Tricuspid valve dysplasia (TVD) in Dogs

Some dog breeds are prone to suffering from a heart defect known as tricuspid valve dysplasia or TVD which is a congenital disorder where valves leaflets and other parts of their hearts are malformed. Fortunately, the condition is not that common but with this said, some breeds are more predisposed to inheriting the disease than others which includes the Pyrenean Mountain Dog. There is a similar condition seen in people which is known as Ebstein's anomaly.

The condition explained

TVD happens thanks to several abnormalities that occur in a dog's heart and not because lesions have formed in it. The condition is due to malformations and/or underdevelopment of valves found in the heart which is typically a shortening of the valve leaflets and chordae tendineae which in a dog's heart, are short anyway. The result is that some parts become stuck to the heart's ventricular wall preventing it from functioning as it should.

When a dog suffers from TVD, they often suffer from other heart issues and defects too which could include the following:

• Mitral valve dysplasia
• Septal defects
• Subarotic stenosis
• Pulmonic stenosis

The condition negatively impacts a dog's heart function in that blood leaks from the right ventricle allowing it to enter their right atrium. This in turn increases the volume of blood that flows into it putting pressure on the heart which builds up over time. The result is that the right ventricle swells to accommodate the extra blood causing the heart to grow larger. This extra pressure over a period of time leads to congestive heart failure on the right side of the heart. The left side of a dog's heart in the meantime becomes smaller and eventually atrophies which in turn leads to a decreased function and blood flow.

How often does TVD occur?

As previously mentioned, there are certain breeds that are more predisposed to suffering from tricuspid valve dysplasia than others, although the good news is that TVD is quite rare. The breeds most at risk include the following:

• Pyrenean Mountain Dog
• Old English Sheepdog
• Great Dane
• Irish Setter
• German Shepherd
• Labrador Retriever

In a study of number of dogs which includes pure and mixed breeds, it was found that TVD was found in a higher percentage pedigree dogs than in mixed breeds where the numbers were low.

Diagnosing the condition

A vet would need to have a dog's full medical history and would need to thoroughly examine them if they are suspected of suffering from TVD. An initial examination would identify a heart murmur although often there are other symptoms present which includes fluid being present in a dog's abdomen which is known as ascites. Studies have shown that dogs develop the condition when they are around 2 years old although older dogs can suffer from TVD too.

Dogs diagnosed with a severe case of TVD would suffer right heart failure which as result means there is also a build of fluid in their abdomens. The sort of tests a vet would want to carry out on a dog suspected of suffering from the condition include the following:

• Thoracic X-rays - this would establish if the size of a dog's heart and if there is any enlargement due to the right ventricle having to accommodate a larger volume of blood
• Electrocardiography - this test helps establish how severe the disorder happens to be
• Echocardiography - this would help establish how enlarged a dog's right atrium is, should it be small, it can be harder to identify

Treatment options

A dog suffering from tricuspid valve dysplasia would need a tremendous amount of palliative care with the end goal being to reduce the amount their abdomens are distended which in turn would make them more comfortable. However, it can prove challenging as preventing a fluid build-up continuing is not always possible. As such a vet may need to remove any fluids found in a dog's abdomen which is a procedure that would need to be frequently repeated as the fluid tends to build up again once it has been removed.

Interestingly, dogs that that suffer right heart failure can continue to have a good quality of life in between having to undergo any procedures although over time, the procedures would need to be done more frequently. As such, it is often much kinder to put a dog suffering from TVD to sleep rather than to let them go through the ordeal on a frequent basis.

Surgically correcting the problem does not prove effective enough for many vets to recommend dogs having their tricuspid valves replaced and most dogs don't survive for very long.