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Care Guide

About Care Guides[x] These care guides are written to help your clients understand common conditions, tests, and procedures, as well as to provide basic information about pet care. They are based on the most up-to-date, documented information, recommendations, and guidelines available in the United States at the time of writing. Pharmaceutical product licensing, availability, and usage recommendations are based on US product information. Use the Download Handout button to generate a PDF for printing or e-mailing to your clients.

Canine Dilated Cardiomyopathy

    • Dilated cardiomyopathy (DCM) is a disease in which the heart muscle becomes stretched, weakened, and unable to contract (and sometimes unable to relax and fill) properly.
    • In most cases, the disease is inherited, but it can behave differently in different dog breeds.
    • For most affected dogs, the long-term outcome is poor. Many dogs die within 2 years of diagnosis.

    What Is Canine Dilated Cardiomyopathy?

    Dilated cardiomyopathy (DCM) is a disease in which the heart muscle becomes stretched, weakened, and unable to contract effectively. The heart chambers (especially the ventricles) become dysfunctional; this can reduce the amount of blood the heart sends out to the body when it contracts (if the left ventricle is affected) as well as the amount of blood that enters the heart from the rest of the body (if the right ventricle is affected). Eventually, the body’s organs (like the kidneys) begin to suffer damage from inadequate blood and oxygen supply. Fluid can accumulate in and around the lungs or in the abdomen, and other complications can occur.

    In general, DCM is a disease of large-breed dogs, but some medium-sized breeds can also be affected. Breeds at risk include Doberman pinschers, Irish wolfhounds, Great Danes, boxers, and cocker spaniels. Interestingly, DCM can behave differently in different breeds. For example, most dogs are affected as adults, but Portuguese water dogs can be affected as puppies. Also, some researchers have reported that boxers are more likely to suffer sudden collapse from DCM compared with other breeds and that the disease may progress more quickly in Doberman pinschers.   

    In most dogs, DCM is an inherited condition, but other causes have been implicated. Deficiencies in carnitine or taurine (an amino acid) have been linked to DCM in some dogs, and some drugs can cause heart damage that leads to DCM. Sometimes, the cause of DCM cannot be determined.

    What Are the Signs of Canine Dilated Cardiomyopathy?

    Heart failure is defined as a condition in which fluid builds up in or around the lungs or in the abdomen as a result of impaired heart functioning. DCM tends to be a very “quiet” disease until enough damage has been done to the heart to cause clinical signs relating to heart failure. The disease can also cause life-threatening heart arrhythmias (irregular heart rate). Signs of DCM can include the following:

    • Coughing, difficulty breathing
    • Weight loss
    • Fainting or collapsing episodes
    • Weakness, exercise intolerance
    • Swollen abdomen (from fluid buildup)

    Sadly, some affected dogs die suddenly without any previous signs of illness. Early detection of DCM through regular veterinary examinations and appropriate screening tests can improve the chances of detecting the disease earlier and initiating appropriate treatment. However, DCM can have a subclinical stage (the stage during which the heart is functioning abnormally, but clinical signs are not evident) that may last for several years, during which time physical examinations may be normal. This complicates early diagnosis in some dogs.

    How Is the Disease Diagnosed?

    DCM must be distinguished from other causes of heart failure, such as heartworm disease and heart defects. The diagnosis of DCM is based on medical history, physical exam findings, and specific tests that look closer at heart functioning and the health of the heart and lungs. During the physical exam, a stethoscope is used to listen to the heart and lungs to detect a heart murmur, abnormal heart rate or rhythm, or chest fluid. Murmurs are “extra” sounds (usually in between the heartbeats) heard when blood is flowing abnormally through the heart. If there is fluid in the chest or lungs, the lungs can sound abnormally loud or quiet. Dogs with DCM may also have weak pulses or low blood pressure because the heart is pumping a reduced amount of blood out to the rest of the body. When DCM is suspected after a physical exam, some or all of these tests may be recommended to confirm the diagnosis:

    • Blood tests and urinalysis: to help check for damage to the kidneys or other organs; heartworm testing may also be recommended
    • Blood pressure check: to determine if the blood pressure is low
    • Radiographs (x-rays): to look for fluid in the chest or lungs and evaluate the size and position of the heart
    • Echocardiogram (heart ultrasound): to measure the thickness of the heart walls, look at overall heart chamber size and contractility, and evaluate the motion of heart valves
    • Electrocardiogram (ECG): to evaluate heart rate and rhythm

    How Is Canine Dilated Cardiomyopathy Treated?

    Some dogs with DCM are experiencing an acute crisis when the vet initially sees them for the disease. In these cases, hospitalization (possibly in a facility that can provide 24-hour critical care) is needed to stabilize the patient and begin diagnostic testing. If a pet is having severe breathing problems or is otherwise unstable, diagnostic tests may be limited until the patient can withstand them—too much stress can be fatal in a dog that is severely ill from heart failure. Emergency measures may include medications to support heart functioning and control arrhythmias, oxygen to ease breathing, and medications or procedures to remove fluid from the abdomen or chest to improve the pet’s comfort and allow the lungs to fill with air more effectively.

    Once a dog has been stabilized and a diagnosis of DCM confirmed, long-term treatment will likely include medication to decrease the amount of work the heart has to perform, improve the heart muscle’s ability to contract, control heart arrhythmias, and help remove fluid from the lungs, chest, and abdomen.

    If a dog develops DCM as a result of taurine or carnitine deficiency, a critical component of treatment is to supplement these compounds on a long-term basis. Your veterinarian may also recommend feeding your dog a diet with reduced sodium content.

    What Is the Outcome for Dogs With This Disease?

    The subclinical stage of DCM (the stage during which the heart is functioning abnormally, but clinical signs are not evident) can last for years in some dogs. Early diagnosis and management of DCM during this stage can improve long-term outcome, but eventually clinical disease and heart failure are still likely to occur.

    For dogs that are already in heart failure due to DCM, the long-term prognosis is poor. Most dogs die from complications within 2 years of diagnosis. Many die much earlier—within months of diagnosis.   

    While your dog is being treated for DCM, your veterinarian may recommend periodic recheck examinations to assess response to treatment. Blood work, x-rays, and cardiac ultrasound may also need to be repeated. In between veterinary visits, watch your dog for coughing, exercise intolerance, weakness, fainting episodes, or abnormal breathing and report any of these problems to your veterinarian right away.

    If a dog has a genetic predisposition to developing DCM, preventing the disease is unlikely. However, regular veterinary visits and early detection (and management) of the disease may be the best way to improve quality of life once the condition develops.