Mitral valve disease is one of the most common causes of congestive heart failure in dogs. While it is less common in cats, it is equally serious. It can’t always be cured, but it can be treated.
What Is Mitral Valve Disease?
The mitral valve sits between the two chambers of the heart on the left-hand side, in much the same way as the tricuspid valve sits between the two right-hand chambers. Both prevent blood from flowing backward as the heart pumps, and either can fail, ultimately causing congestive heart failure. Mitral valve failure is more common than tricuspid valve failure and has somewhat different symptoms and causes.
The mitral valve can fail in either of two ways:
- Valve degeneration prevents the valve from closing completely, allowing some blood to flow backward when the heart pumps.
- Valve stenosis prevents the valve from opening completely.
The two have different causes, but since both problems cause an increase in blood pressure behind the valve, they have similar symptoms.
Symptoms of Mitral Valve Problems
In both dogs and cats, valve stenosis and valve deterioration can have some or all of the following symptoms, depending on severity:
Coughing is specific to mitral valve problems, because blood backs up into the pulmonary veins and causes fluid leakage into the lungs. Tricuspid problems involve swelling of the abdomen instead.
Valve deterioration also causes a heart murmur. If the animal has trouble breathing, and valve deterioration is an issue, lying down will make breathing even more difficult.
Valve stenosis is often present from birth and can stunt an animal’s growth.
What Causes Mitral Valve Disease?
Degenerative valve disease (DVD) itself has no known cause, though there may be a genetic link, at least in dogs. Small dog breeds are generally more at risk, and the disease develops earlier and usually progresses faster in Cavalier King Charles Spaniels. Infections and major surgery can also cause valve degeneration.
Mitral valve stenosis can be caused by a genetic problem, especially in Newfoundland and Bull Terrier dogs and Siamese cats. Bacterial infections or cancer of the heart can also cause stenosis. In cats, thyroid tumors are a common, if somewhat indirect cause of heart valve stenosis.
Diagnosis and Treatment
The first sign of mitral degeneration is a heart murmur, but the problem typically does not require treatment at that stage. Valve stenosis also begins with mild symptoms that might not initially require treatment. Your pet will have to be monitored, however, since both problems get worse over time. Your vet can use heart sounds, lung sounds, x-rays, angiograms, and other tests to confirm the diagnosis and assess the progress of the disease.
Sometimes there is an underlying cause, like an infection, that can be cured. If not, your vet will use medication and rest to slow the disease and keep your pet comfortable for as long as possible. In humans, heart valve problems can be fixed surgically, but for various reasons heart surgery is rarely an option for dogs and cats. Instead, your vet will monitor the situation closely and may recommend hospitalization or cage rest to help get your furry friend through a crisis. With luck and lots of TLC, your dog or cat might have months or even years to enjoy with you.
The Bottom Line
Properly diagnosing a heart valve problem is a job for a vet. If your cat or dog seems slow, tired, or weak for no good reason, has unexplained fluid buildup, or has trouble breathing, that is a medical emergency and means that it is time to call a vet. If a diagnosis of mitral valve disease comes back, know that the situation is serious but not hopeless. You can still help your dog or cat have a good life.
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