Mitral Valve Disease (MVD) in Dogs: Stages & Treatment

Quick Answer
  • Myxomatous mitral valve disease (MMVD, often called MVD) is the most common acquired heart disease in dogs and makes up about 75% of canine heart disease.
  • A heart murmur is often the first finding. Many dogs feel normal for months to years before any signs of congestive heart failure appear.
  • Treatment depends on ACVIM stage. Stage B1 is usually monitored, Stage B2 often starts pimobendan, and Stages C-D need heart-failure medications and closer follow-up.
  • The EPIC study found that pimobendan delayed the onset of congestive heart failure or cardiac death by about 15 months in dogs with Stage B2 disease and cardiomegaly.
Estimated cost: $250–$3,500

What Is Mitral Valve Disease?

Mitral valve disease in dogs is usually myxomatous mitral valve disease (MMVD), a progressive wear-and-tear change of the mitral valve. That valve sits between the left atrium and left ventricle. As it thickens and loses its normal shape, it no longer seals tightly, so some blood leaks backward each time the heart contracts. Your vet may call this mitral regurgitation.

That backward leak creates turbulence, which is why your vet often hears a heart murmur before your dog seems sick. Over time, the left atrium and then the left ventricle may enlarge because they are handling extra volume. If the heart can no longer compensate, pressure rises and fluid can leak into the lungs. That is left-sided congestive heart failure (CHF).

The course is highly variable. Some dogs live for years with a murmur and never develop CHF. Others progress more quickly, especially if they are small-breed, older, or genetically predisposed. Staging matters because the best next step is different for a dog with a mild murmur than for one with an enlarged heart or fluid in the lungs.

MMVD is especially common in small and toy breeds, and risk rises with age. It is uncommon in young dogs unless they are in a strongly predisposed breed, especially the Cavalier King Charles Spaniel.

Signs of Mitral Valve Disease in Dogs

  • Heart murmur found by your vet during a routine exam, often before any symptoms are visible
  • Coughing, especially at night, after activity, or when excited
  • Exercise intolerance or tiring sooner on walks
  • Faster sleeping or resting breathing rate
  • Increased breathing effort, open-mouth breathing, or obvious respiratory distress
  • Restlessness at night or trouble getting comfortable
  • Reduced appetite or lower energy
  • Weakness, fainting, or collapse (syncope)
  • Weight loss or muscle loss in more advanced disease
  • Blue, gray, or very pale gums during an episode, which is an emergency

Early MMVD often causes no outward symptoms at all. A murmur may be the only clue, and that does not automatically mean your dog is in heart failure. As disease progresses, coughing, tiring more easily, and a rising sleeping respiratory rate become more concerning.

When to worry more: if your dog is breathing faster than usual while asleep, working hard to breathe, cannot lie down comfortably, faints, or has blue-gray gums, see your vet immediately. A normal resting or sleeping respiratory rate is often around 15-30 breaths per minute. A consistent trend above about 30-35 breaths per minute, especially with effort or cough, deserves prompt veterinary guidance.

What Causes Mitral Valve Disease?

MMVD is a degenerative disease, not an infection and not something a pet parent causes. The valve tissue and supporting structures gradually change over time. The exact trigger is not fully understood, but genetics clearly matter in many dogs.

The biggest risk factors are breed, age, and body size. Small-breed and toy-breed dogs are affected far more often than large dogs. Risk also rises as dogs get older, and males may be affected earlier or more severely in some populations.

Breeds commonly overrepresented include Cavalier King Charles Spaniels, Dachshunds, Miniature and Toy Poodles, Chihuahuas, Yorkshire Terriers, Maltese, Miniature Schnauzers, Shih Tzus, Pomeranians, and Cocker Spaniels. Cavaliers deserve special mention because they often develop disease younger than other breeds and are at particularly high inherited risk.

Dental disease does not cause MMVD, although older small dogs may have both problems at the same time. Good dental care still matters for overall health, but it does not prevent this valve degeneration.

How Is Mitral Valve Disease Diagnosed and Staged?

Diagnosis starts with your vet hearing a left-sided systolic heart murmur on exam, but a murmur alone does not tell the whole story. The most useful test for confirming MMVD and deciding stage is an echocardiogram, which shows the valve, measures chamber size, and helps determine whether the heart is enlarged enough to change treatment.

Chest X-rays help assess heart size and look for pulmonary edema if CHF is suspected. Blood pressure, blood work, and sometimes NT-proBNP or cardiac troponin can add context. An ECG may be recommended if your dog has fainting, an irregular rhythm, or advanced disease.

The ACVIM staging system guides care:

  • Stage A: at-risk breed, no murmur or structural disease yet
  • Stage B1: murmur present, but no clinically important heart enlargement
  • Stage B2: murmur plus heart enlargement consistent with preclinical MMVD
  • Stage C: current or past congestive heart failure
  • Stage D: heart failure that is no longer controlled with standard therapy

The B1-to-B2 transition is especially important because that is the stage where pimobendan is commonly recommended. If your dog has a new murmur, asking whether an echocardiogram is needed is one of the most useful next steps.

Treatment Options for Mitral Valve Disease

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Monitoring-focused care for Stage B1 or early workup

$250–$900
Best for: Dogs with a newly discovered murmur, dogs in Stage B1, or pet parents who need to prioritize the most decision-changing tests first
  • Office exam and murmur monitoring
  • Baseline chest X-rays and/or referral echocardiogram when staging is needed
  • Home sleeping respiratory rate tracking
  • Weight management and practical exercise guidance
  • No daily heart medication for most Stage B1 dogs
  • Repeat imaging every 6-12 months if your vet recommends it
Expected outcome: Often good for months to years. Many Stage B1 dogs remain stable for a long time, and some never develop congestive heart failure.
Consider: This approach relies on monitoring rather than early medication. It keeps costs lower up front, but it is important not to skip rechecks because treatment recommendations can change once enlargement develops.
Most Common

Stage-based medical management, including pimobendan for B2 and CHF therapy for Stage C

$700–$2,200
Best for: Dogs with confirmed Stage B2 disease or dogs with controlled congestive heart failure that can be managed medically at home with regular follow-up
  • Echocardiogram to confirm Stage B2 or Stage C
  • Pimobendan for dogs with Stage B2 disease and cardiomegaly
  • For Stage C: furosemide plus pimobendan, often with an ACE inhibitor such as enalapril or benazepril
  • Possible addition of spironolactone depending on your vet's plan
  • Chest X-rays to confirm and monitor pulmonary edema
  • Kidney value and electrolyte monitoring after medication changes
  • Daily home respiratory rate tracking and symptom log
Expected outcome: Stage B2 dogs may stay symptom-free substantially longer with pimobendan. After CHF begins, many dogs still have meaningful good-quality time with medication, often many months and sometimes longer than a year, but response varies.
Consider: Medication becomes ongoing, recheck testing matters, and diuretics increase thirst and urination. Kidney values can shift, so doses often need adjustment over time.

Cardiology-guided care for refractory or complicated disease

$1,800–$3,500
Best for: Dogs in Stage D, dogs with repeated CHF flare-ups, significant arrhythmias, pulmonary hypertension, or pet parents who want specialist-guided options for a complex case
  • Veterinary cardiology consultation and repeat echocardiography
  • Hospitalization for oxygen support and injectable diuretics during decompensation
  • Escalation from furosemide to higher-intensity diuretic plans such as torsemide or combination diuretics when appropriate
  • ECG and antiarrhythmic therapy if rhythm problems develop
  • Pulmonary hypertension treatment such as sildenafil when indicated
  • Thoracocentesis if pleural effusion is present
  • Structured quality-of-life planning and palliative support
Expected outcome: Guarded. Some dogs stabilize and gain additional comfortable time, but refractory heart failure usually means the disease is entering a more fragile phase.
Consider: This tier involves the highest ongoing cost range, more frequent visits, and more medication changes. It can improve comfort and control in selected dogs, but it also asks more of the pet parent and the patient.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Mitral Valve Disease

Bring these questions to your vet appointment to get the most out of your visit.

  1. What ACVIM stage do you think my dog is right now, and what findings support that stage?
  2. Does my dog need an echocardiogram now, or can we start with chest X-rays and monitoring?
  3. Is my dog still Stage B1, or is the heart enlarged enough to fit Stage B2 and start pimobendan?
  4. What sleeping respiratory rate should make me call, and can you show me how to count it correctly?
  5. If my dog is coughing, do you think it is from heart failure, airway disease, or pressure from an enlarged heart?
  6. What blood work do we need before and after starting heart medications?
  7. What activity level is safe for my dog, and are there situations like heat or strenuous exercise we should avoid?
  8. When would a cardiology referral meaningfully change my dog's treatment options?

Living with Mitral Valve Disease

MMVD cannot usually be prevented, but careful monitoring can make a real difference. One of the most useful home tools is the sleeping respiratory rate. Count breaths when your dog is fully asleep and relaxed. One rise and fall of the chest equals one breath. Tracking the trend matters more than a single number.

In many dogs, a normal sleeping rate is around 15-30 breaths per minute. If the rate is consistently above about 30-35, or if breathing looks more effortful than usual, contact your vet. This can be an early clue that fluid is building in the lungs or that the current plan needs adjustment.

Daily life often stays fairly normal in earlier stages. Keep your dog at a healthy weight, avoid extreme exertion, and follow the recheck schedule your vet recommends. Most dogs do not need sodium restriction in preclinical disease unless your vet specifically advises it. Once CHF develops, diet and medication routines become more important.

For predisposed breeds, especially Cavalier King Charles Spaniels, early screening matters. If your dog is a high-risk breed and your vet hears a murmur, asking about timing for an echocardiogram is a practical next step.

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