An electrocardiogram (ECG) often shows enlargement of the left ventricle. A chest x-ray may show evidence of CHF. An ultrasound of the heart and Doppler flow study allow precise evaluation of the severity of the stenosis. The ECG, chest x-ray, and echocardiogram are repeated at varying intervals to monitor the progression of the stenosis. A heart catheterization is done before valve surgery. Symptoms usually do not develop until after age 50, but individuals may have had a heart murmur at an earlier age.