Monday, April 16, 2012

Veterinary Cardiology – Dilated Cardiomyopathy

Dilated Cardiomyopathy (DCM) is the most common cause of heart disease in large and giant breed dogs.  It usually occurs in middle-aged to older dogs, although any age can be affected. (For more information about veterinary cardiology services, see this veterinary cardiology page)

DCM Disease Background

In dogs affected with DCM, the heart muscle (myocardium) become weakened and enlarges, or dilates, over time.  As the heart muscle becomes weakened, the pump function (contractility) of the heart is impaired.  The major pumping chambers of the heart (the right and left ventricles) cannot eject the normal amount of blood with each heart beat.  The ventricles must dilate to accommodate this extra volume, which can lead to enlargement of the atria and eventually congestive heart failure.  Congestive heart failure means that fluid has built up within the lungs (pulmonary edema), abdominal cavity (ascites), or chest cavity (pleural effusion).
The dilated heart may cause the valves separating the ventricles from the atria (either mitral- left or tricuspid- right) to leak.  This backwards flow of blood is called regurgitation and may produce a heart murmur that can be heard with a stethoscope.  Sometimes an extra heart sound (gallop) or an abnormal rhythm may also prompt your veterinarian to recommended further work-up for DCM.
If no underlying cause can be found, the disease is referred to as Idiopathic DCM. We are not sure why this happens in some dogs and not in others, but a genetic basis is suspected given that certain breeds are predisposed.  Etiologies such as infections (myocarditis), nutritional deficiencies, or arrhythmias can also produce a type of DCM.  In cats and some dog breeds (such as Cocker Spaniels), taurine deficiency can be to blame, especially if the animal is fed an alternative diet.

Diagnosing DCM

Your regular veterinarian may recommend having your pet evaluated by a cardiologist if abnormalities are found during routine physical examination or if your pet is displaying symptoms of heart disease.
Dr. Emily Olson is a board-certified veterinary cardiologist at VRCC.  After reviewing information supplied by your veterinarian, she will obtain a complete medical history and discuss any concerns that you may have about your pet’s health.  Dr. Olson will then perform a thorough physical examination to check for any abnormal heart or lung sounds, arrhythmias, changes in pulses, or other abnormal findings.
She may then recommend running tests such as radiographs (x-rays) of the chest, an echocardiogram (ultrasound of the heart), laboratory work, blood pressure and an ECG (electrocardiogram), depending on your pet’s needs.  These tests are non-invasive and sedation is rarely required.  All tests can be performed during the visit, and results will be discussed with you prior to taking your pet home.

Treating DCM

Regular monitoring allows us to start treatment as soon as it becomes necessary. By starting treatment early, we can maximize your pet’s quality of life for as long as possible. In patients with DCM and signs of heart failure, it is common to prescribe your pet a combination of drugs. Therapy is aimed at maximizing the heart’s efficiency at pumping blood to the body and reducing the excess fluid build up in the body.
There is no known cure for idiopathic DCM.  In breeds that do not typically develop idiopathic DCM, it may be indicated to test for possible underlying causes.  If a cause can be found, different treatments may be recommended and often the prognosis is improved.
Arrhythmias, or abnormal electrical activity within the heart causing an irregular rhythm, can occur as a consequence (or occasionally the cause) of the disease.  This is especially common in large breed dogs affected with DCM.  If the arrhythmia is causing a problem for your pet, additional medications might be prescribed to improve the heart rhythm.

Prognosis of Dilated Cardiomyopathy

It is difficult to predict the life expectancy for any individual patient with DCM. Some dogs live for months to years with minimal to no symptoms, while some dogs rapidly worsen and only live for a few weeks to months. Complications such as arrhythmias or high pressure in the lung (pulmonary hypertension) can worsen the prognosis.
Other factors influencing the prognosis in your pet include the disease severity at the time of diagnosis, response to medications, and whether any other diseases (such as kidney problems) are also present.

Monitoring Signs for DCM

Closely monitoring your pet’s symptoms and communicating with your veterinary team is extremely important.  Since this disease is progressive, it is common for an individual pet to need dosing and medication changes over the course of their disease. With your help, we can identify which changes need to be made as early as possible. If your pet is experiencing symptoms, please contact us right away so that we can ensure the optimal therapy for your pet.
  • One easy way to monitor your pet at home is by checking their resting respiratory rate.  When your pet is sleeping or resting quietly (not panting), count how many times they take a breath in one minute (or count the number of breaths taken in 30 seconds and multiply by 2).  In most pets, this can be done by watching or feeling their chest rise and fall with each breath.  This should be done 2 to 3 times per week, and the rate recorded in a log. If you notice a trend that the rate increasing and is repeatable on several occasions, your pet may need to be evaluated.
  • In addition to respiratory rate, please monitor your pet for clinical signs such as coughing, decrease in activity level, decreased appetite, unexpected weight loss, collapse, or swelling of the abdomen (belly).
  • If you ever notice that your pet is having difficulty breathing or appears unable to catch their breath, collapses, or otherwise appears to be in distress, please seek immediate veterinary care.

    VRCC is open and staffed with a veterinarian 24 hours a day, 7 days a week, in order to care for your pet in any emergency.

    Call 804.784.8722 (804.784.VRCC)

    See our Emergency Vet Page and download the admission form

    Get directions to VRCC Veterinary Emergency Room

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