Heart Failure Due To Valve Defect in Dogs

Within your dog’s heart, there are four valves, but it is the mitral valve that most commonly leaks. Since the heart is a pump that pushes blood into the lungs and the rest of the body, this leak produces a major malfunction in the system. The leak causes the heart to work harder, the lungs will fill with fluid (pulmonary edema), and the blood in your dog’s body is not getting enough oxygen. There are many causes of mitral valve insufficiency, such as infection, age, infection (endocarditis), but the most common cause is congenital. Smaller dogs, such as Shih Tzus, Poodles, and Terriers are most susceptible to this disorder. Mitral valve insufficiency eventually will cause heart failure unless you catch it early and if it is treatable. However, the disease is progressive and will get progressively worse as time goes on.

Heart failure due to valve defect (mitral valve insufficiency) is a leaky heart valve (usually the mitral valve) that causes heart failure. It is also the most common cause (75%) of heart failure in dogs. The mitral valve is supposed to separate the left atrium from the left ventricle, but it can thicken and become deformed due to age, disease, congenital defect, or injury. If the valve leaks, the blood will travel back into the left atrium (regurgitation), which causes the atrium to swell and cause a backup of fluid in the lungs from all the pressure.

• Coughing during exertion (gradually increases to coughing all the time)
• Exercise intolerance
• More panting than usual
• Loss of appetite
• Weight loss
• Weakness
• Fast breathing
• Trouble with breathing
• Blue skin and mucous membranes
• Fainting
• Agitation
• Heart murmur (usually only noticed by the veterinarian)
• Decreased pulse (usually only noticed by the veterinarian)

• Lyme disease
• Plaque build-up
• Age (middle aged and older)
• Infection (endocarditis, myocarditis, untreated periodontal disease)
• Genetics (Boston Terriers, Cavalier King Charles Spaniels, Chihuahuas, Dachshunds, Fox Terriers, Lhasa Apsos, Maltese, Pomeranians, Poodles, Pugs, Schnauzers, Whippets, and Yorkies)

As with any visit, the veterinarian will ask for your dog’s medical history (ex. recent illnesses, changes in eating or exercise habits, changes in food, etc.) while giving your dog a thorough physical exam including heart rate, blood pressure, and body temperature. Then some tests will need to be done to verify what the veterinarian suspects. These tests are:

• Complete blood count (CBC)
• Blood gases
• Blood chemistry panel
• Urinalysis
• Electrolyte panel
• Digital radiographs (x-rays) of the chest to look for fluid in the lungs and size of the heart
• Electrocardiogram (EKG or ECG)  to check the electrical impulses and determine how much deterioration there is in the valves

If the veterinarian thinks it is necessary, he may run some other tests, such as:

• Ultrasound of the heart
• Echocardiography to see the structure of the valves and heart and how they are functioning as well as how the blood is flowing (Doppler echo)
• MRI

The veterinarian may also decide to send your dog to a canine heart specialist (cardiologist) for further testing.

Many dogs with mitral valve insufficiency will be fine for years without any symptoms at all and may not need any medication. The veterinarian will prescribe a special food with low sodium for your dog and regular check-ups are essential.

If your dog is showing symptoms of congestive heart failure, such as difficulty breathing, pulmonary edema, and heart murmur, your veterinarian will most likely prescribe some medication that can help. Some of these medications are:

• Diuretics to reduce fluid build-up (furosemide, hydrochlorothiazide)
• Ace inhibitors for high blood pressure (lisinopril, enalapril, benazepril)
• Heart muscle strengthening medicine (digoxin)

There is more therapy to do for your dog, such as a proper diet, regular but restricted light exercise as long as it is easily tolerated, and there is surgery as well. The surgeries that can be done to help your dog are still relatively new and very expensive, but can give your dog back a normal long life he would otherwise not have. Mitral valve plasty (MVP) is a surgery to repair the valve that is already in your dog’s heart. Mitral valve replacement (MVR) is an easier surgery but it requires a lifetime of anticoagulants.

It is essential that the medication and dosage prescribed be followed exactly for the health of your dog. Since mitral valve insufficiency is progressive, the treatment will be altered as your dog’s condition worsens. These medications are palliative, and not curative.

Many dogs that are diagnosed with mitral valve insufficiency live for many years without progressing to heart failure. However, once your dog is diagnosed with heart failure, the disease will usually progress and be fatal within one year or less.