Restrictive cardiomyopathy is the second most commonly diagnosed heart complaint in our feline patients. If restrictive cardiomyopathy has been identified in your cat then you probably have a lot of questions. While your vet is always there to support you, this blog is here to help aid your understanding of this condition and cover some of the key points.
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What is restrictive cardiomyopathy in cats?
The heart is made up of four chambers, two atria and two ventricles. The atria receive and squeeze blood down into their corresponding ventricle below them. The ventricles’ job is then to squeeze blood back up and out of the heart through major blood vessels, where it travels around the body (from the left ventricle) and to the lungs to receive oxygen (from the right ventricle).
In restrictive cardiomyopathy, the left ventricle becomes stiffened
This is due to an increased amount of scar tissue (collagen) that has formed on the inner lining of the ventricle. This causes it to lose its elasticity stopping the heart chamber from relaxing and filling with blood as well as it would do normally. Restrictive cardiomyopathy can develop secondary to other issues such as endomyocardial fibrosis. However, in many cases, it is unknown why this condition has occurred, though it may be hereditary in nature.
When the left ventricle is not able to fill as normal, this can lead to an increased amount of pressure in the left atrium, gradually causing it to increase in size. Left-sided heart failure occurs because blood flow is compromised through the heart. It is this cardiac failure, and the resultant fluid build-up in the lungs, that causes some of the symptoms listed below.
In some cats, thromboembolisms (blood clots) occur secondary to their heart complaint
This is due to the increased turbulence in the way that the blood is flowing. This can cause sudden and dramatic signs such as paralysis or strokes.
What are the symptoms of restrictive cardiomyopathy in cats?
One of the issues with this disease is that clinical symptoms may not be apparent until quite far along in the disease process. We don’t exercise cats in the same way as we do dogs, so there is no opportunity to spot subtle signs, like exercise intolerance. Cats may spend more time resting and sleeping but this often goes unnoticed, especially as most of these animals are ageing.
Sometimes a heart murmur is detected when your vet listens to the chest with a stethoscope. This may occur as an incidental finding at a routine appointment like a vaccination, or because you have noticed your cat isn’t quite right and have taken them in for a check-up.
The following would be considered classic signs of a deteriorating heart issue in cats, including restrictive cardiomyopathy –
- Difficulty breathing
- Faster or more laboured breathing
- Loss of appetite
- Weight loss
- Lethargy
- Sudden loss of use of one or more legs (caused by a blood clot)
- Vomiting
- Sudden death
This condition is most commonly seen in middle-aged to older cats.
How is restrictive cardiomyopathy diagnosed?
The first indication that your cat has a heart complaint might be when your vet listens to their chest. The most common abnormality your vet might hear is a heart murmur, a small abnormal whooshing sound due to an unusual flow of blood in the heart. Sometimes a gallop rhythm or some other arrhythmia might be heard, which is an abnormal pattern of the heartbeats. However, in some cases, your cat’s heart may sound completely normal.
If your vet is suspicious of a heart problem, then the next step might be an echocardiogram. This is a non-invasive ultrasound examination of the heart, which allows the scanning vet to take measurements of your cat’s heart as well as see how well it beats.
Further tests may be required in some instances, including radiography (X-rays) which give an overall picture of your cat’s chest and can be helpful to identify fluid in the lungs. It also allows your vet to check for other issues like tumours.
Blood tests may be advised to rule out other disease processes that could be contributing to your cat’s symptoms. There are also specific blood tests which look for N-terminal pro-B type natriuretic peptide (NTproBNP) and cardiac troponin-I (cTnI). These are cardiac biomarkers, released if the heart muscle is under stress or strain. This test is useful if your vet is uncertain whether it is your cat’s heart causing their problems or not.
Electrocardiography (ECG) may be used in some animals to measure the heart’s electrical activity and blood pressure monitoring can be helpful too.
How is restrictive cardiomyopathy treated in cats?
Unfortunately, there is no cure for restrictive cardiomyopathy in cats, and treatment depends on what stage of the disease they are in. There is no standard consensus on what treatment cats should receive but it may be as follows –
Mild or asymptomatic cases
These cats may receive no therapy at this point
Cats that have no symptoms but evidence of left atrial enlargement
They may be treated with cat-safe doses of drugs like clopidogrel (a drug that reduces the risk of your cat developing blood clots) with or without aspirin (another drug that can help with blood clots).
Cats with evidence of congestive heart failure
Cases may be treated with diuretics such as furosemide which helps reduce fluid build-up, as well as an angiotensin-converting enzyme (ACE) inhibitor such as benazepril (which helps widen blood vessels and lower blood pressure, making things easier for the heart to pump against). Other drugs may be considered as well.
And cats with aortic thromboembolism (ATE)
Cats that have a thromboembolism (blood clot) blocking the flow of blood to their limbs will require emergency pain relief and medications like clopidogrel and aspirin. Physical therapy can also be helpful, but in many cases, the prognosis is very poor.
What is the prognosis for my cat?
Sadly, once diagnosed with restrictive cardiomyopathy the long-term prognosis for your cat is poor. This is considered an end-stage condition, with most cats developing clinical symptoms and deteriorating. In one study most cats died as a result of their heart disease within a year of diagnosis. As previously discussed, thromboembolism is also a big risk for these cats causing sudden issues like paralysis, strokes or even death.
You must administer any medication that your vet has recommended for your cat as this will help to improve their quality of life and potentially their longevity. If you have any questions about your cat’s condition then you must raise them with your vet, as each cat is different in terms of the stage of the disease they are at.
Final thoughts
Restrictive cardiomyopathy is a serious and life-limiting heart complaint. While some medications can help your cat, there is sadly no cure. Issues that can be seen with this condition, like breathing problems or sudden paralysis, are emergencies and you should contact your vet as soon as possible for help.
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