When the heart muscle functions abnormally, it is called a cardiomyopathy. There are three types of cardiomyopathies seen in dogs and cats, all of which decrease the heart's ability to pump the blood around the body.

The most common cardiomyopathy in cats is hypertrophic cardiomyopathy. In this disease, the walls of the lower chambers of the heart (ventricles) thicken and fail to lead to enlargement of the upper chambers of the heart (atria). Maine Coon cats are especially at risk for this disease.

Some cats have unclassified cardiomyopathies, in which the ventricular muscle is dysfunctional and first unable to fill and eventually unable to pump normally. In these cases, the atria are severely enlarged. In both hypertrophic and unclassified cardiomyopathies, blood may swirl around the enlarged atria and form clots which may travel (emboli) to various organs.

The most common cardiomyopathy in dogs is dilated cardiomyopathy. In this disease, the heart muscle becomes weak and floppy. Although the heart is able to fill, it cannot contract well enough to pump blood around the body adequately, often resulting in left atrial enlargement and fluid in the lungs (pulmonary edema). Doberman Pinschers and Boxers are especially at-risk for this condition.

Symptoms of cardiomyopathies include: fatigue, inability to exercise, coughing, fainting, fluid build-up (in the lungs, abdomen or limbs), and emboli (in the kidneys, brain or limbs). Symptoms often arise suddenly without prior illness. In fact, it is not unusual for owners to be unaware of the animal's condition until it is in heart failure or paralyzed with cold extremities (seen in cats with emboli).

Although cardiomyopathies have no cure, they may be treated. Early detection is necessary to provide optimal treatment. Routine check-ups improve changes of early detection. Abnormal heart sounds (murmurs) and rhythms (arrythmias) may be detected by your veterinarian with a stethoscope. Once a heart condition is discovered, further diagnostic work should be done to determine the cause and severity of disease. X-rays demonstrate heart size and show whether fluid is present in and around the lungs, electrocardiograms classify arrythmias, bloodwork shows if any other organs are malfunctioning and an ultrasound of the heart (echocardiogram) is used to examine the heart beating and to make a diagnosis. Once a diagnosis has been made, medication, exercise restriction and dietary change often lessen the severity of symptoms and prolong life.

The writers are Dr. Steven B. Holzman, Dr. William R. Haagenson, Dr. Angela N. Martin and Dr. Loretta Dougherty. They are associated with the Nassau-Suffolk Veterinary Hospital of Farmingdale.