Mitral Regurgitation (MR)

Roughly 1 in 10 dogs will develop some sort of heart disease. Mitral regurgitation (MR) is a heart disease caused by a degenerative process that occurs in most dogs as they age. This process causes the mitral valve (found between the upper and lower left chambers of the heart) to leak.


Signs and Symptoms

In dogs with MR, the leak in the valve can progressively worsen so that the left ventricle is pumping a significant amount of blood backwards through the leaky valve; this causes the first sign of the disease, a heart murmur. Since the heart also has to pump a normal amount of blood forwards, the left ventricle slowly enlarges. Also, the left atrium enlarges to accommodate the backflow through the mitral valve.

As the pressure in this chamber increases, it is transmitted back to the blood vessels in the lungs and, if the pressure is high enough, fluid can exude (leak slowly) into the alveoli (air sacs) in the lungs. This is called pulmonary edema or congestive heart failure. In many dogs this causes a cough. However, some dogs don’t cough when this occurs. Instead, they breathe faster (more than 40 breaths per minute) or with too much effort. Clinical signs of heart failure include: gagging, hacking cough, and lack of stamina.

Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from mitral regurgitation (MR) or another serious condition, a veterinary specialist is available at an ExpertVet certified hospital.