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Cardiomyopathy in Cats: What to Know About DCM and HCM

Let’s get down to the nitty-gritty of feline cardiomyopathy.

British shorthairs may be more at risk for cardiomyopathy than some other cat breeds. By: ToNic-pics

If this morning’s clinic is anything to go by, heart disease in cats is very common (actually, it’s not — it just seemed that way).

The day started with an inpatient, Pepsi. This ragdoll cat has a heart condition known as cardiomyopathy. He had previously gone missing and not taken his heart meds for a full 3 weeks. He was found in the nick of time, ice-cold and close to death. But, happily, Pepsi responded well to intensive care; now his purrs are so loud it makes it difficult to monitor his heart.

Then, ironically, morning clinic ended with another cat with a heart problem. This feline, Milly, was at the other end of the scale. She had been diagnosed with heart disease last year but was well enough not to need meds. However, this was about to change.

Milly hadn’t eaten for days and yet gained weight. The extra weight wasn’t down to calories but retained fluid that had leaked out of her creaky circulation. Time to get Milly started on meds to shift that fluid and get her feeling well again.

Both cats were suffering from a disease of the muscle of the heart wall called hypertrophic cardiomyopathy (HCM). What are the odds of seeing 2 cats with the same heart condition in 1 morning? Pretty low, but there we are.

Cats vs. Dogs

Cats are not small dogs. This definitely holds true for affairs of the heart. Whereas leaky heart valves are the most common cause of heart disease in dogs, this is not so for cats.

Our feline friends are more likely to suffer from a problem with the muscle of the heart. The technical term is cardiomyopathy — “cardio” refers to heart, “myo” to muscle, and “pathy” to pathology or disease. The problem for affected cats is that the heart is basically a big muscle. Mess with its muscle fibers, and the heart can’t pump properly.

Types of Heart Disease in Cats

The condition comes in 2 forms: Dilated and hypertrophic.

  • Dilated cardiomyopathy (DCM): Refers to a big, saggy heart, the equivalent of a balloon that’s no longer stretchy because it’s been blown up and deflated too many times.
  • Hypertrophic cardiomyopathy (HCM): This time, the heart appears the right size on the outside, but the wall is thickened internally, which means the pumping chamber is reduced in size.

The thing is, the heart’s ability to pump is cut right down, resulting in poor circulation. The body makes adjustments to try and cope, but eventually these no longer work, and the cat becomes sick. This had happened to both Pepsi and Milly.

Dietary deficiencies and high blood pressure may cause cardiomyopathy in cats. By: knmurphy

Causes of Cardiomyopathy

Sadly, some breeds seem more at risk than others, which suggests a genetic cause. This seems to be the case with Pepsi. Those breeds topping the charts when it comes to HCM include:

Also, ill health that puts the heart under strain can cause physical damage to the muscle of the heart wall. The most common reasons include:

Sometimes, however, no underlying cause is found, as was the case with Milly.

Signs of HCM

Here’s another difference between cats and dogs. Whereas heart disease in dogs often causes them to cough, it is rare in cats. Our feline friends are much more secretive at hiding illness, so they never do anything as conveniently obvious as coughing.

Instead, the cat becomes quiet and sleeps more than usual. If you are super observant, you may notice their breathing is rapid and shallow or notice that their heart is racing.

Because they don’t want to take time out from breathing to eat, their appetite may drop off, so they lose weight. They don’t groom either, so their coat becomes dull. The vague, easy-to-miss signs make it tough to know when to seek help.

Treatment for Cardiomyopathy

I’m thrilled Pepsi responded so well (from close to death to greedy eater in less than 24 hours). We’ve yet to see what the future holds for Milly.

It’s not possible to reverse the physical changes within the heart, but there are medications that make it easier for the heart to pump more effectively. In fact, we have quite an armory of options when it comes to heart medications. Some examples include:

  • Diuretics: Also known as “water tablets,” these shift the fluid that builds up in the lungs or tummy as a result of sluggish circulation.
  • ACE inhibitors: These drugs make it easier for the heart to push blood round the body.
  • Beta blockers: A symptom of heart failure is a racing pulse. However, when the heart pumps too quickly, it doesn’t get a chance to refill with blood. Beta blockers help control a racing heart, giving it time to fill more effectively.
  • Clot busters: A serious complication of heart disease is the likelihood of a blood clot. This could cause a stroke or paralysis with life-threatening consequences. Drugs are available that reduce the risk.

Learn more about HCM from the vet in this video:

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The Heart of the Matter

All of which goes to show how hard it is being a cat’s human at times. Is your super-chill kitty who sleeps all day sick or merely having a snooze? It can be tricky to tell.

Long story short, it’s best to get them checked by a vet, especially if they’re not eating. The vet will examine the cat, listen to their heart and lungs, and possibly scan her heart to reach a diagnosis. Although medication can’t cure the condition, it can slow its progression.

If Pepsi hadn’t come off his meds, then he probably wouldn’t have been so sick. So keep your fingers crossed for Milly.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Nov. 3, 2017.