Mitral Valve Disease in Dogs

The mitral valve is the valve between the left atrium and left ventricle. In a normal heart, blood flow goes one way from atria to ventricle.  

MV=mitral valve

One of the most common cardiac issues we see in dogs affects this valve. In fact, it’s been reported that 75% of cardiac cases in dogs are due to this.

It is usually a problem in small breed dogs, though any dog can develop it. There appears to be a genetic link in some breeds, most notably the Cavalier King Charles spaniel. 

The valve loses its “seal” due to damage that results in a leak where blood can flow backward into the atrium when the heart pumps blood from the left ventricle out into circulation. So since less is now going OUT then is supposed to, the heart has to make up for it by pumping more, eventually causing a larger leak and this becomes a progressively worsening condition. At the end, the dog will go into left sided heart failure which causes fluid build-up in the lungs. 

The good news is that most dogs with this do fine and aren’t even clinical, sometimes for years or NEVER. So we often find a murmur in an otherwise healthy patient or one that is in for another problem. Once again, we need an ultrasound to confirm this is truly what is going on.  For monitoring purposes, we can use routine chest xrays to watch for changes in the size of the heart. If things do progress to the point that the dog becomes clinical, we can use medications to help. These include diuretics (like furosemide - aka Lasix), drugs that help the heart function better (Pimobenden, Digoxin, etc) and cough suppressants. 

Only 25% of dogs with this die FROM this. However, if they are in heart failure, 50% will die in the first year.