Heart disease is a very common presentation when a patient visits a vet clinic. If cardiac problems are suspected, the diagnostic pathway may include a history and physical exam, blood tests, and diagnostic imaging – typically, radiography and/or ultrasound.
Understanding how to utilize the vertebral heart score as part of radiographic interpretation is a vital tool in veterinary practice.
The vertebral heart score: what is it for?
The vertebral heart scale/score (VHS) system was designed as a way to objectively measure the cardiac size from X-rays. Developed by Drs. James W. Buchanan and Jorg Bücheler at the University of Pennsylvania found a good correlation between heart size and vertebral column length, It allows for the evaluation of heart size despite variations in breed, size, and conformation of canine patients.
The vertebral heart score has been shown to correlate well with other methods of assessing cardiac size, such as echocardiography.
Why do we use the vertebral heat score?
While a full cardiac work-up may include an echocardiogram and an electrocardiogram, thoracic radiography is an important tool in the veterinary clinic and can be a cost-effective option for the diagnostic process, particularly for assessing cardiomegaly.
The guidelines for managing cardiac disease have progressed rapidly over the last few years. Accurate methods for staging and monitoring the progress of the disease are more important than ever, to allow for timely interventions at the appropriate stage of the disease.
The use of radiographs and the VHS have three main indications:
As part of a diagnostic pathway, alongside a clinical history, physical examination, and any other diagnostic tests
Monitoring of patients with suspected cardiac disease
Monitoring the progression of heart disease
Radiography and VHS measurements have also been proven useful in differentiating whether a cough is cardiogenic or pulmonary – or mixed.
Mitral Valve Disease (MVD)
MVD is a hugely common cardiac disease in dogs and is often diagnosed presumptively after basic diagnostics such as a physical examination and thoracic x-rays, particularly in high-risk smaller breed dogs.
The ACVIM consensus statement recommends that dogs with a new murmur should have thoracic radiographs taken as a baseline, and then annually.
In Cavalier King Charles Spaniels, serial VHS measurements have been shown to be predictive of the onset of congestive heart failure, with the rate of change in VHS measurements rapidly increasing in the 6-12 months prior to onset.
Cats
The VHS can also be used in cats. It has shown promise in the diagnosis of congestive heart failure in dyspneic cats, which can be difficult due to the propensity to pleural edema. However, cats in CHF often have a degree of pleural effusion which can obscure the cardiac apex and thus make measuring the VHS difficult.
Measuring the Vertebral Heart Score in Dogs
So how do we measure the VHS? Here’s a quick guide:
Take a lateral thoracic radiograph, with clear delineation of thoracic vertebrae T4-T12
Measure the long axis of the cardiac silhouette, from the ventral margin of the carina of the mainstem bronchus to the apex (L)
Measure the short axis, perpendicular to the long axis, at the widest part of the cardiac silhouette (S)
Transfer these measurements to the thoracic vertebrae, starting at the cranial edge of T4, and count how many vertebrae fit within the measurement for each one
Add the two measurements (vertebrae contained within L + vertebrae contained within S) to give you the total VHS
There is a handy guide here.
Interpretation of the VHS
The published range for a normal dog is 9.2-10.3 on a lateral radiograph. Any score above 10.5 should be considered to indicate cardiomegaly. The normal range for cats is 6.7 to 8.1.5
Further considerations
There are some points to consider in the clinical setting when interpreting a VHS.
Breed
The VHS was designed to produce a standard measurement across any breed, size, or conformation of a dog, and this appears correct for the majority of dogs. However, more recent research has found some variation in certain breeds.
These include the Boxer, Bulldog (English and French), Pug, Cavalier King Charles Spaniel, Boston Terrier, Whippet, Labrador Retriever, and Pomeranian, which are now known to have average VHS scores above the standard range.6-7
In some of these breeds, such as the Bulldog, changes to the size and shape of the vertebrae may be a cause of these increased values. Care should be taken in interpreting VHS in any dogs with abnormal thoracic vertebrae.
Observer variability
Studies show that there is some variation between individual assessments of the VHS. If using the VHS as a monitoring tool for ongoing disease, the same clinician should interpret successive radiographs.
Pericardial effusion
The presence of a pericardial effusion will increase the VHS and should be a consideration for any dog with cardiomegaly seen on an x-ray.
Normal values
Heart size within the normal range on X-rays does not rule out cardiac disease, and the VHS should be used as part of a wider diagnostic process.
Summing up
The VHS was designed as an objective measure of cardiac size on X-rays. It is an important tool in veterinary medicine, providing a useful tool in both the diagnosis and monitoring of cardiac disease.
References
Buchanan JW. A vertebral scale system to measure heart size in radiographs. Vet Clin North Am Small Anim Pract. 2000 Mar;30(2):379-93
Guglielmini C, Diana A, Pietra M, Di Tommaso M, Cipone M. Use of the vertebral heart score in coughing dogs with chronic degenerative mitral valve disease. J Vet Med Sci. 2009;71(1):9-13
Atkins C, Bonagura J, Ettinger S, et al. Guidelines for the diagnosis and treatment of canine chronic valvular heart disease. JVIM. 2009;23(6):1142-1150
Lord PF, Hansson K, Carnabuci C, Kvart C, Häggström J. Radiographic heart size and its rate of increase as tests for the onset of congestive heart failure in Cavalier King Charles spaniels with mitral valve regurgitation. JVIM. 2011;25(6):1312-1319
Sleeper MM, Roland R, Drobatz KJ. Use of the vertebral heart scale for differentiation of cardiac and noncardiac causes of respiratory distress in cats: 67 cases (2002-2003). JAVMA. 2013;242(3):366-371
Jepsen-Grant K, Pollard RE, Johnson LR. Vertebral heart scores in eight dog breeds. Vet Radiol Ultrasound. 2013;54(1):3-8
Lamb CR, Wikeley H, Boswood A, Pfeiffer DU. Use of breed-specific ranges for the vertebral heart scale as an aid to the radiographic diagnosis of cardiac disease in dogs. Vet Rec. 2001;148(23):707-711.
