Recommendations that have been deleted or superseded are not incor- porated. The text supporting the new and modified recommendations is provided. After the preliminary recommendation and text were drafted for percutaneous approaches to occlusion of the left atrial appendage (LAA), it was appreciated that the primary author of the section had, by strict cri- teria, an RWI relevant to the section. Task Force and organizational leadership directed that both the rec- ommendation and text be discarded and the section be constructed de novo by both a new primary author and new primary reviewer, both without RWI. This new section was thoroughly reviewed by the entire writing group, and the de novo formulated recommendation, as with all recommendations in the focused update, was formally voted on by the writing group. 1.2. Organization of the Writing Group For this focused update, representative members of the 2014 AF writing committee were invited to participate, and they were joined by additional invited members to form a new writing group, referred to as the 2018 AF Guideline Focused Update Writing Group. Members were required to disclose all RWI relevant to the data un- der consideration. The group was composed of clinicians with broad expertise related to AF and its treatment, in- cluding the areas of adult cardiology, electrophysiology, cardiothoracic surgery, and heart failure (HF). The writ- ing group included representatives from the ACC, AHA, HRS, and the Society of Thoracic Surgeons. 1.3. Document Review and Approval The focused update was reviewed by 2 official re- viewers each nominated by the ACC, AHA, and HRS; 1 AHA/ACC lay reviewer; 1 organizational reviewer from the Society of Thoracic Surgeons; and 29 in- dividual content reviewers. Reviewers abbreviated RWI information is published in this document (Ap- pendix 2), and their detailed disclosures are available online. 