Dilated Cardiomyopathy (DCM)
This information is not meant to be a substitute for veterinary care.
Always follow the instructions provided by your veterinarian.
Anatomy of the heart of a dog
What is it?
DCM is a disease of the heart muscle that results in weakened
contractions and poor pumping ability. As the disease progresses the heart
chambers become enlarged, one or more valves may leak, and signs of
congestive heart failure develop. The cause of DCM is unclear in most cases,
but certain breeds appear to have an inherited predisposition. Large breeds
of dogs are most often affected, although DCM also occurs in some smaller
breeds such as cocker spaniels. Occasionally, DCM-like heart muscle
dysfunction develops secondary to an identifiable cause such as a toxin or
an infection. In contrast to people, heart muscle dysfunction in dogs and
cats is almost never the result of chronic coronary artery disease ("heart
What are the signs of this disease?
Early in the disease process there may be no clinical sign detectable, or
the pet may show reduced exercise tolerance. In some cases, a heart murmur
(usually soft), other abnormal heart sounds, and/or irregular heart rhythm
is detected by your veterinarian on physical examination. Such findings are
more likely as the disease progresses.
As the heart’s pumping ability worsens, blood pressure starts to increase
in the veins behind one or both sides of the heart. Lung (pulmonary)
congestion and fluid accumulation (edema) often develop behind the left
ventricle/atrium. Fluid also may accumulate in the abdomen (ascites) or
around the lungs (pleural effusion) if the right side of the heart is also
diseased. When congestion, edema and/or effusions occur, heart failure is
present. Weakness, fainting episodes, and unfortunately, even sudden death
can result from heart rhythm disturbances (even without "heart failure"
What are the signs of heart failure?
Dogs with heart failure caused by DCM often show signs of left-sided
congestive failure. These include reduced exercise ability and tiring
quickly, increased breathing rate or effort for the level of their activity
excess panting, and cough (especially with activity). Sometimes the cough
seems soft, like the dog is clearing its throat. Poor heart pumping ability
and arrhythmias can cause episodes of sudden weakness, fainting, or sudden
death as noted above. Some dogs with DCM experience abdominal enlargement or
heavy breathing because of fluid accumulation in the abdomen or chest,
respectively. Presence of any of these signs should prompt a visit to your
veterinarian to determine if heart failure (or another disease) has
More advanced signs of heart failure could include labored breathing,
reluctance to lie down, inability to rest comfortably, worsened cough,
reduced activity, loss of appetite, and collapse. A veterinarian should be
consulted right away if these signs occur. Signs of severe heart failure may
seem to develop quickly with DCM, but the development of underlying heart
muscle abnormalities and progression to overt heart failure probably takes
months to years.
How is this disease diagnosed?
A cardiac exam by a veterinarian can detect abnormal heart sounds (when
present) and many signs of heart failure. Usually chest radiographs
(x-rays), an electrocardiogram (ECG), and echocardiogram are performed to
confirm a suspected diagnosis and to assess severity. Echocardiography also
can be used to screen for early DCM in breeds with a higher incidence of the
disease. Resting and 24-hour (Holter) ECGs are sometimes used as screening
tests for the frequent arrhythmias that usually accompany DCM in some
breeds, especially boxers and Doberman pinchers.
What can be done if my pet has this disease?
Asymptomatic (subclinical) cases of DCM may be treated with enalapril
ACE inhibitor to slow progression
of the changes leading to heart failure. Other medications and strategies
are also used as signs of heart failure develop and/or if rhythm
abnormalities are present. Therapy is always tailored to the needs of the
individual patient. Since this disease is not reversible and heart failure
tends to be progressive, the intensity of therapy (for example, the number
of medicines and the dosages used) usually must be increase over time.
with a heart rhythm disturbance due to cardiomyopathy had a defibrillator
surgically placed to control his heart rate.
This Pet Health Topic was written by
O. L. Nelson, DVM, MS,
Diplomate ACVIM (Cardiology & Internal Medicine) Washington State
Washington State University assumes no liability for injury to you
or your pet incurred by following these descriptions or procedures.
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