Implications of stroke risk criteria on the anticoagulation decision in nonvalvular atrial fibrillation - The anticoagulation and risk factors in atrial fibrillation (ATRIA) study

Background-Warfarin dramatically reduces the risk of stroke in patients wit h nonvalvular atrial fibrillation (NVAF) but increases the likelihood of bl eeding, Accurately identifying patients who need anticoagulation is critica l. We assessed the potential impact of prominent stroke risk classification schemes on this decision in a large sample of patients with NVAF. Methods and Results-We used clinical and electrocardiographic databases to identify 13559 ambulatory patients with NVAF from July 1996 through Decembe r 1997, We compared the proportion of patients classified as having a low e nough stroke risk to receive aspirin using published criteria from the Atri al Fibrillation Investigators (AFI), American College of Chest Physicians ( ACCP), and the Stroke Prevention in Atrial Fibrillation Investigators (SPAF ), In this cohort, AFI criteria classified 11% as having a low stroke risk, compared with 23% for ACCP and 29% for SPAF (kappa range, 0.44 to 0.85). T his 2- to-3-fold increase in low stroke risk patients by ACCP and SPAF crit eria primarily resulted from the inclusion of many older subjects (65 to 75 years +/- men >75 years) with no additional clinical stroke risk factors. Conclusions-The age threshold for assigning an increased stroke risk has a dramatic impact on whether to recommend warfarin in populations of patients with NVAF, Large, prospective studies with many stroke events are needed t o precisely determine the relationship of age to stroke risk in AF and to i dentify which AF subgroups are at a sufficiently low stroke risk to forego anticoagulation.