Mitral Valve Disease in Canines: An analysis by Joanna Woodnutt, MRCVS, reviewed by Brittany Kleszynski, DVM on June 30, 2025, and initially published on June 20, 2023.
Mitral valve disease (MVD), also known as degenerative mitral valve disease (DMVD) and myxomatous mitral valve disease (MMVD), is a common and life-limiting condition in dogs, accounting for 75% of all canine heart problems. The treatment and management of MVD vary according to the disease stage, classified as A, B1, B2, C, and D.
Stage A (at risk, no murmur or clinical signs): Dogs in this stage are at high risk but do not currently have any abnormalities. No medical treatment is needed, and careful yearly auscultation is recommended to monitor for the appearance of a murmur or clinical signs.
Stage B1 (presence of murmur but no heart enlargement): In this stage, a murmur can be heard but there is no heart enlargement, typically no medication is required yet. However, a low sodium diet may be advised to help reduce strain on the heart, and monitoring for progression is important.
Stage B2 (heart murmur with evidence of cardiac enlargement): The cornerstone of management in this stage is treatment with pimobendan, a drug that improves heart contractility and delays heart failure. ACE inhibitors such as enalapril or benazepril may also be considered, though pimobendan is emphasized as the primary treatment. Surgical and advanced interventional procedures exist but are limited in availability and may carry risks, especially in certain breeds like Cavaliers.
Stage C (dogs with clinical signs of congestive heart failure): Medical therapy aims to control symptoms. This includes continuation of pimobendan, use of diuretics like furosemide (Lasix) to manage fluid accumulation, ACE inhibitors, and possibly beta blockers to control heart rate. Antibiotics and bronchodilators may be used if lung complications occur. Regular monitoring and adjustments to treatment are essential.
Stage D (end-stage or refractory heart failure): Management involves more intensive treatment to improve quality of life, often involving adjusted or increased doses of medications used in stage C, and consideration of surgical or hybrid interventions where available. Prognosis becomes guarded, and specialized care may be needed.
Throughout all stages, routine monitoring with physical exams, blood panels, echocardiograms, chest radiographs, and ECGs every 3-12 months helps guide treatment modifications. Regular check-ups with a veterinarian and considering only buying puppies from parents who are regularly undergoing heart checks can lead to early diagnosis and treatment.
As the disease progresses, dogs may exhibit symptoms such as coughing, lethargy, reluctance to exercise, breathlessness/fast breathing, difficulty breathing, weight loss, fainting, and collapse. The cost to treat MVD in dogs increases over time, with regular consultations, medications, and hospital stays becoming more frequent in later stages.
In summary, treatment escalates from monitoring and diet in early stages to pimobendan and medications for heart failure in later stages, with surgical options currently limited primarily to advanced or refractory cases. It's estimated that about 3.5% of all dogs attending a veterinary practice will have MVD at any one time, with the incidence increasing as dogs age. Some dog breeds are more prone to MVD, including Cavalier King Charles Spaniels, Miniature Schnauzers, Miniature Poodles, Shih Tzu, Maltese, Cocker Spaniels, Chihuahuas, and Pomeranians.
At stage D, standard treatments are no longer effective, and advanced or even surgical treatments are necessary to maintain the dog's quality of life. End-stage MVD in dogs requires careful monitoring of the dog's quality of life, and euthanasia may be considered when it becomes poor.
Preventing MVD in dogs is difficult, but keeping the dog's teeth clean can reduce the risk of bacteria in the blood damaging the heart valves. The stages of MVD were suggested by the world's top canine cardiologists in the ACVIM consensus, and they are useful for planning treatment. The progression of MVD is unpredictable, making it a challenging condition to manage, but with proper care and monitoring, many dogs can live comfortably for several years.
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