🫀 Mitral Valve Disease in Dogs: A 2025 Vet Guide to MMVD Diagnosis, Treatment & Prognosis 🐶

By Dr Duncan Houston, BVSc

Mitral valve disease, also called MMVD (myxomatous mitral valve disease), is the most common heart condition in dogs — especially in small-breed, older pets. Despite its prevalence, MMVD often remains unnoticed until it progresses. But with proper veterinary guidance and monitoring, many dogs can live comfortably for years. Let’s break it down. 🐾

💡 What Is MMVD?

MMVD affects the mitral valve, which lies between the left atrium and left ventricle of the heart. When healthy, this valve ensures blood flows one way. But in MMVD, the valve degenerates, thickens, and fails to close tightly — causing blood to leak backward. This condition is also known as:

• 🫀 Chronic mitral valve disease
• 🫁 Degenerative mitral valve disease
• 💧 Mitral insufficiency
• 💓 Endocardiosis

The leak leads to left-sided congestive heart failure (CHF) in some dogs, particularly as the disease progresses. 💔

🐶 Which Dogs Get MMVD?

MMVD is mostly seen in small-breed, middle-aged or senior dogs. About 10% of older small dogs have the condition. Some breeds, like the Cavalier King Charles Spaniel, are genetically predisposed and may show signs as early as 4 years old. 🧬

📈 How Does MMVD Progress?

The progression varies. In about 75% of dogs, MMVD does not lead to serious problems, and they eventually pass from unrelated causes. But in the remaining 25%, CHF develops and requires medical management. ⚠️

🔍 Clinical Signs of MMVD

Early MMVD is often detected during a routine check-up when a vet hears a heart murmur. Owners usually notice no symptoms until the disease becomes severe. 🩺

Symptoms of CHF in Dogs:

• 🐕 Persistent coughing
• 💤 Lethargy or reduced activity
• 😮‍💨 Labored or rapid breathing (especially at rest or sleep)
• 😵 Fainting or collapse (less common)

Sometimes, owners may feel a vibration in the chest — like purring — which is actually the murmur caused by the leaking valve. 💓

🧪 Diagnosing MMVD

Most vets diagnose MMVD based on:

• 📅 Age
• 🐶 Breed
• 🎧 Presence of a characteristic left-sided murmur

To determine the severity, diagnostic imaging like chest X-rays or an echocardiogram (ultrasound of the heart) is used. These help assess heart enlargement — a sign of disease progression. 🖼️

Key Observations:

• 🔹 Mild MMVD: Little to no change in heart size
• 🔹 Moderate MMVD: Enlarged heart without severe distortion
• 🔴 Severe MMVD: Significant enlargement of the left atrium and ventricle

An echocardiogram can also detect pulmonary hypertension and chordae tendinae rupture — both potential complications. 📉

💊 Treating MMVD

🕒 Subclinical Phase (Before CHF)

At this stage, dogs often show no symptoms. The goal is to slow disease progression. Medications considered include:

• 💊 Pimobendan – Proven to delay CHF onset in dogs with moderate heart enlargement
• 💊 ACE inhibitors – May help but less proven
• 💊 Spironolactone – Sometimes used with other meds

Note: Starting medication too early may not be necessary — your vet will recommend it once heart enlargement is evident on imaging. 🧠

❤️ CHF Treatment

Once CHF begins, medications aim to:

• 🫁 Reduce fluid buildup in the lungs
• 💓 Improve heart function
• 🧂 Control salt and fluid retention

Common treatments include:

• 💊 Pimobendan
• 💊 Furosemide (diuretic)
• 💊 ACE inhibitors
• 💊 Spironolactone

🍴 Diet & Lifestyle Tips

High-sodium foods can trigger CHF symptoms. Avoid feeding your dog:

• 🧀 Cheese
• 🥩 Deli meats
• 🥨 Salty snacks like chips and pretzels

This issue is so common during parties that vets call it “Super Bowl Syndrome.” 🎉

📌 Use no-salt-added peanut butter to hide pills, or ask your vet about compounding pharmacies for liquid meds. 🥄

🏃 Activity Guidelines

Exercise should be gentle. Avoid activities that cause panting or collapse. Play and walks are fine as long as your dog isn’t overexerted. 🐕🌳

💓 Surgical Options

While human patients often undergo valve replacement, surgery for dogs is rare — but not impossible.

🇯🇵🇬🇧🇫🇷 Veterinary centers in Japan, the U.K., and France now offer mitral valve repair surgeries with encouraging success rates. If you're interested, consult directly with one of these international programs. ✈️

📊 Monitoring at Home

Your vet may recommend tracking your dog’s sleeping respiratory rate. This simple, at-home method can alert you to changes in heart function.

• ✅ Normal: < 30 breaths per minute while sleeping
• ⚠️ Increased rate: Call your vet within 24 hours

Frequent rechecks (every 6–12 months, or more often in advanced cases) help your vet adjust medication and monitor kidney health, especially when diuretics are used. 🩺

📉 Prognosis: What to Expect

🟢 Mild MMVD: Most dogs never develop CHF and live normal lives
🔴 With CHF:

• 50% survive about 9–10 months after CHF onset
• 80% pass away before 18 months
• 🌈 A few may live 2+ years with good management

📱 Ask A Vet: Your MMVD Companion

Managing mitral valve disease takes a team — and you don’t have to do it alone. With the Ask A Vet App, you can:

• 📊 Log breathing rates
• 💊 Track medication schedules
• 💬 Chat with licensed vets 24/7

Visit AskAVet.com or download the app for full support in managing your dog’s heart health. 🐶❤️

🧠 Final Thoughts from Dr Duncan Houston

Mitral valve disease is one of the most common heart problems in dogs — but with early detection, the right meds, and careful monitoring, many dogs enjoy long, happy lives. 🐾

Be proactive. Know the signs. And don’t hesitate to reach out to your vet — or Ask A Vet — to help your pup live their best life. 🐕🫀