Degenerative Mitral Valve Disease in Dogs
A dog’s heart has four chambers and a system of one-way valves that keep blood from flowing backwards as it makes its way through the body. The valve between the lower left chamber (the left ventricle) and the upper left chamber (the left atrium) is called the mitral valve. Over time, this valve can degenerate leading to a cardiac condition known as Mitral Valve Disease (MVD).
An estimated 10 percent of dogs develop some form of heart disease in their lifetimes, and roughly 75 to 80 percent of those are due to problems with the mitral valve. MVD is more common in smaller breeds (see list below) and older dogs.
In the article that follows, you can learn more about MVD, including how we diagnose and treat it at Evergreen Animal Clinic.
Causes
The primary cause of Mitral Valve Disease is degeneration of the valve as dogs age, typically by around five or six years old. The pressure created when the left ventricle contracts and pumps blood out to the body causes the mitral value to wear out. The valve thickens and the edges begin to roll up, or prolapse, causing some of the blood to flow backward into the left atrium. The high pressure of the blood’s movement causes an audible murmur that we can detect during an examination. This is referred to as a leaky valve, Mitral Valve Insufficiency (MVI) or mitral regurgitation.
Symptoms
In the early stages of MVD, your dog may have no clinical signs of a problem. You bring her in for a routine checkup only to find she has a heart murmur, usually an early indicator of the disease. Murmurs can be present months or years before your dog shows any outward symptoms.
Over time, because the left side isn’t pumping properly, the heart becomes less efficient. Eventually, the left ventricle becomes enlarged and fluid begins to accumulate in the lungs. This often leads to a gagging reflex. Your dog may have a chronic cough or act as if he’s trying to clear his throat.
Other signs are lack of stamina or exercise intolerance, an increased respiratory rate, and even fainting, which can happen if your dog experiences abnormal heart rhythms.
Dogs with advanced or severe MVD may exhibit symptoms consistent with congestive heart failure. Heart failure occurs when the heart can no longer pump a sufficient supply of blood for the body to function. Dogs with heart failure usually present as sick, whereas dogs with heart murmurs may have few, if any, clinical signs until heart failure develops.
Sudden death from MVD is uncommon, though dogs with a heart murmur are at increased risk.
Breeds
Though all dog breeds can experience degenerative heart disease, these smaller breeds are more susceptible:
Diagnosis
Since a heart murmur, heard loudest on the left side of the chest, is a telltale symptom of MVD, the first thing we’ll do during our examination is listen to your dog’s heart and lungs with a stethoscope. This will help us ascertain the quality of the pulse, heart rate, rhythm, and whether a murmur is present. It can also detect whether there is fluid in the lungs, called pulmonary edema.
We may order an echocardiogram, which is an ultrasound of the heart, to assess blood flow, to evaluate the heart and valve structures. Or we may perform an electrocardiogram (ECG) to measure the electrical activity of your dog’s heart, looking for any abnormal rhythms.
Chest radiographs (x-rays) are useful in spotting an enlarged heart, the presence of fluid in the lungs, enlarged blood vessels or other evidence of upper airway collapse. We start with a baseline radiograph to establish the initial severity of the disease. We are likely to suggest repeat radiographs every three months to a year to track progression of the disease.
Finally, we might take blood and urine samples to test for such things as liver or kidney function, which can deteriorate in dogs with heart disease.
Treatment
The most common form of treatment for mitral valve disease is medication which is designed to treat the symptoms of the disease rather than the underlying cause. These medications fall into several categories and may be used alone or in conjunction with one another.
Diuretics
These are used to help minimize fluid buildup by stimulating the kidneys to remove excess fluid from the body. Our two most commonly prescribed diuretics are furosemide and spironolactone.
Vasodilators
These drugs help lower your dog’s blood pressure by dilating her veins and arteries, permitting better blood flow. Angiotensin-converting enzyme (ACE) inhibitors are one form of vasodilator that prevents the production of enzymes that narrow your pet’s blood vessels. Benazepril and enalapril are two of the ACE-inhibitors we commonly use to treat dogs, in part because they can be used long-term. Nitroglycerin also dilates the veins leading to the heart muscle and allows blood to flow more freely throughout the body, however dogs quickly build up a tolerance to it so we only use it in a crisis.
Beta Blockers
Beta blockers work by slowing down the heart and lowering blood pressure. Drugs such as atenolol, sotalol, propranolol and, more recently, carvedilol are among those we prescribe to help relieve the symptoms of heart failure.
Inotropes
These drugs function by helping to improve heart muscle strength, as well as lowering blood pressure in the veins and arteries. We generally use Vetmedin (pimobendan).
Diet
Limiting your dog’s salt intake may help prevent excessive fluid retention, so we may prescribe a low-salt or low- sodium diet.
Triple Therapy
Many times, we prescribe several of the medications above in conjunction with one another to treat different aspects of the disease: for example, fluid buildup, vasodilation and muscle function. We refer to this as triple therapy.
Surgery
Medical management is the primary mode for treating MVD. Very few dogs undergo valve surgery in the US, though Europe tends to do more of these types of surgeries.
Prognosis
The severity of your pet’s condition and her early response to treatment are the best indicators of her overall longevity.
Progression of the disease varies from dog to dog, with some living the rest of their lives with no significant deterioration and others where the disease advances rapidly, leading to premature death. Dogs that seem to stabilize quickly after beginning treatment will likely have a good quality of life for many more months or years.
If you own one of the breed’s mentioned in this article, or if your dog is exhibiting any of the behaviors listed above, it might be a good time to schedule a checkup with us.
A dog’s heart has four chambers and a system of one-way valves that keep blood from flowing backwards as it makes its way through the body. The valve between the lower left chamber (the left ventricle) and the upper left chamber (the left atrium) is called the mitral valve. Over time, this valve can degenerate leading to a cardiac condition known as Mitral Valve Disease (MVD).
An estimated 10 percent of dogs develop some form of heart disease in their lifetimes, and roughly 75 to 80 percent of those are due to problems with the mitral valve. MVD is more common in smaller breeds (see list below) and older dogs.
In the article that follows, you can learn more about MVD, including how we diagnose and treat it at Evergreen Animal Clinic.
Causes
The primary cause of Mitral Valve Disease is degeneration of the valve as dogs age, typically by around five or six years old. The pressure created when the left ventricle contracts and pumps blood out to the body causes the mitral value to wear out. The valve thickens and the edges begin to roll up, or prolapse, causing some of the blood to flow backward into the left atrium. The high pressure of the blood’s movement causes an audible murmur that we can detect during an examination. This is referred to as a leaky valve, Mitral Valve Insufficiency (MVI) or mitral regurgitation.
Symptoms
In the early stages of MVD, your dog may have no clinical signs of a problem. You bring her in for a routine checkup only to find she has a heart murmur, usually an early indicator of the disease. Murmurs can be present months or years before your dog shows any outward symptoms.
Over time, because the left side isn’t pumping properly, the heart becomes less efficient. Eventually, the left ventricle becomes enlarged and fluid begins to accumulate in the lungs. This often leads to a gagging reflex. Your dog may have a chronic cough or act as if he’s trying to clear his throat.
Other signs are lack of stamina or exercise intolerance, an increased respiratory rate, and even fainting, which can happen if your dog experiences abnormal heart rhythms.
Dogs with advanced or severe MVD may exhibit symptoms consistent with congestive heart failure. Heart failure occurs when the heart can no longer pump a sufficient supply of blood for the body to function. Dogs with heart failure usually present as sick, whereas dogs with heart murmurs may have few, if any, clinical signs until heart failure develops.
Sudden death from MVD is uncommon, though dogs with a heart murmur are at increased risk.
Breeds
Though all dog breeds can experience degenerative heart disease, these smaller breeds are more susceptible:
- Cavalier King Charles Spaniel (particularly predisposed)
- Cocker Spaniel
- Maltese
- Chihuahua
- Miniature Poodle
- Boston Terrier
- Fox Terrier
- Shih Tzu
- Miniature Schnauzer
- Doberman Pinscher
- Dachshund
- Whippet
- Pomeranian
Diagnosis
Since a heart murmur, heard loudest on the left side of the chest, is a telltale symptom of MVD, the first thing we’ll do during our examination is listen to your dog’s heart and lungs with a stethoscope. This will help us ascertain the quality of the pulse, heart rate, rhythm, and whether a murmur is present. It can also detect whether there is fluid in the lungs, called pulmonary edema.
We may order an echocardiogram, which is an ultrasound of the heart, to assess blood flow, to evaluate the heart and valve structures. Or we may perform an electrocardiogram (ECG) to measure the electrical activity of your dog’s heart, looking for any abnormal rhythms.
Chest radiographs (x-rays) are useful in spotting an enlarged heart, the presence of fluid in the lungs, enlarged blood vessels or other evidence of upper airway collapse. We start with a baseline radiograph to establish the initial severity of the disease. We are likely to suggest repeat radiographs every three months to a year to track progression of the disease.
Finally, we might take blood and urine samples to test for such things as liver or kidney function, which can deteriorate in dogs with heart disease.
Treatment
The most common form of treatment for mitral valve disease is medication which is designed to treat the symptoms of the disease rather than the underlying cause. These medications fall into several categories and may be used alone or in conjunction with one another.
Diuretics
These are used to help minimize fluid buildup by stimulating the kidneys to remove excess fluid from the body. Our two most commonly prescribed diuretics are furosemide and spironolactone.
Vasodilators
These drugs help lower your dog’s blood pressure by dilating her veins and arteries, permitting better blood flow. Angiotensin-converting enzyme (ACE) inhibitors are one form of vasodilator that prevents the production of enzymes that narrow your pet’s blood vessels. Benazepril and enalapril are two of the ACE-inhibitors we commonly use to treat dogs, in part because they can be used long-term. Nitroglycerin also dilates the veins leading to the heart muscle and allows blood to flow more freely throughout the body, however dogs quickly build up a tolerance to it so we only use it in a crisis.
Beta Blockers
Beta blockers work by slowing down the heart and lowering blood pressure. Drugs such as atenolol, sotalol, propranolol and, more recently, carvedilol are among those we prescribe to help relieve the symptoms of heart failure.
Inotropes
These drugs function by helping to improve heart muscle strength, as well as lowering blood pressure in the veins and arteries. We generally use Vetmedin (pimobendan).
Diet
Limiting your dog’s salt intake may help prevent excessive fluid retention, so we may prescribe a low-salt or low- sodium diet.
Triple Therapy
Many times, we prescribe several of the medications above in conjunction with one another to treat different aspects of the disease: for example, fluid buildup, vasodilation and muscle function. We refer to this as triple therapy.
Surgery
Medical management is the primary mode for treating MVD. Very few dogs undergo valve surgery in the US, though Europe tends to do more of these types of surgeries.
Prognosis
The severity of your pet’s condition and her early response to treatment are the best indicators of her overall longevity.
Progression of the disease varies from dog to dog, with some living the rest of their lives with no significant deterioration and others where the disease advances rapidly, leading to premature death. Dogs that seem to stabilize quickly after beginning treatment will likely have a good quality of life for many more months or years.
If you own one of the breed’s mentioned in this article, or if your dog is exhibiting any of the behaviors listed above, it might be a good time to schedule a checkup with us.
