In cardiomyopathy, your cat's heart muscle becomes either thicker or thinner than normal.  This can be the primary problem, or it can be secondary to other illnesses such as kidney failure, dietary deficiency, or hyperthyroidism.  Hyperthyroidism is one of the most common causes of cardiomyopathy in middle-aged to older cats.

Cats in the early stages of disease may not have any signs at all.  As the disease progresses, cats develop signs consistent with three particular types of problems:

Congestive heart failure:  Congestive heart failure is the most common form of illness associated with cardiomyopathy (see also Heart disease).  The heart cannot efficiently pump blood, so cats become listless and tire easily.  Fluid can build up in the chest, causing difficult breathing and coughing, or in the abdomen, which may appear bloated.

Thromboembolic disease:  The changes in the heart muscle result in changes in the blood flow within the heart.  This increases the risk of a blood clot, or thrombus, forming, which can travel into smaller blood vessels and block the flow of blood to important organs.  When the blood clot, or thrombus, travels into the bloodstream, then it is called an embolus.  These emboli commonly lodge at the end of the cat's aorta, where it branches into the two main arteries that provide the blood supply to the rear legs.  This very painful condition, known as a saddle thrombus, causes paralysis in the rear legs and (often) death.

Hypertension:  High blood pressure, or hypertension, often develops when the heart muscle is thickened.  It can cause spontaneous bleeding, such as nose bleeds or bleeding within the eye, which can lead to retinal problems and blindness.  It is difficult to measure blood pressure in cats, so hypertension is often diagnosed only after problems have developed.

A tentative diagnosis of heart disease can be based on signs of illness, but a more definite diagnosis requires chest x-rays, an electrocardiograph (ECG), and an echocardiogram.  Examination of the blood vessels of the retina (in the eyes) may show changes, including small areas of bleeding that can be an early indication of hypertension.  Other specific tests may be needed to determine if cardiomyopathy is secondary to another disease.

Treatment involves correcting any underlying problems, as well as treating the specific type of cardiomyopathy that has developed.  A number of medications may be needed, including those to reduce blood pressure, the workload on the heart, the risk of blood clots, and the heart rate.  Other medications affect the contraction of the heart itself.  A low-salt diet may also be part of treatment.  Your veterinarian will recommend an appropriate treatment plan depending on your cat's specific clinical situation.  Remember that you should never give any medications to your cat unless specifically instructed by your vet.

The long-term outlook for a cat with cardiomyopathy depends on the underlying cause and the severity of the problem.  With proper treatment, some cats remain stable for several years.

Q&A

What is cardiomyopathy in cats?

Cardiomyopathy translates literally to “disease of the heart muscle.”  The heart muscle is weakened and may be thicker or thinner than normal, depending on the underlying problem.

What causes cardiomyopathy in cats?

Cardiomyopathy can be a primary problem, but often occurs secondary to other illnesses such as kidney failure, dietary deficiency, or hyperthyroidism. 

Are there different types of cardiomyopathy in cats?

Feline cardiomyopathy can show up as three distinct forms: congestive heart failure, thromboembolic (ie, blood clot) disease, or hypertension (ie, high blood pressure).  The most common form is congestive heart failure, in which the weakened heart cannot efficiently pump blood, leading to fluid build up in the chest or abdomen. 

How is cardiomyopathy in cats diagnosed?

A tentative diagnosis can be based on signs of illness, but a more definite diagnosis requires an electrocardiograph (ECG) and/or medical imaging (eg, X-rays).

Written and reviewed by John A. Bukowski, DVM, MPH, PhD
and Susan E. Aiello, DVM, ELS