1. Introduction
The Vertebral Heart Score (VHS) is one of the most widely used radiographic tools in veterinary cardiology, providing an objective method for assessing cardiac size on thoracic radiographs. While the original VHS reference range (mean ~9.7 ± 0.5 vertebrae) was developed for mixed-breed dogs, decades of research and clinical experience have shown that breed-specific anatomy significantly influences normal cardiac silhouette appearance. As a result, applying a single “one-size-fits-all” reference can lead to overdiagnosis or underdiagnosis of cardiomegaly in certain breeds.
Breed-specific VHS values exist because of differences in thoracic conformation, vertebral body length, chest depth, and skull type (e.g., brachycephalic vs. dolichocephalic). For example, brachycephalic breeds such as Bulldogs and Pugs naturally have higher VHS values due to barrel-shaped chests, whereas deep-chested breeds like German Shepherds and Doberman Pinschers often have lower or more elongated cardiac silhouettes.
Using the correct breed reference is critical for accurate clinical decision-making. Misinterpretation of VHS can result in unnecessary echocardiography, inappropriate initiation of cardiac medications, or missed early-stage heart disease. This is particularly important in breeds predisposed to specific cardiac conditions, such as myxomatous mitral valve disease (MMVD) in Cavalier King Charles Spaniels or dilated cardiomyopathy (DCM) in Doberman Pinschers.
This comprehensive chart is designed as a practical clinical reference. Clinicians should use it alongside proper radiographic technique, consistent measurement methods, and correlation with physical examination and echocardiographic findings. The tables below summarize the most commonly cited breed-specific VHS values and available Vertebral Left Atrial Size (VLAS) references to support accurate and confident interpretation.
2. Complete VHS Reference Table
| Breed | Mean VHS | SD | 95% Range | Notes |
|---|---|---|---|---|
| Mixed Breed / General | 9.7 | 0.5 | 8.7–10.7 | Standard reference |
| Cavalier King Charles Spaniel | 10.6 | 0.5 | 9.6–11.6 | Very high MMVD prevalence |
| Chihuahua | 10.0 | 0.6 | 8.9–11.0 | Apple-head conformation |
| Pug | 11.25 | 0.62 | 10.1–12.8 | Brachycephalic |
| French Bulldog | 11.2 | 0.6 | 10.0–12.4 | Brachycephalic |
| English Bulldog | 12.0 | 0.7 | 10.6–13.4 | Highest breed-specific |
| Boston Terrier | 11.0 | 0.6 | 9.8–12.2 | Brachycephalic |
| Boxer | 11.6 | 0.8 | 10.0–13.2 | High normal VHS |
| Dachshund | 9.7 | 0.5 | 8.7–10.7 | Similar to general |
| Maltese | 9.53 | 0.46 | 8.6–10.5 | Toy breed |
| Yorkshire Terrier | 9.5 | 0.5 | 8.5–10.5 | Toy breed |
| Pomeranian | 10.4 | 0.5 | 9.4–11.4 | Toy breed |
| Labrador Retriever | 10.8 | 0.6 | 9.6–12.0 | Large breed |
| German Shepherd | 9.5 | 0.5 | 8.5–10.5 | Deep-chested |
| Whippet | 10.5 | 0.4 | 9.7–11.3 | Sighthound |
| Greyhound | 10.6 | 0.5 | 9.6–11.6 | Sighthound |
| Doberman Pinscher | 9.7 | 0.5 | 8.7–10.7 | DCM concern |
| Golden Retriever | 10.1 | 0.5 | 9.1–11.1 | Large breed |
| Beagle | 9.8 | 0.5 | 8.8–10.8 | Standard |
| Border Terrier | ~10.35 | – | 9.7–13.0 | Wide range |
3. Complete VLAS Reference Table
The Vertebral Left Atrial Size (VLAS) measurement is increasingly used to assess left atrial enlargement, particularly in dogs with suspected or confirmed MMVD. Unlike VHS, breed-specific VLAS data are more limited, but several clinically useful references exist.
| Breed | Mean VLAS | SD | Upper Reference Limit | Notes |
|---|---|---|---|---|
| Mixed Breed / General | 1.9 | 0.3 | ≤ 2.3 | Standard reference |
| Cavalier King Charles Spaniel | 2.1 | 0.3 | ≤ 2.5 | Early LA enlargement common |
| Chihuahua | 2.0 | 0.3 | ≤ 2.4 | Toy breed variability |
| Pug | 2.2 | 0.4 | ≤ 2.8 | Brachycephalic |
| French Bulldog | 2.3 | 0.4 | ≤ 2.9 | Limited data |
| Dachshund | 1.9 | 0.3 | ≤ 2.3 | MMVD-prone |
| Maltese | 1.9 | 0.3 | ≤ 2.3 | MMVD-prone |
| Yorkshire Terrier | 2.0 | 0.3 | ≤ 2.4 | MMVD-prone |
| Pomeranian | 2.1 | 0.3 | ≤ 2.5 | Toy breed |
| Labrador Retriever | 1.9 | 0.3 | ≤ 2.3 | Large breed |
| Doberman Pinscher | 1.8 | 0.3 | ≤ 2.2 | DCM focus |
Note: For many breeds, VLAS interpretation should prioritize trend analysis and correlation with echocardiography rather than strict cutoffs.
4. How to Use This Reference
Finding Your Patient’s Breed
Begin by identifying whether your patient belongs to a breed with established VHS or VLAS data. If a specific reference exists, always prioritize it over the general mixed-breed range. This is especially important for brachycephalic and sighthound breeds, where normal values deviate substantially from the standard reference.
Mixed Breed Considerations
For mixed-breed dogs, assess overall thoracic conformation. A mixed dog with a deep chest and long limbs may align more closely with sighthound or shepherd-type references, while a compact, barrel-chested dog may resemble brachycephalic norms. In uncertain cases, the general VHS reference (9.7 ± 0.5) remains appropriate.
When to Use General vs. Breed-Specific Values
Use general references when:
- No reliable breed-specific data exist
- The dog is a complex mix with no dominant conformation
- Radiographic positioning is suboptimal
Use breed-specific values when:
- The breed is clearly identified
- The patient belongs to a breed with known cardiac predispositions
- VHS values fall near diagnostic decision thresholds
Interpreting Borderline Cases
Borderline VHS or VLAS values should never be interpreted in isolation. Consider:
- Clinical signs (cough, exercise intolerance, murmur grade)
- Serial radiographs for trend analysis
- Echocardiographic confirmation when progression is suspected
A single mildly elevated measurement may represent normal anatomy rather than disease.
5. Breeds Without Specific Data
Despite extensive research, many breeds still lack validated VHS or VLAS reference ranges. In these cases, careful extrapolation and conservative interpretation are essential. Select comparison breeds with similar size, chest conformation, and skull type rather than relying solely on body weight.
When no suitable comparison exists, use the general reference range and place greater emphasis on longitudinal monitoring. Establishing an individual baseline in young or healthy adult dogs can be extremely valuable, allowing future measurements to be compared against that patient’s own normal rather than a population average.
Clinicians should also be cautious not to overinterpret mild increases in VHS in the absence of clinical or echocardiographic evidence of disease. When uncertainty remains, echocardiography remains the gold standard for definitive cardiac assessment.
As research continues, breed-specific reference ranges will expand. Until then, informed clinical judgment—supported by structured references like this chart—remains the cornerstone of accurate radiographic cardiac evaluation.
Individual Breed Guides
- Cavalier King Charles Spaniel VHS & VLAS Guide - MMVD-prone breed with critical cardiac monitoring needs
- Chihuahua VHS & VLAS Reference - Toy breed cardiac measurements
- Pug VHS & VLAS Guide - Brachycephalic breed considerations
- Dachshund VHS & VLAS Assessment - Chondrodystrophic breed measurements
- Maltese VHS & VLAS Reference - Toy breed cardiac values
Related Resources
- VHS (Vertebral Heart Score) Complete Guide - Learn the fundamentals of VHS measurement
- VLAS (Vertebral Left Atrial Size) Guide - Understanding left atrial measurements
- MMVD in Dogs: Complete Guide - Understanding mitral valve disease progression and management