What exactly
is Dilated Cardiomyopathy?
DCM defines a condition where the heart muscle (myocardium) becomes very
thin and is unable to contract normally. Since the myocardium cannot work
effectively to pump blood out of the heart, the heart becomes enlarged.
Subsequent back up of blood into the left atrium and ultimately into the
lungs occurs commonly. This back up of blood into the lungs results in
pulmonary edema and is a sign of congestive heart failure.
What causes
DCM?
While there have been many theories as to the cause of DCM, the exact
mechanism is still not entirely understood. It is believed that the
majority of cases have a familial or genetic component. One reason for
this theory is the preponderance of the disease in specific breeds such as
the Doberman Pinscher, Great Dane or Boxer however, specific genetic
evidence is still lacking. In Portuguese Water Dogs on the other hand, the
disease has been found to be linked to an abnormal gene.
T
here is a small
population of dogs in which DCM may have a nutritional component. Taurine
is an amino acid required for the development and function of normal
muscle, including heart muscle. Pets that develop DCM on taurine deficient
diets, such as vegetarian diets, may benefit from supplementation. It is
important to note however, that not all cases that are supplemented with
taurine will improve. L-carnitine is
another amino acid that has been implicated in the development of DCM in
people. There is little evidence in dogs however to suggest that
supplementation with carnitine reverses cardiac dysfunction.It is difficult
to firmly establish a link between taurine or carnitine deficiency and
heart disease however because measurement of these compounds in the blood
is not an accurate reflection of their levels in the myocardium.
What are the
signs of DCM?
The signs of DCM can vary widely and may depend on the breed of dog.
Coughing, labored breathing, episodic weakness or fainting are signs often
seen in Dobermans. Unfortunately sudden death may also occur in patients
with this problem. Respiratory signs are seen due to pulmonary edema
and/or heart enlargement. Other large breed dogs may have fluid
accumulation in the abdomen (ascites) or in the chest cavity (pleural
effusion). Other signs may include loss of appetite, pale gums, elevated
heart rate or lethargy.
How is DCM
diagnosed?
Often, a thorough physical exam coupled with the signs and the breed, are
sufficient to make a presumptive diagnosis of DCM. Some tests that help
support the diagnosis are an ECG (electrocardiogram) and x-rays of the
chest. The ECG often indicates an arrhythmia (abnormal heart rhythm) and
an elevated heart rate. The chest x-rays will verify an enlarged heart and
we may also see evidence of congestion in the lung tissue (pulmonary
edema). There is a
certain subset of dogs in which there is not any heart enlargement but who
have abnormal heart rhythms. These dogs may still be classified as early
DCM. A definitive
diagnosis of DCM is made by performing an ultrasound of the heart
(echocardiogram). An echocardiogram allows us to visualize the interior of
the heart and assess its function. Measurements of the wall thickness and
pumping capability of the heart can be made as well. Your veterinarian
may also perform blood tests to look for any underlying medical condition
that may be contributing to the heart disease and to ensure there are no
metabolic problems present that will affect therapy.
How is DCM
treated?
Unfortunately DCM is not reversible however; there are certain medications
that may help for a period of time. Some of the more commonly used drugs
are diuretics; drugs that may help increase the contractile ability of the
heart; drugs that may decrease the heart rate or drugs that decrease the
work that the heart has to do to function. Drug choices often depend on
your pets’ signs and health status so your veterinarian will help tailor a
treatment plan that is most appropriate for each case.
Prognosis
Even with optimal therapy, the long-term survival of patients with DCM is
highly variable. Initial response to therapy may also play a role in
determining long-term prognosis. Previous studies have indicated that DCM
in Dobermans carries a worse prognosis than in other breeds however, it is
ultimately a terminal illness in all cases. 
