When the heart can’t deliver enough blood to the body and fluid consequently backs up into a cat’s lungs, it’s called congestive heart failure. There are many causes of congestive heart failure in cats. Most commonly it results from a condition that causes the walls of the heart to thicken (hypertrophic cardiomyopathy), but it can also be brought on by thyroid disease, high blood pressure, or birth defects, among other possibilities.

A cat with congestive heart failure may have trouble breathing, may be weak or tired, might refuse to eat, and could die suddenly. Depending on the underlying problem, treatment may help reverse congestive heart failure, and there are medications to reduce symptoms


Congestive heart failure is a broad medical term that means that a cat’s heart can’t deliver enough blood to his or her body. It can be caused by a failure of the left side, right side, or both sides of the heart.

When the heart starts to fail in its ability to pump adequate amounts of blood, the body can usually compensate to ensure that tissues receive the blood and oxygen they need. As the heart disease increases in severity, however, these compensatory mechanisms become overwhelmed. The heart is then unable to pump enough blood to the body so that the fluid backs up, most often into the lungs. This causes congestion of the lung tissue –– hence the term congestive heart failure.

Though many conditions can lead to congestive heart failure in cats, one of the more common causes is hypertrophic cardiomyopathy. In this condition, the muscular walls of the heart become so thickened that they are unable to stretch and fill with adequate amounts of blood to pump to the body. As a result, fluid will back up into or surround the lungs, making breathing difficult. Fluid may also back up into the abdomen, but this is less common in cats than in dogs who suffer similar cardiac conditions.

Other causes of congestive heart failure in cats include:

  • Hyperthyroidism
  • High blood pressure
  • Heart valve deficiencies or blockages
  • Defects in the heart walls
  • Fluid in the sac surrounding the heart
  • Blood clots within the heart
  • Heart rhythm abnormalities
  • Heartworm disease
  • Tumors
  • Anemia (low numbers of red blood cells)
  • Pregnancy
Congestive heart failure can occur at any age, in any breed, and in cats of any gender, but it happens most often in middle-aged to older cats.

Symptoms and Identification

In the early stages of congestive heart failure, cats might show no signs at all. As the disease progresses, signs can include:

  • Difficult or rapid breathing
  • Blue or gray gums or tongue
  • Loss of appetite
  • Weakness or lethargy (tiredness)
  • Collapse
  • Hind limb paralysis
  • Sudden death
Congestive heart failure is usually diagnosed based on symptoms and physical examination findings, in which fluid in the lungs causes them to sound congested when your veterinarian listens with a stethoscope. To definitively diagnose the condition and determine its cause, veterinarians will usually recommend a number of tests, such as:

  • Blood and urine tests, including CBC, biochemical panel, thyroid hormone test, heartworm test, FeLV/FIV test, and urinalysis
  • Chest radiographs (X-rays) to assess the heart, blood vessels, and lungs
  • An electrocardiogram (ECG)
  • An echocardiogram (an ultrasound exam to evaluate heart structure and function)
  • Blood pressure measurement
Referral to a veterinary cardiologist may be recommended.

Affected Breeds

All cat breeds may be affected by congestive heart failure, but Maine Coon cats may be genetically predisposed to certain types of CHF.


In some cases, such as congestive heart failure that is caused by hyperthyroidism, treatment of the underlying condition may resolve some or all of the heart problems. If the problem is caused by a congenital condition (a heart defect that the cat has had since birth), surgical repair may be an option. In most cases, however, the problem cannot be cured. Nonetheless, treatment can almost always help improve cats’ quality and length of life.

Cats with severe congestive heart failure may require initial hospitalization and oxygen therapy. If fluid surrounds the lungs (pleural effusion) or is found in the sac surrounding the heart (pericardial effusion), it may need to be removed to improve breathing and help the heart pump more efficiently.

There are plenty of medications veterinarians recommend to help reduce fluid buildup, improve heart function, and/or normalize heart rhythms. A low-sodium diet may also be recommended to help prevent fluid accumulation.

Most cats with congestive heart failure require medications for the remainder of their lives. Periodic blood tests, radiographs, and echocardiograms are often needed to monitor treatment success and disease progression.


There is no known means of prevention of feline congestive heart failure except through judicious breeding programs designed to eliminate any hereditarily affected animals from the gene pool.

This article has been reviewed by a Veterinarian.