Cats are a little sneakier with their hearts, and because of this are a little more confusing. Not only do they hide signs of heart disease as much as possible, but sometimes their heart can be very sick and they feel fine.
Staging of cats is similar:
Stage A cats are cats at risk for problems – those with heart murmurs or predisposed breeds/age.
Stage B occurs when cats have remodeling due to heart disease – this is when we want to catch them.
Stage C, as in dogs, indicates heart failure – either treated or untreated.
Stage D is again refractory to treatment.
Cats get a few different types of heart failure, but for the most part their heart muscle gets too big and strong for its own good. It doesn’t relax enough to let blood flow correctly. Sometimes they have a murmur, but sometimes they don’t. Sometimes they get a progression of disease, sometimes they don’t (Confusing right?!?). Unlike dogs, a plain x-ray can’t tell how severe the disease is and listening to the heart with a stethoscope can’t always tell the whole story. This is why cats are so much harder to catch and treat for heartworm disease than dogs.
So what’s the big deal with cats and their hidden heart disease? Previously, we recommended that every cat with a murmur (those in Stage A) have a heart ultrasound to make sure that the inside of the heart was still behaving itself. This was expensive for owners and often a poor screening test for cats to make sure they were normal (not because it didn’t give good information, but because murmurs are very common and normal results are frequent). What has changed now is a test that can screen for underlying disease with only three drops of blood and is much less expensive than a ultrasound of the heart. It detects products that are secreted from heart muscle when the muscles themselves are stretched or stressed. A positive result means that a heart ultrasound must be performed and will likely show changes of the heart (putting us in Stage B and making us monitor for progression of heart disease).
Since cats don’t show signs of heart disease or failure, this test will allow us to find those cats who are hiding their heart disease without ultrasounding every feline who is at risk. With better, easier, and cheaper screening tests, we can begin to classify and find potentially hidden heart disease sooner and prevent future crises from occurring.
If you have stuck with me until this point, congratulations! Even through the information, I still hope you can see how exciting some of these new tests, studies, and classification systems are. If we can find it, name it, and know how the disease process usually behaves, then we can go a long way in treating and preventing the “putting out fires” method of veterinary medicine we unfortunately have been used to!
– Doc Cleland