Your Dog and Mitral Valve Disease

Mitral Valve Regurgitation:  Small breed dogs (generally those under about 35 pounds) commonly develop mitral valve regurgitation.  This is a leak in the mitral valve that allows some blood to flow backward through the valve.  The mitral valve is located in the heart between the left atrium, which receives blood from the lungs, and the left ventricle, which pump blood to the body.  When this valve becomes leaky, some of the blood that should be pumped to the body is actually pumped back up into the left atrium (toward the lungs).  We can detect this leak by listening to your dog's heart with a stethoscope.  The leak results in turbulent blood flow which creates an abnormal heart sound called a murmur.  At first, it may only be a very small amount of blood that is leaking back through the valve, and this may not have any clinical significance.  So your dog may not feel any effect from a small leak (a grade 1 or 2 murmur).  However, as this leak becomes worse, and more blood is allowed back into the left atrium with each heartbeat, the blood pressure in the left atrium and in the lungs will increase.  This increase in pressure will eventually become great enough that some of the fluid portion of the blood (plasma) will begin to leak into the air spaces (alveoli) in the lungs.  This is the beginning of congestive heart failure and is the point at which we need to start medical therapy.  

Mitral valve disease in dogs is a condition that we can manage successfully for a very long time in many cases.  There are a number of drugs that can help keep your dog stable, and out of congestive heart failure.  One of the keys to successful therapy, however, is knowing when it is time to start treatment, or to make adjustments to your dog's current treatment.  The section below will teach you how you to monitor your dog at home.  Taking time to do this will help us stay a step ahead of your dog's heart disease and keep them feeling strong and healthy.   

Monitoring Your Dog's Heart Condition at Home:  The very first sign we can detect as an indication of congestive heart failure is an increase in your dog’s respiration rate while he is asleep.  This is called the sleeping respiratory rate, or SRR.  To measure the SRR, you simply need to watch your dog while he or she is asleep, and count the number of breaths he takes in one minute.  You count one breath each time you see the chest rise and fall.  In a normal dog, this number should be under 30. 

We recommend that you start by doing this once daily for a week to get some baseline data, and then perform the measurement once weekly.  If you begin to notice an increase in the rate you should check it more frequently.  If the SRR is showing a consistent increase, or if it measures above 30, you should contact us; it is time for us to check your dog.  

It is very important to be sure you measure the rate while your dog is ASLEEP!  This eliminates any other factors that could result in an increased respiratory rate.  

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