Patients with AF undergoing cardioversion Patients with AF of . h or unknown duration undergoing elective cardioversion Minimum wk anticoagulation before and wk after cardioversion No anticoagulation Death Nonfatal strokes Nonfatal major extracranial bleeds Systemic embolism Cohort studies Abbreviated precardioversion anticoagulation TEE-guided cardioversion No anticoagulation RCTs Cohort studies Patients with AF of h duration undergoing elective cardioversion Anticoagulation before cardioversion No anticoagulation before cardioversion Cohort studies Patients undergoing urgent cardioversion for hemodynamically unstable AF Anticoagulation before cardioversion No anticoagulation before cardioversion Cohort studies Patients undergoing elective or urgent cardioversion for atrial utter Anticoagulation before and after cardioversion No anticoagulation Cohort studies ACS acute coronary syndrome; AF atrial brillation; MI myocardial infarction; RCT randomized controlled trial; TEE transesophageal echocardiography; VKA vitamin K antagonist. www.chestpubs.org CHEST / 141 / 2 / FEBRUARY, 2012 SUPPLEMENT e537S tic plaque in the descending aorta seen on transesophageal echo- cardiography [TEE] or a history of peripheral arterial disease) independently predicts stroke risk among patients with AF.21-23 1.4.3 Stroke Risk Strati cation Schema: Many risk strati - cation schema, which use various combinations of the risk fac- tors discussed previously, have been developed to aid clinicians in the assessment of stroke risk in patients with nonrheumatic AF (Table S13).12 Despite substantial efforts in this eld over the past several decades, all available schema have only modest ability to predict stroke in patients with AF, with C statistics typi- cally between 0.55 and 0.70.4,24-43 (A C statistic of 0.50 indicates a model that does not discriminate better than chance alone, and a C statistic of 1.00 indicates perfect discrimination.) 