Heart Valve Malfunction in the Dog (Mitral Insufficiency)
This
information is not meant to be a substitute for veterinary care. Always follow
the instructions provided by your veterinarian.
Anatomy of the heart of a dog
Many dogs slowly develop degenerative thickening and progressive deformity
of one or more heart valves as they age. In time, these changes cause the valve to leak.
The mitral valve is most commonly affected. This valve separates the blood
collecting chamber (left atrium) from the pumping chamber (left ventricle) leading to the
body. Some dogs also develop these changes in the tricuspid valve, which separates
the collecting (right atrium) and pumping (right ventricle) chamber leading to the lungs.
Certain breeds have an inherited predisposition to this disease.
Degenerative valvular disease is slowly progressive over years and is non-reversible. The
volume of blood that leaks back into the atrium with each heartbeat tends to increase
slowly over time. However, many dogs with this disease never develop signs of congestive
heart failure even though they may have a loud murmur.
Early in the disease process, your veterinarian may hear a soft murmur when the affected
valve starts to leak. There usually is no noticeable change in the dog’s activity
level or behavior for a long period of time. Gradually, though, the valve leak tends to
get worse and the heart slowly enlarges. If the leak becomes severe, blood may start to
back up behind the heart – usually into the lungs. This causes lung congestion and
fluid accumulation (edema). When lung congestion and edema occur, congestive heart failure
is present.
Reduced exercise ability may be the first sign of heart failure.
Most dogs with heart failure caused by degenerative valve disease show signs of
"left-sided" congestive failure. These signs include tiring quickly, increased
breathing rate or effort for the level of activity, excessive panting, and cough
(especially with activity). The presence of any of these signs should prompt a
visit to your veterinarian to determine if heart failure (or another disease) has
developed.
More advanced signs of heart failure could include labored breathing, reluctance to lie
down, inability to rest comfortably, worsened cough, reduced activity, and loss of
appetite. Your veterinarian should be consulted right away if these signs occur.
Some dogs that become symptomatic from their heart disease develop fluid in the abdomen
(ascites); others have episodes of sudden weakness or fainting that can
result from irregular heartbeats or other complications.
As long as no sign of heart failure develops, no treatment is necessary, although
reduction of dietary salt intake is often advised. Again, there are many dogs with
degenerative valvular disease that never progress to heart failure.
However, if
heart failure develops, several medications and other strategies are used to control the
signs. Since the disease is not reversible and heart failure, when it occurs, tends to be
progressive, the intensity of the therapy (including the number of medicines and dosages
used) usually must be increased over time.
Therapy is always tailored to the needs of the individual patient.
This Pet Health Topic was written by
O. L. Nelson, DVM, MS, Diplomate ACVIM (Cardiology
& Internal Medicine) Washington State University.
Washington State University assumes no liability for injury to
you or your pet incurred by following these descriptions or procedures.
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Last Edited: Dec 21, 2007 3:28 PM
