Heart disease · Updated 2026-09-29
Mitral valve disease in dogs
The most common heart disease in dogs: a leaky valve that can lead to heart failure, especially in small breeds.
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Signs to watch for
- Heart murmur found at a check-up
- Cough
- Faster breathing at rest
- Tiring on walks
- Fainting
Causes and risk factors
Age-related thickening of the mitral valve; strongly inherited in breeds such as the Cavalier King Charles Spaniel.
How veterinarians diagnose it
Listening to the heart, chest X-rays and heart ultrasound (echocardiography).
Treatment and management
Some dogs with an enlarged heart benefit from medication before signs appear; heart failure is treated with several medications.
Prevention
Not preventable; breeding schemes with heart screening reduce risk.
Outlook
Many dogs live years with a murmur; once heart failure develops, treatment extends good-quality life.
Common questions
- What are the signs of mitral valve disease in dogs?
- Heart murmur found at a check-up; Cough; Faster breathing at rest; Tiring on walks; Fainting.
- What causes mitral valve disease in dogs?
- Age-related thickening of the mitral valve; strongly inherited in breeds such as the Cavalier King Charles Spaniel.
- How is mitral valve disease in dogs diagnosed?
- Listening to the heart, chest X-rays and heart ultrasound (echocardiography).
- How is mitral valve disease in dogs treated?
- Some dogs with an enlarged heart benefit from medication before signs appear; heart failure is treated with several medications.
- Can mitral valve disease in dogs be prevented?
- Not preventable; breeding schemes with heart screening reduce risk.
- When should I contact a veterinarian?
- Count your dog's breaths while it sleeps. Over 30 breaths a minute, repeatedly, needs a vet call.
Preparing for a mitral valve disease in dogs consultation
- Record when these signs began and how they changed: Heart murmur found at a check-up; Cough; Faster breathing at rest. Record appetite, water intake, toileting and any medicines or supplements.
- The listed urgency is prompt; worsening breathing, collapse, seizures or severe pain can make any situation an emergency. Ask the clinic rather than relying only on this category.
- Ask what else could explain the signs, which tests would change the plan and how discomfort will be managed. Symptoms alone cannot confirm this condition.
- Before going home, agree what to monitor, when to recheck and which signs mean calling sooner. Follow the individual treatment plan; do not copy another pet's prescription.
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Sources on this topic
Pages on this specific subject from recognised organisations. They are cited for further reading and do not mean the organisation has reviewed this page.
- Myxomatous Mitral Valve Disease — NC State Veterinary Hospital Cardiology
- Chronic Degenerative Valve Disease in Dogs: In Depth — VCA Animal Hospitals
Guidance libraries and further reading
These organisations publish relevant guidance. Their links are further reading, not evidence that they have reviewed this page.