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However, in the spirit of full disclosure, this information is recorded in the online disclosure table containing all author health care relationships. Document Development and Approval The Writing Committee convened by conference call and e-mail to finalize the document outline, develop the initial draft, revise the draft per committee feedback, and ultimately sign off on the document for external peer review. All participating organizations participated in peer review, resulting in 48 reviewers representing 1087 comments. Comments were reviewed and addressed by the writing committee. A member of the ACCF TF CECD served as lead reviewer to ensure that all comments were addressed adequately. Both the Writing Committee and TF CECD approved the final document to be sent for board review. The ACCF Board of Trustees, AATS Council, SCAI Board of Directors, and STS Board of Directors reviewed the document, including all peer review comments and Writing Committee responses, and approved the document in January 2012. The AHA, ASE, EACTS, HFSA, Mended Hearts, SCA, SCCT, and SCMR endorsed the document in January 2012. This document is considered current until the TF CECD revises or withdraws it from publication. 1.2. Purpose of This Document Transcatheter aortic valve replacement (TAVR) offers new and potentially transformational technology for patients with severe aortic valvular stenosis who are either extremely high-risk candidates or inoperable for surgical aortic valve replacement (AVR) or who are inoperable by virtue of associated comorbidities. In the future, this technology may be utilized in lower risk surgical candidates. An estimated 40,000 patients have received TAVR worldwide. Multiple single and multicenter registries, and a single randomized trial, have documented favorable outcomes using a wide spectrum of endpoints, including survival, symptom status, quality of life, and need for repeat hospitalization. The implementation of TAVR into the flow of patient care is complex, involving consideration of several key factors such as clinical site selection, operator and team training and experience, patient selection and evaluation, procedural performance and complication management, and postprocedural care. Collaborative stakeholder involvement is required in the management of this high-risk patient population with extensive coexistent medical conditions. A previously published document by ACCF and STS identified a high-level series of issues to be addressed regarding this technology. This current collaborative expert consensus document, which involves 12 professional societies, addresses these issues in greater detail with the intent to examine the current state of the evidence, facilitate the integration of this technology into the armamentarium of therapeutic options for patients with aortic valvular stenosis, and to enable responsible adoption and diffusion of this promising technology. This document has focused on published data; it must be remembered that there is only 1 single completed randomized trial, although others are in progress or planned; much of the data in this expert consensus document is based upon information from studies and registries, both surgical and TAVR, which are frequently retrospective and include self-reported clinical events rather than adjudicated events. 2. BACKGROUND AND HISTORICAL ASPECTS The most common cause of valvular aortic stenosis (AS) in adults is calcification of a normal trileaflet or congenital bicuspid valve. Calcific AS is characterized by lipid accumulation, inflammation, fibrosis, and calcification and is common in the United States. It typically presents in older individuals (ie,>75 years) in contrast to bicuspid AS, which presents a decade or more earlier. Rheumatic AS, uncommon in the Western world, occurs due to fusion of the commissures with scarring and calcification of the cusps, and retraction of the leaflets resulting in the valve being both regurgitant and stenotic. Pathophysiology and Clinical Course In adults with valvular AS, the obstruction develops gradually, typically over many years during which the left ventricle (LV) adapts to the systolic pressure overload with progressive concentric hypertrophy that results in diastolic dysfunction, reduced coronary reserve, myocardial ischemia,and eventually, depressed contractility resulting in LV systolic dysfunction. Ultimately, in some patients, heart failure or sudden death occurs. Typically, patients with AS are free from cardiovascular symptoms (ie, angina, syncope, and heart failure) until late in the course of the disease. However, once symptoms manifest, the prognosis is poor, with the interval from the onset of symptoms to the time of death being approximately 2 years in patients with heart failure, 3 years in those with syncope, and 5 years in those with angina. Gardin et al. reported that among symptomatic patients with moderate-to-severe AS treated medically, mortality rates after the onset of symptoms were approximately 25% at 1 year and 50% at 2 years,16 with approximately 50% of deaths being sudden.