Heart Muscle Disease in Cats
The heart has four chambers: two chambers at the top, the right and left aorta; and two chambers on the bottom, the right and left ventricles. Dilated cardiomyopathy (DCM) is a heart disease that affects the ventricular muscle. It is characterized by dilated, or enlarged heart chambers, and reduced contraction ability. That is, a reduced ability to push blood out of the respective ventricle. DCM causes the heart to become overloaded, and will often lead to congestive heart failure. Before 1987, DCM was one of the most common heart diseases in cats. This is suspected to have been related to a dietary deficiency of the amino acid taurine. DCM in cats is now relatively rare, since most cat food manufacturers began adding taurine supplements to their foods, further confirming the relationship.
Some breeds, such as the Burmese, Abyssinian, and Siamese, are more commonly affected by DCM. The disease will usually affect cats between the ages of 2 to 20 years, but the average age of onset is ten years old.
Symptoms and Types
Cats suffering from reduced cardiac blood flow due to DCM will exhibit symptoms of depression, loss of appetite, and weakness. Reduced flow due to blockage of a blood vessel, thromboembolism, may be apparent as sudden onset of pain and partial paralysis (paraparesis). A physical exam may discover a low, high, or normal heart rate, a soft heart murmur, a galloping rhythm, hypothermia, a weak left cardiac impulse, and quiet lung sounds.
While taurine deficiency greatly contributed to the onset of secondary feline DCM in the past, the underlying cause in the majority of DCM cases today remains unknown. In some families of cats, a genetic predisposition has been identified.
In addition to a thorough physical examination of the heart, certain medical tests are needed to diagnose DCM and exclude other diseases. An electrocardiogram (or EKG) recording can be used to examine the electrical currents in the heart muscles, and may reveal any abnormalities in cardiac electrical conduction (which underlies the heart’s ability to contract/beat), and can also help your veterinarian to determine the origin of the abnormal heart rhythms, if they are present. X-ray imaging of the chest (thoracic radiographs) may reveal heart enlargement and accumulated fluids in the chest. Echocardiograph (ultrasound) imaging is required for a confirmed diagnosis of DCM. This test will enable your veterinarian to visually examine the size of the heart and the ability of the ventricular muscle to contract. An echocardiograph may reveal thin ventricular walls, an enlarged left ventricle and left atrium, and low contraction ability, confirming a diagnosis of DCM.