A normal ratio is close to 1.0, whereas a ratio of 0.25 corresponds to a valve area 25% of normal for that patient, which is consistent with severe AS and is a predictor of symptom onset and adverse 5. The degree of aortic valve calcification is a strong predictor of clinical outcome, even when evaluated qualitatively by echocardiography.33 Quantitation of aortic valve calcium by CT imag- ing is especially useful in patients with low-flow, low-gradient AS of unclear severity with either a normal or reduced LVEF. Sex-specific Agaston unit thresholds for diagnosis of severe AS are 1300 in women and 2000 in men. These differ- ent thresholds reflect the contribution of leaflet fibrosis, in addition to calcification, to increased leaflet stiffness in women. CT imaging also is used for procedural planning in patients under- going TAVI, for measurement of annulus area, leaflet length, and the annular to coronary 3.2.1.2. Diagnostic Testing: Changing Signs or Symptoms In patients with known valvular AS, repeat TTE is pru- dent when physical examination shows an increase in the loudness of the murmur, the murmur peaks later in systole, the A2 component of the second heart sound is diminished or absent, or symptoms occur that might be attributable to AS. Repeat TTE is also appropriate in patients with AS who are exposed to increased hemo- dynamic demands, either electively, such as with non- cardiac surgery or pregnancy, or acutely, such as with a systemic infection, anemia, or gastrointestinal bleeding. In these clinical settings, knowledge of the severity of valve obstruction and LV function is critical for optimiz- ing loading conditions and maintaining a normal car- diac output. 3.2.1.3. 