Talking To Your Vet About Heart Valve Malfunction In The Dog (Mitral Insufficiency)

What Is Mitral Insufficiency?

When dogs develop diseases that affect the heart muscle and cause degenerative thickening of the heart walls and leaky valves, the mitral valve is the most commonly affected valve. The mitral valve separates the left atrium from the left ventricle. Some dog breeds inherit this disease, and some just develop it with no prior problems in their lineage. The cause is not completely known, but degenerative valvular disease is not reversible.

Signs and Symptoms of Mitral Insufficiency

Many heart diseases result in congestive heart failure, but mitral insufficiency isn’t necessarily one of them. Although they may develop the classic heart murmur, they may never exhibit signs of congestive heart failure.

Early on in the disease’s progression, your veterinarian may notice a faint murmur as the valve begins to leak. Your dog might not present any of the other symptoms that come with heart disease, such as fainting, lethargy, panting, or coughing. As the leak worsens, the heart enlarges and the blood becomes backlogged in the heart and leaks into the lungs. This will cause those symptoms to appear, and a diagnosis of congestive heart failure will follow. This progression is slow never becomes this severe and for some dogs. However, if you or your vet suspects it, here are some things to watch for:

    • Reduced exercise ability
    • Increased respiratory rate
    • Increased panting
    • Cough with activity
    • Avoidance to laying down
    • Loss of appetite
    • Restlessness while resting


Some dogs have ascites or abdominal fluid, while others have acute weakness or fainting. Most dogs develop an irregular heartbeat. As long as your dog is asymptomatic for heart failure, he will not be treated for anything. You may find it beneficial to reduce his salt intake.

Remember that a diagnosis of degenerative valvular disease is not a death sentence. Some dogs never progress to heart failure. If your dog does enter into the stages of heart failure, there are several medications and therapies to help delay the symptoms, but an aggressive approach needs to be taken.