Mitral Valve Disease in Cavaliers: What Every Owner Needs to Know
Mitral Valve Disease (MVD), also known as Myxomatous Mitral Valve Disease (MMVD), is the most common heart disease affecting Cavalier King Charles Spaniels and remains one of the leading causes of death within the breed.
While MVD can affect many breeds of dogs, Cavaliers are particularly predisposed due to an inherited genetic susceptibility. Understanding the condition, recognising the early signs, and seeking veterinary care promptly can help affected dogs maintain a good quality of life for many years.
What Is Mitral Valve Disease?
The heart contains four valves that ensure blood flows in the correct direction through the heart chambers.
The mitral valve sits between the:
Left atrium (upper chamber)
Left ventricle (lower chamber)
In a healthy heart, this valve closes tightly every time the heart contracts.
In dogs with MVD, the valve gradually thickens and degenerates. As the disease progresses, the valve no longer closes properly, allowing blood to leak backwards from the ventricle into the atrium. This backward flow of blood is known as mitral regurgitation.
Over time, the heart must work harder to compensate for the leaking valve. Eventually, enlargement of the heart chambers may occur, and in some dogs, congestive heart failure develops.
Why Are Cavaliers So Affected?
Mitral Valve Disease occurs in many breeds, particularly small and medium-sized dogs. However, Cavalier King Charles Spaniels develop the disease earlier and more frequently than almost any other breed.
Research has shown that:
Approximately 50% of Cavaliers have a detectable heart murmur by five years of age.
Most Cavaliers will develop some degree of mitral valve degeneration during their lifetime.
The condition often develops years earlier in Cavaliers than in other breeds.
The disease is believed to be inherited through a complex combination of multiple genes, influenced by environmental factors.
At present, there is no DNA test available that can reliably predict whether a dog will develop MVD.
What Happens Inside the Heart?
As the mitral valve becomes thicker and less efficient:
Blood begins leaking backwards.
The heart works harder to maintain circulation.
The left atrium enlarges.
The left ventricle may enlarge.
Pressure within the lungs can increase.
Fluid may accumulate in the lungs, leading to congestive heart failure.
The progression of the disease varies considerably between individual dogs. Some Cavaliers may live many years with a mild murmur and never develop heart failure, while others experience more rapid progression.
What Are the Early Signs?
One of the challenges of MVD is that many dogs show no obvious signs during the early stages. In fact, the first indication is often a heart murmur detected during a routine veterinary examination.
Early Signs May Include:
A newly detected heart murmur
Reduced exercise tolerance
Mild tiredness after activity
Slightly increased sleeping
Occasional coughing
Increased respiratory rate during rest
Because these changes can be subtle, many owners simply attribute them to ageing.
Signs of Advanced Disease
As the condition progresses, more noticeable symptoms may develop. These can include:
Persistent Coughing
A cough associated with MVD is often most noticeable:
At night
Early in the morning
After exercise
When excited
Exercise Intolerance
Affected dogs may:
Tire more quickly
Refuse walks
Slow down during exercise
Struggle with stairs
Increased Breathing Rate
An increased resting respiratory rate is often one of the earliest indicators that congestive heart failure may be developing.
Breathing Difficulties
Fluid accumulation within the lungs can result in:
Rapid breathing
Laboured breathing
Open-mouth breathing
Respiratory distress
Fainting or Collapse
Although less common, severe cardiac disease may occasionally lead to episodes of collapse.
How Is MVD Diagnosed?
Physical Examination
The first clue is often the detection of a heart murmur by a veterinarian. However, a murmur alone does not determine how advanced the disease is.
Echocardiography (Cardiac Ultrasound)
The gold standard for diagnosis is an echocardiogram performed by a veterinary cardiologist.
This allows detailed assessment of:
Mitral valve structure
Severity of valve leakage
Heart chamber size
Overall heart function
Chest Radiographs
X-rays may be used to assess:
Heart enlargement
Lung changes
Evidence of heart failure
Electrocardiography (ECG)
An ECG may be recommended if arrhythmias are suspected.
What Should You Do If You Suspect Your Cavalier Has MVD?
If you notice any of the following:
A persistent cough
Reduced exercise tolerance
Increased sleeping
Rapid breathing
Difficulty breathing
Collapse
Arrange a veterinary examination as soon as possible.
Early diagnosis allows more accurate monitoring and can identify dogs that may benefit from treatment before heart failure develops.
If your Cavalier develops breathing difficulties or respiratory distress, seek emergency veterinary care immediately.
Monitoring at Home
One of the simplest and most valuable things owners can do is monitor their dog's resting respiratory rate. When your dog is asleep:
Count the number of breaths taken in one minute.
Record the number regularly.
Notify your veterinarian if the rate begins increasing consistently.
Many cardiologists consider a resting respiratory rate persistently above 30 breaths per minute worthy of investigation.
What Treatments Are Available?
There is currently no cure for MVD. However, modern veterinary medicine can significantly improve quality of life and, in many cases, prolong survival. Treatment depends on the stage of disease.
Stage B1
Dogs have a murmur but no significant heart enlargement.
Typically:
No medication is required.
Regular monitoring is recommended.
Stage B2
Dogs have a murmur and measurable heart enlargement but have not yet developed heart failure.
Studies have shown that the medication pimobendan can delay the onset of congestive heart failure in appropriate patients.
Stage C
Dogs have developed congestive heart failure.
Treatment commonly includes:
Pimobendan
Diuretics (such as furosemide)
ACE inhibitors (in selected cases)
Additional cardiac medications as required
Stage D
Advanced heart failure may require:
Multiple medications
Frequent monitoring
Specialist management
Treatment plans are tailored to the individual dog.
Can MVD Be Prevented?
Because MVD has a strong inherited component, it cannot currently be prevented entirely.
However, owners can help support cardiovascular health by:
Maintaining Good Dental Health
Severe periodontal disease can allow bacteria to enter the bloodstream and contribute to systemic illness.
Regular dental care includes:
Tooth brushing
Veterinary dental examinations
Professional dental treatment when required
Maintaining a Healthy Weight
Obesity places additional strain on the cardiovascular system and can worsen clinical signs.
Feeding a Balanced Diet
Commercially formulated complete diets provide essential nutrients required for normal heart function.
Routine Veterinary Checks
Regular examinations allow early detection of heart murmurs and facilitate timely referral to a veterinary cardiologist when appropriate.
Cardiology Services in Queensland
Queensland is fortunate to have access to several highly experienced veterinary cardiologists who provide:
Heart murmur screening
Echocardiography
Cardiac disease diagnosis
Ongoing management plans
Early assessment by a veterinary cardiologist can provide valuable information about disease severity and future monitoring requirements.
Mitral Valve Disease is an unfortunate reality for many Cavalier King Charles Spaniels, but early detection and modern treatment options have dramatically improved outcomes for affected dogs.
Many Cavaliers diagnosed with MVD continue to enjoy excellent quality of life for years following diagnosis.
The key is awareness. Understanding the condition, attending regular veterinary examinations, monitoring for subtle changes, and seeking specialist advice when required can make a significant difference to both longevity and quality of life.
By working closely with your veterinarian and veterinary cardiologist, you can ensure your Cavalier receives the best possible care throughout every stage of this common but manageable condition.
References
Atkins, C., Bonagura, J., Ettinger, S., Fox, P., Gordon, S., Haggstrom, J., Hamlin, R., Keene, B., Luis-Fuentes, V., & Stepien, R. (2009). Guidelines for the diagnosis and treatment of canine chronic valvular heart disease. Journal of Veterinary Internal Medicine, 23(6), 1142–1150. https://doi.org/10.1111/j.1939-1676.2009.0392.x
Boswood, A., Haggstrom, J., Gordon, S. G., Wess, G., Stepien, R. L., Oyama, M. A., Keene, B. W., Bonagura, J., MacDonald, K. A., Patteson, M., Smith, S., Fox, P. R., Sanderson, K., Woolley, R., Szatmári, V., Menaut, P., Church, W. M., O'Sullivan, M. L., Jaudon, J. P., ... Watson, P. (2016). Effect of pimobendan in dogs with preclinical myxomatous mitral valve disease and cardiomegaly: The EPIC study. Journal of Veterinary Internal Medicine, 30(6), 1765–1779. https://doi.org/10.1111/jvim.14586
Cavalier King Charles Spaniel Club, UK. (2024). Mitral valve disease information for owners. https://www.thecavalierclub.co.uk
Häggström, J., Hansson, K., Kvart, C., & Swenson, L. (1992). Chronic valvular disease in the Cavalier King Charles Spaniel in Sweden. Veterinary Record, 131(24), 549–553.
Keene, B. W., Atkins, C. E., Bonagura, J. D., Fox, P. R., Haggstrom, J., Fuentes, V. L., Oyama, M. A., Rush, J. E., Stepien, R., & Uechi, M. (2019). ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. Journal of Veterinary Internal Medicine, 33(3), 1127–1140. https://doi.org/10.1111/jvim.15488
Merck & Co., Inc. (n.d.). Myxomatous mitral valve degeneration in dogs. In Merck Veterinary Manual. https://www.merckvetmanual.com
Veterinary Cardiologists Australia. (n.d.). Cardiology services and heart disease screening. https://www.vetcards.com.au
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