How serious are heart murmurs in cats? How are heart murmurs graded?

Original Question: Hello, I was just at my vet tonight with my cat but still have questions and left feeling quite confused. I went for his regular physical - he is an indoor neutered male grey Tabby that is 4-years-old and turning 5 this July - 14.4lbs (he is a very solid tall cat not overweight). Up until 1 week ago he has been perfectly healthy in all aspects. Last week in the middle of the night I woke to the sound of his nails scratching thought he was playing but I could tell he was right by my bed on the ground so I turned on the light to look and he seemed to be breathing fast so I thought maybe he fell. I was shocked when I saw his hind legs only kicking out and then stopped within seconds so I thought maybe he was trying to stand up but couldn't? As I sat with him and petted him he was looking at me and looking around and his breathing slowed - this was in less than a minute that his breathing slowed. I rubbed his hind legs and stretched them out to make sure he didn't hurt his hind legs and they seemed fine then I picked him up and lied with him and he calmed further and seemed fine stayed with me there. Then after about 5-10 min he went to move and I placed him on the ground and he walked fine then he ate a bit. I watched him and he seemed fine the rest of the night and each day thereafter the eating, drinking behaviour that was all normal. I informed my vet tonight and he discussed seizures, and possible triggers to epilepsy etc. During the exam he noted a heart murmur stage 3-4 and the last time he was there in 2014 he did not have it. I was told this is common in dogs but very rare in cats and he cannot tell the specifics of the murmur because a cat’s heart is so small and would need a cardiologist consult us. He said it was concerning and has not seen a lot of cats with it and cats don't show symptoms like dogs and they can be fine one day and then for lack of a better term just drop dead with this. He isn't a cardiologist so he doesn't know what the course of treatment would be and he said it's not an emergency referral just an outpatient? I was left confused and wondering if I should go to another vet for a second opinion or book the referral to the cardiologist? I understand an exact answer or cause cannot be given without diagnostics but I'm trying to understand if it was the stage 3-4 murmur, the episode he had last week and I'm concerned if they could be linked or are separate? Online I see there are varying degrees of concern with murmurs depending on cause but it is fairly common in cats and dogs. He has no other symptoms and seems well otherwise. Just wondering how rare this is and if I should get a second opinion which would be cheaper than going to the cardiologist or if they would just end up sending me to a cardiologist anyway? Your advice would be greatly appreciated. Thank you." - Jennifer - Jennifer

How serious are heart murmurs in cats? How are heart murmurs graded? Jul 21, 2017

Hi Jennifer,

Thanks for your question.

There are a few questions here so I’ll answer them in two parts.

How serious are heart murmurs in cats?

First off, I’m sorry to hear that you are a little confused after an appointment with your veterinarian. When we hear a murmur in the heart we do have difficulty knowing whether there is severe heart disease or if the murmur is innocent. The higher the grade the murmur is, the more likely it is serious and could cause clinical problems including cardiac arrest.

How are heart murmurs graded?

The fact that he suggests this murmur is grade 3 or 4 makes it a more serious concern – murmurs are graded from 1 to 6. To evaluate heart murmurs in cats, the first test I would have performed is a cardiac ultrasound. It’s true that cardiologists will perform this test but there are ultrasonographers who travel around to clinics who do it as well. There are quite a few of them and it’s likely that your veterinarian may know of one and could give them a call and book an appointment at your current clinic so that you don’t have to go elsewhere. The ultrasound is a very thorough test and it should be able to pinpoint the source of the murmur, the type of heart disease, whether treatment is necessary, and the course of treatment as well as indicate the severity of the condition.

I would also recommend that you perform routine blood work to make sure that there are no other underlying conditions. There are many reasons for seizures and if what your cat experienced truly was a seizure and it occurs again, I would recommend you start performing a work-up with your veterinarian to determine the cause of the seizures.

All the best.

Dr. Clayton Greenway

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How serious are heart murmurs in cats? How are heart murmurs graded?
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How serious are heart murmurs in cats? How are heart murmurs graded?
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When we hear a murmur in the heart we do have difficulty knowing whether there is severe heart disease or if the murmur is innocent. The higher the grade the murmur is, the more likely it is serious and could cause clinical problems including cardiac arrest. Heart murmurs are graded from 1 to 6.
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Healthcare for Pets
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