There are four chambers in the cat’s heart: two top chambers (the atria) and two bottom chambers (the ventricles). There are valves that separate the top chambers from the bottom chambers, called the atrioventricular (AV) valves.
The valve on the right side of the heart is called the tricuspid valve, and it has three parts. The valve on the left side of the heart is called the mitral valve, and it has two parts.
As the heart contracts, the blood is pumped from the right ventricle into the lungs. and from the left ventricle out to the rest of the body. Healthy AV valves prevent the back flow of blood (regurgitation) from the ventricles to the atria during heart contractions.
What does it mean that my cat has been diagnosed with atrioventricular (AV) valve dysplasia?
Atrioventricular (AV) valve dysplasia is a developmental malformation of the mitral or tricuspid valve that allows a back flow of blood into the left atrium (mitral valve dysplasia) or the right atrium (tricuspid valve dysplasia). Dysplasia may occur in both the mitral and tricuspid valves, but this is not a common condition.
Are some breeds more likely than others to be born with abnormal AV valves?
AV valve dysplasia is one of the most common cardiac abnormalities diagnosed in cats. An associated heart condition is hypertrophic cardiomyopathy in which the walls of the heart become thickened and the heart chambers become smaller. This condition puts tremendous back-pressure on the valves, contributing to their deterioration.
There may be a breed predisposition to mitral valve dysplasia in Sphinx cats. Tricuspid valve dysplasia occurs more frequently in Chartreaux and Siamese cats.
What are the signs of AV valve dysplasia?
The signs of AV dysplasia are variable, but most often begin within the first few years of life, usually younger than age two. Signs may include exercise intolerance, accumulation of fluid in the abdomen, weight loss, and stunted growth. Difficulty breathing or collapse may occur if congestive heart failure develops.
Signs specific to mitral valve dysplasia (left side of the heart) include:
- heart murmur, possibly with vibrations that can be felt on the side of the chest
- rapid breathing
- coughing from fluid accumulation in the lungs
- bluish discoloration of the mucous membranes when inadequate oxygen is being circulated by the failing heart
Signs specific to tricuspid valve dysplasia (right side of the heart) include:
- heart murmur, possibly with vibrations that can be felt on the side of the chest
- enlarged or pulsing jugular veins in the neck
- accumulation of fluid in the abdomen or the soft tissues of the legs
Your veterinarian will want to take radiographs (X-rays) of your cat’s chest as part of the diagnostic plan. Ultrasound imaging of the heart (echocardiography) generally provides a definitive diagnosis and monitors progression of heart failure.
How is AV valve dysplasia treated?
Treatment of AV valve dysplasia is focused on managing signs of congestive heart failure and/or disturbances in heart rhythm, generally using medications. Sometimes fluid will be removed from the chest or abdomen. Your cat’s activity may need to be restricted based on their exercise tolerance. Your cat may faint with increased exercise or if the heart suddenly beats in a rapid, irregular rhythm. Nutritional changes may be recommended to restrict sodium. Your veterinarian will determine which medications to prescribe.
Unfortunately, the prognosis for AV valve dysplasia is guarded to poor. Affected cats should not be used for breeding due to the heritability of valvular disease.
