Cat VHS: Normal Values & How to Measure

Vertebral Heart Score (VHS) is a quick, reproducible radiographic measure of feline cardiac silhouette size. First described for cats by Litster and Buchanan in 2000, it remains a standard screening tool — especially when echocardiography is unavailable or contraindicated by patient stress. This guide covers the evidence-based normal values, correct measurement technique, and the clinical limits every practitioner should understand.

Normal VHS Values in Cats

The foundational reference remains the Litster & Buchanan study (JAVMA 2000), which evaluated 100 clinically normal cats:

The Cardiac Education Group (CEG) Practice Pointer on VHS and VLAS (September 2024) uses a working reference of VHS = 7.7 for a normal cat heart. There has been no consensus revision of the Litster range in the 25 years since publication.

Breed Variation

Persians and other brachycephalic breeds trend higher due to thoracic conformation — a normal Persian may exceed the 8.1 ceiling without cardiac disease. Always interpret breed-adjusted when available.

Clinical Cutoffs

Subsequent research has defined working thresholds for disease probability:

• VHS < 8.0 — normal cardiac silhouette
• VHS 8.0 – 9.3 — gray zone; echocardiography indicated
• VHS > 9.3 — high probability of cardiac disease (Hall et al. 2015)
• VHS > 8.0 — associated with 2.2× increased risk of hypertrophic cardiomyopathy (Schober et al. 2014)
• L-VHS ≥ 7.9 with moderate-to-severe left atrial enlargement was a strong discriminator between healthy and cardiac-disease cats (Guglielmini et al., 2014)

How to Measure Cat VHS (Step-by-Step)

Measurement technique mirrors the canine method. Use the following procedure on a right or left lateral thoracic radiograph (Ghadiri et al. 2008 found no significant difference between R vs L recumbency in cats):

1. Long axis (L): Draw a line from the ventral aspect of the carina to the most distal cardiac apex. This typically runs through the center of the left atrium.
2. Short axis (S): Draw a perpendicular line at the widest heart dimension, usually at the level of the caudal vena cava.
3. Transpose to the spine: Beginning at the cranial edge of T4, count each axis in units of vertebral bodies (to the nearest 0.1 v).
4. Sum: VHS = L + S.

Imaging Requirements

• Respiratory phase: Inspiratory films are preferred — expiration artificially enlarges the silhouette.
• Positioning: True lateral with superimposed ribs; rotation distorts the measurement.
• Body condition: Obese cats with pericardial fat pads can appear to have larger silhouettes. Note BCS in the report.
• Age: Published reference ranges are for adult cats. Kittens and very senior cats may differ.

Why VHS Misses Preclinical HCM

Hypertrophic cardiomyopathy is the most common cardiac disease in cats, affecting an estimated 1 in 7 of the general cat population (Payne et al. 2015). But early HCM is a disease of concentric left ventricular hypertrophy — the wall thickens inward, into the ventricular lumen, without enlarging the external silhouette.

This is why VHS — a silhouette measurement — is insensitive for preclinical HCM. The silhouette only enlarges once:

• Left atrial dilation develops (secondary to diastolic dysfunction), or
• The cat progresses to congestive heart failure with pulmonary edema or pleural effusion

The ACVIM Consensus Statement on Feline Cardiomyopathies (Luis Fuentes et al., JVIM 2020) is explicit: echocardiography is the diagnostic gold standard, and radiographs are used to assess heart failure — not to screen for preclinical disease. The CEG Recommendations for Preclinical Feline HCM (2024) reinforce this: radiographs should not be relied upon for early screening.

When Is VHS Still Useful in Cats?

Despite its insensitivity for preclinical HCM, VHS remains a valuable part of feline cardiac workup in several scenarios:

• Triage of the dyspneic cat — rapid assessment of silhouette size before echocardiography
• Screening when echo is unavailable — first-line tool in general practice
• Monitoring known cardiac patients — serial VHS tracks progression or response to therapy
• Heart failure assessment — detecting pulmonary edema, pleural effusion, LA enlargement signs
• Documenting cardiomegaly for referral to a cardiologist
• Stress-sensitive cats — radiographs require less restraint than echocardiography in some patients

A Note on VLAS in Cats

Vertebral Left Atrial Size (VLAS) is a validated canine measurement with a cutoff of 2.3v for left atrial enlargement. VLAS has not been validated in cats. The CEG September 2024 Practice Pointer states explicitly that canine VLAS cutoffs should not be applied to feline patients. Suggestive findings on a cat radiograph (e.g., VLAS > 2.3) may raise suspicion but cannot be used as a diagnostic threshold.

Common Pitfalls

• Obesity and pericardial fat — the most common cause of falsely elevated feline VHS
• Expiratory radiograph — enlarges the silhouette by 0.5–1.0 v
• Oblique positioning — adds perceived width
• Missing the valentine shape — a dilated LA in cats produces a characteristic valentine-shaped silhouette on DV; always evaluate both projections
• Over-relying on VHS in HCM workup — normal VHS does not rule out HCM; if clinical suspicion exists, refer for echocardiography

Summary

• Normal feline VHS: 6.7 – 8.1 vertebrae (mean 7.5). CEG uses 7.7 as a practical reference.
• Technique: Long axis (carina to apex) + short axis (widest perpendicular), summed against the spine starting at cranial T4.
• Clinical cutoffs: < 8.0 normal; 8.0–9.3 gray zone (echo recommended); > 9.3 high probability of disease.
• Limitation: VHS is insensitive for preclinical HCM. Use echocardiography when HCM is suspected.
• Breed adjustment: Persians and Maine Coons run higher than DSH baseline.
• VLAS is not validated in cats — do not apply canine cutoffs.

For AI-assisted VHS measurement on feline radiographs, RadAnalyzer's cardiac analysis tool applies species-specific landmarks and returns a VHS value with reference-range interpretation in seconds.

References

1. Litster AL, Buchanan JW. Vertebral scale system to measure heart size in radiographs of cats. JAVMA. 2000;216(2):210-214.
2. Cardiac Education Group. Practice Pointer: Evaluating Radiographic Heart Size using VHS and VLAS. September 2024.
3. Luis Fuentes V, Abbott J, Chetboul V, et al. ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. J Vet Intern Med. 2020;34(3):1062-1077.
4. Guglielmini C, Diana A, Santarelli G, et al. Accuracy of radiographic vertebral heart score and sphericity index in the diagnosis of cardiomegaly in cats. J Feline Med Surg. 2014;16(10):816-825.
5. Schober KE, Wetli E, Drost WT. Radiographic and echocardiographic assessment of left atrial size in 100 cats with acute left-sided congestive heart failure. Vet Radiol Ultrasound. 2014;55(4):359-367.
6. Sak D, Karadağ-Sari E. A radiographic study on the vertebral heart score in Persian cats. Anat Histol Embryol. 2021;50(4):683-689.
7. Ghadiri A, Avizeh R, Rasekh A, Yadegari A. Radiographic measurement of vertebral heart size in healthy stray cats. J Feline Med Surg. 2008;10(1):61-65.
8. Cardiac Education Group. Recommendations for the Diagnosis of Preclinical Feline Hypertrophic Cardiomyopathy. 2024 update.