Dear Max,

You had a heart murmur.

The first time I took you to the veterinarian for your kitten vaccines, she heard a mild murmur. When she was listening to your heart with her stethoscope, the lub-dub had an extra sound, meaning that the flow of the blood was not smooth. There is a good article here with audio files of heart sounds.

The problem with cats and heart murmurs is that the murmur tells you nothing about the possibility of disease. In dogs, the murmur can tell you a lot. In cats, a murmur could simply be due to positioning or how nervous you were. But it could also mean serious disease. In general, mild murmurs like yours are not as likely to indicate a problem as a more severe murmur. But cats don’t like to follow rules or guidelines, especially when humans put them into textbooks.

Then there’s the whole issue of heart disease in cats. It’s hard to diagnose. Normal chest x-rays with a normal looking heart aren’t enough. One of the nasty and more common types of feline heart disease, called hypertrophic cardiomyopathy (HCM), doesn’t change the way the heart looks on an x-ray. You need a cardiac ultrasound, or echocardiogram, done by a specialist, with measurements of the blood flowing inside the heart, to diagnose this disease.

It wasn’t available ‘back then’, but nowadays there is a blood test (NT-proBNP) that can show if there is stress on the heart muscle. This might be useful to determine whether changes in lungs seen on an x-ray are due to heart disease, but other problems can cause high levels of proBNP. At this point, it’s not a way to tell if a murmur is benign or not.

Cats with heart disease also hide it. Between their natural instinct to hide a problem, and the ability of the cardiovascular system to adjust as the heart weakens, you often don’t know there’s a problem with a cat’s heart until they are in the midst of a life-threatening crisis.

As if that isn’t complicated enough, there is still not a lot of evidence or even agreement among specialists (veterinary cardiologists) about what kind of medications work best in cats with heart disease before it causes signs of illness. A couple things they all agree upon, high blood pressure needs to be treated, and if a heart problem is confirmed, then using medication to prevent blood clots is a good idea.

And then we get to the practical part. A cat with heart disease or heart failure needs daily medication. Sometimes more than once a day. Usually more than one medication. Of my cats, there have been some I could pill, some I could bribe and one in particular (you’ll hear about Tinky later) who I could not medicate by mouth.

There is one new, simple way to help monitor for heart failure and to assess if the medication is effective. It’s called SRR, for Sleeping Respiratory Rate. You can do this easily at home by counting how many breaths in a minute when your pet is sleeping.

Luckily, we didn’t need to deal with heart failure, but I sure learned a lot when I researched it.

What did I learn about heart disease in cats from you, Max?

• Heart murmurs don’t necessarily equal heart disease in cats.
• Heart disease is harder to diagnose in cats, and may also be harder to manage.
• Some cats with heart murmur live a normal, healthy life and never develop heart disease.
• The knowledge of heart disease in cats is changing rapidly as research and clinical experience teach us.