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Tricuspid valve dysplasia is caused by a congenital birth defect (meaning it is present before or at birth) that results in a heart valve that is abnormally shaped. The condition is most common in large-breed, male dogs but may occur in cats, as well. A heart murmur may be an early warning sign. Affected animals may also experience a bloated, fluid-filled belly; weakness; exercise intolerance; and difficulty breathing. Treatment may include a low-sodium diet, exercise restriction, and drugs to help the heart beat more efficiently, as well as medications to treat fluid retention. In severe cases, surgical replacement of the valve may be recommended.
Some background: The heart muscle is a pump that moves blood through the four chambers with involuntary contractions that promote the one-directional flow of the blood. The valves between the chambers prevent the backflow of blood into the preceding chamber, thus keeping the blood moving in the direction it should. When the valves are misshapen or otherwise poorly formed, some blood can move backward, not forward, in the heart. This means the heart has to work harder to pump the volume of blood the body needs for normal functions.
When the tricuspid valve, which is between the right atrium and right ventricle, fails to form a tight seal, the blood pumped from the atrium into the ventricle is regurgitated into the atrium. The degree of dysplasia will determine how much blood moves the wrong way and, hence, the severity of signs.
Large-breed dogs are most commonly afflicted, with male dogs overrepresented.
Dogs may be diagnosed with a heart murmur before the onset of any signs of tricuspid valve dysplasia. If the murmur is progressive or significant, veterinarians will recommend radiographs (X-rays), EKGs (electrocardiograms), and echocardiograms (heart ultrasounds).
X-rays may show an enlarged right side of the heart, while the EKG may reveal abnormal heart rhythms caused by this enlargement. The best tool, however, is the echocardiogram. This kind of imaging tool visualizes the abnormal shape of the valve and the degree of blood regurgitation that is occurring.
The most common signs of tricuspid valve dysplasia are related to the disorder veterinarians call right-sided heart failure. With this condition, dogs will have distended abdomens due to the fluid accumulation (ascites) that occurs when the blood backs up on its way back to the heart. They may also experience exercise intolerance and difficulty breathing if they’re unable to get enough oxygen into their blood as a result of the poor volume of blood reaching their lungs (blood from the right side of the heart flows into the lungs to receive oxygen).
Occasionally, life-threatening abnormal heart rhythms may result. These can lead to sudden death.
Larger-breed dogs are predisposed to this hereditary disease, especially the German Shepherd, Golden Retriever, Great Dane, Labrador Retriever, and Weimaraner.
In most cases, treatment is aimed at easing the signs of the disease, rather than repairing the valve. Treatment may include low-sodium diets, exercise restriction, and medications to help the heart pump more efficiently and remove excess fluid from the body. In severe cases that don’t respond to medical management, surgical replacement of the valve may be recommended.
Affected dogs should be removed from the breeding pool. Since very mild forms of the disease may be undetected through conventional means, screening dogs within highly affected breeds (with echocardiography) prior to breeding may be helpful.
This article has been reviewed by a Veterinarian.
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