Cardiomyopathy means disease of the heart muscle; feline hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. It can be primary or idiopathic i.e. with no known cause, and is typically seen in younger (usually male) cats.

Or it can be secondary meaning resulting from other disease conditions e.g. kidney problems, diabetes, hyperthyroidism, etc. This is typically seen in older cats, and in some ways is more challenging to treat.


Boo Boo my fluffy black boy, the love of my life developed HCM as a result of kidney insufficiency around age 10. Three and a half months after his passing, as karma would have it, Boo sent me Trikki, an even fluffier orange fella who as it turned out had primary HCM. Nine years later, Trikki's still as playful as ever, and doing really well thanks to all I learned from Boo Boo.

Cats with hypertrophic cardiomyopathy have excessive thickening (stiffening) of the left ventricular wall, the papillary or small muscles that anchor the heart valves, and the thin membranous structure between the two atria or the thick muscular structure between the two ventricles called the septum.

Symptoms of hypertrophic cardiomyopathy

Many cats with hypertrophic cardiomyopathy are asymptomatic. Sometimes there is no inkling of a problem until "sudden death". Yet another reason to treasure each day with our little ones.

When cats do display symptoms, one sees inappetance, poor energy including not as much interest in playing. If the problem is more serious, there can be difficulty breathing. Sometimes there is a cough as well. Your cat's vet can tell a lot by listening to the heart with a stethoscope e.g. a heart murmur, a gallop rhythm/irregular heart rhythm, and/or a rapid heart rate.
[Handsome Boo Boo a few months after his diagnosis]

Handsome Boo Boo a few months after his diagnosis

S/he may elect to do a chest x-ray to check for pulmonary edema and/or heart enlargement.

If some or all these signs are present, the vet may refer you to a cardiac specialist who in turn will perform an Electrocardiography (ECG) or ultrasound scan to confirm if the heart walls are thickened. If at all possible, get Doppler imaging because it will provide information regarding blood flow direction and velocity.

It is important to get a copy of your cat's ultrasound report so you can be proactive. Monitor your cat's blood pressure and get an honest evaluation from the cardiologist as well as your regular vet regarding risk of CHF and/or saddle thrombosis (left atrial enlargement is one clue).

Heart Murmurs

Heart murmurs are abnormal, extra sounds that are of a relatively long duration. A heart murmur occurs when there is turbulence to the normal flow of blood through the chambers of the heart, and is usually due to a problem in a heart valve. When a valve is thickened or damaged and unable to close fully, some of the blood escapes around the valve. A vet can hear a squishing sound which confirms that blood is leaking out of the heart valves during contraction.

Murmurs are graded from I to VI based on the loudness. But loudness does not always mean heart damage or even that it is severe. Conversely many cats with severe HCM have barely detectable murmurs. The best determinant of what's going on with your cat's heart is color Doppler echocardiography.undefinedundefined
[Trikki (12) diagnosed with a Grade III murmur is as feisty and playful as ever]

Murmurs are usually seen in older cats but it is not uncommon to see them in young kitties. In fact, many kittens are born with murmurs and outgrow them later in life. A lot of cats with murmurs live long healthy lives.

A murmur present since birth that does not cause problems e.g. kitten plays normally, isn't lethargic, or tires easily, isn't as significant as one developed later in life especially if accompanied by symptoms.

When older pets have a valve-related murmur, the incomplete valve closure is often due to bacterial deposits on the valves. A very common source of this bacteria is dental disease, so it's important to keep your kitty's teeth and gums in good condition. A heart murmur can also be caused by severe anemia.

Congestive Heart Failure

When the volume of blood to the right side of the heart is greater than the heart's capacity to move it along, fluid builds up and congestion occurs behind it. This causes an abnormal accumulation of fluid in the abdominal cavity and/or the lungs and chest cavity, which results in congestive heart failure (CHF).

Sometimes you can hear the fluid by means of a stethoscope but this takes some practice (ask your vet or vet tech for help and/or check the references below). Often the cat displays some obvious signs like poor appetite, panting, coughing after even the slightest exertion and blue lips/tongue/gums. Kitty may appear to be out of breath, and not so often your cat may even throw up a reddish colored fluid. This may or may not be accompanied by fainting spells. CHF is a very serious disease and as such, any troubling signs warrant an immediate trip to the vet (emergency or regular).

Also, in advanced stages, CHF can lead to (or be caused by) renal failure, spleen and liver enlargement, and fluid in the abdomen. This fluid can be aspirated by a vet but sedation is required, so this is not a risk-free procedure :(
Aortic thrombosis or saddle thrombus

Another complication of heart disease in cats is the development of a blood clot. A clot can form in the heart's left atrium and make its way through the blood stream. One place it can lodge is at the branch of the aorta that feeds the back legs. This effectively cuts off blood flow and can lead to either partial or full paralysis of the hind legs.

Your cat will exhibit lameness or paralysis of the hind legs. They might also feel cold to the touch, and your cat might cry out in pain. This is a very serious life-threatening condition, and extremely painful. It requires immediate care, so do not wait even if it means an ER visit.


If the heart problems are as a result of hyperthyroidism, diabetes, renal failure and/or high BP, then treating those problems is critical as well. HCM must be treated early, and aggressively.

Avoid commercial foods (especially dry formulations) which are very salty. If possible, prepare a home-made diet for your cat with no added salt. Add at least 500 mg even 1,000mg if possible, of taurine to your cat's food daily or give by mouth in the form of a capsule/tablet. Dietary sources are tricky because a) you'd need a lot, and b) the only two reliable sources of taurine amounts in heart are - 652mg/kg of (as-fed) weight in beef heart as per Spitze et al, and Laidlaw lists pork heart taurine content to be 2000mg/kg (dry weight IIRC, don't have the paper handy because they moved it, will post when I find the new link).

Allopathic treatment for CHF consist of the use of Lasix (especially if fluid is present in the lung cavity). This drug will rob the rest of the body of valuable moisture and minerals like Potassium, Magnesium, etc.

Other allopathic drugs such as Cardizem (Diltiazem), Fortekor (Benazpril), and Norvasc are usually prescribed, but read the side-effects carefully, and check the PDR. Most of these drugs can cause renal problems and an irregular heartbeat, both of which an HCM kitty may already have.

Cats are *very* sensitive to Aspirin so check with more than one vet before you decide to administer it to your cat. It has caused horrid side-effects in cats on my list, so we've come up with a better alternative – Nattokinase.

Note: Herbal alternatives to Aspirin (such as Meadowsweet and White Willow Bark) are deadly, so do not even consider them.

Herbs, vitamins, and supplements: (daily, based on a 9lb cat)

For diagnosed CHF:

Dandelion Leaf: A better option than Lasix, is the herb Dandelion, mother nature's purrfect diuretic. Get the leaf either in tea bags or in loose dried form, and brew tea using the infusion method.

Depending on the size of your cat, and severity of the problem, you can give 1 to 4 5ml syringes (from the baby section of the drug store). A strong brew would be 2 teaspoons per cup of boiled water, whereas a maintenance formula would be 1 teaspoon per cup of boiled water; adjust the strength based on your cat's situation.
For saddle thrombosis prevention in lieu of asprin:

Lumbrokinase (derived from earthworms): 20mg for an average-sized cat


Nattokinase: 75 mg split into 2 doses. Nattokinase is prepared from fermented soy beans. I've checked, and this is the only form of soy safe for cats. But as with everything, please do your own research and be aware that cats like people can be allergic to soy, so be watchful for any side-effects/soy allergies when giving Natto. Make sure the brand does not contain Vit K (it should say so, if it doesn't call and ask), and has no funky ingredients. Two decent formulations are Doctor's Best and NOW capsules.

For all heart conditions:

  • L- taurine powder or capsule: 500 - 1,000mg
  • Coenzyme Q10 a.k.a. CoQ10: 30 - 60 mg
  • L-Carnitine - 250 mg
  • Fish body oil e.g. salmon, sardine, anchovy, or krill oil: 500 – 1,000mg per day

Vitamins and minerals need to supplemented more aggressively if kitty is on diuretics. The only two cat multivitamin formulas that aren't as bad are LEF Cat Mix and NuCat/Tabby Tabs tablets (not oil). Trace minerals can be a good ideas as well. Futurebiotics and Source Naturals brands have the least icky inactive ingredients.

[Handsome Silver Chan enjoyed many years of good health on a similar heart regimen]

Note: Introduce amino acids L-Carnitine and L-taurine slowly. My cat Trikki and one other are the only ones in 11 years of the list who get the trots from amino acids (learned this the hard way:); why take a chance with yours, right?

I hesitate to mention another wonderful herb - Hawthorne Berry – because although I love it, many don't. It has a mild diuretic action and is an all-round cardio tonic. It too can be given as a tea or in capsule/tincture form. The concern about using Hawthorne Berries in HCM, where the heart muscle contracts too much, revolves around one of Hawthorne's actions - increase in strength of heart's contraction. Please do not use this herb without checking with someone who knows what they're talking about, and as with any herb, check for herb-drug interactions.

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References and Notes

Great site with information as to normal vs abnormal sounds for the heart (follow the links on the left)
Count how many beats (2 consecutive sounds count as 1 heartbeat) per 15 seconds times 4 to get beats per minute. Cats' resting heart rate has quite a range. In the 140-180 range is typically okay (check with your vet to be sure). Trikki's normal resting rate is 160, and has always been, but at the vet's it's scary high.

If your cat's purring too much, you can put him up on the counter or turn on the faucet or you can make a noise a bit outside his range of sight so it arouses his curiosity. That'll make him stop purring enough to listen to his heart. I had to do this with Boo Boo because he had a neat loud purr and was a lovebug. Trikki OTOH doesn't purr; he's too annoyed when he's being messed with (which he defines very loosely)! Yell

The above site also has info on lungs:
You can hear there how there's a sort of crackling or even what can be characterized as popping sound if there is fluid build-up.

Etienne Côté , DVM, DACVIM Ann Marie Manning , DVM, DACVECC Dawn Emerson ? Nancy J. Laste , DVM, DACVIM Rebecca L. Malakoff , DVM Neil K. Harpster , VMD, DACVIM, Assessment of the prevalence of heart murmurs in overtly healthy cats, Journal of the American Veterinary Medical Association, August 1, 2004, Vol. 225, No. 3, Pages 384-388
"Heart murmurs were detected in 22 of the 103 (21%) cats. Echocardiography was performed in 7 of those 22 cats. The echocardiogram was considered normal in 1 cat; in the other 6 cats, diagnoses included hypertrophic cardiomyopathy(interventricular septal hypertrophic form [IVSH]; n = 4), left ventricularconcentric hypertrophy with valvular disease (1), and equivocal IVSH (1)."

Babble alert: In the above study they found murmurs to be quite common in "overtly healthy cats". I plan to get the full-text version at some point (too many articles to read, too little time). Until then, just spitballing here - it does make one wonder what results would be for the 15 cats with murmurs that didn't have ECGs. Will also have to wait to find out on what basis these 7 were tested (maybe higher grade murmur or x-ray results) because had they tested them as well and results similar, it would be a scary statistic - might almost 1/5th of cats have "latent" heart disease? Given how it's all inter-related - kidney failure, hyperthyroidism, diabetes, etc. makes one wonder about how even without outward symptoms, HCM in cats is causing/affecting other diseases.

Natto articles:

A 2003 paper with basic info on Natto's actions

Purification and characterization of a fibrinolytic enzyme produced by Bacillus amyloliquefaciens DC-4 screened from douchi, a traditional Chinese soybean food

A newer (2008) review of various clinical studies e.g. on Natto's beneficial effect on hypertension and ability to break up fibrin clots:

A Comprehensive Scientific Review of Nattokinase

Natto allergy cautions:

A case of "late-onset" anaphylaxis caused by fermented soybeans; Natto

Late-onset anaphylaxis after ingestion of Bacillus Subtilis-fermented soybeans (Natto): clinical review of 7 patients.