Using Vertebral Heart Score to Detect Cardiac Enlargement in Dogs

In the Literature

Puccinelli C, Citi S, Vezzosi T, Garibaldi S, Tognetti R. A radiographic study of breed-specific vertebral heart score and vertebral left atrial size in Chihuahuas. Vet Radiol Ultrasound. 2021;62(1):20-26.

The Research …

Identifying cardiac enlargement on thoracic radiographs can be challenging. Phase of respiration, body condition, and chest shape can give the false impression of an enlarged heart. Vertebral heart score (VHS) was previously proposed as a way to detect cardiac enlargement independent of conformation.¹ Using this method can help measure the long and short axes of the heart and compare them with the number of vertebrae the measurements span. A canine reference value of 9.7 (± 0.5) was established, and studies have shown it is reasonably sensitive for true cardiomegaly (ie, few false-negative results) when enlargement is substantial²; however, further studies have found that some breeds can exceed this normal limit.^3,4

This study examined a small cohort (n = 30) of healthy adult Chihuahuas. VHS of these dogs was significantly greater than the reference canine VHS value originally noted, but almost all dogs had VHS <10 (± 0.6). These higher values were only noted in right (not left) lateral recumbency, suggesting they may not reflect a true difference. From a clinical perspective, clinicians could safely identify a lack of cardiac enlargement in Chihuahuas using the historical reference limit of 9.7 (± 0.5).

VHS can be used when cardiac disease resulting in ventricular volume overload is suspected. Measurement from left and right lateral views should not differ enough to warrant separate reference limits.⁵ Many digital radiography systems provide software to measure VHS, and artificial intelligence is being developed to automate the process. VHS, however, can be subject to error and requires proper imaging (eg, lack of obliquity) and correct placement of the calipers to identify the 2 cardiac lines. Ultimately, VHS should not be used alone to identify cardiac enlargement; integration using measurements with subjective assessment, clinical presentation, and patient signalment should be used.

According to recent recommendations, treatment with pimobendan in dogs with mitral valve disease should be considered when VHS is >10.5,⁶ although this may not be the best approach because of the breed effect on VHS observed by other researchers. A study examining the use of pimobendan in dogs with preclinical mitral valve disease suggested VHS should be >11.7 before pimobendan is considered.⁷ If a correctly measured VHS is >11.7, the probability of at least moderate cardiomegaly is high.

… The Takeaways

Key pearls to put into practice:

• VHS can help identify cardiac enlargement, but not cardiac disease.

• VHS should not be used as the sole method of determining cardiac enlargement.

• VHS reference limits of some breeds differ from the historic reference limit.