More on VHS and VLAS measurement in specific breeds....

Breed-Specific Vertebral Heart Size and Vertebral Left Atrial Size Reference Intervals in Yorkshire Terriers, Pomeranians, Pugs, and Boston Terriers

Lisa A. Murphy, Cesar Munoz, Charlotte I. Zepeda, Nicole Piscitelli, Jessica Gentile-Solomon, Donald Szlosek, Reid K. Nakamura

Background
Vertebral heart size (VHS) is a widely used method for assessing cardiac size in dogs, but breed-specific reference intervals are necessary due to anatomical variations among breeds. Previously published VHS reference values for some breeds were based on small sample sizes, limiting their reliability. This study aimed to establish updated breed-specific VHS and vertebral left atrial size (VLAS) reference intervals for Yorkshire Terriers (YTs), Pomeranians (POMs), Pugs, and Boston Terriers (BTs) using a large dataset.

Methods
This observational study retrospectively analyzed radiographs submitted to IDEXX Telemedicine Consultants from January to March 2023. Dogs were included if they had 2- or 3-view thoracic radiographs with no evidence of cardiopulmonary or systemic disease. A single board-certified cardiologist measured VHS and VLAS on right lateral radiographs using standardized techniques. Statistical analyses followed Clinical and Laboratory Standards Institute guidelines.

Results
A total of 483 YTs, 380 POMs, 391 Pugs, and 196 BTs met the inclusion criteria. The VHS reference intervals (vertebrae) were:
-YTs: 9.0–11.4
-POMs: 9.5–12.0
-Pugs: 9.7–12.0
-BTs: 9.7–13.0

The VLAS reference intervals (vertebrae) were:
-YTs: 1.7–2.4
-POMs: 1.7–2.6
-Pugs: 1.7–2.7
-BTs: 1.6–2.7

Pugs and BTs had a high frequency of VHS measurements at 12 vertebrae, which may reflect anatomical variations or undetected cardiac pathology.

Limitations
The study was retrospective and relied on telemedicine-submitted radiographs, potentially introducing variability in imaging techniques. Dogs were excluded based on the absence of reported heart murmurs or systemic disease, but occult cardiac conditions could not be ruled out without echocardiography. VHS and VLAS values were measured only on right lateral radiographs, limiting direct comparisons with other views.

Conclusions
This study provides updated breed-specific VHS and VLAS reference intervals for YTs, POMs, Pugs, and BTs. The findings highlight the importance of using breed-specific values to avoid misdiagnosing cardiomegaly. Further research is warranted to refine reference intervals for other breeds and evaluate VHS in different radiographic projections.

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