OBJECTIVES: ASA/AHA guidelines for stroke prevention in patients with non-valvular atrial fibrillation (NVAF) recommend anticoagulant (AC) therapy with a vitamin K antagonist (e.g., warfarin) for patients without hemorrhagic contraindication.  Bridging with low molecular weight heparin (LMWH) was recently added to these guidelines (Class IIa), but with little supportive evidence (Level of Evidence C). Little is known about the use of AC therapy in the inpatient setting and how it relates to hospital length of stay (LOS). METHODS: Patients with an NVAF discharge diagnosis between 7/1/04-9/30/09 were identified from administrative claims data representing over a hundred US hospitals. Inpatient AC use by drug type was reported to identify patients receiving warfarin alone and in combination with LMWH/pentasaccharide (PS) or unfractionated heparin (UFH), indicative of bridging.  LOS was measured and reported by AC combinations.  Non-parametric statistical tests were used to compare LOS among patients receiving warfarin only to those with bridge therapy. RESULTS: Of 6340 NVAF patients, 76% received inpatient AC therapy, with 3037 (48%) receiving warfarin.  Of patients receiving warfarin, 64% were bridged with another AC.  LMWH/PS was the most common bridge agent (45% of all bridged patients), followed by UFH (36%), and by LMWH/PS and UFH combined (18%).  The mean LOS for patients receiving bridge therapies was 6.3 days (SD=6.1) compared to 4.2 days (SD= 3.1) for warfarin alone, p<.0001.  By bridging drug type, mean LOS was 5.6 days (SD=5.3) for LMWH/PS; 6.0 days (SD=4.9) for UFH, and 8.4 days (SD=8.4) for LMWH/PS and UFH. CONCLUSIONS: Less than half of all NVAF patients received warfarin while hospitalized.  Among those taking warfarin, bridging with other anticoagulants was common and was associated with longer LOS than patients receiving warfarin alone.