Heart Valve Narrowing (Mitral and Tricuspid) in Dogs

The mitral valve and the tricuspid valves are the “atrioventricular valves”; that is, they are the valves between the left atrium and ventricle and between the right atrium and ventricle, respectively. Mitral valve disease, including stenosis, is a common cause of congestive heart failure in dogs, and must be treated as soon as possible. Valve stenosis (narrowing of the valves) stops the valve from opening completely, which will cause the blood pressure to build up behind the valve. Mitral valve stenosis is more commonly seen in the Mastiff, Newfoundland, German Shepherd, Great Dane, and Bull Terrier. Tricuspid valve stenosis is more common in Labrador Retrievers, Great Pyrenees, Weimaraners, Labrador Retrievers, Papillons, and Old English Sheepdogs. However, both mitral and tricuspid valve stenosis is possible in any breed.

Heart valve narrowing (stenosis) occurs in the mitral or tricuspid valves in your dog’s heart, slowing down the flow of blood. Mitral stenosis causes the left atrium (upper heart valve) of the heart to enlarge from the build-up of blood, which will in turn cause high blood pressure in the lungs. This pressure will eventually lead to fluid in the lungs, bringing loss of blood flow to the brain. Tricuspid stenosis occurs in the right side of the atrium (upper heart valve), causing swelling and pressure in the ventricle, reducing the amount of blood that reaches the lungs. The cause of mitral or tricuspid stenosis is usually genetic, occurring more often in certain breeds, but other causes are possible.

Although the symptoms of mitral valve stenosis and tricuspid valve stenosis are similar, there are some symptoms that are only seen in one or the other. This is a list of the most common symptoms:

Mitral Valve Stenosis

• Cough
• Inability to exercise much
• Fainting (syncope)
• Breathing problems with exertion
• Pale or bluish skin color (cyanosis)

Tricuspid Valve Stenosis

• Fluid in the abdomen, swelling (tricuspid valve stenosis)
• Stunted growth
• Spitting up blood
• Swollen abdomen

Types

• Mitral valve stenosis is the narrowing of the mitral valve, stopping the valve from opening fully
• Tricuspid valve stenosis is the narrowing of the tricuspid valve, causing restricted blood flow

Most cases of valve stenosis (mitral and tricuspid) are congenital (present at birth), but there are a few other causes such as:

• Endocarditis (inflammation of the inner lining of the heart)
• Cardiac neoplasia (heart cancer)
• Hypertrophic cardiomyopathy (thickening of the heart muscle)
• Fibrous scarring

The veterinarian will do a complete physical to check your dog for a heart murmur, crackles in the lungs, jugular vein inflammation, and cyanosis. In addition, your dog’s blood pressure, respirations, heart rate, height, and weight will be noted. The examination will also include palpation of the lymph nodes, legs, and abdomen. Close examination of your dog’s ears, eyes, skin, mouth, and teeth will be done as well.

They will perform a complete blood count, blood chemical panel, blood gases, and urine analysis. Chest and abdominal radiographs (x-rays) will be done to view the size of the heart. An electrocardiography (EKG) will show any problems with the heart’s electrical activities, which is a simple and painless test. Also, an echocardiogram (ultrasound) of the heart confirms the diagnosis with moving pictures taken by using high frequency sound waves. This is also a simple and painless test which does not expose your dog to any unnecessary radiation from x-rays.

The veterinarian may also think it is necessary to perform an angiography, which includes using a contrast liquid to examine the blood vessels. They will most likely sedate your dog for this procedure because it requires a catheter being inserted into an artery and guided to the area of interest. With all of these tests, the veterinarian should have a clear view of what is causing the mitral or tricuspid valve stenosis, and what may be done to treat the problem. The veterinarian may also refer you to a veterinary cardiologist to get a better diagnosis and treatment plan.

The veterinarian will probably want to hospitalize your dog until his heart is stable, providing IV fluids, oxygen therapy, and medication for inflammation and high blood pressure. While there is no real cure for mitral or tricuspid valve stenosis, it is possible to perform a surgical valve repair or replacement. This is a risky surgery, which includes a cardiopulmonary bypass and many possible side effects or concerns. The veterinarian may also prescribe an ACE inhibitor (blood pressure), beta blockers (atenolol), sotalol, digoxin, nitroglycerin paste, or steroids to control the fluid build-up.

Your dog will have to be on a low sodium diet for the rest of his life, and take medication to control blood pressure as well. Be sure to follow up with your veterinarian when you are supposed to, and call him if you have any questions or concerns.