Myxomatous Mitral Valve Disease (MMVD)
What is MMVD?
Myxomatous Mitral Valve Disease is a degenerative condition where the mitral valve - which separates the left atrium from the left ventricle - gradually deteriorates and begins to leak. As the valve leaks more, the left atrium and ventricle enlarge to accommodate the extra blood volume. Eventually, this can lead to congestive heart failure. MMVD is the single most common heart disease in dogs, affecting nearly all Cavalier King Charles Spaniels by age 10 and a significant percentage of other small breeds.
Disease stages
MMVD is classified using the ACVIM staging system: Stage A (at risk, no disease), Stage B1 (murmur present, no heart enlargement), Stage B2 (murmur + heart enlargement - treatment with pimobendan begins), Stage C (congestive heart failure - multiple medications needed), and Stage D (refractory heart failure).
Key research
The EPIC study showed that starting pimobendan at Stage B2 delays the onset of heart failure by approximately 15 months (median time to CHF: 1,228 days vs 766 days).
Breeds affected by MMVD
Medications commonly used for MMVD
Furosemide (Lasix, Salix)
A powerful diuretic used to remove excess fluid from the body when DCM has progressed to congestive heart failure. Essential for managing fluid in the lungs or abdomen.
Benazepril (Fortekor)
An ACE inhibitor commonly prescribed to reduce cardiac workload in dogs with DCM. By relaxing blood vessels, benazepril makes it easier for a weakened heart to pump blood effectively.
Spironolactone (Aldactone)
A gentle diuretic that works alongside furosemide to provide additional fluid removal while protecting against potassium loss. Spironolactone also blocks aldosterone, a hormone that contributes to harmful heart remodeling in DCM.
Medications are determined by your veterinarian based on your dog's individual condition and stage. This list represents commonly used medications for MMVD.
Articles about MMVD
Exercise and Activity for Dogs with MMVD
Stage-by-stage exercise guidelines for dogs with Myxomatous Mitral Valve Disease - how to keep your dog active, happy, and safe at every point in the disease.
14 min read · Living with Heart Disease
Supplements for Dogs with Heart Disease: What the Evidence Says
An evidence-based guide to cardiac supplements for dogs - taurine, L-carnitine, CoQ10, and omega-3s reviewed with published research, dosing guidelines, drug interactions, and what to avoid.
16 min read · Diet & Supplements
Heart Disease in Cavalier King Charles Spaniels: An Owner's Guide
Why Cavalier King Charles Spaniels are uniquely predisposed to MMVD, what to expect, screening recommendations, the MVD breeding protocol, and how to give your Cavalier the best possible outcome.
15 min read · MMVD
The Complete Guide to MMVD (Mitral Valve Disease) in Dogs
Everything you need to know about Myxomatous Mitral Valve Disease in dogs - the most common acquired heart disease in canines. Staging, treatment, the EPIC study, prognosis, and what to expect.
19 min read · MMVD
Your Dog Has a Heart Murmur: What You Need to Know
Your vet heard a heart murmur - now what? Learn what heart murmurs mean in dogs, the grading system, when to worry, and why the most common cause in small breeds is highly treatable.
16 min read · MMVD
MMVD Stages Explained: What B1 and B2 Mean for Your Dog
A detailed breakdown of the ACVIM staging system for Myxomatous Mitral Valve Disease - from Stage A through Stage D - with a deep dive on the critical B1 vs B2 distinction that determines when treatment begins.
14 min read · MMVD
Screening recommendations by breed
| Breed | Start age | Frequency | Tests |
|---|---|---|---|
| Cavalier King Charles Spaniel | 1 year old | Annually (echocardiogram + auscultation) | Echocardiogram, Cardiac auscultation |
| Chihuahua | 5–6 years old (or earlier if murmur detected) | Annually once murmur is detected (echocardiogram) | Cardiac auscultation, Echocardiogram |
| Dachshund | 5–6 years old (or earlier if murmur detected) | Annually once murmur is detected (echocardiogram) | Cardiac auscultation, Echocardiogram |
| Cocker Spaniel | 4–5 years old | Annually (echocardiogram + taurine levels if DCM suspected) | Echocardiogram, Blood taurine levels |
| Pomeranian | 5–6 years old (or earlier if murmur detected) | Annually once murmur is detected | Cardiac auscultation, Echocardiogram |
| Yorkshire Terrier | 5–6 years old (or earlier if murmur detected) | Annually once murmur is detected | Cardiac auscultation, Echocardiogram |
Action plan
MMVD Action Plan: What to Do After Diagnosis
Step-by-step guide for owners navigating a MMVD diagnosis, including questions to ask your cardiologist, monitoring tips, and lifestyle adjustments.
Find a veterinary cardiologist near you
Early diagnosis from a board-certified cardiologist is the single most impactful thing you can do for a dog with MMVD.
Disclaimer:This content is for educational purposes only. It is based on published veterinary research and community experience, but is not written by a veterinarian and does not constitute medical advice. Every dog is different. Always consult your veterinarian or a board-certified veterinary cardiologist before making any changes to your dog's care, diet, or treatment plan.