3 Dangers of an Enlarged Heart in Cats The Serious Risks of Cardiomegaly

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If your cat has been diagnosed with an enlarged heart, it's important to learn all that you can about this condition and the steps you can take to ensure that it doesn't cause additional serious health complications.

Cardiomegaly is a broad term used to describe any condition that causes an enlarged heart. A cat with an enlarged heart is at risk for developing several health problems, and as a pet parent, it is useful to be aware of the different types of cardiomegaly, the dangers, and what you can do to prevent and treat the condition. Read on to learn what you need to know.

2 Types of Cardiomegaly

There are two types of cardiomegaly:

  • Hypertrophic: The most common type of cardiomegaly, it is characterized by a thickening of the heart muscle tissue in response to a heavy workload. This type of cardiomegaly causes poor heart function and obstruction of blood flow. This can result in a buildup of fluid pressure in the lungs. And also the development of blood clots in the heart. Heart failure is common, as is paralysis if blood clots are present.

  • Dilative: Refers to a dilation, or enlargement, of the heart muscle tissue. Although relatively rare in cats, dilated cardiomyopathy is an example of this type of cardiomegaly. With DCM, the heart’s walls become flimsy and weak as the muscular tissue dilates, making it difficult for blood to flow forward from the heart. This often results in heart failure.

3 Dangers of an Enlarged Heart

Cats with cardiomegaly are at risk for developing several conditions. These are the 3 most common dangers of an enlarged heart in cats.

  • Congestive heart failure: This occurs when the cat’s heart is not able to adequately distribute blood throughout the body. When this happens, other body systems must take on some of the work and end up becoming easily overwhelmed, leading to a buildup of fluids anywhere in the body, but most often in the lungs. Fluid in the lungs causes congestion and makes it difficult for oxygen to enter the bloodstream. Shortness of breath and lethargy are the usual symptoms of this condition.


  • Thromboembolic disease: An enlarged heart results in abnormal blood flow, and this can increase the risk of developing a blood clot — or a thrombus — within the heart. This clot can travel down the aorta artery and become lodged at its base, which is known as the saddle. The saddle delivers blood to the cat’s hind legs, and if there is a clot, it becomes an obstruction that cuts off the blood supply. This extremely painful condition can affect one or both of the cat’s hind legs and results in paralysis. It can also cause circulatory shock and/or heart failure, which can be fatal.

  • Hypertension: Hypertension, or high blood pressure, is often a cause of cardiomegaly. Even when it is not the cause, cats with an enlarged heart are at risk of developing it. High blood pressure is when the blood moving through the body is being pushed too hard against the veins. For cats, this can result in several complications, including nosebleeds, hemorrhaging within the eye, retinal detachment, and sudden blindness.

Prevention and Treatment of an Enlarged Heart in Cats

Many cases of cardiomegaly are congenital, meaning that the enlarged heart is caused by structural problems that have been inherited and/or present since birth. Cardiomegaly can also be caused by certain health conditions, including hypertensionhyperthyroidismkidney failure, and in the case of dilated cardiomyopathy, a deficiency of the essential amino acid taurine. The best way to prevent cardiomegaly is to visit your vet for regular check-ups. Your veterinarian may be able to identify an enlarged heart and prescribe a supplement like Nordic Naturals Omega 3 before it causes serious health complications.

The treatment for an enlarged heart will depend on whether or not an underlying cause has been identified. If the cause of your cat’s enlarged heart is known, then that cause will be treated, and your cat’s condition will likely improve or be reversed entirely.

If the cause is not known (i.e., idiopathic), treatment will vary depending on your cat’s specific condition. Medications, including diuretics, beta-blockers, calcium channel blockers, and ACE inhibitors, can all improve heart function. Aspirin may be used to reduce the risk of blood clots, and drugs like Benazepril lower blood pressure in cases of hypertension.

Surgery may be appropriate for some cats with certain congenital heart defects.

Causes of Cardiomegaly

Cardiomegaly, or an enlarged heart, is a common condition in cats and can be caused by many things. Listed below are some of the most common causes:

Thyroid disease – Hyperthyroidism occurs when your cat's thyroid gland produces too much of the thyroid hormone thyroxine (T4). Symptoms include weight loss despite normal appetite, increased appetite despite normal weight, frequent urination, vomiting, diarrhea, anxiety, panting during exercise, rapid heartbeat, excessive thirstiness with excessive drinking at inappropriate times during the day, and excessive drinking late at night. And also with redness around the eyes due to dilated blood vessels in the head/face area. Your vet might prescribe Methimazole for cats in case there is a thyroid issue. Feliway makes products that can be used for anxiety. Feliway Diffuser and Feliway Optimum are good options. For nausea, there’s Cerenia for dogs and cats. 

Heart disease - Your cat's heart may not function properly because of congenital defects. Or from acquired diseases such as valvular insufficiency, myocardial infarction (heart attack), or dilated cardiomyopathy.

Heartworms -  These parasites are transmitted to your cat when he is bitten by an infected mosquito or flea. They can cause severe damage to your pet's heart and lungs if left untreated for long periods. You need to be aware of both heartworm prevention and heartworm medicine, commonly referred to as a cat dewormer. Interceptor, Interceptor Plus, and Drontal for cats are all good examples of a dewormer for cats.

Symptoms and Diagnosis of Cardiomegaly

Cardiomegaly is a fairly common condition in cats and can be caused by a range of underlying conditions. The symptoms of cardiomegaly include:

• Shortness of breath

• Coughing or wheezing

• Loss of appetite

• Lethargy (tiredness) or weakness

If you think your cat has cardiomegaly, it's important to schedule an appointment with your veterinarian right away. Your vet will perform a thorough physical examination and may recommend diagnostic tests such as chest X-rays, ultrasounds, or blood work. Sometimes an enlarged heart can also be detected on routine blood tests, so it's always a good idea to ask your vet if these are recommended for any new health issues you might notice in your pet.

Cardiomegaly can be a dangerous condition for cats. If your cat is showing signs of cardiomegaly, it’s important to take them to the vet as soon as possible. Your vet will be able to diagnose them and start treatment if needed. There are also some steps you can take at home, like increasing exercise and keeping an eye out for any changes in behavior or appetite, which may indicate that your kitty needs more medical attention than usual.

More on Heart Disease

How to Treat Heart Disease in Pets
Nutrition for Dogs and Cats With Heart Disease
Cat Heart Murmur Treatment Options

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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