What is Tricuspid Valve Dysplasia?
While any abnormality of the valve can be called TVD, the most commonly occurring issue is short or missing chordae tendineae. This causes the papillary muscles to attach directly on the valve leaflets, which then causes the leaflets to thicken. Blood leaks from the lower section to the upper section of the right side of the heart. This leads to the right atrium enlargement, and the entire left side of the heart decreases in size and function. Tricuspid valve dysplasia worsens over time. In severe cases, this eventually leads to congestive heart failure of the right side of the heart. The condition is generally discovered in cats under two years of age.
The tricuspid valve is the valve that separates the top half of the right side of the heart (the right atrium) from the bottom half (the right ventricle). This valve is composed of various parts, including papillary muscles, leaflets, and chordae tendineae. If any abnormality of these parts is present from birth it is referred to as tricuspid valve dysplasia (TVD). This defect results in the valve not being able to close properly. Malformation of the tricuspid valve is rare in cats, however, it is recorded.
Symptoms of Tricuspid Valve Dysplasia in Cats
The first noticeable sign that a cat has tricuspid valve dysplasia is often the accumulation of fluid in the abdomen. This is called “ascites”. This issue is a symptom of many different health problems, and differentiation will be needed to identify TVD. Signs to watch for include:
- Tachypnea (rapid breathing)
- Hepatomegaly (enlarged liver)
- Pleural effusion (fluid around the lungs)
- Jugular vein distention
- Ascites (fluid in the abdomen)
Causes of Tricuspid Valve Dysplasia in Cats
Defects of the tricuspid valve are often coupled with other genetic malformations. Mixed breeds seem to carry this hereditary problem as much or more than purebred cats. Possible causes of the deformity include:
- Inheriting a defective or mutated gene from one or both parents
- The mother of the cat being exposed to chemicals or harmful bacteria while pregnant
Diagnosis of Tricuspid Valve Dysplasia in Cats
Issues of the heart may be found at the cat's first examination by a veterinarian. During an examination with a stethoscope, the vet may notice the cat's heartbeat has a murmur. If the murmur is the loudest above the right apex of the heart. The heart rhythm may also be irregular. If the defect has become very large, no murmur may be noticed due to blood passing quickly between the chambers of the right side. A thoracic x-ray will reveal if the right atrium is enlarged. It has often expended so much that the left atrium has been significantly pushed over.
An electrocardiogram may be used to see abnormal electrical activity of the heart. An echocardiogram (ultrasound of the heart) can help reveal the extent of the damage caused by the defect. In severe cases, the right atrium may be larger than the rest of the heart combined. The left side may have shrunk to the point where it is difficult to find on an ultrasound. The septal leaflets may not be moving much and the papillary muscles may be incorrectly positioned. Microbubbles can be used during the ultrasound for a clearer visual of blood flow. If tricuspid valve dysplasia is present, the bubbles will stay in the right atrium for a longer period of time.
Treatment of Tricuspid Valve Dysplasia in Cats
Appropriate treatment will depend on the severity of the defect present. Mild cases may not require any treatment. The goal for most cats with TVD is to delay the onset of heart failure and to enrich the cat's quality of life.
A prescription of medication can help to reduce the amount of fluid building up in the body. Medication cannot cure the issue, however, it can improve the cat's day to day life. Ongoing administration of drugs such as furosemide and angiotensin converting enzyme (ACE) inhibitors are often used for this purpose.
If the cat has been prescribed medication, fluid will still slowly accumulate in the abdominal cavity. This fluid will need to be drained on a regular basis to minimize the discomfort of the cat. As the defect degenerates, intervals between drainage will become shorter.
In rare instances, your veterinarian may recommend open heart surgery to replace the deformed tricuspid valve with a bioprosthetic valve made of your cat's tissue combined with a stent. This is a last resort option that carries many risks. It is only offered in a small number of locations.
Recovery of Tricuspid Valve Dysplasia in Cats
Cats with very mild cases of tricuspid valve dysplasia often go on to live long and normal lives without human intervention. Cats who have undergone surgery carry a much more guarded prognosis. If the cat survives the surgery, strict at-home care must be given to support the healing process. The incision should be monitored daily to ensure that it is clean and that no signs of infection exist. All activity will need to be limited during this time. The survival rate of this surgery is currently less than 33%, and many cats who have undergone the surgery develop tricuspid stenosis (narrowing of the valve).
If your cat has been given a prescription for medication, administer all drugs as advised. The cat will need regular visits to the veterinarian for fluid removal and re-evaluation of organ function associated with medication. Your vet may give you the option to drain fluid out of your cat at home, showing you how to properly perform the procedure. As the defect will continue to get worse until constant drainage is necessary, often cats with TVD will eventually require euthanization. It is worth noting that the quality of life in between drainages can be excellent, and the process may lengthen the cat's life by years. Cats with this defect should not be bred.