Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

334 •DOG OWNER’S HOME VETERINARY HANDBOOK
blood pressure in the atrium and causes it to enlarge. Because the mitral valve
is invariably involved, chronic valvular disease is also sometimes called mitral
valve disease or mitral regurgitation.
The hallmark of chronic valvular disease is a loud heart murmur heard over
the left side of the chest. A chest X-ray, ECG, and echocardiogram may show
an enlarged left atrium, thickened valves, or a ruptured cord (muscle band). If
the tricuspid valve is involved, there will be a loud heart murmur heard over
the right side of the heart. It is important to exclude heartworms as a cause of
a right-sided heart murmur.
Signs of congestive heart failure can be attributed to low cardiac output
and lung congestion. They include a cough that occurs after exercise and/or is
worse at night; lethargy and tiring easily; and fainting spells often related to
cardiac arrhythmias.
Treatment: Many dogs with uncomplicated heart murmurs associated with
chronic valvular disease remain asymptomatic for years. The disease, however,
is chronic and progressive. Treatment should be started at the first signs
of impending heart failure (coughing, easy tiring). The outlook depends on
how far the disease has progressed and the general health and age of the dog.
(For more information on treatment, see Congestive Heart Failure, page 339.)
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 fail.
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. Hypothyroidism has 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