FELINE CARDIOMYOPATHY
CARDIOMYOPATHY
is a disease of the heart muscle which results from either a very thickened heart muscle (resulting in very small heart chambers) or a very dilated (stretched) heart muscle (with very large heart chambers). These two forms are called restrictive and dilatative cardiomyopathy. Both forms result in a heart that is unable to function properly in pumping blood throughout the body. Symptoms of heart failure may occur gradually, but since the cat is very good at hiding symptoms of heart disease the first sign an owner may notice is a sudden onset of labored, open-mouth breathing or collapse. Since most cats sleep much of the day and are often not very active, owners may miss early symptoms such as tiring easily or breathing harder with exercise than is normal.Causes of cardiomyopathy are often unknown, but the following medical problems have been identified:
TAURINE DEFICIENCY. Taurine is an essential amino acid that was not identified as such until the 1980’s. It was found to be lacking in many commercial cat foods at that time. Since being identified as a problem, cat food manufacturers have corrected this dietary deficiency, so it is rare today to see cardiomyopathy caused by lack of taurine unless the cat has been on an inadequate diet. Dog food is not supplemented with taurine as cat foods are, so dog food should never be a major part of a cat’s diet.
HYPERTHYROIDISM, a condition resulting from elevated thyroid hormone levels, can also cause the problem.
Cardiomyopathy may also be inherited. It seems to be more prevalent in certain breeds and family lines of cats.
In most cases an actual cause of the disease is not identified.
Cardiomyopathy develops slowly over a long period of time before clinical signs become evident. Although older cats can get the disease, it is most frequently diagnosed in young cats who had previously appeared perfectly healthy to their owner. As we stated, cats have the ability to hide the disease until the very late stages. For this reason, most cases are not discovered until late in the disease process, when treatment is not as effective. Screening tests, such as an annual or pre-anesthetic EKG test or blood pressure screening, are a great way to catch this disease early, before symptoms appear. Cardiomyopathy, as with many diseases, is most treatable in the early stages, before damage is severe.
EARLY SIGNS include inactivity, often not noticed by the owner, and poor appetite. Severe signs of heart failure don’t usually become evident until just before death. The major sign of heart failure in the cat is labored breathing. Labored breathing occurs because of the inability of the heart to pump blood to the body, as well as accumulation of fluid in the lungs. Panting or open mouth breathing in a cat is a red flag that should prompt you to call your veterinarian or head for an emergency hospital immediately.
A major complication of this cardiomyopathy is the tendency to develop BLOOD CLOTS in the heart chambers. These blood clots escape the heart and travel through the arteries until reaching a point too small for them to continue. The clot then obstructs blood flow to the rest of the body from that point on. The most common location of this obstruction is where the aorta, the major blood vessel leaving the heart, splits to go down each rear leg. When this happens, the cat is suddenly in great pain and becomes quickly paralyzed in the rear legs. This is the first sign of cardiomyopathy in many cats-and often the reason the cat is brought to the veterinary clinic.
DIAGNOSIS is confirmed by an ECG, chest radiographs (x-rays) and, most importantly, an ultrasound (sonogram) of the heart called an echocardiogram. Although the dilatative form of cardiomyopathy appears as an enlarged heart on an x-ray, the restrictive cardiomyopathy heart is often normal in size and shape on a radiograph. In the future, as ultrasound equipment becomes less expensive and more available, routine screening echocardiograms will probably lengthen the lives of millions of cats by earlier diagnosis of the disease.
TREATMENT will not cure the condition but may prolong the quality of life for the cat for quite some time. Treated cats have lived 3 years after diagnosis. Treatment is directed at helping the heart function better, with less effort. Your cat will need frequent rechecks by your veterinarian to monitor the disease and its treatment. Medications must be given on a regular basis at the appropriate times and may include:
- Diuretics to remove excess fluid
- Medications to dilate the arterial walls making it easier for the blood to flow
- Blood thinners
- Heart stimulants
- Salt-restricted diets
If a blood clot is present, pain medication is needed and the prognosis for recovery is guarded. Cats are too small for the techniques used to remove blood clots in humans and clot-busting drugs like TPA have not been used or tested in cats. Intensive care may be needed for many days.
