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How can vets tell what's wrong with my pet's heart?

Heart problems are very common in dogs and cats, especially now they’re living longer. However, heart conditions aren’t all the same disease - even if they tend to have very similar symptoms. So, how can we tell what disease is causing the problem - and therefore how best to treat it?

How do we pick up heart problems?

The basis of any diagnosis is what we call a “clinical history”. This involves a full description of what symptoms you (as the owner) have noticed, when they started, how often they occur, and if there are any known triggers.

This can help us to narrow down the possible causes - for example, a dog who has always had bluish gums and fainting fits is more likely to have a congenital heart defect (such as a “hole in the heart”). If it came on suddenly after an infection, viral myocarditis (infection of the heart muscle) is much more likely.

Clinical Examination

There is a reason we listen to your pet’s chest every time we see them for a check up! Many heart conditions present with a “murmur” - an abnormal noise caused by turbulent bloodflow through the heart. The exact location of the murmur and how loud it is may suggest a cause - although it is not usually possible to diagnose heart problems just from listening to them, it’s great for picking them up in the first place! The only complication, of course, is that many puppies and even some kittens have murmurs quite naturally when they’re young (called functional murmurs) but usually grow out of them by 6 months of age. Likewise, a very dehydrated or anaemic animal may have a murmur due to compensatory mechanisms in the heart (a flow murmur).

We can also detect abnormal heart rhythms (arrhythmias) - although again, we cannot always diagnose the exact cause, it’s pretty obvious that something’s wrong! Comparing the heart rate (by listening) and the pulse rate (by feeling for their pulse) can detect a “pulse deficit”, a sign of a serious cardiovascular malfunction.

We also like to listen to the lungs - the end stage of heart disease is congestive heart failure, which results in fluid building up on the lungs (pulmonary oedema). In mild cases, this is difficult to detect, but once it reaches a certain level of severity, the lungs sound “crackly” when we listen, due to fluid bubbles.

Other things we can look for during an examination include fluid build up in the abdomen (ascites); jugular pulses; altered blood pressure; and the degree of oxygenation of the bloodstream (by looking at the gum colour).

If we find something abnormal, suggestive of a heart problem, in the history or the clinical exam, our vets will generally recommend more tests to determine the problem. These tests may include:
Blood Tests

There is a blood test called ProBNP that is a good early marker of heart disease - essentially, it is increased if the heart muscle is stretched or stressed. In cats, we usually use it to screen cats for heart disease before symptoms occur; whereas in dogs, although we can use it for this, it is also used to establish a baseline so that heart function can be monitored over time.


In many case, the first stop when a dog or a cat is diagnosed with suspected heart disease is an X-ray. This shows us two things: firstly, how large the heart is (diseased hearts usually swell); and secondly, to give us an idea of how much fluid is building up in the chest.

Measuring the heart isn’t as easy as most people think (remember how many different sized dogs and cats there are out there!) so we use something called a “vertebral heart score” where we compare the size of the heart to the bones of the spine. A normal score for a dog would be between 8.7 and 10.7 (in other words, length and width of the heart added together are about the same as 9-10 vertebrae). For cats, it should be less than 8.

Echocardiography (Heart Scan)

In many ways, this is the single most useful test that we can do in a dog or a cat with heart issues. Until a few years ago, this was only routinely done by specialist cardiologists; however, our vets can now do it in-house.

A heart scan uses an ultrasound machine to generate a moving, real time image of the inside of an animal’s heart. It allows us to measure the size of the chambers, the thickness of the wall, how well the walls are moving (i.e. how strong the heart’s contractions are), see any narrowing in the valves or great vessels, and even measure blood flow through the heart.

In most cases, a heart scan can be done conscious - with the dog or cat lying on a table being scanned from underneath (usually through a hole cut in the table). However, although it isn’t painful or even really uncomfortable, many dogs and cats dislike being held still, so we’ll often ask you to stay in with them. If necessary, a mild sedative can be given.


All the previous tests have concentrated on the function of the heart; an ECG (or electrocardiogram) shows us the the electrical activity of the heart. It is invaluable for detecting and diagnosing abnormalities of the heart rhythm (arrhythmias). If they’re really complicated, we can even send the results away to an expert veterinary cardiologist, who will be able to give us their advice.

Once we have a diagnosis, we can start treatment! The earlier we make a diagnosis, the more effective treatment is likely to be; however, it also means that the symptoms and the changes are likely to be more subtle.

If you think that your pet may have a heart problem, don’t delay - bring them in for a check up right away!


Rushcliffe Vets
Rushcliffe Vets
How can vets tell what's wrong with my pet's heart?