One of the most common diseases of the most popular purebred cats: hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. About one in seven cats may develop it in their lifetime.

In the following article we will discuss the characteristics, causes, symptoms, treatment and prevention of hypertrophic cardiomyopathy in cats.

What is hypertrophic cardiomyopathy?

Like the human heart, the cat’s heart is made up of four chambers: two smaller chambers at the top, the left and right atria, and two larger chambers at the bottom, the left and right ventricles. The right atrium is responsible for pumping oxygen-depleted blood from the body to the right ventricle, which transports the blood to the lungs to be oxygenated and used by the body and to release carbon dioxide, which is then disposed of. The left atrium is responsible for pumping oxygenated blood from the lungs to the left ventricle, which then pumps the blood back into the body, allowing cells and organs to function properly. Because the left ventricle has to pump oxygenated blood to the body, its muscular walls are thicker than those of the right ventricle.

When the walls of the left ventricle become enlarged and overly thickened, hypertrophic cardiomyopathy develops. The narrowing of the left ventricle’s interior caused by this muscle thickening prevents it from filling properly and reduces its efficiency. Thus, less oxygenated blood can reach the body in one heartbeat than in a healthy heart, resulting in the heart beating faster than normal. This increased workload increases the oxygen demand on the heart muscle, which can also interfere with heart function.

This is the cause of hypertrophic cardiomyopathy in cats

One of the most common causes is congenital heart muscle disease. This is often linked to a genetic predisposition to HCM, which is present in many cat breeds, including:

• the Maine coon;
• the Persian;
• the Ragdoll;
• the Chartreux ;
• the Sphinx;
• the Norwegian Forest Cat;
• the Bengal;
• the Turkish van-cat;
• the American shorthair;
• and the British shorthair.

These breeds are the most affected because they are more likely to carry a gene mutation called A31P, which is responsible for maintaining heart muscle health. In addition to genetics, there are a number of medical reasons for the disease. Hormonal conditions such as hyperthyroidism or acromegaly, which stimulates the growth of the muscular walls in the left ventricle. Cancer in the heart can also increase the size and thickness of the left ventricle walls. Other diseases not related to the heart, such as kidney disease, can cause high blood pressure in the body, putting extra strain on the left ventricle as it works harder than normal to pump blood to the body into blood vessels with elevated pressure. Over time, this increased effort thickens the walls of the ventricle and narrows the inner chamber.

Symptoms of HCM

• Loss of appetite;
• heart murmurs;
• abnormal heart rhythm;
• blood clots, which can cause pain, i.e. excessive vocalisation, difficulty walking, cold hind limbs, vomiting and difficulty breathing;
• heart failure;
• fluid in the lungs that can cause breathing difficulties and wheezing;
• difficulty breathing;
• fluid in the abdomen that causes visible abdominal swelling;
• the colour of the gums is pale, grey or blue;
• blue insoles and nail beds;
• a weak or unstable pulse;
• tiredness during play or exercise;
• lethargy and weakness;
• fainting and collapse;
• sudden death.

Treatment of hypertrophic cardiomyopathy

There are several medicines that can help treat cats suffering from the disease. In addition to medication, some cats also have a routine procedure to remove excess fluid accumulated in the lungs. Cats who develop severe, acute HCM and heart failure may require hospital oxygen therapy. Anxious cats may be given sedatives as stress can cause breathing difficulties and increase the risk of heart failure.

Unfortunately, there is no definitive cure for HCM. Asymptomatic cats can live a normal lifespan, but the disease usually worsens over time. Once symptoms appear, cats usually have about 2 years to live. Cats that develop blood clots, heart failure and/or low body temperature usually have a shorter survival time; this may be 6 months or less.

It is important to provide the cat with as calm an environment as possible. Make sure there are several undisturbed, quiet, comfortable places in the home where they can rest. Diet is another important factor that can improve the quality of life for cats with HCM. As the disease can cause a loss of appetite, it is essential that the kitten is fed a high quality, tasty, protein-rich diet. Furthermore it is important that cats taking heart failure medication may lose too much vitamin B through their urine and may need vitamin B supplementation.

It is critical in this situation that you work closely with your vet to determine what is best for your pet.

Treatment of HCM

Because HCM can be inherited or be the result of other medical conditions, the disease is difficult to prevent. Responsible breeders should test susceptible cat breeds for the A31P gene mutation to ensure that breeding stock individuals do not pass on two mutated gene copies.

General care and proper nutrition for all cats can do much to support heart health and prolong the symptom-free phase of HCM. Annual screening is particularly important for cats at higher risk. These include older animals and those that show a predisposition to the disease.