Heart Disease in Dogs: Chronic Valvular Disease and Dilated Cardiomyopathy
Dilated cardiomyopathy is a disease in which the heart chambers enlarge and
the walls of the ventricles become thin. The heart muscle weakens and begins to
Dilated cardiomyopathy is the most common cause of congestive heart failure
in large and giant breed dogs.It is rare in toy breeds and small dogs. A high
incidence is found in Boxers, Doberman Pinschers, Springer Spaniels, and
American and English Cocker Spaniels. Other breeds affected include German
Shepherd Dogs, Great Danes, Old English Sheepdogs, St. Bernards, and
Schnauzers. Most dogs are 2 to 5 years of age at the onset of symptoms. The
majority are males.
In most cases the cause of dilated cardiomyopathy is unknown. Myocarditis,an
inflammation of the heart muscle, may precede dilated cardiomyopathy in some
dogs. Hypothyroidismhas been associated with dilated cardiomyopathy. A genetic
or familial basis has been proposed for giant and large breed dogs.
Cardiomyopathy related to taurine and/or carnitine deficiency is seen in
American Cocker Spaniels, Boxers, and possibly Golden Retrievers,
Newfoundlands, and other breeds.
The signs of dilated cardiomyopathy are the same as those of congestive
heart failure and cardiac arrhythmias. Weight loss can occur in a matter of
weeks. Affected dogs are lethargic, tire easily, breathe rapidly, and cough
frequently, sometimes bringing up bloody sputum. Coughing is especially common
at night. A swollen abdomen (called ascites)may be noted. Cardiac arrhythmias
can cause weakness and collapse.
The diagnosis of dilated cardiomyopathy is based on ECG changes showing
cardiac arrhythmias, a chest X-ray showing enlarged heart chambers, and an
echocardiogram showing the characteristic pattern of a failing heart
Treatment: Treatment is directed at improving the force of the heart muscle,
controlling arrhythmias, and preventing the buildup of fluid in the lungs and
abdomen (see Congestive Heart Failure). Many dogs benefit from the addition of
taurine and/or carnitine to their diet. The prognosis for long-term survival is
guarded. With excellent medical control, some dogs may live for a year or more.
Death usually occurs as the result of a sudden cardiac arrhythmia. Some dogs
will drop dead without any noticeable signs beforehand.