There are three general types of heart muscle disease that affect cats, all of which greatly compromise the cat's health because they result in the heart being unable to pump blood properly. Each of these diseases is serious, but affected cats often can be managed for long periods with appropriate medication. Also, with early detection and the initiation of preventive health strategies, a veterinarian can greatly improve the cat's quality of life.
One form of feline heart muscle disease, called dilated cardiomyopathy, occurs when the heart chambers become big and dilated, like a "flabby balloon." With dilation, the heart muscle is often weakened dramatically so that it cannot contract with the normal amount of force. This disease was very common before it was recognized that the majority of cases were due to a dietary deficiency of the amino acid taurine. Since commercial diets now adequately are supplemented with taurine, this disease is uncommon.
Hypertrophic cardiomyopathy, the most common form of feline heart muscle disease, occurs when the lower left chamber of the heart, called the left ventricle, thickens and stiffens, while the top left chamber, the left atrium, enlarges. This thickened left ventricle does not leave much room in the chamber to fill with blood. Thus, smaller than normal amounts of blood are pumped out of the heart with each contraction. Additionally, this thickening of the heart muscle increases the heart's own consumption of oxygen, which is needed to supply the additional muscle present. If these oxygen demands are not met, then cell death occurs and leads to areas of scarring in the heart muscle.
A third form of heart disease is called restrictive cardiomyopathy. It also has been called intermediate cardiomyopathy because it has characteristics of both dilated and hypertrophic cardiomyopathy. With this form of the illness, the walls of the cat's heart develop fibrosis, which is the replacement of normal heart tissue with scar tissue that does not function as well. This scarring makes the heart stiff and less effective as a pump.
Occasionally, cats with heart disease will develop a condition that leads to complete or partial paralysis of their back legs. With rapid attention, this condition sometimes can be treated, but more often than not, affected cats will die or be put to death humanely.
