Myxomatous Mitral Valve Disease (MMVD)

Understanding Cavalier King Charles Spaniel Heart Disease and Why Responsible Breeding Matters

If you own a Cavalier King Charles Spaniel, or you're considering bringing a Cavalier puppy into your family, understanding Myxomatous Mitral Valve Disease (MMVD) is essential. Myxomatous Mitral Valve Disease is the most significant inherited health condition affecting the breed and remains the leading cause of death in Cavalier King Charles Spaniels worldwide.

The good news is that responsible breeders, veterinary cardiologists and breed clubs around the world are working together to improve the long-term heart health of Cavaliers through carefully managed breeding programmes and comprehensive health screening.

Choosing a puppy from a breeder who follows these recommendations gives you the best opportunity of welcoming a healthy Cavalier King Charles Spaniel into your family while helping preserve the future of this wonderful breed.

What is Myxomatous Mitral Valve Disease (MMVD)?

Myxomatous Mitral Valve Disease, commonly abbreviated to MMVD, is a progressive degenerative disease affecting the mitral valve, one of the four valves inside the heart. The mitral valve sits between the heart's left atrium and left ventricle and acts as a one-way door, ensuring blood flows in the correct direction. In dogs affected by Myxomatous Mitral Valve Disease, the valve gradually becomes thickened, distorted and less able to close properly. As this happens, blood begins leaking backwards through the valve each time the heart beats. This is known as mitral regurgitation.

Over time, the heart must work increasingly harder to compensate. Eventually the heart enlarges, and in advanced cases fluid may accumulate in the lungs, resulting in congestive heart failure (CHF). Myxomatous Mitral Valve Disease is a progressive disease. It cannot currently be cured, but it can often be managed successfully for many years with appropriate veterinary care.

Why Are Cavalier King Charles Spaniels So Prone to Myxomatous Mitral Valve Disease?

While Myxomatous Mitral Valve Disease occurs in many breeds, the Cavalier King Charles Spaniel is unique because:

  • It develops the disease more frequently than almost any other breed.

  • It often develops at a much younger age.

  • The disease has a strong inherited (genetic) component.

Research suggests that the breed's relatively small genetic foundation has contributed to the high prevalence of inherited heart disease. Importantly, Myxomatous Mitral Valve Disease is not caused by poor care, poor diet or lack of exercise. It is primarily an inherited disease. This is why responsible breeding plays such a critical role.

Can Responsible Breeding Reduce Myxomatous Mitral Valve Disease?

Yes. Although Myxomatous Mitral Valve Disease cannot currently be eliminated entirely from the breed, scientific research has demonstrated that carefully managed breeding programmes can reduce the incidence of early-onset Myxomatous Mitral Valve Disease.

Responsible breeders help achieve this by:

  • Having breeding dogs examined annually by a board-certified veterinary cardiologist

  • Delaying breeding until dogs reach an appropriate age

  • Selecting breeding dogs with healthy hearts

  • Considering the heart health of parents, grandparents and siblings

  • Following recognised breeding protocols developed specifically for Cavalier King Charles Spaniels

In contrast, breeding dogs without heart screening or ignoring known heart disease in breeding lines perpetuates inherited disease and undermines efforts to improve the long-term heart health of the breed. Every puppy purchased from a breeder who follows recommended heart-screening protocols supports responsible breeding and contributes to the future health and welfare of the Cavalier King Charles Spaniel.

What Happens Inside the Heart?

As Myxomatous Mitral Valve Disease progresses:

  • the mitral valve thickens

  • the valve becomes misshapen

  • blood leaks backwards through the valve

  • the heart enlarges

  • pressure builds within the heart

  • fluid may eventually accumulate within the lungs

This progression can take years. Many dogs live happily for a long period before developing symptoms.

Early Warning Signs

One of the challenges of Myxomatous Mitral Valve Disease is that affected dogs often appear perfectly healthy during the early stages. In fact, many owners have no idea their dog has heart disease until a veterinarian detects a heart murmur during a routine examination.

Possible early signs include:

  • Reduced stamina

  • Mild exercise intolerance

  • Increased sleeping

  • Becoming tired more quickly

  • Slightly faster breathing after exercise

Many dogs show no outward signs at all.

Common Symptoms of Advanced Myxomatous Mitral Valve Disease

As the disease progresses, dog owners may notice:

  • Persistent coughing

  • Difficulty breathing

  • Rapid breathing while resting

  • Reduced willingness to exercise

  • Fatigue

  • Collapse or fainting episodes

  • Weight loss

  • Reduced appetite

  • Distended abdomen (in advanced disease)

These symptoms warrant prompt veterinary assessment.

Is Myxomatous Mitral Valve Disease Painful?

Myxomatous Mitral Valve Disease itself is not generally considered a painful disease. However, advanced heart disease can significantly reduce a dog's quality of life.

Dogs with congestive heart failure may experience:

  • breathlessness

  • fatigue

  • reduced exercise tolerance

  • difficulty sleeping comfortably

  • anxiety associated with struggling to breathe

These symptoms are distressing for both the dog and their family and require veterinary treatment.

How is Myxomatous Mitral Valve Disease Diagnosed?

Diagnosis usually begins with a routine veterinary examination.

Your veterinarian may detect a:

  • heart murmur

  • abnormal heart rhythm

  • enlarged heart

Further testing may include:

Cardiac Auscultation

Listening to the heart with a stethoscope.

Echocardiography (Heart Ultrasound)

The gold standard for diagnosing Myxomatous Mitral Valve Disease.

An echocardiogram allows a veterinary cardiologist to evaluate:

  • valve function

  • blood flow

  • chamber size

  • disease severity

Chest X-rays

Used to assess:

  • heart enlargement

  • fluid within the lungs

  • congestive heart failure

Blood Pressure Measurement

Provides additional information about cardiovascular health.

Blood Tests

Sometimes recommended to assess overall health before beginning medication.

Should My Cavalier See a Veterinary Cardiologist?

Yes. Because Cavaliers are predisposed to Myxomatous Mitral Valve Disease, many veterinarians recommend regular cardiac examinations throughout life. Breeding dogs should undergo annual examinations by a veterinary cardiologist.

Pet Cavalier King Charles Spaniels with heart murmurs often benefit from referral to a cardiologist for echocardiography and ongoing management.

Can Myxomatous Mitral Valve Disease Be Cured?

Unfortunately, no. Myxomatous Mitral Valve Disease cannot currently be cured. However, many dogs enjoy an excellent quality of life for years with appropriate monitoring and treatment. Early diagnosis is one of the most important factors influencing long-term management.

How is Myxomatous Mitral Valve Disease Treated?

Treatment depends on the stage of disease. Some Cavalier King Charles Spaniels require only regular monitoring. Others benefit from medication designed to reduce the workload on the heart and delay progression.

Common medications include:

  • Pimobendan

  • Diuretics

  • ACE inhibitors

  • Spironolactone

  • Other medications depending on the individual dog

Treatment plans should always be developed by your veterinarian or veterinary cardiologist.

Living with a Cavalier Diagnosed with Myxomatous Mitral Valve Disease

Many Cavalier King Charles Spaniel dogs continue enjoying wonderful lives after diagnosis.

Successful management often includes:

  • regular veterinary examinations

  • repeat echocardiograms

  • monitoring resting respiratory rate

  • administering medication every day

  • maintaining a healthy body weight

  • moderate exercise

  • avoiding obesity

Owners should carefully monitor changes in breathing, appetite and energy levels.

What Does Treatment Involve?

Managing Myxomatous Mitral Valve Disease requires commitment.

Owners should be prepared for:

  • lifelong medication

  • regular veterinary visits

  • specialist cardiology appointments

  • periodic imaging

  • ongoing monitoring at home

  • increasing treatment as the disease progresses

Costs vary depending on disease severity, medications and specialist care.

How Can Puppy Buyers Reduce Their Risk?

No dog breeder can guarantee that a Cavalier puppy will never develop Myxomatous Mitral Valve Disease. However, responsible breeders significantly reduce the likelihood of early-onset disease by following recommended heart-screening protocols.

Before purchasing a Cavalier King Charles Spaniel puppy, ask the breeder:

  • Have both parents undergone annual heart examinations by a veterinary cardiologist?

  • May I see the cardiologist's certificates?

  • At what age were the parents bred?

  • What is the heart history of the grandparents?

  • Do you follow recognised Cavalier breeding protocols?

A responsible dog breeder will happily answer these questions and provide documentation.

Why Your Choice of Breeder Matters

Every dog puppy purchase influences the future of the Cavalier King Charles Spaniel breed. When buyers choose puppies from breeders who invest in comprehensive health testing and responsible breeding practices, they support programmes designed to reduce inherited disease.

Conversely, purchasing puppies from breeders who ignore recommended heart screening perpetuates demand for dogs bred without regard for inherited heart disease and undermines efforts to improve the long-term health of the Cavalier King Charles Spaniel. By choosing a responsibly bred, health-tested puppy, you are investing not only in your own dog's future but also in the future of the breed.

In Conclusion

Myxomatous Mitral Valve Disease remains one of the greatest health challenges facing the Cavalier King Charles Spaniel. While it cannot currently be eliminated or cured, responsible breeding, early diagnosis and advances in veterinary cardiology are helping more Cavaliers live longer, healthier and happier lives.

If you are looking for a Cavalier King Charles Spaniel puppy in Queensland or Australia, choose a dog breeder who places health above convenience, follows recognised heart-screening protocols and is committed to the lifelong welfare of every puppy they breed. Your decision today can make a meaningful difference to the future health of this extraordinary breed.

References

  1. Keene BW, Atkins CE, Bonagura JD, et al. ACVIM Consensus Guidelines for the Diagnosis and Treatment of Myxomatous Mitral Valve Disease in Dogs. Journal of Veterinary Internal Medicine. 2019.

  2. Boswood A, Häggström J, Gordon SG, et al. Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease (EPIC Study). Journal of Veterinary Internal Medicine. 2016.

  3. American College of Veterinary Internal Medicine (ACVIM) Consensus Guidelines

  4. CavalierHealth.org – Mitral Valve Disease Information Library

  5. The Kennel Club (UK) – Cavalier King Charles Spaniel Health Information

  6. American Veterinary Medical Association (AVMA) – Heart Disease in Dogs

Disclaimer

The information provided in the Cavalier Knowledge Centre is intended for general educational purposes only and is not a substitute for veterinary advice, diagnosis or treatment.