Heart disease is a common illness in dogs of all breeds. Dilated cardiomyopathy is a specific type of heart disease that affects the heart muscle and is generally seen in large and giant breeds of dogs.
What is Canine Dilated Cardiomyopathy (DCM)?
Dilated cardiomyopathy (DCM) in dogs affects the ability of the heart muscle to be able to contract adequately. Because the heart is unable to contract normally, the individual chambers of the heart enlarge in an attempt to compensate for the increased blood volume, leading to an enlarged heart.
What are the Symptoms of Dilated Cardiomyopathy (DCM) in a Dog?
The symptoms seen in dogs affected with dilated cardiomyopathy may result from congestive heart failure, which occurs as the pressure within the heart chambers increases to the point where fluid begins to leak out of the blood vessels and into the lungs (causing pulmonary edema and left-sided heart failure) or into the chest and abdominal cavities (causing right-sided heart failure). In other cases, symptoms may be due to cardiac arrhythmias that occur as a result of the diseased heart muscle.
The most common signs seen in dogs suffering from dilated cardiomyopathy are:
- loss of appetite
- lethargy
- pale gums
- increased heart rate
- coughing
- difficulty breathing
- rapid breathing
- shortness of breath
- weight loss
- exercise intolerance
- weakness
- fainting
- ascites (bloated abdomen)
- sudden death
What Causes Dilated Cardiomyopathy in Dogs?
In most cases, dilated cardiomyopathy (DCM) is an inherited disorder with specific breeds being predisposed to develop the disease. In fewer cases, dietary deficiencies, infectious diseases and toxins have been documented as the cause. Known dietary causes are deficiencies in taurine and L-carnitine. The most common infectious cause is parvovirus infection in very young puppies. The most common toxin associated with DCM is doxorubicin (Adriamycin®), a drug used in chemotherapy.
Breeds of dogs known to be predisposed to canine dilated cardiomyopathy include:
- Doberman Pinschers
- Great Danes
- Boxers
- Newfoundlands
- Portugese Water Dogs
- Dalmatians
- Cocker Spaniels
Though large and giant breed dogs are most often affected by DCM, small breed dogs can sometimes be affected as well.
How is Canine Dilated Cardiomyopathy Diagnosed?
Diagnosis of canine dilated cardiomyopathy starts with a thorough physical examination and may also involve an electrocardiogram (ECG), chest radiographs and/or an echocardiogram (ultrasound study of the heart). In dogs already showing symptoms consistent with DCM, arrhythmias may be present on an ECG, the heart may be enlarged radiographically and an echocardiogram will indicate a decrease in the contractility of the heart.
Screening for dilated cardiomyopathy is encouraged for breeding animals of predisposed breeds. Screening may involve the use of a Holter monitor (a 24 hour ambulatory ECG) to monitor for arrhythmias. Arrhythmias are often present before significant changes occur in the contractility of the heart muscle. An echocardiogram may also be recommended but the results may be questionable in the early stages of disease.
How is Dilated Cardiomyopathy Treated in Dogs?
The method of treatment is based on the clinical signs of the individual dog. Drugs such as ACE inhibitors (enalapril, benazepril), diuretics (furosemide, spironolactone), digoxin and pimobendan are often used. For dogs in which dietary deficiencies are suspected in playing a role, supplementation may be recommended. If fluid has accumulated in the chest or abdominal cavities, physically removing the fluid may be recommended to provide more comfort for the dog.
Medical therapy may help increase the survival time of dogs with DCM. However, dilated cardiomyopathy is a progressive disease and is usually irreversible. It is usually fatal and sudden death, sometimes before other symptoms of heart failure have developed, has been documented relatively frequently.
Canine dilated cardiomyopathy is one of the most common heart diseases seen in dogs and is a frequent cause of heart failure in large and giant breed dogs in particular. Usually an inherited disease, DCM can be passed from parents to puppies and breeding stock should be screened for the disease.
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