Degenerative changes thicken the valve, causing it to leak. When the disease and leakage progress, the heart enlarges. Predisposed breeds include Cavalier King Charles Spaniels and Dachshunds and other breeds – although the genetics are being investigated, the disease is very common in small breed dogs as they age. Though many dogs are affected in their later years, only about 25-50% of those with MMVD experience clinical signs of congestive heart failure (CHF, or fluid build-up within the
lungs).

How is MVD diagnosed?

A distinctive heart murmur is the most common initial sign of mitral valve disease. The murmur is caused by the valve leak. Chest X-rays or an echocardiogram (ultrasound of the heart) or both are used to assess the severity of the leak, and the extent of heart enlargement. A blood test for heart disease (NTproBNP) can also be used to help determine the severity of the heart disease.

How is MMVD treated?

Treatment depends on the severity of the valve leak. Mild leakage with minimal or no heart enlargement is typically monitored at regular intervals without treatment (Stage B1). Dogs with heart enlargement (Stage B2) benefit from medication to delay the onset of CHF. Dogs that experience CHF (Stage C and D)require additional medication, and some dogs need to be hospitalized for heart failure treatment. Because medications only control the clinical signs of CHF and do not treat the primary valve problem, definitive treatment is surgical repair of the mitral valve. At this time, surgical treatment is not widely available. The possibility of valve repair can be discussed with your cardiologist. There are other palliative and interventional treatment options that can also be discussed such as left atrial decompression and transcatheter
edge to edge mitral valve clip.

How is MMVD monitored by my veterinarian and my cardiologist?

Although an echocardiogram is often initially performed during the diagnosis, regular echocardiograms may not be needed, and chest x-rays may provide a more cost effective means of monitoring disease progression. Re-evaluations for asymptomatic dogs are typically performed every 6-12 months depending on the degree of heart enlargement. Dogs that have experienced CHF are followed more closely with blood pressure and bloodwork, typically every 3-6 months or after medication changes.

How can I tell how my dog is doing at home?

Dogs with minimal heart enlargement should be treated as normal dogs, requiring only usual (annual or semiannual) monitoring. The first signs of CHF often include shortness of breath, exercise intolerance, or cough – these signs should prompt a call and usually a vet visit. In dogs that have experienced an episode of CHF, monitoring the breathing rate during sleep or complete rest provides a sensitive indicator of how they’re doing – normal is less than 30 breaths/min. There are smartphone apps (Cardalis, My Pet’s Heart2Heart) that can help to obtain and track the breathing rate.

Is diet important?

While some salt restriction (e.g. avoidance of high salt treats) is ideal for most dogs with significant MMVD, and moderate salt restriction aids CHF treatment, it’s important that your dog’s appetite remains good, and his or her caloric and protein needs are met. Avoiding non-traditional grain free diets rich in legumes, such as lentils, chickpeas and green peas, is advised.

What is the prognosis with MMVD?

Many older dogs affected with MVD will not have their lifespan limited by their heart disease. The rate of disease progression varies, but it most often takes years before clinical signs of CHF develop. After CHF develops, dogs are expected to continue to have an excellent quality of life with treatment, and most survive for an additional 12-18 months, although their survival time varies widely.