Heart Murmurs in Cats

There are few things guaranteed to worry a cat guardian more, than when the vet casually mentions, “Do you know your cat has a heart murmur?”

A thousand thoughts (none of them good) fly through your mind at once. Numb from worry, the only coherent words you can string together are, “Is it serious?”

An Awkward Question

Actually, as a vet the “Is it serious?” question pushes a lot of buttons. You see, it’s often impossible on first hearing to know if the murmur is significant or not. But the answer, “It’s difficult to say,” is not the reassuring response an owner wants.

The trouble is that heart murmurs in cats are complicated, and span the full range of outcomes from innocent murmurs to life-threatening conditions. But to work out the difference often requires tests – such as blood tests, x-rays, and a heart scan – before the vet can say, “Nope, nothing to worry about.” It’s great news to hear your cat is well, but not such great news for your pocket after forking out for the tests.

If you feel the whole situation is unsatisfactory, then it may help to better understand what a murmur is, what causes them, and why some cause problems and others don’t.

Heart Murmur 101

There’s a big difference between a heart murmur and heart failure.

A heart murmur is sound created due to turbulent blood flow in the heart. This can be the result of causes such as:

• Heart enlargement (dilated cardiomyopathy)
• Thickening of the heart muscle (hypertrophic cardiomyopathy)
• Heartworm
• Stiff valve leaflets
• Blood abnormalities such as severe anaemia
• Anatomical abnormalities such as a hole in the heart
• Bizarre blood vessel plumbing into the heart.

Heart disease or failure is when the heart can no longer function effectively and there is inadequate blood flow to the organs. Symptoms include:

• Rapid shallow breathing
• Reluctance to move or jump
• Poor appetite
• Unusual tiredness
• Pale or grey gums
• A swollen belly

The take home message is a murmur indicates turbulent blood flow, and not necessarily that the cat is about to expire. Some murmurs are ‘innocent’ and don’t need treatment or worrying about. However, the problem lies in that some murmurs are serious, and recognizing them isn’t always easy.

Does My Cat Need Tests?

As a responsible cat owner you want to do the right thing. But, you don’t want to put your cat through unnecessary stress. Be honest with your vet. Good questions to ask are:

• Are these tests essential or nice-to-know?
• What happens if I do nothing?
• Which single test is least stressful and / or best value for money?
• What would you do if it were your cat? (Always a classic for making your vet think a bit harder!)

Vets put murmurs into categories of loudness, ranked from Grade I (very quiet, only heard via a stethoscope in quiet room) to Grade VI (the murmur is so loud it can be heard with a naked ear near the chest wall.)

In itself, the loudness of a heart murmur in cats isn’t necessarily an indicator of seriousness. That said, vets are more proactive with the louder murmurs because there’s an increased risk of heart disease.

Does my Cat Have Heart Disease?

Now we’re cutting to the heart of the matter. Your vet will be alert for signs your cat’s heart is struggling such as an irregular heart rhythm, an abnormal heart rate, congested lungs, and / or general signs of ill health.

To fully answer the question requires tests. A rundown includes:

• Screening blood tests: This checks for anaemia (indicate numbers of red blood cells makes the blood too thin, which causes turbulent blood flow in the heart) or conditions such as overactive thyroid glands (hyperthyroidism makes the heart work too hard, which can cause a murmur).
• X-rays: Sometimes the signs of heart disease and respiratory disease are very similar. A chest radiograph can give invaluable information.
• proBNP blood test: This test measures the levels of a natural protein released from the heart muscle. When the heart is struggling, the levels of proBNP rise. Thus a high result is a strong pointer that heart imaging is required.
• Cardiac ultrasound: This is the gold standard. The ultrasound gives a real-time image of the heart as it pumps, how well the valves meet together, and the thickness of the heart walls.

Each cat is an individual with their own murmur. Some cats won’t need all the tests. For example, if you skip straight to the gold standard and an ultrasound, you can skip the proBNP test. But if you are worried about sedating your cat for a scan and want to be sure it’s essential, then running the proBNP first can reassure you.

What are the Treatment Options?

After all this, is the information just academic or can something be done to treat heart murmurs in cats?

The vast majority of the times a problem is diagnosed, there are treatment options to extend or improve life. This doesn’t mean a cure, but slowing up the deterioration and giving a better quality of life.

As well as excellent heart meds now available, it’s also important to correct any underlying health problems. A great example is the cat with overactive thyroid glands. By bringing the thyroid hormones down to normal, a big strain is removed from the heart. Indeed, not all hyperthyroid cats with struggling hearts need specific heart meds, but do very well just by managing their thyroid levels.

So now you see when you ask “Is it serious?” the vet pauses and a takes a deep breath. The answer “It’s difficult to tell,” isn’t skirting around the issue but being truthful. And yes, getting an answer means spending money. . . regardless of whether there’s a problem at the end of it.

Do your own heart good! Stroke a cat today.