Tricuspid Valve Dysplasia

Note: We do not currently have a health liaison for this disorder. If you would like to volunteer, please contact president@samoyedhealthfoundation.org and we will be happy to answer any of your questions. For a description of the position, please click on disorder health information liaison or health information reviewer.

Thank you to Joy Ritter for putting together this article for SCARF.

There are four chambers in a dog’s heart, two atria and two ventricles. Blood returning from the body enters the right atrium and is sent to the right ventricle. The right ventricle pumps the blood to the lungs where it is oxygenated. This blood then returns to the heart, to the left atrium. The oxygenated blood is sent from the left atrium to the left ventricle, which pumps it to the rest of the body via the aorta.

There are one-way valves between each atrium and ventricle so that when the ventricles contract, blood is not forced back into the atria. The mitral valve is between the left atrium and ventricle; the tricuspid valve is between the right atrium and ventricle.

In Tricuspid Valve Dysplasia (TVD), the valve between the right atrium and ventricle is malformed. If the valve doesn’t function properly, some blood returns to the right atrium with each heartbeat, less blood is pumped to the lungs, and less blood is able to return from the body to the heart.

The severity of the malformation can range from mild to severe. In mild cases, the heart may be able to compensate by pumping harder and the dog may not show any signs of a problem. In dogs with a more severe valve malformation, the right side of the heart pumps harder and harder, and enlarges due to the extra work. As the valve gets worse, the heart eventually cannot compensate, and cannot pump enough blood to the body. With medical treatment these dogs may be able to survive for a while, but usually die by 3 years.

Signs and Symptoms

Possible heart murmur, upper right quadrant of heart
Exercise intolerance, lethargy, lack of appetite
Pale gums, fainting spells
In severe cases, right side congestive heart failure
Inability to maintain correct weight

Causes

Congenital (present at birth due to developmental problems or genetics.);
Inheritable in some breeds.
Cause unknown in Samoyeds at this time. Not commonly found in Samoyeds

Risk Factors

Parent(s) with disease, if inheritable. Otherwise unknown at this time.

Diagnostic Tests

Manual Auscultation (listening with a stethoscope) by board certified cardiologist, followed by
Color Doppler echocardiography (type of ultrasound) to definitively diagnose the disease

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

Mild forms, no treatment necessary.
Moderate to severe forms, relief of symptoms as necessary (diuretics, blood pressure medications for heart failure relief and slow heart function), under the direction of a veterinary cardiologist, if possible.
Nutritional supplementation as necessary to maintain weight.
Prognosis for mild forms, is good with guarded care. Whether the condition is caused by developmental problems or genetics, the offspring of such an animal often have a more severe form of the disorder; therefore, it would be unwise to breed an animal diagnosed with a mild condition.
Prognosis for moderate to severe forms, VERY poor. Usually fatal by 3 years.
Replacement of valve through surgery has not proven a good option, due to success rate and cost in canines.

Management

From an owner’s perspective:

The mild form of TVD is self limiting. Dog should be spayed/neutered to prevent accidental breeding. Nutritional advice would be to keep the dog at optimum weight. Overweight dogs put a strain on the heart (already stressed). Underweight due to nutritional challenges also puts stress on the heart. Treat symptoms as they arise and have periodic (annual) checkups with a cardio vet to assess progression of the disease. Allow the dog to self limit his exercise. No FORCED exercise (pulling, sledding, jogging, etc.).

Moderate/severe form of TVD has a poor outcome. Symptoms can be treated, but dogs with moderate/severe TVD rarely live longer than 3 years of age.

References

Understanding Canine Congestive Heart Failure from the Matthew J. Ryan Veterinary Hospital, University of Pennsylvania School of Veterinary Medicine
Canine Heart Anatomy (Web archive) by Rachel Peeples, DVM