of Studies With No Therapy With VKA Relative Effect CI) With No Therapy With VKA CI) Quality of Evidence Burden of treatment (important outcome) N/A No serious limitations No serious limitations No serious limitations No serious limitations N/A N/A N/A VKA . no therapy Warfarin: daily medication, lifestyle limitations, dietary restrictions, frequent blood testing and clinic visits High AFASAK Atrial Fibrillation Aspirin and Anticoagulation; ATRIA Anticoagulation and Risk Factors in Atrial Fibrillation; BAATAF Boston Area Anticoagulation Trial for Atrial Fibrillation; CAFA Canadian Atrial Fibrillation Anticoagulation; EAFT European Atrial Fibrillation Trial; IPD individual patient data; N/A not applicable; RR risk ratio; SPAF Stroke Prevention in Atrial Fibrillation; SPINAF Stroke Prevention in Nonrheumatic Atrial Fibrillation. See Table and legends for expansion of other abbreviations. a Pooled estimates of treatment effect in this evidence pro le are from a meta-analysis conducted for these guidelines, including data from RCTs of adjusted-dose VKA therapy vs no antithrombotic therapy (AFASAK I, BAATAF, CAFA, EAFT, SPAF I, SPINAF). b From Go et al, which reported a mortality rate of per person-y in untreated (no warfarin) patients from an observational study (ATRIA cohort). The majority of the patients in ATRIA had a CHADS score of 1. c VKA therapy likely does not lead to any reductions in all-cause mortality compared with no therapy in low-risk patients with a CHADS score of because there is evidence suggesting that absolute reductions in ischemic stroke heavily depend on stroke risk (eg, small reductions at low CHADS score), whereas the absolute increase in intracranial hemorrhage is relatively consistent across CHADS categories (Singer et al ). d Intracranial hemorrhage includes intracerebral, subdural, and subarachnoid bleeds. 