Enlarged Heart (Dilated Cardiomyopathy) in Dogs

With dilated cardiomyopathy (DCM) the heart muscle becomes thinner than normal, is weakened, and results in poor pumping ability, valve leakage and arrhythmia. This loss of the heart’s ability to properly contract is a common acquired disease of the heart in dogs. It is predominantly seen in male middle-aged canines. Large breed dogs are most predisposed but many other dogs are known to be susceptible. The large breed dogs are the Doberman Pinscher, Boxer, Irish Wolfhound, Great Dane, Scottish Deerhound, Labrador Retriever, Newfoundland Retriever, Saint Bernard, and German Shepherd. In addition, Dalmatians, Welsh Corgi, Tibetan Terriers, and Spaniels (specifically American Cocker, English Cocker, and Springer) are prone to acquiring an enlarged heart.

Dilated cardiomyopathy is a disease in which the heart muscle becomes enlarged and weak. Loss of ability to contract is a main component of the condition, affecting both left and right sides of the heart. The chambers of the heart (atria and ventricles) are put under great strain due to enlargement and impairment of function.

The signs of dilated cardiomyopathy can vary from pet to pet depending on the stage of the disease. If you see your canine companion exhibit any of the following symptoms, be sure to contact your veterinarian for an appointment, or if needed seek assistance at the emergency clinic.

• Exercise is becoming difficult to manage
• He tires easily
• He is reluctant to partake in activity
• He is panting excessively
• He coughs or clears his throat often
• He appears weak
• There has been an episode of fainting
• Weight loss is apparent
• His abdomen seems enlarged (fluid accumulation can cause this)
• His breathing is heavy

In later stages of dilated cardiomyopathy, your pet will have additional signs of discomfort.

• Reluctance to lie down
• Loss of appetite
• Inability to get comfortable
• Collapse

Unfortunately, with this condition, sudden death may occur.

An enlarged heart is an acquired condition; the specific cause is presently unknown. Factors that are thought to contribute are as follows.

• Breed disposition
• Low thyroid
• Prolonged arrhythmias
• Ischemia
• Amino acid deficiencies (typically taurine and carnitine)
• Toxicity
• Infection

As a result of these causes congestion, edema, and effusion lead to heart failure.

When you bring your canine companion to the veterinarian for his appointment, a physical examination may alert your veterinarian to the heart issue right away. Upon listening to the heart, she could hear abnormal sounds like a murmur or arrhythmia. Your dog’s pulse could be weak. 

These signs will indicate that further investigation is warranted. There are a few tests that can be ordered which are very accurate in diagnosing a condition such as dilated cardiomyopathy. Chest radiographs can show that your dog’s heart is most likely enlarged, which is a benchmark sign of this type of heart ailment. An electrocardiogram can confirm the existence of arrhythmia and irregularities with the left atrium and ventricle. The use of an ultrasound and quite possibly a 24 hour Holter monitor can give more information on the state of inflammation and blood flow of the heart.

If there is an underlying condition contributing to the dilated cardiomyopathy, treatment can be greatly improved with concurrent therapy. In the case of amino acid or enzyme disturbances, supplementation (for example taurine) has been shown to help improve changes that are occurring in the heart. 

Delaying the progression of the enlarged heart and the symptoms that result is key because dilated cardiomyopathy has no cure. The therapy chosen will be to give comfort to your dog and to slow the changes associated with the disease. Medication to aid in the contraction of the heart muscle, diuretics to decrease fluid retention, and drugs to stabilize heart rhythm are essential to treatment. The response of your pet to these therapies will depend on his age and how advanced the condition was at time of diagnosis.

The prognosis for canines diagnosed with dilated cardiomyopathy is guarded. The condition usually progresses fairly quickly but depending on the stage at time of discovery as well as the breed of your dog may determine the outcome. Dogs survive from a few months to a few years, with the average being around one year after symptoms are seen. As the disease progresses, the medications your pet is taking will need to be adjusted. Follow up appointments will be required to monitor the condition of the heart. Blood tests must be done at regular intervals to check on the effects of medication on kidney function. Keep in contact with your veterinarian, and do not hesitate to call her her or take your pet to the clinic if you feel his condition is changing, or if he is showing signs of advanced heart problems.