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Without treatment, heart valve malformation is likely to result in irreversible heart damage or life-threatening congestive heart failure (CHF). The condition often causes emotional distress and the possibility of early death is highly likely. Cats displaying common symptoms should be taken for a veterinary examination immediately, as early detection is a critical factor in the likelihood of recovery.
Heart valve malformation, also called atrioventricular valve dysplasia (AVD), is one of the most common congenital heart defects found in cats. The condition occurs when valves either don’t close completely, allowing blood to flow through when it shouldn’t, or have narrowed to the extent that blood outflow is obstructed. The disorder is usually inherited and most commonly detected in kittens or cats up to a few years of age.
Symptoms of heart valve malformation will depend on the location and size of the irregularity. When the mitral valve has been impacted, the cat may display one or more of the following symptoms:
Less commonly, the dysplasia is found in the tricuspid valve. This causes a different set of symptoms including:
Heart valve malformation is categorized depending on which valve has been impacted and whether the valve is dilated or narrowed.
Heart valve dilation occurs when the superior chamber of the heart (atrium) expands and the rear chamber of the heart (ventricle) enlarges.
Mitral valve dilation - causes blood to build up in the lungs.
The opposite condition occurs when the heart valves narrow, also called stenosis. This causes the atrium of the heart to dilate while the ventricle shrinks.
Heart valve malformation is typically caused by an inherited birth defect. Hypertrophic cardiomyopathy secondary to a thyroid tumor has also been linked to the condition. Siamese breeds are most likely to be impacted, and male cats are more likely to develop congestive heart failure as a result of the malformation.
The treating veterinarian will review the affected cat’s full health history and discuss details regarding onset and severity of symptoms. If available, a family history may help to aid in diagnosis. A standard set of laboratory tests will be ordered including complete blood count (CBC), chemical blood profile, and urinalysis. These tests are ordered to rule out the presence of other conditions and, in most cases, normal results are expected.
Visual diagnostic testing will likely be needed to check for heart abnormalities. This may include X-rays, echocardiography, and thoracic radiography. An electrocardiogram (EKG) will help to determine whether the heart is functioning normally and indicate the presence of abnormal heart rhythms. When a heart valve malformation is present, it is common for the heart to emit a “swooshing” sound (murmur) which can be heard with a stethoscope.
If the cat has already developed congestive heart failure (CHF), hospitalization and intensive care will be needed for a chance at recovery. In most cases, the recommended course of treatment will depend on the severity of the condition.
Medical treatment is usually focused on managing symptoms and improving the cat’s overall quality of life. If fluid is retained in the lungs or abdomen, it may need to be drained and diuretics may be prescribed. In some cases, vasodilators will be used to expand the blood vessels. Abnormal heart rates may be regulated using the antiarrhythmic drug digoxin.
In rare cases, surgical correction of the defect may be recommended. This is often not a viable option as survival rates tend to be quite poor.
Following treatment, the outlook for affected cats will depend greatly on the extent of the condition. If the defect is very minor, the cat may be able to adapt and live a normal lifespan. In most cases, prognosis ranges from guarded to poor.
Follow-up veterinary care will be needed at least every three months to determine whether the condition has improved. It is likely that X-rays, EKG, and echocardiography will be performed during each appointment. Treatment recommendations may need to be adjusted depending on the results.
A balanced, low-sodium diet will likely be recommended to reduce fluid retention. Efforts should be made to keep the cat calm and restrict exercise, as over-exertion can be fatal to cats suffering from congestive heart failure. In order to reduce the possibility of passing the condition on to future generations, it is recommended that affected cats be spayed or neutered once they are healthy enough to undergo surgery.
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