Myxomatous Mitral Valve Disease (MMVD) in Dogs
If your dog has been diagnosed with a heart murmur, you’re probably wondering what it means and what comes next. One of the most common causes behind heart murmurs in dogs, especially mature, smaller breeds, is Myxomatous Mitral Valve Disease (MMVD). In this article, we’ll explore what MMVD is, the signs to watch for, how it’s treated, and how TACC helps dogs live longer, healthier lives through expert diagnosis and care.
What is Myxomatous Mitral Valve Disease (MMVD)?
MMVD, also called chronic valvular disease or mitral valve degeneration, is a progressive condition where the mitral valve in the heart becomes thickened and leaky. This valve normally controls blood flow between the left atrium and the left ventricle. But when it's damaged, blood leaks backward, causing dilation to the heart and increasing stress within the heart.
Who's Most at Risk?
This condition tends to affect:
- Small breed dogs
- Older dogs, although some breeds, like Cavalier King Charles Spaniels, are at a higher risk and can develop MMVD at a younger age
How Does MMVD Progress?
The tricky thing about MMVD is that it often starts without any obvious signs. Your pup might feel perfectly fine, but during a regular checkup, your veterinarian hears a murmur. That’s the first clue. Over time, the disease progresses in stages:
- Stage A: An at-risk patient, with no murmur (ie a 9-year-old dog weighing less than 25 lbs, or a Cavalier King Charles Spaniel at any age)
- Stage B1: Murmur is present, but no heart enlargement
- Stage B2: Heart enlargement is visible on an echocardiogram, but no symptoms
- Stage C: Past or present signs of heart failure begin (e.g., coughing, fatigue)
- Stage D: Advanced heart failure that’s difficult to control with standard therapy
At TACC, our board-certified cardiologists use advanced echocardiography to pinpoint the exact stage and start treatment early—when it can make the biggest difference.
How is MMVD Treated?
Treatment depends on the stage of the disease. Here’s a breakdown:
Stage B2:
- Medication: Vetmedin (pimobendan) is prescribed
- Goal: Delay the onset of heart failure and improve heart function
Stage C or D:
- Combination therapies: May include diuretics (like furosemide), ACE inhibitors (enalapril or benazepril), and ARN inhibitors (sacubitril/valsartan)
- Goal: Manage symptoms, reduce fluid buildup, and enhance quality of life
Surgical options for mitral valve repair or replacement exist at select specialty centers, though they’re not widely available or suitable for every pet.
What Signs Should You Watch for at Home?
Sometimes the early signs are subtle and easy to miss. Keep an eye out for:
- Decreased energy or tiring more quickly
- Coughing, especially at night or after exercise
- Rapid or labored breathing
- Fainting or collapsing spells
- Increased respiratory rate while resting or sleeping
A normal resting breathing rate is fewer than 35 breaths per minute. If you’re consistently counting more than that, or see rates over 60, that could be an emergency.
Frequently Asked Questions (FAQs)
How is MMVD treated?
Available medical treatments are designed to slow the disease, ease symptoms, and improve quality of life. In a few specialized centers, heart surgery (valve repair or replacement) is possible, but it is not widely available or feasible in all patients.
How long can my dog live with MMVD?
Many dogs with only a heart murmur (early MMVD) may live their normal life span without ever developing heart failure. Starting early therapy, if indicated, will slow progression into heart failure. If heart failure develops, treatment with a board-certified cardiologist can often give your dog a year or more of good quality life, depending on their response to medication and how early treatment is started.
Should my dog have exercise restrictions?
Most dogs with MMVD benefit from light to moderate daily activity, such as short walks. This helps maintain muscle tone and mental health. Strenuous exercise, long hikes, or intense play should be avoided, especially once symptoms appear. Ask your cardiologist for advice specific to your pet.
Does diet matter for MMVD?
Excess salt (sodium) can make fluid retention worse, but restricting sodium too early in the disease state is also detrimental. Your cardiologist may suggest a prescription cardiac diet in later stages of the disease, but in early stages, keeping your dog on a balanced, high-quality diet is best.
What medications are used for MMVD?
Common medications include:
- Vetmedin – helps the heart pump more effectively and delays onset of heart failure.
- Diuretics (e.g., furosemide) – helps remove excess fluid volume when congestive heart failure is present.
- ACE inhibitors (e.g., enalapril, benazepril) and Spironolactone – help reduce the damaging response from the kidneys during heart failure and diuretic administration.
- ARN inhibitor (sacubitril/valsartan) - keeps the heart’s natural sodium and water excreting systems and blocks the damaging response from the kidneys.
Your dog may need one or several of these medications depending on the stage of disease.
Will medications make my dog sick?
Most dogs tolerate heart medications very well. The most common side effects are increased thirst and urination from diuretics, or occasional stomach upset. At TACC, our team carefully monitors patients with exams, blood work, and imaging to ensure medications stay safe and effective, adjusting treatment as the disease changes over time.
How often should my dog be checked?
For dogs with just a murmur, no symptoms with no required medications, a checkup every 6–12 months is typical. Once medication is started or if heart failure develops, visits may be needed every 3-6 months or more frequently in severe disease (stage D). At The Animal Cardiology Center, our cardiologists create a personalized recheck schedule for each patient. Frequent and planned, well-timed visits allow us to adjust treatment before problems become emergencies. However, if changes in clinical signs are seen at home, then a recheck examination should be made prior to the prescribed time.
Final Thoughts: Your Partner in Pet Heart Health
MMVD might sound scary at first, but with early detection, personalized care, and expert guidance from The Animal Cardiology Center, you and your pet can face it head-on, armed with the most up-to-date knowledge. If you’ve noticed a murmur, cough, or any unusual signs, don’t wait. Schedule an appointment with our board-certified cardiologists today.
