There are four major valves in the heart that control the passage of blood. Any of these valves can be damaged by disease or by a mechanical factor such as a toxic drug. The first indication of valvular disease is usually an abnormal heart murmur. This is evidence that one or more valves are no longer functioning properly. Left untreated, the condition may progress until the patient experiences shortness of breath, fatigue, inability to exercise as before, and edema. Such abnormal valve function is evaluated by a test called echocardiography which allows the heart to be imaged so that abnormalities can be found. Medication may hemp control the problem but frequently valve replacement is the only option.