Symptoms and Management of Mitral Valve Insufficiency in Dogs

HeartQ&AMeongsiljang Veterinary Advisory Board

Here’s a summary of the causes, stage-by-stage symptoms, treatment medications, and home care tips for mitral valve insufficiency in dogs.

What is Mitral Valve Insufficiency in Dogs?

A veterinarian examining a small dog’s heart with a stethoscope

Mitral valve insufficiency in dogs is a heart condition where the mitral valve thickens due to myxomatous degeneration and fails to close properly, causing blood to flow backward. The most important thing is early detection and consistent management. In the early stages, there are no symptoms, making it difficult for owners to notice, but if a heart murmur is detected during a regular checkup, the progression of the disease can be significantly slowed. For small breed dogs or those over 7 years old, make sure to have a heart auscultation performed annually.

Causes and Risk Factors

Mitral valve insufficiency is one of the most common acquired heart diseases in dogs. The tissues that make up the mitral valve undergo myxomatous degeneration, causing the valve to thicken and stretch (valvular hypertrophy and prolapse). When the valve fails to close properly, blood flows backward into the left atrium, and the heart compensates by gradually enlarging both the left atrium and left ventricle.

Age: Typically diagnosed in middle-aged dogs and older, but it can be detected as early as 1–2 years of age in predisposed breeds.

Sex: Males tend to develop the condition at a younger age than females.

Weight: Most common in small-breed dogs, also seen in medium breeds, and frequently occurs in breeds such as Chihuahuas, Dachshunds, and Miniature Poodles.

Genetics: A polygenic predisposition involving multiple genes has been identified, particularly in breeds like the Cavalier King Charles Spaniel.

5-Stage Classification of Mitral Valve Insufficiency

Item	Stage A	Stage B1	Stage B2	Stage C	Stage D
Heart Condition	At-risk breed but no disease yet	Heart murmur present but normal heart size	Heart murmur + confirmed cardiac enlargement	Onset of congestive heart failure	End-stage, unresponsive to standard treatment
Symptoms	None	None	None or mild	Coughing/dyspnea/decreased appetite	Severe dyspnea/ascites/syncope
Management	Annual regular checkups	Follow-up exams every 6-12 months	Consider starting medication	Aggressive drug therapy	Intensive inpatient care

Based on the American College of Veterinary Internal Medicine staging classification

Key Symptoms Not to Miss

As mitral valve regurgitation progresses, the following symptoms may appear. If you notice several of these occurring at once, seek veterinary care promptly.

Dry cough: A persistent, hacking dry cough that worsens, especially in the early morning or during excitement.

Exercise intolerance: Reluctance to go for walks or tiring quickly and collapsing.

Rapid breathing: A resting respiratory rate exceeding 40 breaths per minute is a warning sign.

Syncope: Sudden weakness leading to fainting or collapse.

Abdominal distension: Fluid accumulation in the abdomen, which can occur if right-sided heart failure develops.

A small dog breathing rapidly while lying on the sofa

Go to the Emergency Room Immediately If You See These Symptoms

If your pet’s resting respiratory rate stays above 40 breaths per minute, they suddenly collapse, or their tongue and gums turn blue (cyanosis), this is an emergency. Coughing up pink froth is also a sign of pulmonary edema. Take your pet to the nearest emergency veterinary clinic immediately.

Stage-by-Stage Treatment Methods

Treatment varies depending on the stage of the disease.

Pimobendan: This is a key medication used from stage B2 onward. It strengthens the heart’s contractions and dilates blood vessels to reduce the heart’s workload. Veterinary cardiology studies have proven its effectiveness in delaying the onset of heart failure.

Diuretics: These help remove fluid buildup in the lungs in stage C and beyond.

Vasodilators: These lower blood pressure, making it easier for the heart to pump blood.

The specific medications and dosages must be determined by a veterinarian based on echocardiogram results. Never adjust your pet’s medication on your own, as this can be dangerous.

A veterinarian explaining the treatment medication to the pet owner.

Home Care Tips

Home care is just as important as medication.

Monitor breathing rate: Count your pet’s breaths for one minute while they are sleeping. A rate of 30 or fewer breaths per minute is normal; if it consistently exceeds 40 breaths per minute, contact your veterinarian.

Weight management: Excess weight places significant strain on the heart. Consult your veterinarian to maintain an ideal body weight.

Low-sodium diet: High-sodium treats can worsen fluid retention. Consider switching to a veterinary-prescribed cardiac diet.

Appropriate exercise: Avoid strenuous activity, but light walks can actually support circulation. Stop immediately if your dog shows signs of fatigue.

A small dog taking a light walk in the park with its owner.

Breeds That Require Extra Attention

Cavalier King Charles Spaniels have the highest incidence of mitral valve insufficiency. Small breeds such as Maltese, Shih Tzus, Poodles, Yorkshire Terriers, Chihuahuas, and Dachshunds are also at high risk. If you own one of these breeds, we recommend annual heart screenings starting at age five.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can mitral valve regurgitation be cured?

Unfortunately, a complete cure through medication alone is difficult. However, with appropriate drug therapy and careful management, we can slow the progression of the disease and maintain your pet’s quality of life. While some veterinary hospitals now offer valve repair surgery, it is expensive and only available at a limited number of facilities.

I was told my pet has a heart murmur. Should I start giving medication right away?

We don’t start medication based on a heart murmur alone. We first assess the heart’s size and function with an echocardiogram, and begin treatment only if the condition is classified as stage B2 or higher. For stage B1, we monitor the progression with follow-up exams every 6 to 12 months.

Can dogs with heart disease still go for walks?

Light walks can actually help improve blood circulation. However, if your pet starts panting heavily or coughing, stop immediately, and avoid exercising on hot or humid days. Please consult with your veterinarian to determine the appropriate exercise intensity for your pet.

Is anesthesia risky if a dog has mitral valve insufficiency?

If your pet’s heart function is compromised, the risk of anesthesia increases. When dental scaling or other surgeries are needed, be sure to share the results of cardiac evaluations with your veterinarian, and ensure your pet undergoes a cardiac stabilization process before anesthesia.

Can heart supplements help?

Supplementing with omega-3 fatty acids or taurine may be helpful. However, nutritional supplements alone cannot halt disease progression, so always consult your veterinarian before administering them. Heart-specific prescription diets often already contain the necessary nutrients.

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References

[1] Ljungvall I, Häggström J. Myxomatous Valvular Disease. In: Textbook of Cardiovascular Medicine in Dogs and Cats.

[2] Sharpe AN, Visser LC. Canine Myxomatous Mitral Valve Disease. In: Small Animal Critical Care Medicine, 3rd Ed.

[3] Keene BW et al. ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. J Vet Intern Med. 2019;33(3):1127-1140.