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What is Cardiomyopathy?

Cardiomyopathy is the word used to describe a disorder or disease that affects the heart muscle. In cats, it is the most common type of heart disease and is the main cause of heart failure.

What are the symptoms of cardiomyopathy?

Whilst most cats show very few or no symptoms whatsoever of heart disease in the early stages, there are some subtle signs of disease that your vet may pick up on physical examination. Murmurs (abnormal muffled sounds), arrythmias (unusual beats or rhythm) or an abnormally high or low heart rate are usually picked up on auscultation of the heart in cats with early cardiomyopathy.

As the disease progresses, the symptoms often become more noticeable by owners. At this stage, the disease is often advanced and more easily diagnosed. The symptoms of advanced disease usually involves an increase in respiratory effort (rapid breathing, panting etc), meowing or panting after being picked up around the chest (causing extra pressure on the thorax), pale gums, cold paws or ears and in extreme cases fainting episodes.

The best way to definitively diagnose cardiomyopathy, is to have a veterinary specialist perform a heart ultrasound (echocardiogram). The ultrasound is able to assess the inner structures of the heart, take measurements of the heart wall, ventricles and chambers, see the blood flow in and out of the heart as well as assessing how well it can contract.

What causes Cardiomyopathy?

Though there is no specific cause for heart disease in cats, there are several factors and pre-existing illnesses that can contribute to the type and degree of cardiomyopathy that may affect a cat. These factors can include:

• Breed predisposition (ie Maine Coon cats)
• Hereditary and genetic causes
• Nutritional – particularly with grain free diets and taurine deficiencies
• Exposure to certain toxins and drugs that effect the heart
• Excessive hormone production
• Overactive thyroid disease
• High blood pressure
• Lymphoma and other malignant tumours
• Other heart diseases – FIP, heartworm etc

Types of Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM): This is the most common form of the disease and is where the muscle wall becomes thickened. The heart wall muscle in cats’ averages 3-5mm in width, whereas cats with HCM, this value often increases to 1cm in width or higher. The heart is unable to relax properly between beats and gets tired easily. As the muscle wall is thickens, it makes the chambers smaller in size to accommodate which then reduces the volume of blood that can enter the heart at any one time and be pumped around the body.

Dilated Cardiomyopathy (DCM): Opposite to HCM, this type of cardiomyopathy is where the walls of the heart become dangerously thin thus allowing the heart to enlarge in size due to the increase amount of blood that can fill the structure. When this happens, the thin heart muscle cannot contract properly and move the blood around the body effectively.

Restrictive Cardiomyopathy (RCM): With this type of disease, the muscle of the heart turns stiff and fibrous. The muscle becomes hard and has little to no elasticity or movement. The heart is unable to fill and pump blood around the body as it is unable to contract and bounce back again. 

Treatment of Cardiomyopathy

Depending on the type of cardiomyopathy that a cat is suffering from, the treatment options may vary. It also depends if the cat has other underlying diseases such as thyroid disease that needs to be treated also. Whilst no medication to prevent the heart disease from progressing, there are some treatment options which may slow down the speed of progression and assist with the symptoms. Some medications that can be used include:

• Diuretics: help by drawing excess fluid away from the heart and lungs which can build up as the heart is unable push fluid around the body as well as it did before
• Pimobendan: helps the heart to contract which in turn improves blood flow to the body
• Beta-blockers: can help to slow the heart rate down which reduces the strain on the heart
• ACE-inhibitors helps to relax the veins and arteries which assists in lowering the blood pressure  

Life Expectancy

Prognosis is extremely variable depending on the type, symptoms and any underlying causes of the cardiomyopathy. Some cats may live for many more years with medications where as sadly, some cats may only have months.

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