Heart disease can be a serious condition in our canine companions, especially when it involves myxomatous mitral valve disease (MMVD). As the most common acquired heart condition in dogs, MMVD affects a significant number of our furry friends, particularly small and older breeds. However, with early detection and proper management, many affected dogs can live long, comfortable lives.
In this article we will explore what MMVD is, how it affects the heart, which breeds are most at risk, what symptoms to look out for, and how your vet can help support your pet’s heart health.
What Is MMVD?
Myxomatous mitral valve disease is a condition where the mitral valve (the valve between the left atrium and left ventricle of the heart) progressively degenerates. This valve plays a crucial role in directing blood flow through the heart.
In a healthy heart, it opens and closes tightly with each heartbeat to prevent blood from flowing backward. In MMVD, the mitral valve becomes thickened and leaky, causing a portion of the blood to flow back from the ventricle into the atrium each time the heart contracts. This backward flow is known as mitral regurgitation.
Over time this action places strain on the heart, reducing its ability to pump blood efficiently. Eventually the heart enlarges and fluid can accumulate in the lungs, leading to the condition known as congestive heart failure.
Which Dogs Are Most Affected?
MMVD is most commonly diagnosed in small-breed, middle-aged to senior dogs. Breeds with a known predisposition include:
- Cavalier King Charles Spaniels (by far the most commonly affected breed)
- Chihuahuas
- Miniature and Toy Poodles
- Cocker Spaniels
- Dachshunds
- Miniature Schnauzers
In Cavaliers, MMVD is so prevalent that many dogs begin to develop murmurs as early as five years of age. Males may be slightly more predisposed than females, and the disease is often progressive, meaning it worsens over time.
Early Signs and Symptoms
One of the earliest signs of MMVD is a heart murmur, which your veterinarian may detect during a routine physical examination. A heart murmur is an abnormal heart sound caused by turbulent blood flow and is often the first clue that a dog may be developing heart disease, even if they appear healthy and symptom-free. It is important to note that a heart murmur is not always an indicator of MMVD and can be caused by other factors.
Over time, as the valve degeneration progresses, you may begin to notice:
- Coughing (especially at night or after exercise)
- Breathing difficulties or rapid breathing
- Reduced stamina or exercise intolerance
- Fainting or collapsing episodes
- Weight loss
- Swollen abdomen (from fluid buildup)
- Restlessness or trouble settling, especially at night
It's worth noting that some dogs may not show signs until their condition has advanced significantly. In fact, a dog may suddenly present with symptoms of congestive heart failure despite having no known history of heart disease - underscoring the importance of regular check-ups.
Diagnosis and Monitoring
When a heart murmur is detected, your vet will recommend a tailored plan based on your dog’s condition. This might include:
Monitoring at Home
You may be advised to keep an eye out for any changes in breathing, coughing or behaviour. Tracking your pet’s resting respiratory rate at home can be an excellent early indicator of fluid accumulation in the lungs.
Chest X-Rays
These allow the vet to assess the size of the heart and look for signs of fluid in the lungs. Radiographs also help determine how advanced the disease is and whether medication is needed.
Echocardiogram (Heart Ultrasound)
In some cases, your pet may be referred to a veterinary cardiologist for an echocardiogram. This non-invasive test provides a clear image of the heart’s structure and function, helping to measure the severity of mitral valve leakage and cardiac enlargement.
Treatment Options
While MMVD is a progressive disease, early intervention and ongoing care can significantly improve a dog’s quality of life. If your pet has mild MMVD without symptoms, regular monitoring may be all that’s required initially.
Once clinical signs develop or if diagnostic imaging shows heart enlargement, medication is usually started to support heart function and reduce fluid accumulation. Common medications include:
- Pimobendan: This is the cornerstone of treatment once symptoms or heart enlargement are present. It improves the heart's ability to pump and helps delay the onset of heart failure.
- Diuretics (e.g. furosemide): Helps remove excess fluid from the lungs or abdomen.
- ACE (angiotensin-converting enzyme) inhibitors (e.g. enalapril, benazepril): Reduce the workload on the heart and improve blood flow.
- Other drugs may be added depending on your dog’s individual needs and response to treatment.
Some dogs can live for several years after being diagnosed with MMVD, especially when the condition is caught early and treated appropriately.
Quality of Life and Long-Term Care
Living with MMVD means regular vet check-ups to monitor heart size, lung health and medication effectiveness. At home, owners can play a crucial role by:
- Monitoring resting breathing rate (normal is under 30 breaths per minute when relaxed or sleeping)
- Providing a calm, low-stress environment
- Maintaining healthy weight - obesity puts extra strain on the heart
- Following medication schedules faithfully
Your vet may recommend rechecks every three to six months or even more regularly if symptoms change.
A Note on Emergency Symptoms
If your dog shows any of the following signs, seek urgent veterinary care:
- Severe breathing distress or gasping
- Collapse or fainting
- Blue or pale (pink to white) gums
- Sudden abdominal bloating
- Inability to settle or extreme restlessness
These may be signs of acute congestive heart failure or a cardiac emergency, requiring immediate intervention.
Hope Through Early Detection
The good news is that with improved awareness and veterinary diagnostics, more cases of MMVD are being caught earlier than ever before. By identifying a murmur during routine exams and tracking subtle changes at home, many dogs receive the support they need before reaching a crisis point.
If you’ve noticed any unusual symptoms in your pet or if you simply want to stay proactive about your dog’s heart health, don’t hesitate to reach out on 02 9416 1300 or book an appointment online. Our veterinary team is here to help you navigate every step of your pet’s heart health journey.