Different diseases involving the heart valves or heart muscle can lead to heart failure. By far the most common type of heart disease seen in dogs, aside from that caused by heartworms, is mitral insufficiency, which involves the heart valve separating the left atrium from the left ventricle. If this valve becomes diseased and fails to close properly when it is supposed to, blood is allowed to flow back into the left atrium when the left ventricle contracts.
This has two effects: (1) The amount of blood pushed forward into circulation by each heart contraction is greatly reduced, which means that the heart (which, remember, is diseased) must work harder than it did when it was healthy to keep up with the body’s demand for blood; and (2) the backup of blood that occurs as a result of the inefficient heart contraction leads to fluid buildup within the lungs, interfering with oxygen exchange between the blood and the lungs. As a result, a vicious cycle develops.
Mitral insufficiency can result from normal wear and tear associated with age, or more importantly it can appear secondary to other diseases, namely, periodontal disease. Bacteria from the diseased teeth and gums can enter the bloodstream and attach to the heart valve, setting up infection and inflammation. Over time, the heart valve becomes damaged and scarred, making it unable to function properly. The end result is often heart failure.
Although their frequency is much less, diseases involving the other valves in the heart can nevertheless occur. Disease of the tricuspid valve, which separates the right chambers of the heart, can occur secondary to age or infection and can interfere with the normal return of blood to the heart from the body. Defects in the pulmonic or aortic valves, which separate the ventricles from the pulmonary vessels and aorta, respectively, are usually congenital (present at birth) and might not be detectable when the dog is young. However, as the dog matures and the requirements placed on the heart increase, signs of heart disease or failure could become apparent.
This has two effects: (1) The amount of blood pushed forward into circulation by each heart contraction is greatly reduced, which means that the heart (which, remember, is diseased) must work harder than it did when it was healthy to keep up with the body’s demand for blood; and (2) the backup of blood that occurs as a result of the inefficient heart contraction leads to fluid buildup within the lungs, interfering with oxygen exchange between the blood and the lungs. As a result, a vicious cycle develops.
Mitral insufficiency can result from normal wear and tear associated with age, or more importantly it can appear secondary to other diseases, namely, periodontal disease. Bacteria from the diseased teeth and gums can enter the bloodstream and attach to the heart valve, setting up infection and inflammation. Over time, the heart valve becomes damaged and scarred, making it unable to function properly. The end result is often heart failure.
Although their frequency is much less, diseases involving the other valves in the heart can nevertheless occur. Disease of the tricuspid valve, which separates the right chambers of the heart, can occur secondary to age or infection and can interfere with the normal return of blood to the heart from the body. Defects in the pulmonic or aortic valves, which separate the ventricles from the pulmonary vessels and aorta, respectively, are usually congenital (present at birth) and might not be detectable when the dog is young. However, as the dog matures and the requirements placed on the heart increase, signs of heart disease or failure could become apparent.
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