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Degenerative valve disease is a condition that leads to degeneration of the heart valves. In the vast majority of cases it involves the valve separating the left part of the heart into left atrium and left ventricle - the mitral valve. For this reason it is often referred to as mitral valve disease (MVD). The valve separating the right part of the heart into right atrium and right ventricle - the tricuspid valve - is also affected in approximately 30% of cases. Uncommonly the aortic or pulmonic valves also present with signs of degeneration. The medical term for degenerative valve disease is "endocardiosis".
Blood arriving from the body and head to the right atrium in the heart passes through the tricuspid valve into the right ventricle before being ejected into the pulmonary artery through the pulmonic valve. This blood is directed to the lungs and after "loading" with oxygen returns to the heart via the pulmonary veins into the left atrium, passes thorugh the mitral valve into the left ventricle and is ejected to the whole body through the aorta.
Stage A - Predisposed breeds (see below) currently without any sign of disease
Stage B1 - Disease is present without signs of heart enlargement nor heart failure
Stage B2 - Disease is present with signs of heart enlargement but no heart failure
Stage C1 - Congestive heart failure in need of hospitalization
Stage C2 - Current or past signs of congestive heart failure on treatment at home
Stage D1 - Refractory heart failure in need of hospitalization
Stage D2 - Refractory heart failure treated at home
Cardiac ultrasound: the valves are thickened and do not close completely. The green color on the right represents regurgitation (leakage) of blood through the "leaky" valve.
Unfortunately a cure does not exist for this condition. A combination of drugs is used to control signs of congestive heart failure and prolong life with the best quality of life possible.
Basic treatment might include a combination of:
Furosemide (a powerful diuretic)- to excrete the excess fluids in the body and treat congestive heart failure
ACE inhibitor- to counteract fluid retention by the kidneys and dilate the blood vessels and lessen the load on the heart
Pimobendan- to improve heart muscle strength and dilate the blood vessels and lessen the load on the heart
Additional drugs might be added by the attending cardiologist:
Spironolactone- to further excrete fluids and counteract heart muscle fibrosis
Amlodipine- to further dilate the blood vessels and lessen the load on the heart
Digoxin and others...
Therapy is lifelong and drugs/dosages are adjusted over time according to disease progression and kidney function among other factors.
After any treatment adjustments a brief re-check at your vet may be necessary. The same blood tests will be repeated to assess the kidneys response to therapy, blood pressure and eventually chest radiographs in case the goal is to assess resolution or improvement of congestive heart failure. Usually this is performed 5-10 days after the initial examination.
Although a proportion of dogs will eventually succumb to this disease, many will live relatively normal lives and pass away from other causes if the disease is appropriately treated. Some dogs will never show any clinical signs even in old age. Given these facts, this disease is often considered a benign condition.
Congestive heart failure
At any time, even with appropriate treatment, an episode of congestive heart failure may occur, typically characterized by labored breathing, cough, exercise intolerance and fatigue. These episodes are usually treatable but it is essential that you seek veterinary care immediately if you recognize these signs, since without proper management death will occur, sometimes quickly, sometimes after a few days.
Chorda tendinea rupture
The mitral valve leaflets are supported by a number of chords - chordae tendineae - similar to the spindles supporting an umbrella. These chords also degenerate and may rupture at any time. If this occurs, the "hole" in the valve will suddenly become much larger and the amount of blood regurgitating into the atrium may increase dramatically. The heart will no longer be able to cope with this and fulminant congestive heart failure and even death may occur. This may occur more readily during periods of fear or excitement.
Left atrial rupture (very rare)
In extreme cases, the left atrium becomes so large and the walls become so thin and fragile that it may rupture. Fortunately this happens rarely but when it does happen, most dogs will die suddenly from significant internal hemorrhage and heart failure. This may occur more readily during periods of fear or excitement.