Using radiographic measurements to assess patient heart size

During an interview with dvm360 at the 2025 Fetch dvm360 Conference in National Harbor, Maryland, Lance Visser, DVM, MS, DACVIM (Cardiology), associate professor of cardiology at the Colorado State University College of Veterinary Medicine and Biomedical Sciences in Fort Collins, discusses 2 primary ways to measure a patients heart size: vertebral heart size (VHS) and vertebral left atrial size (VLAS). VHS is a traditional length and width measurement of the cardiac silhouette, while VLAS is a newer, left-heart-specific measurement focusing on the width of the left atrium.

Below is a partial transcript, edited lightly for clarity

Lance Visser, DVM, MS, DACVIM (Cardiology): Assessing heart size, I think, should definitely involve measurements. I think that's going to be best practice in combination with your subjective or qualitative assessment if the heart looks big, but I think measuring it, particularly if you're not viewing thoracic radiographs regularly, and even if you are, like myself as a cardiologist, we would still recommend measuring heart size on radiographs. So there's 2, I guess you could say main or primary measurements. There are more that are being studied. So makes a lot of new measurements coming out. It's kind of a hot topic in veterinary cardiology, if you will. But the main ones with the most literature behind them are the kind of good old vertebral heart size. That's kind of that length and width measurement of the cardiac silhouette from the right lateral radiograph graphic projection.

The newer one is called vertebral left atrial size. Or we often abbreviate VLAS, V, L, A, S, that's, that is a is a newer measurement, as I said, and it's more specific to left heart size, which is really what we're most concerned about in these patients. And it's not that vertebral heart size is worse, at least in this context. It's just not necessarily a left heart specific measurement. And they're both pretty simple. They're VHS, or vertebral heart size is kind of that length and width measurement. And vertebral left atrial size is really just measuring the width of the left atrium radiographically. So it uses the carina as kind of a baseline or starting point, and then you're going to measure the caudal aspect of the left atrium at the point where the left atrium intersects with the dorsal border of the caval vena cava.