Mitral valve disease in dogs: symptoms, breeds & testing

Mitral valve disease, also known as endocardiosis, is the most common heart disease affecting older dogs, especially small to medium breeds. It develops slowly over years, often showing no symptoms until dogs are well into their senior years, sometimes over ten years old. This condition progressively worsens the quality of life due to heart function decline and usually leads to congestive heart failure.

Understanding Mitral Valve Disease in Dogs

The mitral valve plays a crucial role in heart function, separating the left atrium and left ventricle. Normally, it opens to allow blood to flow into the ventricle and closes to prevent backflow. In mitral valve disease, the valve thickens and deforms due to plaque-like build-up, allowing blood to leak back into the atrium during contraction. This backward flow causes a heart murmur and forces the heart to work harder, which can mask early symptoms but ultimately leads to heart enlargement and failure.

Common signs of the disease once advanced include an unproductive dry cough, worsening particularly during the night or after exercise, breathlessness, and reduced tolerance to physical activity.

Who Develops Mitral Valve Disease and Why?

Mitral valve disease often has a hereditary component, especially in certain vulnerable breeds. However, ageing itself significantly increases risk, so older dogs, including those from breeds without a family history, can be affected. Males tend to be twice as likely to develop the condition as females.

Breeds Most Prone to Mitral Valve Disease

While any dog can develop mitral valve disease, several breeds are at notably higher risk. The Cavalier King Charles spaniel is the breed most commonly affected, with a risk around twenty times higher than other dogs. Other predisposed breeds include the Chihuahua, miniature poodle, Norfolk terrier, and the miniature Schnauzer.

Is There Pre-Breeding Screening for Mitral Valve Disease?

Due to the hereditary tendencies seen particularly in some breeds like the Cavalier King Charles spaniel, breed clubs and welfare organisations have advocated for formal screening and DNA testing protocols. Unfortunately, the complex nature of the disease has limited the development of reliable genetic tests.

Instead, the Kennel Club recommends annual veterinary examinations by a cardiologist or experienced vet using auscultation (listening to the heart with a stethoscope) to detect early murmurs indicative of disease onset. This method, however, cannot guarantee a dog will not develop the disease later, as symptoms and murmurs may appear unpredictably over time.

Because of these uncertainties, mandatory registries excluding affected dogs are not currently feasible. Responsible breeding practices focus on regular health checks and careful consideration of breeding pairs to minimise hereditary risk and promote overall heart health.

Living with Mitral Valve Disease in Dogs

While mitral valve disease cannot be cured, many dogs live comfortable lives with appropriate veterinary care. Treatment focuses on managing symptoms and slowing disease progression, often using medications like pimobendan for early stages and diuretics, ACE inhibitors, or spironolactone when congestive heart failure develops. Regular check-ups help to monitor the condition and adjust treatments as necessary to maintain the dog's quality of life.

Frequently Asked Questions

How early can mitral valve disease be detected?

Quick Answer: Early detection usually happens during veterinary auscultation when a heart murmur is first heard, often before symptoms arise.

Because mitral valve disease develops gradually and symptoms can be subtle or absent for years, regular veterinary check-ups are vital, especially in predisposed breeds. A heart murmur detected with a stethoscope is often the first indicator, prompting further diagnostic tests if needed.

Can mitral valve disease affect younger dogs?

Quick Answer: Although typically a concern for older dogs, some breeds can develop mitral valve disease at younger ages due to hereditary factors.

While ageing significantly increases risk, breeds like Cavalier King Charles spaniels can show changes earlier in life. Despite this, clinical signs usually appear in middle-aged to senior dogs. Responsible breeders and owners should be vigilant about heart health monitoring throughout a dog's life.

How can I reduce the risk of my dog developing mitral valve disease?

Quick Answer: While genetic risk can't be eliminated, choosing dogs for breeding that have clear veterinary heart checks and maintaining overall health can help reduce risk.

Good nutrition, controlling body weight, avoiding strenuous exertion in affected dogs, and regular veterinary monitoring can help manage and delay the severity. For breeders, adhering to recommended screening practices and avoiding breeding dogs with early signs is essential for reducing prevalence in future generations.

Where can I find reputable Cavalier King Charles spaniel puppies?

Reputable Cavalier King Charles spaniel breeders can be found through breed clubs and the Kennel Club Assured Breeder Scheme. It's important to look for breeders who perform health checks including heart screening. Responsible breeders aim to minimise hereditary diseases such as mitral valve disease and provide lifelong support for their puppies.

Always ensure your puppy's breeder follows ethical standards and prioritises the health and welfare of their dogs.