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 attacks").
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" signs).
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 developed.
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®
or
another
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.
Recently a
Boxer dog
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 University.
Washington State University assumes no liability for injury to
you or your pet incurred by following these descriptions or procedures.
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Last Edited: Dec 19, 2007 2:09 PM
