The STS estimated surgical risk score pro- vides a useful measure of the extent of patient comorbidities and may help identify which patients will benefit from TAVI. Patients with a mechanical impediment to SAVR, such as a por- celain aorta or prior chest radiation damage, may have better outcomes after TAVI than do frail patients or those with moderate to severe disease in more than one other organ system.12,14,34 The likely benefits and risks of TAVI are considered in weighing the risk benefit ratio of intervention in an individual patient. TAVI is not recommended in patients with 1) a life expectancy of <1 year even with a successful procedure or 2) those with a chance of survival with benefit of <25% at 2 years. CLINICAL STATEMENTS AND GUIDELINES 9. Percutaneous aortic balloon dilation has a role in treating children, adolescents, and young adults with AS, but its role in treating older patients is very limited. The mechanism by which bal- loon dilation modestly reduces the severity of stenosis in older patients is fracture of calcific deposits within the valve leaflets and, to a minor degree, stretching of the annulus and separa- tion of the calcified or fused commissures. Immediate hemodynamic results include a Table 14. 