Feline Heart Disease

What kinds of heart disease do cats get?

Most cats with heart disease have a form of cardiomyopathy, which is a disease of the heart muscle:

Cardio = heart
Myo = muscle
Pathy = disease

In comparison, dogs generally develop problems with their heart valves (e.g. mitral valve insufficiency) or the lining of the heart (endocarditis). People can develop cardiomyopathy, valve disease, endocarditis and other cardiac conditions.

There are four types of cardiomyopathy in cats:

Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Dilated Cardiomyopathy
Unclassified Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM)

Hypertrophic Cardiomyopathy is by far the most common heart disease diagnosed in cats. In HCM, the heart muscle becomes very thick. The thick muscle causes two problems: 1. the heart does not relax easily, so it cannot accept the entire amount of blood; and 2. the thick muscle is overactive and pumps too quickly. It can also pump irregularly resulting in a cardiac arrhythmia. HCM is generally considered to be hereditary in cats. Certain breeds are prone to HCM. These include Maine Coons, Persians, and Ragdolls. There is a DNA test for HCM now available for Maine Coon cats.

Restrictive Cardiomyopathy (RCM)

Restrictive Cardiomyopathy is being recognized more frequently in cats. This condition results in fibrous (scar) tissue forming in the heart muscle which causes it to be stiff and less flexible. This results in poor pumping ability of the heart. The cause of RCM is unknown in cats.

Dilated Cardiomyopathy (DCM)

Dilated Cardiomyopathy is rare these days. It was diagnosed frequently until the late 1980’s when it was discovered that a deficiency of taurine (an amino acid) in a cat’s diet resulted in this disease. DCM is characterized by very thin walls that pump very weakly. It is almost the opposite of HCM. Since the 1980’s, most commercial cat food produced in the U.S. is adequately supplemented with taurine. We still see DCM sometimes, but it is usually not due to a taurine deficiency.

Unclassified Cardiomyopathy

Unclassified Cardiomyopathy is the term used for heart muscle disease that does not fit into any of the other categories.

Other causes of heart disease in cats are less common and include: congenital abnormalities, infections, valve defects, and cancer.

How do I know if my cat has heart disease?

Heart disease may be suspected if your veterinarian hears a heart murmur or an arrhythmia while examining your cat.

A heart murmur is an abnormal sound made during the heart beat. Blood normally flows in a smooth route through the heart. When the heart is diseased, this causes the blood to flow abnormally, either with turbulence or the wrong way through a heart valve (“leaky valve”), both of which result in a murmur.

An arrhythmia is an irregular beating of the heart. Just like us, cat hearts have a normal, regular beat (i.e. lub-dub, lub-dub). When your veterinarian hears an irregular beating of the heart (e.g. lub-dub-dub, lub-lub-dub), this is called an arrhythmia.

More severe signs of heart disease may be detected at home:

One sign is breathing rapidly or with difficulty. This is caused by the inability of the heart to pump blood effectively, so that it backs up into the lungs resulting in fluid accumulation in the lungs. This is called congestive heart failure.
Another sign is paralysis of one or more legs, most commonly the rear legs. This is caused by a blood clot lodging in the main artery to the leg and preventing blood from getting to that limb. This is called aortic thromboembolism.
Both of these are emergencies and your cat should be seen be a veterinarian as soon as possible.

In some cats, just like in some people, there is no sign of heart disease. The heart sounds normal through the stethoscope and there are no symptoms at home. (In one recent study, 68% of cats with cardiomyopathy did not have a heart murmur.) These cats may die without warning (similar to cardiomyopathy in young human athletes).

Cardiomyopathy is usually diagnosed in middle-aged cats, but can be found in kittens as young as 6 months.

What tests are run to determine the cause?

Heart murmurs and arrhythmias indicate that there is a problem with the heart, but do not indicate the precise problem. Other tests need to be run to determine the specific form of heart disease and determine treatment. These tests include:

Echocardiogram – an ultrasound of the heart. This test allows us to look inside the heart, see it pumping, monitor the blood flow, evaluate the valves, and measure the thickness of the heart walls. This is the most important test because in almost all cases we can make a diagnosis from the “echo”.
Chest radiographs – x-rays of the heart and lungs. Radiographs tell us about the size of the heart and whether heart failure is present (fluid in the lungs or chest cavity).
Electrocardiogram (ECG) – measures the electrical impulses in the heart. This test is used most commonly for cardiac arrhythmias.
Blood pressure. Some cats with heart disease have hypertension. Hypertension may be the cause of the heart disease or a result of it.
Blood chemistries and complete blood count. These test for hyperthyroidism (a common cause of heart disease) and for secondary problems from heart disease.

At Cat Care Clinic, we call do all of these tests in our clinic. To help ensure the correct diagnosis and best treatment, we consult with a cardiologist for both the echocardiograms (echo’s) and the electrocardiograms (ECG’s).

What happens if my cat gets heart disease?

Some cats with mild heart disease are stable and live a normal life. Other cats with moderate or severe disease may develop complications from their heart disease. It is difficult and sometimes impossible to predict which cats will develop complications and which will not. The most common complications seen are:

Congestive heart failure (CHF)

Heart failure means the heart has lost the ability to pump blood effectively throughout the body. As a consequence, the veins become over full and fluid leaks out of the veins into other parts of the body. In cats, the excess fluid is usually found in the lungs or floating free in the chest cavity around the lungs. Any form of cardiomyopathy can lead to CHF.

CHF is suspected when your cat has difficulty breathing (rapid breathing, breathing with the mouth open, blue mucous membranes) and it is diagnosed by radiographs (x-rays). Treatment consists of medications to reduce the amount of fluid in the body (diruetics, vasodilators) and sometimes drawing the fluid off of the chest with a needle and syringe.

CHF is a life-threatening condition. Your cat needs to be seen by a veterinarian as soon as possible if you suspect your cat has CHF.

Thrombus

A thrombus is a blood clot. When the heart is diseased, blood does not flow freely through it, and slow-flowing blood will form a clot. These clots can then be expelled from the heart as it pumps, and they can lodge in critical arteries, such as arteries to the lungs, kidneys, intestines, legs, or to the heart itself.

A common place for a clot to lodge is at the end of the aorta (the main blood vessel exiting the heart). When this happens, blood flow is blocked to the rear legs and a cat can become paralyzed. This is an excruciatingly painful condition and your cat should be seen by a veterinarian immediately.

A thrombus is difficult to treat, but some cats can recover. However, once a cat develops a clot, they are more likely to get another one even if they are treated.

Although all forms of cardiomyopathy can lead to clot development, cats with more severe heart disease are more prone to clots. An echocardiogram is the best test to see if your cat has heart disease severe enough to lead to clots. Sometimes clots can even be seen inside of the heart with the echo.

Hypertension

Hypertension is high blood pressure. As a complication of heart disease, it is most commonly seen with HCM. Blood pressure in cats is measured using a pediatric blood pressure cuff and a doppler monitor. If left untreated, hypertension in cats can lead to blindness, kidney damage, neurologic damage, and/or worsening of heart disease.

What is the treatment for cardiomyopathy?

There is no cure for cardiomyopathy. Treatment consists of oral medication, most of which is life-long.

The medicine depends of the form of cardiomyopathy. Most medicines used for cat heart disease are actually human heart drugs. The most commonly used medicines are beta-blockers used to slow the heart rate (e.g. Tenormin), calcium channel blockers for relaxing the heart muscle (e.g. Cardizem, Norvasc), ace-inhibitors to ease the effort of pumping (e.g. Vasotec), and diuretics to reduce amount of fluid (e.g. Lasix).

These medicines usually come in pill form, but any of them can be formulated into a liquid if that is easier for your cat to take. Most of these medicines will be life-long.

What is my cat’s prognosis?

Your cat’s prognosis generally depends on the form and severity of his/her heart disease, although in many cases, the progression of heart disease is hard to predict.

Most cats with mild disease will live a normal life, but in rare instances, they can die suddenly without warning.
Cats with moderate heart disease are the most difficult to predict. Some can live for years; others will develop complications and die within weeks to months. They can also die without warning.
Cats with severe disease generally have a poor prognosis. These cats usually don’t live longer than six months after diagnosis.

What should I look for at home?

As an owner of a cat with cardiomyopathy, you should be very sensitive to changes in your cat’s condition and should not hesitate to call our office if you are concerned. We will show you how to monitor your cat’s respiratory (breathing) rate at home because an increased rate may be a sign that a problem is developing. Cats with heart disease do not cough like dogs or people, but often exhibit open-mouth breathing or panting.

Call your veterinarian if you observe any of the following:

Difficult or rapid breathing
Collapse
Paralysis of any leg
Not eating