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Mitral Valve Disease – Dogs


Small dog chasing a pink ball through grass

Have you ever noticed your dog coughing after they are excited or noticed them having difficulty breathing after walks? There can be many causes of coughing in dogs – but today I am going to provide some information on Mitral Valve Disease.

Mitral Valve Disease is the most common form of heart disease in small breed dogs (Yorkies, Chihihuas, Shih Tzus, and of course the Cavalier King Charles, etc). Mitral Valve disease is typically a chronic and often progressive disease. 10% of small breed dogs have some form of Mitral Valve Disease.

So what is a Mitral Valve?

The Mitral Valve is a valve on the left side of the heart between the left atrium and left ventricle. With disease and denegation, the valves thicken and lose their ability to close appropriately. The result is blood flowing backwards in the heart (from the ventricle back into the atrium). This is commonly heard in the form of a heart murmur. A heart murmur is a sound we as Veterinarians hear when listening with our stethoscopes to the pet’s heart; it can be an indication of turbulent or abnormal blood flow through a heart. As Mitral valve disease progresses, patients can eventually end up with Congestive Heart Failure where their heart is no longer able to compensate for the abnormal blood flow in the heart. Thankfully, Mitral Valve Disease tends to be a slowly progressing disease. over 75% of patients with Mitral Valve Disease will pass away from some other condition – not cardiac in origin.

So, if we hear a heart murmur in your pet– we will likely recommend starting with baseline chest x-rays to evaluate the size of your patient's heart, and determine if there is any sign of congestive heart failure. If there is heart enlargement or signs of congestive heart failure on the xray we will recommend an echocardiogram or heart to measure the thickness of the walls of the heart, the size of the chambers of the heart and measure blood flow through the heart. With an echocardiogram, we can also measure blood pressure through the heart and valves surrounding the heart, allowing us to determine if there is evidence of pulmonary hypertension.

How do we treat patients with Mitral Valve Disease?

If your pet is in subclinical disease (evidence of disease but not in heart failure yet), the goal is for us to slow the progression of the disease. We often will start these patients on a medication called Vetmedin which has been shown to extend the time it takes to move from subclinical disease to congestive heart failure. Vetmedin is a medication that helps the heart pump more efficiently by opening up blood vessels taking blood away from the heart and increases the strength of contractions of the heart. Basically, it allows the heart to not to have to work as hard. Sometimes in subclinical disease we may also start a blood pressure medication if your pet is showing signs of high blood pressure.

If your pet is in clinical disease or Congestive Heart Failure, coughing, exercise intolerance, lethargy, increased resting respiratory rate and effort, and radiographic changes indicating pulmonary edema we will be more aggressive in our treatment. These patients will be started on Vetmedin as well as it helps promote stronger heart contractions even though they are already in clinical disease. We will also add on a diuretic – typically Furosemide and often Spironolactone. These medications help drain fluid out of the body and get rid of inflammation in the lungs that is associated with pulmonary edema, helping to decrease coughing in our patients. We will also start a blood pressure medication – either Enalapril or Benazepril to help decrease blood pressure in the body and make it easier for blood to circulate through the body, lessening the stress on the heart.

Many patients, once diagnosed with Congestive Heart Failure and started on medication, will begin to live more comfortable lives as their energy and quality of life improves with the medication. We recommend that if your pet has a heart murmur you start monitoring their resting respiratory rate. When a pet is sleeping their normal resting, respiratory rate should be in the normal range, one of the first signs of heart failure progression is increase in the resting respiratory rate. A normal resting respiratory rate would be under 30 -36 breaths per minute. If you get in the habit of monitoring your pet’s breathing at home and notice an increase in the number of breaths per minute, it’s a sign the disease might be progressing. If we can catch disease early and help slow the progression of disease and provide medication that can help improve your pet’s clinical signs and quality of life.

Feel free to reach out to one of our Team Members or Veterinarians if your pet has a heart murmur and you are concerned about them having Mitral Valve Disease.