Subaortic stenosis is a congenital condition that is seen most commonly in certain large breed dogs. Subaortic stenosis is a narrowing that occurs below the aortic heart valve which impedes the flow of blood from the left ventricle of the heart into the aorta. This condition can usually present itself as a murmur heard by auscultation with a stethoscope within the first year of a dog’s life.
If a murmur is found, then an echocardiogram should be performed on a regular basis to look at the way the heart is functioning. The prognosis for this disorder depends on the severity and progression of disease within the individual animal. If it is a mild case, then many animals survive into adulthood. If it is more severe, the prognosis is more guarded.
Surgical correction requires open heart surgery and has not met with much success. A procedure called balloon valvuloplasty is often recommended for animals with moderate to severe disease. This procedure dilates the stenotic area by blowing up a balloon instead of it. The severity of the narrowing can often be reduced by this procedure but sometimes the severity reverts back to the original state.
Medical therapy is usually employed in the more severe cases to control symptoms, but this condition is not curable. Balloon valvuloplasty was shown to be equivalent to medical therapy in survival time in one study but the combination of medical therapy and balloon vavuloplasty has not been evaluated. Sudden death due to irregular heartbeats and congestive heart failure are both possibilities with severe disease.