Download Tricuspid and Mitral Valve Dysplasia

Tricuspid and Mitral Valve Dysplasia
Rebecca E. Gompf, DVM, MS, DACVIM (Cardiology)
BASIC INFORMATION
Description
The mitral valve is the valve between the two chambers on the
left side of the heart, and the tricuspid valve separates the two
chambers on the right side of the heart. Valves function to keep
blood flowing in one direction through the heart and to the lungs
and body. Dysplasia is malformation of the valve that results in
stiffness and decreased ability to open properly, leakage, or both.
Dysplasia is a congenital defect that is present at birth.
When dysplasia causes the valves to leak, blood flows in the
wrong direction. This increases the workload of the heart and makes
the affected side dilate. Eventually right- or left-sided heart failure
may occur. If the valve is also stiff and does not open adequately,
the large chamber (ventricle) on the affected side of the heart does
not fill properly with blood. This also contributes to heart failure.
Causes
Most of these defects are spontaneous and occur randomly. They
may be inherited in some breeds, such as the Labrador retriever,
bull terrier, German shepherd dog, golden retriever, Great Dane,
mastiff, Newfoundland, Old English sheepdog, Rottweiler, and
Weimaraner. They have also been reported in cats.
Clinical Signs
Most puppies and kittens have no signs, but a murmur may be discovered on physical examination. If the dog or cat is older, signs
of heart failure may be present. With mitral dysplasia, most animals are normal until they develop signs of left heart failure by 6-9
months of age. Exercise intolerance, lethargy, labored breathing,
increased respiratory rate, and coughing may be noted.
Animals with mild tricuspid dysplasia may never develop
signs. Animals with more severe tricuspid dysplasia are often normal until their right atrium enlarges and develops an abnormal
heart rhythm called atrial fibrillation. This often occurs between
4 and 7 years of age. Once atrial fibrillation is present, exercise
intolerance, lethargy, and abdominal fluid may develop. Cats may
develop fluid in their chest and have trouble breathing.
If the animal has a second congenital heart defect, such as an
atrial septal defect, fatigue and bluish discoloration of the gums
may be noted.
Diagnostic Tests
If a heart murmur is discovered, chest x-rays and an echocardiogram (heart ultrasound) with Doppler capabilities are often needed
to identify the exact defect and determine its severity. An electrocardiogram (ECG) is done if an arrhythmia is detected.
TREATMENT AND FOLLOW-UP
Treatment Options
Treatment is usually given to animals that are in heart failure.
Once left or right heart failure develops, the following medications may be started:
• An angiotensin-converting enzyme (ACE) inhibitor, such
as enalapril or benazepril, helps control fluid accumulation and improves the function of the failing heart. The
main side effect is weakness from hypotension (low blood
pressure).
• Diuretics, such as furosemide or thiazides, are used to decrease
fluid accumulation in the lungs or other parts of the body and
may be combined with spironolactone (another diuretic). Side
effects include dehydration and electrolyte abnormalities.
These drugs also increase water consumption and urine output,
so provide plenty of water at all times.
• Pimobendan increases the heart’s ability to pump blood and
may improve the animal’s quality of life. Most dogs and cats
tolerate this drug very well, but watch for any decrease in appetite, vomiting, or diarrhea.
• If the animal is in atrial fibrillation, digoxin may be used alone
or combined with a beta-blocker, or a calcium channel blocker
(diltiazem) may be used to slow the heart rate.
If the dysplastic valve is stiff and does not open properly, your animal may be referred to a specialist for possible balloon dilation. In
the United States, surgery to repair or replace these valves can be
done at only a few veterinary specialty facilities.
Follow-up Care
Yearly echocardiograms are often recommended for animals with
mild dysplasia to monitor their heart function and any changes in
the heart. More frequent monitoring and testing are needed for animals in heart failure. (See also the handouts on Congestive Heart
Failure.)
Prognosis
Animals with mitral valve dysplasia usually develop left heart failure before 6-9 months of age and rarely survive past 1 year even
with therapy. Animals with mild tricuspid dysplasia typically have
no problems, but dogs with more advanced tricuspid dysplasia
may develop atrial fibrillation between 4 and 7 years of age. Once
atrial fibrillation develops, right heart failure eventually occurs.
With medical management, these dogs usually live an additional
6-12 months.
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