Mitral Valve Disease in Dogs

Mitral Valve Disease in Dogs Your dog may be perfectly fine, with no outward signs of disease, when suddenly, on a routine visit to the vet, the latter may tell you they have noticed a murmur, and tell you that your beloved pooch has mitral valve disease. Mitral valve disease is, in fact, much more common that you might suspect, affecting around one in 10 dogs. Let’s explore further.

How the Heart Works

In order to understand this disease better, it is vital to have a basic knowledge of how the heart works. The heart comprises four chambers (two upper chambers called atria and two lower ones called ventricles). Each chamber has a valve, whose job is to stop blood from flowing backwards to where it shouldn’t go. The mitral valve is the valve situated between the left ventricle and atrium. When the mitral valve leaks, blood flows back into the left atrium (i.e. it flows in the wrong direction). This causes the left atrium to enlarge and fluid to accumulate in the lungs because of increased volume and pressure. In older dogs, the mitral valve can thicken and ‘flop down’, preventing it from closing properly and thus leading to leakage. Mitral valve insufficiency can also be cause by the breakage of chordae tendinae (the chords that hold the valve leaflets in place), and by an infection called endocarditis.

Breeds Prone to Mitral Valve Disease

Certain breeds are more prone to mitral valve disease, especially small breed dogs, including Boston Terriers, Cavalier King Charles Spaniels, Miniature Poodles, Cocker Spaniels, Dachshunds, and Pomeranians. The disease can also occur in mixed breed and bigger dogs.

Signs of Mitral Valve Disease

Sometimes, there are no obvious signs. Typical symptoms include increase tiredness, coughing, difficulty breathing, breathing quickly, fainting, and weakness.


Normally, your veterinarian will be able to hear a murmur. An X-ray may be undertaken to determine the presence/amount of fluid in the lungs and the size of the heart. As the disease worsens, the heart grows larger. Your vet may refer you to a specialist so that an echocardiography can be undertaken. This test allows the specialist to view, not only the size of the heart and the way the muscle and valves work, but also the blood flow/level of regurgitation. Your veterinarian may also perform additional tests (such as blood and urine tests) to see how your dog’s other organs are working.


When a murmur is very mild, your vet may recommend a ‘wait and see’ approach. Some dogs do fine without any medication at all but others can worsen quickly, suffering from edema (fluid build-up in the lungs, which is noticeable because the dog begins to breathe with difficulty; often, owners observe that their dog’s belly moves while the it breathes, which indicates there is a problem). If you notice ‘belly breathing’ or difficulty with respiration, take your dog to the vet immediately; this is an emergency and your dog could pass away he is not treated quickly. Your dog may have to stay overnight at emergency, where he will be given diuretics (to get rid of the fluid build-up), in addition to any other medication the emergency vet sees fit.

Your vet will most probably put your dog on a course of medications which will normally include diuretics (such as Furosemide) and ACE inhibitors (to lower blood pressure and reduce resistance to blood flowing out of the heart), and which might include Digoxin (to strengthen heart contractions), Vetmedin (touted as somewhat of a ‘miracle drug’ by many dog owners, it helps the heart pump blood more efficiently).

Since dogs with congestive heart issues tend to cough, your vet may also recommend a homeopathic syrup to soothe the throat (cough suppressants such as codeine should be avoided because a dog needs to cough in order to rid the lungs of excess fluid). It is also vital that you limit the amount of salt your dog eats (special food is available for dogs with heart disease) and the amount of exercise it undertakes. Keep your dog’s stress levels low, too, since canines can pick up on human stress. Remember the many times your dog has helped you in tough times; be there for them when they need you, providing lots of love and attention and ensuring all medications are taken on time (otherwise, they may not be as effective as they should be). Finally, take your dog for frequent check-ups and bear in mind that the disease may require several X-rays and vet visits. Your pooch is worth every second and penny spent.


How well your dog reacts to the medication is a very individual matter. Some dogs progress quickly from mitral valve disease to congestive heart failure. Others react well to the medication and last two to three years longer or even more. It is vital to obtain early diagnosis so your dog can be placed on the correct medication.

Article sent in by Sally France

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