Understanding Heart Disease in Cats: Types, Causes, and Complications

Heart disease in cats can have a variety of causes, including genetic factors, age, and other diseases. Many types of heart disease in cats progress over time, and often, regardless of type, cats do not show signs of disease until it is advanced. Some complications can be sudden and life-threatening, but with early diagnosis and treatment, many cats with heart disease can live for years.

Types of Cat Heart Disease

Heart disease in cats falls into two main categories:

• Congenital heart defects are present at birth and are less common in cats than dogs. Common types include leaky valves (mitral valve dysplasia or aortic stenosis or holes in the heart such as patent ductus arteriosus [PDA] or ventricular septal defect [VSD]). These are often suspected if a murmur is heard in a young cat and may cause poor growth, low energy, and exercise intolerance.
• Acquired heart disease develops later in life and includes conditions like cardiomyopathy or valve issues. Acquired heart disease is cats may also be primary, with no known cause, or secondary, resulting from other conditions like hyperthyroidism or high blood pressure.¹

Primary Heart Disease in Cats^1-3

Cardiomyopathy refers to diseases that affect the heart muscle itself. This is the most common type of heart disease in cats. It includes several forms:

• Hypertrophic cardiomyopathy (HCM). The most common type of cardiomyopathy. The heart muscle becomes thick, making it harder to pump blood.  
• Restrictive cardiomyopathy (RCM). The heart becomes stiff, reducing its ability to fill with blood.
• Dilated cardiomyopathy (DCM). The heart muscle becomes weak and stretched. This is now rare due to improved feline nutrition.
• Arrhythmogenic cardiomyopathy (AC). A very rare condition in cats, this form affects the electrical system of the heart and can lead to irregular heartbeats and heart muscle damage.
• Nonspecific. Some cats show heart changes that don’t match a specific type, often with enlarged upper chambers.
• Transient myocardial thickening (TMT). A rare, temporary thickening of the heart muscle, usually seen in younger male cats after stress, trauma, or corticosteroid administration. While the exact cause is still unknown, some experts believe it may be related to inflammation or swelling of the heart muscle. TMT often improves with time and care.

Sometimes, the valves of the heart do not function properly. This condition can allow blood to flow backward and strain the heart. Heart valve disease is less common in cats than in dogs but can still occur.

Secondary Heart Disease (Caused by Another Condition)^3-5 

These types of heart disease are caused by other health issues:

• High blood pressure (hypertension). High blood pressure can strain your cat’s heart, causing the heart muscle to thicken and sometimes affecting the heart valves. This may lead to abnormal heart sounds like murmurs or gallops. While heart failure from high blood pressure is rare, it can occur, especially with certain treatments like IV fluids. With proper medication, some heart changes may improve.  
• Thyrotoxic heart disease. Caused by hyperthyroidism, a common condition in older cats. The high levels of thyroid hormone make the heart work too hard, which can lead to thickening of the heart muscle and eventual heart failure.4
• Heartworm disease. Heartworm disease, although more common in dogs, can affect cats as well. In dogs, it mainly affects the heart, but in cats, it mainly affects the lungs, causing coughing, breathing problems, or sudden collapse, even with just a few worms. For cats, there is no approved cure, so monthly prevention recommended by your veterinarian is the best protection.
• Acromegalic heart disease. Rare in cats, this is caused by excessive growth hormone due to a condition called hypersomatotropism. It can lead to changes in the heart muscle over time.
• Medication effects on the heart. Some medications can affect a cat’s heart. One example is doxorubicin, a chemotherapy drug that has been linked to heart damage in some cats. Corticosteroids, often used to treat inflammation, have also been associated with triggering heart failure in cats with underlying or undiagnosed heart disease.

What Causes Heart Disease in Cats?

In many cats, the exact cause of heart disease is not always known. Factors such as genetics and breed, age, nutrition, and environment can play a role in the development of heart disease in your cat.

Genetics and Breed

Genetics and breed may play a role in several types of heart disease in cats. HCM can affect any cat, but certain breeds are more likely to develop it. These include American and British shorthairs, Bengals, Birmans, Chartreux, Himalayans, Maine Coons, Norwegian Forest Cats, Persians, Ragdolls, Scottish Folds, Siberians, and Sphynxes.^2,3,6

Genetic mutations linked to HCM have been found in certain breeds. However, not all cats with these mutations develop HCM, and some without them still do.^6-8

Ask your veterinarian if your cat would benefit from genetic testing or heart screening. 

Age-Related

So how common is heart disease in cats? Heart disease is especially common in senior cats, where conditions like hypertrophic cardiomyopathy occur more frequently, even without other health problems.2,9 In older cats, other age-related conditions such as high blood pressure or hyperthyroidism can also put extra strain on the heart, potentially leading to heart disease or heart failure if not managed.

Nutritional

Taurine is an essential nutrient for cats. It plays an important role in heart health and helps the heart muscle contract properly. Previously, a lack of enough taurine in cat food was a common cause of heart disease. Today, this condition is not as common because high-quality cat foods now include the proper amount of taurine to keep cats healthy.¹

Environmental

Your cat’s environment can also play a role in heart health. Ongoing stress may put strain on the heart, especially in cats with underlying heart conditions. In some cats, especially those with hidden or early heart disease, a stressful event can suddenly trigger heart failure. Situations like surgery, undergoing anesthesia, or receiving intravenous (IV) fluids may cause heart strain.³

Heartworm disease is spread by mosquitoes and can affect indoor as well as outdoor cats. Using year-round heartworm disease prevention is an important step in supporting your cat’s health.5 As previously mentioned, even though this disease tends to cause heart issues in dogs, with cats it usually affects their lungs. If you notice any respiratory issues, contact your veterinarian as they will be the best person to check for heartworm disease or any other underlying conditions. 

Common Consequences of Heart Disease in Cats⁴

Two of the most serious complications of feline heart disease are arterial thromboembolism (ATE) and congestive heart failure (CHF). Both ATE and CHF in cats are life-threatening and require immediate veterinary attention.

ATE happens when a blood clot forms in the heart and travels to a smaller artery, most often blocking blood flow to the back legs. This causes sudden pain, weakness, or even paralysis. Cats may cry out, drag their legs, or seem unable to walk. ATE is often linked to HCM.

CHF occurs when the heart can no longer pump blood effectively, leading to a buildup of fluid in or around the lungs. This can cause labored or rapid breathing, lethargy, or a decreased appetite. In some cases, fluid may also collect in the chest or abdomen.

Contact your veterinarian right away if your cat shows any of the following:

• Rapid or labored breathing
• Open-mouth breathing or panting when not anxious or hot, and not typical for your cat
• Sudden weakness or collapse
• Inability to use the back legs or dragging one or both legs
• Signs of pain, especially in the back or hind limbs
• Severe lethargy or unresponsiveness

Talk to your veterinarian to better understand your cat’s condition, expected disease progression, and prognosis.

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References

1. Kittleson MD, Côté E. The Feline Cardiomyopathies: 1. General concepts. J Feline Med Surg. 2021;23(11):1009–1027.

2. Fuentes VL, Abbott J, Chetboul V, et al. ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. J Vet Intern Med. 2020;34(3):1062–1077.

3. Kittleson MD, Côté E. The feline cardiomyopathies: 2. Hypertrophic cardiomyopathy. J Feline Med Surg. 2021;23(11):1028–1051.

4. Tilley LP, Smith FWK, Sleeper MM, Kraus MS. Manual of Canine and Feline Cardiology [e-book]. 6th ed. Elsevier; 2025.

5. Nelson CT, McCall JW, Moorhead A, et al. American Heartworm Society Feline guidelines for the prevention, diagnosis, and management of heartworm (Dirofilaria immitis) infection in cats. 2024. 

6. Fries R. Hypertrophic cardiomyopathy–advances in imaging and diagnostic strategies. Vet Clin North Am Small Anim Pract. 2023;53(6):1325–1342. 

7. Longeri M, Ferrari P, Knafelz P, et al. Myosin‐binding protein C DNA variants in domestic cats (A31P, A74T, R820W) and their association with hypertrophic cardiomyopathy. J Vet Intern Med. 2013;27(2):275–285.

8. Turba ME, Ferrari P, Milanesi R, et al. HCM‐associated ALMS1 variant: allele drop‐out and frequency in Italian Sphynx cats. Anim Genet. 2023;54(5):643–646.

9. Payne JR, Brodbelt DC, Fuentes VL. Cardiomyopathy prevalence in 780 apparently healthy cats in rehoming centres (the CatScan study). J Vet Cardiol. 2015;17:S244–S257.