulmonary or systemic disease. All measurements were performed by a single board-certified cardiologist to ensure consistency. Notable findings include an elevated VHS reference interval for French Bulldogs (9.9v–13.0v), which is considerably higher than the other breeds studied and the commonly cited general canine reference range of approximately 8.5v–10.5v. Greyhounds, Norwich Terriers, and Brittany Spaniels also demonstrated higher VHS upper limits compared to several other breeds. VLAS reference intervals were relatively consistent across breeds, ranging from approximately 1.6v–2.6v. These breed-specific reference intervals are clinically important because applying a universal VHS or VLAS threshold to morphologically diverse breeds risks both overdiagnosis and underdiagnosis of cardiomegaly and left atrial enlargement. Clinicians interpreting thoracic radiographs in these breeds should apply the appropriate breed-specific values rather than relying solely on general canine reference ranges, particularly when assessing patients for early or subclinical cardiac disease such as myxomatous mitral valve disease, where accurate left atrial sizing is essential for staging and treatment decisions.

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