“It is only with the heart that one can see rightly; what is essential is invisible to the eye.”
-Antoine de Saint-Exupery
Of course, this quote doesn’t refer to radiographic interpretation of the heart… But prior to gaining confidence in cardiac x-ray interpretation, maybe it does feel like some of those cardiac changes on x-ray images are subtle, even “invisible…” Confidence and x-ray interpretation skills come with experience, but new and experienced veterinarians alike can benefit from having a systematic approach and being armed with a few simple tips. To boost confidence and accuracy when interpreting x-ray images of the heart, take at least two views, use the vertebral heart score, learn variations of “normal,” evaluate non-cardiac structures, and seek an expert second opinion. Read on to learn more…
Take At Least Two Views So Nothing Is Missed
Taking orthogonal views (views at perpendicular or 90-degree angles to one another) is a best practice for radiographs of any part of the body—and the heart is no exception. While it may be tempting to shoot a quick lateral view to evaluate heart size when you hear a murmur, it’s always helpful to have as much information as possible. That additional information comes from a second view, which may clearly show a lesion that was hard to see on the first image. A right lateral and VD (or DV, if the patient can’t lie on their back) view together are a common and practical combination. Many experts also recommend including a left lateral view of the thorax, for a total of three views.
Use the Vertebral Heart Score for a Standardized Measurement
The vertebral heart score (VHS) is a valuable (and simple to perform, even if you’re still gaining clinical experience) tool. That’s because the VHS is measured—which takes away some of the “guess work” or subjective interpretation.
As a simple overview, you can obtain the VHS with these steps…
- • Take a lateral thoracic radiograph.
- • Measure the heart on its long axis (tracheal carina to the apex of the heart) and mark this length on a piece of paper (or on the screen if your digital software allows).
- • Measure the widest/thickest part of the heart, perpendicular to the first measurement.
- • Find the 4th thoracic vertebra (T4).
- • Place the first measurement along the thoracic vertebrae starting at the cranial edge of T4, and measure how many vertebrae fall into that measurement.
- • Repeat for the second measurement.
- • Add those two numbers together.
A normal VHS is 8.5-10.7 for dogs. There is some individual and breed variation, so be sure to interpret findings as part of the whole clinical picture.
Become Familiar With Variations of “Normal,” To Build Interpretation Confidence
A normal heart can look different between individuals and breeds. That’s especially true for brachycephalic breeds, whose conformation may make their heart look larger relative to their thorax, when compared to a breed with a more “standard” conformation. So, how do you gain confidence in calling a heart “normal?” Practice by evaluating the heart on ALL radiographs where the heart is visible, even when heart problems are not suspected. That experience will add up and eventually make interpretations faster and easier
Evaluate Other Structures for Further Evidence of a Heart Problem
If changes to the cardiac silhouette are subtle, it may help to look at the whole picture—including the lungs, thorax, and beyond—for more information.
A few examples of things you may notice include:
- • Changes to pulmonary blood vessels.
- • Pulmonary edema.
- • Pulmonary infiltrates (for example, with heartworm disease).
- • Pleural effusion.
- • In the abdomen, look for ascites or an enlarged liver.
Many of these radiographic findings can have other causes unrelated to the heart, so be sure to interpret findings with the entire clinical picture.
Get an Expert Second Opinion for Peace of Mind
Whether you’re a new practitioner or an experienced veterinarian, it helps to use all the resources you have at your disposal. Specialist consults are a great way to offer your patients and clients excellent medical care and a great customer experience. Clients are used to radiologists interpreting their own x-rays when they go to the hospital, so they often appreciate this same service being offered to their pets. And it never hurts to get a second set of eyes (from a radiology specialist) for peace of mind, especially on tough to interpret cases.
By taking at least two views, using the VHS, becoming familiar with all the ways normal can look, evaluating non-cardiac structures, and obtaining an expert second opinion, you’ll have every degree of confidence when you interpret your radiologic studies of the canine heart. All of this means better care for your patients, efficiency in your practice flow, and peace of mind for you.