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MMVD is common in dachshunds

Myxomatous mitral valve disease or MMVD in dogs

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Myxomatous mitral valve disease (MMVD) is the most common heart disease in dogs. It accounts for around 75% of all diagnosed heart conditions.

It is one of those diseases you should be aware of, especially if you own a small breed dog. 

Disclaimer: All content and information on this website are for informational and educational purposes only and do not constitute veterinary medical or pet health care advice. 

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Other names of MMVD in dogs

The disease has many names, such as

  • degenerative mitral valve disease
  • chronic degenerative valvular disease
  • degenerative atrioventricular valve disease
  • canine mitral valve endocardiosis
  • canine mitral valve regurgitation (although this one, strictly speaking, is more of a feature of MMVD than a proper disease name) and others. 

What is the mitral valve?

The dog’s heart has four chambers: the atrium and the ventricle on the left side and the atrium and the ventricle on the right.

The mitral valve lies on the left, between the left atrium and ventricle.

It helps blood flow in only one direction – from the atrium to the ventricle – and prevents it from flowing back.

There is another atrioventricular valve that does the same function on the right side. It is called a tricuspid valve. We mention it here because, in some dogs with MMVD, both the mitral and the tricuspid valves are affected by the disease.

What happens in MMVD in a dog?

In mitral valve disease, the mitral valve becomes distorted.

When the left ventricle contracts and sends blood to the whole body through the aorta, some blood also leaks through the valve back to the left atrium.

That leakage is called a mitral valve regurgitation. Because of this, the left atrium and the left ventricle experience an increase in blood volume and pressure inside them.

When that pressure becomes too high, it leads to pulmonary edema (edema of the lungs) and breathing difficulties.

Veterinarians call it left-sided congestive heart failure.

Unfortunately, in acute cases, it can even lead to the death of the animal.

What dog breeds are predisposed to mitral valve disease?

Cavalier King Charles Spaniels, toy and miniature poodles, dachshunds, and other small dog breeds frequently get MMVD.

This disease is typical of older dogs but can sometimes be diagnosed earlier in life. Larger dogs and mixed-breed dogs can also get it.

What causes MMVD in dogs?

Although much research is underway, the exact cause is still unknown. Genetic components play a role in some breeds.

What about Cavalier King Charles Spaniels?

One of the breeds in which genetics proved to be important in MMVD is the Cavalier King Charles Spaniel. The disease affects many, if not most, of these dogs.

There is a great website on Cavalier health and diseases that shares extensive current information on MMVD, including recent research advancements. We highly recommend you visit it.

Stages of MMVD in dogs

For canine mitral valve disease staging, veterinarians currently use the ACVIM (that stands for American College of Veterinary Internal Medicine) classification.

There are 4 main stages (A, B, C, D), and only dogs in stages C and D have symptoms of congestive heart failure.

Stage A

Here we have dogs that do not have the disease yet but are at a very high risk of it. All Cavalier King Charles Spaniels, for example. 

Stage B1 and B2

Stage B dogs do have the disease, and there is a heart murmur on auscultation, and the mitral valve changes and regurgitation on heart ultrasound. Sometimes, veterinarians will also see heart enlargement on ultrasound or chest radiographs.

Those dogs whose hearts are not yet enlarged or the enlargement is not pronounced enough (there are certain criteria for this) are in stage B1 mitral valve disease, while those with an enlarged left side of the heart are in stage B2. 

Stage C

This is the stage where veterinarians place dogs that already have or previously had clinical signs related to lung congestion (congestive heart failure), with breathing difficulties, cough, and exercise intolerance being the most common symptoms.

Stage D

Stage D dogs have end-stage congestive heart failure and are not doing fine on standard therapy anymore.

They might require very high doses of diuretics, a change of diuretic, or the addition of other medications to control breathing problems and cough.

Symptoms of MMVD in dogs

Once the disease progresses to congestive heart failure, signs of lung edema and advanced MMVD can be noticed. They are:

  • Faster breathing with extra effort
  • Cough
  • Decreased exercise tolerance
  • Fainting, which owners can sometimes describe as seizures.

Non-specific symptoms can be seen too, such as

  • Decreased appetite
  • Weight loss.

In terminal condition with life-threatening lung edema one can also see

  • Extreme difficulty breathing
  • Froth going out of the mouth.

With well-adjusted treatment which is started early, symptoms of congestion might disappear temporarily. But beware that congestive heart failure needs constant treatment to control signs and prolong your pet’s life. 

Diagnosis of MMVD in dogs

To confirm a diagnosis of myxomatous mitral valve disease, veterinarians perform a heart ultrasound. It allows one to see mitral valve changes and regurgitation and perform many important measurements. 

Exam with auscultation (listening to heart and lung sounds), radiographs to check on heart size and lungs, ECG, blood pressure measurements, and blood work can also play an important role in assessing a pet with MMVD. 

Treatment of MMVD in dogs

To treat MMVD, veterinarians prescribe medications such as:

  • diuretics – to get rid of fluid in the lungs
  • medications to increase cardiac contractility
  • medications to counteract harmful disease mechanisms.

Most of them are started in stage C when symptoms are noticed. However, some are used in stage B2 in order to extend the time before congestive heart failure onset. 

Medical therapy cannot cure MMVD but can, sometimes drastically, increase the quality of life and lifespan of our pets. 

To try to cure the disease, canine mitral valve surgery can be done in some dogs. The surgery cost is high, and it is not universally available. But do talk to your veterinarian to discuss your options.

Moderate dietary sodium restriction for dogs with mitral valve disease is frequently recommended.

It is also important to prevent weight loss and ensure that your pet eats enough and has balanced food.

Talk to your veterinarian about a diet that will work best for your dog and how to implement it. 

Treatment of life-threatening lung edema

Myxomatous mitral valve disease can lead to lung edema that endangers the life of a dog.

Bring your pet to the nearest veterinarian immediately if you notice symptoms like breathing problems (fast and/or labored breathing), cough, or froth out of the muzzle!

A veterinarian might need to hospitalize your dog and provide emergency treatment, which can include oxygen, multiple medications to decrease edema and help the heart and lungs function, and, in some cases, other life-saving procedures.

Unfortunately, the emergency therapy is not always effective. And even with the most dedicated and caring owners and timely veterinary help, pets can die from lung edema.

How long will my dog live with mitral valve disease?

Some dogs with MMVD live for years, never develop heart failure and die of unrelated causes in old age.

Dogs with symptoms of pulmonary edema have a much higher chance of not surviving for longer than a few years, even with the proper treatment.

In acute cases, the survival time may be even less – days or months.

Remember, early diagnosis, regular veterinary check-ups, and well-adjusted treatment are very important for prolonging life. 

How to care for a dog with MMVD

It is very important to follow the treatment plan and not to skip medications. Also, never stop treatment without your veterinarian’s advice.

Breathing rate counting and diuretic dose adjustments

A regular breathing rate measurement is a good habit to learn for every owner who has a dog with MMVD.

It is equally useful for dogs who do not have symptoms, as well as for those already in congestive heart failure. 

You can easily do it by counting the number of breaths – “chest movements” – per minute in a sleeping or resting dog.

Inhalation (chest going up) and exhalation (chest going down) are counted as 1.

Preferably, your pet should not see you counting and paying attention to them. To achieve that, count from far away. Any interaction with the owner (even just looking at you) will increase the rate, and measurement will not be trustworthy. 

In dogs without symptoms, respiratory rate measurement helps predict the onset of congestive heart failure and start treatment at the right time. Know your dog’s “normal” (baseline, with no pulmonary edema) rate and measure it regularly per your veterinarian’s advice. Let your vet know if it starts to increase over time or if it exceeds 30/min. 

Measurements should be taken more frequently in a dog with congestive heart failure (stages C and D), per your pet veterinarian’s advice. The sleeping or resting breathing rate should generally stay under 30/min.

Treatment adjustments may be frequently needed in dogs with stages C and D (those with congestive heart failure). Your pet’s breathing rate will help you and your veterinarian guide those adjustments.

Keep in touch with your vet and let them know about any new or returning symptoms, such as increased respiratory rate, cough, decreased appetite, or others. 

MMVD dog diet

Follow your vet’s advice on feeding your pet. Some vets will recommend moderate salt restriction.

Let them know if your dog refuses to eat the new diet. Proper calorie intake and maintaining an ideal body weight is very important for pets with heart disease.

Sometimes, mixing wet and dry food together, warming it, or offering different foods might help feed dogs with decreased appetite. 

Additional supplements, depending on the situation and blood work results, can be recommended.

Stress and MMVD in dogs

Stress-free life is a must for dogs with heart conditions, especially when they are already in congestive heart failure.

Any stress can provoke or worsen symptoms of pulmonary edema and, in dogs with advanced disease, can even lead to death.

Physical exercise and walks in MMVD

There is no rule that would suit every dog, as the amount of recommended physical activity depends heavily on the condition of an individual patient at a specific time. 

Full cessation of physical activity can be detrimental, but excessive activity can also be dangerous.

Talk to your dog’s veterinarian about the amount of physical activity your pet can handle safely now. Remember that this can change as the disease progresses.

Canine mitral valve degeneration vs dilated cardiomyopathy

Besides myxomatous mitral valve disease, there is another common dog heart disease called dilated cardiomyopathy (DCM).

It differs from mitral valve degeneration in many ways in terms of causes, affected breeds, and course of the disease. 

But what DCM and MMVD have in common is that they both can cause congestive heart failure and, at that stage, have very similar symptoms, diagnostic plan, and treatment. 

References