Dilated Cardiomyopathy
What exactly is dilated cardiomyopathy (DCM)?
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 caused dilated cardiomyopathy?
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.
There 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.
There 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 dilated cardiomyopathy?
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 dilated cardiomyopathy 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 dilated cardiomyopathy 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.
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