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This page is in serious need of updating, which I hope to complete during 2017. In the meantime, please click here for more up to date information.


What is It?






Commonly Used Heart Medications

Beta blockers ACE inhibitors Calcium channel blockers Broncho-dilators Diuretics Aspirin


Other Heart Conditions

Heart Murmurs

Congestive Heart Failure (CHF)

Harpsie's Experiences



This page covers what I learned about hypertrophic cardiomyopathy during the five years when I thought we were living with it!


What is It?


There are various kinds of heart disease but hypertrophic cardiomyopathy (HCM) is probably the most common one in cats. Cardiomyopathy means disease of the heart muscle, and in HCM the left ventricle of the heart, which pumps blood through the aorta, the body's largest artery, is thickened. This thickening stops the heart expanding properly. 


HCM may be caused by a hyperactive thyroid - in fact, Gulf Coast Veterinary Specialists claim that 87% of hyperthyroid cats will have some degree of HCM. Other possible causes include high blood pressure or chronic renal failure, but it is also possible for a cat to have HCM without any associated disease. 



Unfortunately many cats are asymptomatic or show very few symptoms, which can make heart disease hard to diagnose and treat. Harpsie was suspected of having heart disease because of a high heart rate on two vet visits (which might just as easily have been caused by stress or "white coat syndrome") and weight loss. Other possible symptoms may include lack of appetite, lethargy and vomiting. You may also see faster breathing (the normal respiratory rate of a cat is around 20-30 respirations a minute).


More Serious Symptoms


Fluid Build-Up/Congestive Heart Failure

More serious symptoms, which require urgent veterinary help, include sudden weight gain, difficulty breathing, coughing or open mouth breathing: these may be a symptom of fluid build-up, which may be a sign of congestive heart failure (CHF). A low body temperature may also be seen in congestive heart failure.


In CHF, fluid collects in the lungs (pulmonary oedema), or around the lungs (pleural effusion) or in the abdomen (ascites). Cancer Back Up explains more about pleural effusion, whilst Health A to Z talks about ascites. A low body temperature may be seen in congestive heart failure.


If left untreated, fluid build-up can kill, so the fluid should be removed. Diuretics in pill form are commonly used to remove excess fluid, but these take a few days to take full effect. For immediate relief, thoracocentesis (needle aspiration) may be performed: this entails inserting a fine needle into the chest and drawing the fluid off. It sounds horrible, but my cat had this done to remove ascites and he didn't even flinch. However, it is a delicate procedure, and skill is required to insert the needle in the right place and remove the correct amount of fluid. But it can be lifesaving.


Saddle Thrombus (Blood Clot in the Legs)

Other symptoms include blindness, which may be caused by untreated high blood pressure; or limping or an inability to use the legs, particularly the hind legs - this may be caused by a blood clot in the aorta which stops the blood supply to the legs (sometimes known as a saddle thrombus). Affected legs are likely to be cold to the touch. This is life-threatening so you should consult a vet as soon as possible. If your vet proposes a treatment plan, make sure it includes painkillers because this is an extremely painful condition.


University of California at Davis discusses blood clots.

Manhattan Cats also has some detailed information on blood clots, including possible treatment options.

Systemic arterial embolism in cats (2007) is a presentation by Dr C Atkins to the World Small Animal Veterinary Association World Congress 2007 which discusses treatment and prevention.

Feline thromboembolism - new clinical perspectives (2007) is a presentation by Dr PR Fox to the World Small Animal Veterinary Association World Congress 2007 which discusses treatment options.



How cats cope with heart disease varies from cat to cat, depending upon how advanced the disease is and how well the cat responds to treatment. Try to keep stress to a minimum. 



The only way to obtain a definitive diagnosis of HCM is by way of echocardiogram (ECG or ultrasound), ideally with Doppler colour flow imaging. Your vet may also wish to run x-rays in order to obtain further information, but x-rays alone will not normally provide a proper diagnosis (although they can be helpful if your vet suspects some kind of lung involvement). If at all possible, ask for a referral to a veterinary cardiologist.


The Feline Advisory Bureau in conjunction with the Veterinary Cardiovascular Society has set up an HCM screening scheme for UK cats.

Feline cardiomyopathy - establishing a diagnosis (2002) Fuentes VL, is a presentation to the 26th Annual Waltham/Ohio State University Symposium

Laboratory tests for the diagnosis of heart disease and failure in dogs and cats (2007) is a presentation by A Boswood to the World Small Animal Veterinary Association World Congress 2007 which discusses the use of "cardiac" laboratory tests.



If your cat's HCM is caused by a hyperactive thyroid (hyperT), treating the hyperT successfully can reverse much or even all of the HCM; while a heart murmur caused by anaemia may also be improved following treatment. Otherwise, HCM cannot be cured but it can be controlled by way of drugs.


Even if your cat appears stable once medication has begun, it is a good idea to have an ultrasound examination of your cat's heart undertaken once every year (or more regularly if your cardiologist advises it) and to review medication at that time if appropriate.


Cats with congestive heart failure may need to have fluid build-up removed from their lungs manually (thoracentesis) or via diuretics, in addition to other treatments. If your cat has CHF, it is worth asking your vet to teach you to listen to your cat's heart so you can monitor for any changes that might indicate an approaching crisis.


Washington State University College of Veterinary Medicine has some suggestions on how to care for a heart patient at home.


Heart Disease Websites


Veterinary Heart Disease Sites

Long Beach Animal Hospital - explains how the heart works, and the Specific Diseases link discusses HCM.

Vetinfo - an overview of feline heart problems and medication by a US vet.

Cardiorespiratory diseases of the dog and cat is the online version of a detailed book by a veterinary cardiologist.


Other Heart Sites

Feline Advisory Bureau - an overview of HCM by the UK feline charity.

Jody Chinitz's Site - this site is by a lady who lost a cat to HCM.

Boo Boo's Story - this is a site about Boo Boo, a cat who was treated for both CRF and HCM using holistic methods.

Ragdolls - Ragdolls (and Maine Coons) can be prone to HCM, and this site has good  pictures of a healthy heart and an HCM-affected heart.


Heart Support Sites

Feline Heart List - a support list for people with cats with heart conditions, where you can obtain feedback on treatments, and support on living with HCM and other feline heart problems.


Commonly Used Heart Medications

HCM is usually treated with drugs and it is fairly common to use more than one heart medication at a time.


Feline cardiomyopathies (2001) is a paper presented by Paul Pion to the World Small Animal Veterinary Association World Congress in 2001, which gives typical heart drug dosages.

The Mayo Clinic has a table showing the mechanism of some of the different classes of heart medications and their possible side effects.


The different drug classes are:


Beta Blockers

Drugs called beta blockers are used to slow a fast heart rate. This is often the treatment of choice in the USA, where a drug called Atenolol  is used. In the UK, a similar drug called Propranolol may be used.


Pharmacokinetics of atenolol in clinically normal cats (1996) Quinones M, Dyer DC, Ware WA & Mehvar R American Journal of Veterinary Research 57(7) pp1050-3 discusses the effects of atenolol on cats.

ACE (Angiotensin-Converting-Enzyme) Inhibitors  

These are drugs which prevent the conversion of a hormone called angiotensin I into another hormone called angiotensin II, the role of which is to constrict blood vessels. Therefore by using these drugs the blood vessels relax and this makes it easier for the heart to pump blood through the body. You should be careful if you are using ACE inhibitors at the same time as potassium supplements, because they may cause potassium levels to become dangerously high.  


ACE inhibitors are a popular treatment for heart disease in the UK, and a commonly used one is Enalapril, the trade name of which is Enacard, which is also available in the USA. Mar Vista Vet has information and cautions on the use of Enalapril, including when using it in conjunction with diuretics such as frusemide (US: furosemide) (see below). Another ACE inhibitor is Fortekor (benazepril), which is licensed for the treatment of renal failure in cats in the UK, Europe and Australia, even for cats without heart disease. 


A newer ACE inhibitor called Ramipril (marketed as Altace or Vasotop) is available in the UK and Europe, though I do not know anybody who has used it for their cat. The efficacy, tolerance and safety of the angiotensin converting enzyme inhibitor ramipril in cats with cardiomyopathy with or without hypertension (2002) Schille F & Skrodski M is a paper presented to the World Small Animal Veterinary Association World  Congress 2002.


Calcium Channel Blockers  

Calcium channel blockers work by slowing the passage of calcium into muscle cells; this makes muscle in the blood vessels relax, so the blood vessels open wider. The most commonly available one in the UK is called Diltiazem which is also available in US. 



These are used in asthma, but can also be used to treat heart problems - they open up constricted airways in the lungs. Millophyline-V (etamiphylline) is commonly used on the UK; theophylline is commonly used in the US and may also be offered in the UK. 


Veterinary Partner has information on the use of theophylline.



Diuretics may be used for congestive heart failure in order to rid the body of excess fluid. The most common one used in the UK is a drug called frusemide (furosemide in USA), which is commonly sold under the name of Lasix, although the name is currently being changed to Salix.  Lasix is very hard on the kidneys, but some people have found that another diuretic, spironolactone, is gentler. However, Lasix is the best choice during times of crisis.


Washington State University College of Veterinary Medicine has information on the different types of diuretics.

Mar Vista Vet has more information on Lasix (frusemide or furosemide), including cautions about using diuretics at the same time as ACE inhibitors.

Pet Place has more information about spironolactone.



Aspirin may be used in an attempt to reduce the chances of blood clots forming. Aspirin can be toxic to cats, who can only metabolise it very slowly, and should only be given to a cat on veterinary advice; it is usually only given in very low doses once every three days. In the USA, cats with HCM are routinely given carefully assessed doses of aspirin in addition to other medications, but if the cat reacts badly, then aspirin is stopped.


Mar Vista Vet has information on aspirin.


Other Heart Conditions


Heart Murmurs

Some cats with HCM may have a heart murmur, although it is also possible to have a heart murmur without having HCM. Heart murmurs are caused by  blood flowing through the heart turbulently rather than smoothly. They are graded from 1 to 6 depending upon their severity, with 1 being the lowest level at which a murmur can be heard and 6 being the most severe, extremely loud murmur, which is often audible without a stethoscope. 


Heart murmurs may or may not need treatment, depending upon their cause and their severity.  Both anaemia and hyperactive thyroid may cause a heart murmur which disappears following suitable treatment.


Merck Veterinary Manual has detailed information on heart murmurs.

University of California at Los Angeles - on this site you can listen to the different types of heart murmur - turn your speakers up loud for best effect. This is a human site but it should still give you an idea of what to listen for.

Heart Sounds - you can listen to various heart sounds here.


Congestive Heart Failure (CHF)

As heart disease progresses, the cat may enter congestive heart failure. Anaemia increases the risk of CHF developing, so should always be treated if present. In CHF, the heart is really struggling to cope and fluid may accumulate in the lungs (pulmonary oedema), or around the lungs (pleural effusion) or in the abdomen (ascites). 


Many cats with CHF only have a short period to live, although it is usually worth trying to control the condition because some cats do better than others. Cats with congestive heart failure may need to have fluid build-up removed from their lungs manually (thoracentesis) or via diuretics, in addition to other treatments. If your cat has CHF, it is worth asking your vet to teach you to listen to your cat's heart with a stethoscope so you can monitor for any changes that might indicate an approaching crisis.


Cancer Back Up explains more about pleural effusion.

Health A to Z explains more about ascites.

Vetgo discusses the usual treatments for congestive heart failure.

Warning signs for congestive heart failure is a helpful site by an individual whose cat, Coco, had both CRF and heart problems, and gives useful information on what to watch for. Coco lived with CHF for quite some time.

Emergency respiratory assessment (2001) Hughes D is a presentation to the World Small Animal Veterinary Association World Congress 2001. It is rather technical but may still be of use.

Effect of coenzyme Q10 therapy in patients with congestive heart failure: a long-term multicenter randomised study (1993) Morisco C, Trimarco B, Condorelli M Clinical Investigation 71 (8 Supp) pp134-6 demonstrated "that the addition of coenzyme Q10 to conventional therapy significantly reduces hospitalization for worsening of heart failure and the incidence of serious complications in patients with chronic congestive heart failure".


Harpsie's Story


Harpsie was tentatively diagnosed with hypertrophic cardiomyopathy (HCM) in August 1999, after heavy breathing at the vet's on two occasions and difficulty walking upstairs (he would go up a few steps, then sit there gasping for breath). An echocardiogram appeared to indicate the presence of heart disease, so Harpsie was placed on heart medications (enalapril, an ACE inhibitor, and Millophyline-V, a bronchodilator). He improved on these medications, and he continued on them for two years (he received regular check ups from the vet during this time).


After two years we took Harpsie to a cardiologist, who examined him via echocardiogram and told us he was no worse, and he thought we could reduce the dose of the enalapril. However, we tried to do this twice, and on both occasions Harpsie immediately developed polydipsia (increased drinking). We waited a while, then tried again, very slowly, and finally succeeded in reducing the dose of enalapril. Harpsie saw the cardiologist every year, and his condition was not worsening, but we kept a very close eye on him.


In 2004 we moved to the USA, and shortly after our move, we came home after a short outing to find Harpsie limping and screaming. Since limping can indicate a saddle thrombus (throwing a blood clot), a very dangerous development, we rushed to the ER, where Harpsie jumped the queue of 20 other patients and was seen immediately. Initial tests seemed to indicate that he had not thrown a blood clot, and it was later determined that the pain and limping were caused by a flare up of his arthritis, probably following a bad jump or fall from the bed while we were out.


We did take Harpsie to see the cardiologist shortly afterwards though, where he was examined thoroughly. We were astounded to be told that they could find no sign of heart disease! For almost five years we had thought Harpsie had heart disease, and he did not! However, we continued with his heart meds because he has asthma, and the bronchodilator helps with that, and he also has proteinuria, and the ACE inhibitor helps with that.






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This page last updated: 10 June 2011


Links on this page last checked: 2 February 2008


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I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who cared for Harpsie with the help of qualified vets. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.


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