Assumptions underlying these estimates are detailed in section of this article. h Rates of nonfatal major extracranial bleeding on aspirin are extrapolated from rates in observational cohorts of patients receiving adjusted-dose VKA therapy (median, and relative risks of major extracranial bleeding associated with VKA therapy (RR, and aspirin (RR, compared with no therapy. i The CI does not exclude the possibility of no effect. j Based on rate of systemic embolism on aspirin of per patient-y reported in the IPD meta-analysis of warfarin vs aspirin by van Walraven et al. www.chestpubs.org CHEST / 141 / 2 / FEBRUARY, 2012 SUPPLEMENT e551S dabigatran over adjusted-dose VKA therapy in sec- tion 2.1.11. The data from RE-LY do not directly address the use of dabigatran in patients with AF and mitral ste- nosis (patients with hemodynamically relevant val- vular disease were excluded from this study), or in patients with AF in other special situations (sections 2.2 and 3.0). Therefore, we have not extrapolated the data from RE-LY to these clinical situations and have instead restricted those recommendations for oral anticoagulation to adjusted-dose VKA therapy. There is direct evidence from RE-LY regarding the use of dabigatran in patients with AF undergoing cardiover- sion, and these data are summarized in section 4.1.1. 2.1.8 Recommendations for Patients With AF at Low Risk of Stroke (eg, CHADS2 Score of 0): Patients at suf ciently low risk of ischemic stroke may opt for no treatment rather than antithrombotic therapy with either aspirin or an oral anticoagulant. For instance, for every 1,000 patients at low risk of stroke with a CHADS2 score of 0, VKA therapy compared with no treatment is anticipated to result in ve fewer nonfatal strokes at the expense of eight more nonfatal major extracranial bleeds and the additional burden of adjusted-dose VKA treatment (Table 3). 