Feline Heart Disease: Causes, Symptoms, and Treatment

(Photo by Elsa Noblet)

A Note from Dr. John:

Hopefully, when you say that your cat has a big heart, you’re talking about his disposition and not the actual size of his heart.  If it’s the former, lucky you!  If it’s the latter, this likely means that your cat has what is called Hypertrophic Cardiomyopathy.

What is Hypertrophic Cardiomyopathy?
Hypertrophic Cardiomyopathy, or HCM, is the most common cause of heart disease in the feline world.  Hypertrophic means “overgrowth” and cardiomyopathy means “disease of the heart.”  Together, you have a fancy way of saying that the heart is abnormally large.  This heart enlargement is caused by inappropriate thickening of the muscle that makes up the wall of the heart. When the walls of the heart get too thick, the heart ventricle is unable to fill appropriately.  This can lead to congestive heart failure, decreased blood pressure, formation of blood clots, and a myriad of other clinical signs.

What causes HCM?
Some cat breeds have gene mutations that cause HCM.  The most common breed to develop the disease is the Maine Coon cat, which has a gene mutation that causes abnormalities in the muscle fiber of the heart.  Ragdoll cats also have a similar gene mutation. Otherwise, HCM is a diagnosis of exclusion, meaning that other underlying causes of heart disease must be ruled out in order to leave you with the diagnosis of HCM.

Hyperthyroidism is the disease most commonly associated with the development of feline heart disease.  If hyperthyroidism is diagnosed and treated appropriately, the underlying heart disease should not progress.

What are the clinical signs of HCM?

The most common clinical sign of HCM in cats is rapid, shallow breathing.  Less common signs include coughing, vocalizing, and inability to use one or multiple legs.  HCM can also cause sudden death in seemingly normal cats.  This is typically due to a blood clot lodging in the heart, lungs, or brain.

How is HCM diagnosed?
HCM is diagnosed based on imaging studies- usually a combination of x-rays and an echocardiogram (an ultrasound of the heart).  X-rays can show an enlarged heart and congestive heart failure.  An echocardiogram allows your veterinarian to measure the degree of heart muscle thickening and to assess whether or not clots are present within the heart.  Blood work should also be checked to look for concurrent diseases.

How is HCM treated?
If HCM is secondary to another condition, (such as hyperthyroidism or hypertension),  then treatment is directed at the primary condition.  In cases of primary HCM, medications are administered daily to manage the existing clinical signs.  Diuretics, such as furosemide, are commonly prescribed for cats with increased respiratory rate and effort.  Beta blocks, such as atenolol, are often prescribed to help slow the heart rate and allow the heart to fill more efficiently.  Blood thinners, such as clopidogrel or aspirin, can also be prescribed.  These medications are typically lifelong treatments.

What is the long-term outlook?

Prognosis with HCM varies depending on the severity of the disease.  Mild disease can be controlled for long periods of time with minimal to no disease progression. Unfortunately, the opposite can also be true.  Severe cases can progress very rapidly. Cats that have entered congestive heart failure may live as little as three to six months. Complications associated with heart disease can be fatal and can even result in sudden death.

Take home message.
Contact your veterinarian if you notice any changes in your cat’s breathing patterns or any sudden changes in general demeanor.  While there are many conditions that can result in these clinical signs, it is best to have your veterinarian evaluate your cat for signs of heart disease.

Our information is not intended to replace the advice of your veterinarian.  Do not use this information for diagnostic purposes. Always take your pet to your veterinarian to obtain a diagnosis and course of treatment.