If your dog has developed leaky valves, you may be wondering "what's a dog mitral valve disease life expectancy?" This is a very good question, considering the important role heart valves play in blood circulation and over all health. In order to better understand the average prognosis for a dog with mitral valve disease and what to expect, it helps to first take a closer look at how a dog's mitral valve works. Veterinarians typically use a staging system to determine the severity of mitral valve disease. Only your vet can determine how much your dog is affected and the prognosis for this disease. In some cases, a referral to a veterinarian specializing in cardiology may turn to be insightful.
A Lesson in Anatomy
Your dog's heart is separated into four chambers with the upper chambers called atria and the lower chambers called ventricles. Between the chambers are special valves which are meant to keep the dog's blood flowing in only one direction.
If one were to follow the blood flow, one would notice that the blood travels from the right atrium to the right ventricle in order to reach the lungs.
Then, once the blood passes through the lungs and gets oxygenated, it goes from the left atrium to the left ventricle in order to reach the body and supply it with freshly oxygenated blood. It is right in between the left atrium and the left ventricle that the mitral valve is located.
It's main objective consisting of closing properly so to prevent backflow of blood back into the left atrium.
When Things Go Wrong
A normal, healthy mitral valve closes properly so to prevent any backflow of blood. Problems start when the mitral valve degenerates and fails to close as it should. Also known as Chronic Valve Disease (CVD) or endocardiosis, mitral valve disease is known for being an age-related thickening of the mitral valve caused by an increase in collagen and elastic fibers.
Failure for the mitral valve to close properly may result in what's known as mitral valve regurgitation, basically, blood leaking back into the atrium. Some blood therefore ends up flowing backwards and a heart murmur may be present. When the condition progresses, the valve reaches a certain point of degeneration where the heart must pump harder to deliver oxygenated blood to the body.
At some point, the affected dog may eventually develops congestive heart failure. Symptoms may include reduced activity levels, labored breathing, coughing, exercise intolerance, and as the conduction progresses, edema and a bluish tinge to the gums and collapse. While congestive heart failure is a possibility, fortunately the disease in most dogs will not progress to the point of causing symptoms.
Mitral valve regurgitation often happens as a result of aging in older, small breed dogs. Most commonly affected breeds include Cavalier King Charles spaniels, toy poodles, cocker spaniels, Pomeranians, Chihuahuas and Yorkshire terriers. At times, mitral valve disease may also affect larger breeds such as German shepherds. The age of onset is typically between the ages of 6 and 10.
Most likely, in mitral valve disease there is a genetic component at play. Interestingly, recently researchers at Colorado State University have found that cells found in diseased heart valves of dogs and humans produce serotonin and that this production may be to blame for the underlying cause for mitral valve disease.
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" The backwards flow of blood causes a lot of turbulence. It would be like a river where suddenly a portion of the river right in the middle started squirting water back upstream against the flow. That turbulence is noisy, and that is often where the heart murmur comes from..." ~Dr. Ralston
At the Vet's Office
The vet will listen to the dog's heart in search of a heart murmur. Further diagnostic tests include chest x-rays electrocardiogram (ECG) and an echocardiogram of the heart.
If there is onset of congestive heart failure the vet will likely prescribe medications. The diuretic drug furosemide may be given so to reduce the buildup of fluids in the lungs. Other drugs that are commonly prescribed include vasodilators such as enalapril, benazapril, pimobendan (Vetmedin)
The drug spironolactone, an aldosterone antagonist, has shown promising results in a study resulting in decreased mortality in human patients suffering from heart disease.
Life Expectancy in Dogs
The life expectancy in dogs with mitral valve disease varies and depends on several individual factors such as the severity of the disease and the treatment chosen. Some dogs may never develop heart failure or die from the disease, while sadly some will perish. Only the vet can ultimately gather an insight as to the prognosis and life expectancy of dogs with this disease.
When looking at statistics though things seem to be on the bright side. As mentioned, most dogs with mitral valve disease do not progress to heart failure. When looking at statistics it was found that 70 percent of pre-clinical dogs that showed symptoms of the disease were still alive after six years. These statistics are very similar to those found among humans.
And the dogs who did eventually develop heart failure had median survival times of 33 months in the case of moderate heart failure and nine months in the case of severe heart failure.
In a study published in the Journal of Veterinary Internal Medicine, administration of the drug spironolactone along with conventional therapy increased survival times in dogs suffering from myxomatous mitral valve disease (MMVD). According to the study, the 18-month survival rate was 84 percent.
Another study revealed instead that dogs with congestive heart failure secondary to mitral valve disease had better quality of life and survival times when they were prescribed pimobendan with or without furosemide compared to other dogs receiving an ACE inhibitor (benazepril) with or without furosemide. Long term median survival times were 415 days fr dogs taking pimobendan versus 128 days for dogs not taking pimobendan.
- Bernay F, Bland JM, Häggström J, et al. Efficacy of spironolactone on survival in dogs with naturally occurring mitral regurgitation caused by myxomatous mitral valve disease. J Vet Intern Med 2010;24(2):331-341.
- Lombard CW, Jons O, Bussadoril CM. Clinical efficacy of pimobendan versus benazepril for the treatment of acquired atrioventricular valvular disease in dogs. J Am Anim Hosp Assoc 2006;42:249-261.
- DVM360: Hot Literature: Spironolactone: A promising adjunctive therapy for myxomatous mitral valve disease.
- DVM360: CVD remains most common cardiac disease in small, medium-sized dogs
- DVM360; Cardiologist searches for keys to mitral valve disease