1.4 Deriving Baseline Risk of Stroke in Patients With AF The risk of stroke varies considerably across different groups of patients with AF.12 Simple validated tools for the assessment of stroke risk in patients with AF help in identifying those who are more likely to bene t than be harmed from antithrombotic therapy. 1.4.1 Pattern of AF: Guidelines have categorized the pat- tern of AF into (1) PAF, in which recurrent episodes terminate spontaneously within 7 days and usually in ,48 h; (2) persistent AF, in which the episode of AF does not self-terminate within 7 days or is terminated by cardioversion; and (3) permanent AF, in which AF is present for some time and cardioversion either has failed or has not been attempted.13 For patients with PAF, periods of sinus rhythm theoretically should lessen the risk of stroke, yet transitions from AF to sinus rhythm may acutely heighten risk in a manner similar to the increase in risk caused by cardioversion. Although some studies suggest that PAF is associated with a lower risk of stroke than persistent or permanent AF, patients with PAF generally are younger and have a lower prevalence of other stroke risk factors, and clinical trial data suggest that PAF confers a relative risk of stroke similar to persistent or permanent AF when controlling for associated stroke risk factors.14-17 Pending further evidence, it seems reasonable to treat patients with PAF in a manner similar to those with persistent and permanent AF; thus, our risk-based treatment recommendations apply to patients with PAF and per- sistent and permanent AF. 