The heart has four valves, one of these being the mitral valve. The purpose of the valves is to control the flow of blood around the heart each time it beats. When the heart beats, the valves allow blood to pass through then close to stop any blood leaking back into the initial chamber. MVD causes the valve between the left atrium and left ventricle to thicken, resulting in the valve not being able to close properly and blood leaking back through as a result. This leak is heard as a heart murmur.
The knock-on effect is that greater pressure is put on the heart to work harder and pump the blood around the body. The heart also enlarges due to the need to pump harder to compensate for the loss caused by the initial backflow (‘regurgitation’). The heart may be able to cope with this over a long period; however, at a certain point, the pressure becomes so high that blood accumulates in the blood vessels of the lungs causing fluid to leak into the lungs – the result is congestive heart failure.
We already know that MVD is a chronic and progressive disease, with the worsening effects outlined above, but that doesn’t mean that all dogs with the disease go on to develop heart failure. The various stages of the condition have been classified as below:
STAGE A – Breeds prone to MVD with no current symptoms or murmur
STAGE B1 – A murmur is present but there are no symptoms and no evidence of heart changes on imaging
STAGE B2 – A murmur is present with signs of enlarged heart but no heart failure
STAGE C – Showing signs of heart failure such as coughing, breathing problems, exercise intolerance, or collapse.
- coughing (after lying down or sleeping, and often worse at night)
- slowing down on walks or displaying low energy in general
- breathing quicker than usual, with breathlessness and/or panting
- weight loss
- fainting or collapsing.
If in any doubt, it is always best to get your dog seen by us. On detection of a heart murmur, further tests may be required to confirm the diagnosis.
MVD can affect any dog, but it is most common in small to medium sized breeds, and dogs that are middle-aged to senior. When it comes to individual breeds, it is once again more common in the:
- Cavalier King Charles spaniel
As it currently stands, there is no cure for the condition. But the advances in modern medicine mean that if the condition is caught early, there is a good chance that dogs can lead happy lives using a combination of drugs to both control the disease and prolong life. Valve replacement surgery is possible in a small number of cases.