Friday, April 13, 2012

Veterinary Cardiology – Chronic Degenerative Valve Disease

Chronic Degenerative Valve Disease (CDVD) is the most common cause of heart disease as well as congestive heart failure in dogs.  It is also known as Mitral Valve Disease, Myxomatous Valvular Disease, and Endocardiosis, among other names.  Most patients affected with this disease are middle aged to older small breed dogs, although it can also affect younger and larger animals. (For more information about veterinary cardiology services, see thisveterinary cardiology page)

CDVD Disease Background

In dogs affected with CDVD, the structural components of the heart valve degenerates over time.  While we do not know the exact cause for the disease, it is likely that there is a genetic basis. This degeneration of valve tissue most commonly affects the mitral valve (which separates the left ventricle from the left atrium), though it can affect any of the heart valves.
As the tissue in the valve degenerates, the leaflets become thickened and irregular. Instead of coming together and creating a tight seal, gaps form between the valve leaflets. Each time the left ventricle contracts, some blood can leak backwards into the left atrium through these gaps. This backwards flow of blood is called regurgitation. Over time, the valve continues to degenerate and the amount of regurgitation increases.
This regurgitation of blood produces turbulence within the heart which can often cause a heart murmur that your veterinarian can hear with a stethoscope.  In some patients, this turbulence is severe enough to cause the chest wall to vibrate which can be felt as a palpable thrill.  The left atrium will enlarge as the amount of regurgitation through the mitral valve increases.  Eventually, the left atrium may not be able to compensate for this extra volume of blood.  This can cause fluid to build up within the lungs, a condition known as congestive heart failure.
Fortunately, this disease process usually occurs gradually over the course of several years. Most animals can compensate for the disease for a long period of time and may never develop signs of heart failure. However, once we identify a patient with this disease, regular monitoring is essential so that we can begin medication at the appropriate time.

Diagnosing Mitral Valve Disease

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 who works 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 Mitral Valve Disease

In most cases, no treatment is needed until a patient starts to show signs or the disease becomes severe. 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 CDVD and signs of heart failure, it is common for your pet to require 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.
Arrhythmias, or abnormal electrical activity within the heart causing an irregular rhythm, can occur as a consequence of the disease.  This is especially common in large breed dogs affected with CDVD.  If the arrhythmia is causing a problem for your pet, additional medications might be prescribed to improve the heart rhythm.

Prognosis for dogs with Chronic Degenerative Valve Disease

The life expectancy for any individual patient with this disease is difficult to predict. Some dogs live for years with no or mild symptoms, while some dogs rapidly worsen and only live for a short time. Complications such as rupture of the chordae tendineae (structures that attach the mitral valve leaflets to the left ventricle), arrhythmias (abnormal heart rhythm), or high pressure in the lung (pulmonary hypertension) can worsen the prognosis. Your pet’s prognosis is also dependent on the severity of the disease when it is diagnosed, how they response to medications, and whether any other health problems are also present.

Monitoring Signs for CDVD

Monitor your pet’s symptoms and communicating with your veterinary team is extremely important in dogs with CDVD.
Your pet’s medications and dosages often need to be adjusted as the disease progresses.  Your communication and at-home monitoring is imperative to allowing us to determine if and when changes need to be made as early as possible to ensure the optimal therapy for each animal.
  • 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 can be done two or three 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 seen.
  • In addition to respiratory rate, please monitor your pet for clinical signs such as coughing more than normal, unexpected decrease in activity level, decreased appetite, weight loss, or swelling of the abdomen (belly).
  • If you ever notice that your pet is having difficulty breathing or appears unable to catch their breath, faints or 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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