PARTICIPANTS : Two hundred thirty-five patients aged 76 and older admitted to a major healthcare network between July 1 , 2001 , and June 30 , 2002 , with atrial fibrillation on warfarin were enrolled .
O O O O O B-OrganismTaxon O O O O O O O O O O O O O O O O O O O O O O O B-DiseaseOrPhenotypicFeature I-DiseaseOrPhenotypicFeature O B-ChemicalEntity O O O