Understanding Mitral Valve Disease in Dogs (Vet-Approved Guide)

Mitral valve disease (often called MVD or degenerative mitral valve disease) is a progressive heart condition where the valve between the left atrium and left ventricle does not close properly. This valve is responsible for keeping blood moving in the correct direction through the heart. When it becomes weakened or thickened, some blood leaks backwards, a process known as regurgitation.

As the valve deteriorates over time, the heart has to work harder to maintain normal circulation. In response, it may enlarge, and fluid can begin to build up in the lungs, especially in more advanced stages.

Mitral valve disease is most commonly seen in small and medium-sized dogs, particularly as they get older. It often develops gradually, with mild changes present long before obvious symptoms appear.

MVD is typically a lifelong, progressive condition. While it cannot be reversed, early detection and appropriate management can significantly slow its progression and help maintain your dog’s quality of life.

Mitral valve disease develops due to a combination of age-related changes and genetic predisposition. The most common underlying cause is myxomatous degeneration, a process where the valve gradually becomes thickened, weakened, and less effective at preventing blood from leaking backwards.

Contributing factors

• Ageing: The risk increases significantly in middle-aged to senior dogs

• Genetics: Some dogs inherit a tendency for early valve degeneration
• Heart structure changes: Over time, the heart may enlarge in response to the leaking valve

While MVD is not caused by lifestyle choices, certain factors can place additional strain on the heart and worsen symptoms over time, including obesity, dental disease, and high stress or anxiety levels.

Breeds at Higher Risk of Mitral Valve Disease

While any dog can develop MVD, it is far more common in small and toy breeds. Breeds with increased susceptibility include:

• Cavalier King Charles Spaniels (particularly high risk, often at a younger age)
• Dachshunds
• Miniature and Toy Poodles
• Chihuahuas
• Shih Tzus
• Pomeranians

If you own one of these breeds, regular veterinary check-ups are especially important, as early changes can occur before noticeable symptoms develop.

Recognising MVD early can make a meaningful difference to how well it is managed. Symptoms often develop gradually, and some dogs show very few signs in the early stages.

Early signs

• A soft, persistent cough, especially at night or after exercise
• Tiring more quickly on walks or during play
• Breathing faster than normal, even when resting
• Reduced interest in physical activity
• Restlessness or difficulty settling, particularly at night

Signs of progression

As the condition advances, signs related to breathing and circulation become more noticeable:

• Rapid or laboured breathing
• Increased effort when inhaling or exhaling
• Panting more often, even in cool conditions
• Pale or slightly bluish gums in more severe cases

Advanced signs and congestive heart failure

In later stages, MVD can lead to congestive heart failure. At this point, symptoms become more serious:

• Frequent or worsening cough
• Marked lethargy or weakness
• Loss of appetite and noticeable weight loss
• Fainting or sudden collapse
• Swollen abdomen due to fluid build-up (less common)

Diagnosing mitral valve disease involves a combination of physical examination and simple diagnostic tests. In many cases, the condition is first suspected during a routine vet visit—often before any obvious symptoms are noticed at home.

Initial Signs Your Vet May Detect

One of the earliest indicators of mitral valve disease is a heart murmur, which your vet can hear using a stethoscope. This sound is caused by blood leaking backwards through the faulty valve.

During a check-up, your vet may:

• Listen for a heart murmur or abnormal heart sounds
• Check your dog’s heart rate and rhythm
• Assess breathing patterns and lung sounds
• Look for subtle signs like increased respiratory rate or effort

A murmur doesn’t always mean advanced disease, but it does signal that further monitoring or testing may be needed.

Common Diagnostic Tests

If mitral valve disease is suspected, your vet may recommend additional tests to better understand the severity and impact on the heart.

These may include:

• Chest X-rays: to check for heart enlargement or fluid in the lungs
• Echocardiogram (heart ultrasound): the most accurate way to assess the mitral valve and blood flow
• Electrocardiogram (ECG): to evaluate heart rhythm
• Blood pressure measurement: to assess overall cardiovascular health

Not every dog will need all of these tests straight away. Your vet will guide you based on your dog’s symptoms and examination findings.

Understanding Disease Stages

Mitral valve disease is often classified into stages, which help guide monitoring and treatment decisions:

• Stage A: Dogs at risk (common in certain breeds) but with no current disease
• Stage B: A heart murmur is present, but no signs of heart failure
• Stage C: Signs of congestive heart failure (such as coughing or breathing difficulty) are present
• Stage D: Advanced disease that requires more intensive management

Knowing your dog’s stage helps determine when treatment should begin and what to expect moving forward.

When to Follow Up

For first-time dog owners, it’s important to understand that diagnosis isn’t a one-time event. Mitral valve disease is typically monitored over time.

Your vet may recommend:

• Regular check-ups every 6–12 months (or more frequently if needed)
• Monitoring your dog’s resting breathing rate at home
• Follow-up imaging to track any progression

Early detection and consistent monitoring allow for timely intervention, helping to slow progression and maintain your dog’s quality of life.

Managing mitral valve disease requires a tailored, long-term approach based on your dog’s stage of disease and individual needs. The goal is to support heart function, reduce fluid build-up, minimise symptoms, and maintain quality of life for as long as possible.

Nutrition and Diet

While diet doesn’t cause mitral valve disease, proper nutrition plays an important role in supporting heart health and overall wellbeing.

Heart-supportive nutrients such as omega-3 fatty acids (EPA and DHA) may help reduce inflammation and support cardiovascular function. These are commonly found in fish oil supplements formulated specifically for dogs.

Balanced, high-quality diets ensure your dog maintains a healthy weight, which is essential for reducing strain on the heart. In some cases, your vet may recommend diets formulated for cardiac support.

Sodium (salt) intake may need to be moderated in dogs with more advanced disease, as excess sodium can contribute to fluid retention. However, restriction should only be done under veterinary guidance.

As with any dietary change, introduce new foods gradually and allow time to assess their impact.

Heart Support Supplements That May Help

In addition to a balanced diet, some supplements may provide added support for dogs with heart disease:

• Omega-3 fatty acids: support heart health and may help reduce inflammation
• Coenzyme Q10 (CoQ10): involved in energy production within heart muscle cells
• L-carnitine and taurine: important for heart muscle function in some dogs

Evidence for supplements can vary, and not all dogs will benefit equally. Always check with your veterinarian before introducing new supplements, as some may interact with medications.

Managing mitral valve disease is an ongoing process, and while it can’t always be prevented, the right approach can help slow its progression and keep your dog comfortable. A combination of regular veterinary care, lifestyle support, and early intervention makes a meaningful difference over time.

Routine Monitoring at Home

Keeping track of subtle changes at home is one of the most valuable tools for managing this condition.

Helpful things to monitor include:

• Your dog’s resting breathing rate (especially when asleep)
• Changes in coughing frequency or severity
• Energy levels and willingness to exercise
• Appetite and general behaviour

Small shifts can be early indicators of progression, even before obvious symptoms develop.

Veterinary Care and Check-ups

Ongoing veterinary care is essential for both prevention (where possible) and long-term management.

Your vet can:

• Detect early heart changes, such as a murmur
• Monitor disease progression over time
• Adjust medications as needed
• Recommend further testing if symptoms change

For dogs at higher risk, regular check-ups are particularly important, even if they appear healthy.

Dental Health Matters

Oral health is often overlooked but can contribute to overall heart health.

• Regular tooth brushing helps reduce harmful bacteria
• Professional dental care may be recommended
• Untreated dental disease can place additional strain on the body

Keeping your dog’s mouth healthy is a simple but important part of long-term care.

Mitral valve disease is a common heart condition in dogs, especially as they age. While it can feel concerning, many dogs live comfortably for years with proper care and monitoring.

Recognising early signs—such as coughing, reduced energy, or changes in breathing—allows for timely treatment and better long-term outcomes. Although the condition can’t be cured, a combination of veterinary care and simple support at home can help maintain your dog’s quality of life.

With guidance from your vet and consistent day-to-day care, you can confidently support your dog through every stage of this condition.

This article was written by Dr. Jack Ayerbe

• American College of Veterinary Internal Medicine (ACVIM). Consensus Guidelines for the Diagnosis and Treatment of Myxomatous Mitral Valve Disease in Dogs. Available at https://onlinelibrary.wiley.com/doi/10.1111/jvim.15488
• VCA Animal Hospitals. Mitral Valve Disease in Dogs. Available at https://vcahospitals.com/know-your-pet/mitral-valve-disease-in-dogs
• Keene, B.W. et al. ACVIM Consensus Update on the Diagnosis and Treatment of Myxomatous Mitral Valve Disease in Dogs (2019 Update). Available at https://onlinelibrary.wiley.com/doi/10.1111/jvim.15488
• Texas A&M University Veterinary Medical Teaching Hospital. Mitral Valve Disease in Dogs. Available at https://vethospital.tamu.edu/small-animal/cardiology/