What is degenerative mitral valve disease (DMVD)?
The heart is made up of four chambers: the left and right atrium, and the left and right ventricle. These chambers each contain a valve that prevents blood from flowing back into the chamber. The mitral valve connects the left atrium and the left ventricle. When the mitral valve isn’t working properly, blood leaks back into the left atrium. Over time, the heart becomes less efficient, eventually leading to congestive heart failure.
Roughly 80% of all heart disease in dogs is caused by mitral valve insufficiency. Older dogs and smaller breeds are at a significantly higher risk of developing DMVD. Male dogs also have a slightly higher rate of the disease.
How DMVD diagnosed?
The most common indicator of DMVD is a heart murmur caused by a leaky valve, which your vet will detect with a stethoscope during a physical exam. A chest x-ray or echocardiogram will then be conducted to determine the severity of the condition, based on the amount of leakage and/or the enlargement of the heart.
Stages of Canine Heart Failure
The American College of Veterinary Internal Medicine identifies four stages of canine heart failure:
- Stage A: No evidence of heart disease, but the dog is at a higher risk of developing it based on genetics (i.e., breed).
- Stage B: A heart murmur is detected, but there are still no signs of clinical heart disease in the dog. (Stage B is broken down into two parts. In Stage B1, there is no cardiac enlargement. In Stage B2, x-rays reveal cardiac enlargement, but the dog is still asymptomatic.)
- Stage C: Treatment becomes necessary, as clinical signs of heart failure (i.e., lethargy, difficulty breathing, coughing) are present.
- Stage D: End stage of the disease, as heart failure no longer responds to standard treatment. At this point, emphasis is shifted on making the dog as comfortable as possible.
How is heart failure treated in dogs?
Treatment typically doesn’t begin until the disease progresses to Stage B2. Until then, dogs should be monitored regularly to determine when to initiate pharmacological intervention. There are a number of medications that have been shown to improve heart function and delay the onset of heart failure:
- Angiotensin converting enzyme (ACE) inhibitors help relax and widen the blood vessels, thereby lowering blood pressure and improving blood flow in the heart. Studies have shown that they can increase survival time in patients.
- Furosemide is a commonly prescribed diuretic used to treat heart failure. It helps to relieve congestion by stimulating the kidneys and promoting urine and sodium excretion. A study from the Journal of Veterinary Internal Medicine found that “[h]igher furosemide dose and non-hospitalization were associated with longer survival.”
There is also some evidence to suggest that the dietary supplement coenzyme Q-10 (or ubiquinol) can be beneficial in the treatment of canine heart disease.
It’s also recommended that dogs with mitral valve disease begin a low-sodium diet in order to prevent excessive fluid retention in the body.
What is the prognosis?
Fortunately, if caught early and treated accordingly, dogs with mitral valve disease can still live long, healthy lives. Life expectancy varies based on the rate of disease progression, but in most cases it takes years for clinical signs of congestive heart failure to develop. At this point, with increased treatment, dogs can still live another year to 18 months.
Sources:
https://onlinelibrary.wiley.com/doi/10.1111/jvim.15488
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5980388/
https://vcahospitals.com/know-your-pet/coenzyme-q-10
