Adequacy of anticoagulation in patients with atrial fibrillation coming to a hospital.

Study Objective. To evaluate the adequacy of anticoagulation in patients with atrial fibrillation (AF) coming to a hospital. Design. Retrospective medical record review Setting. Tertiary care hospital. Patients. Consecutive patients with a history of AF who had been prescribed warfarin and who had the international normalized ratio (INR) measured when they arrived at the hospital. Those who developed AF as a complication during hospitalization were excluded. Measurements and Main Results. Of 1085 patients, 375 (mean age 73 yrs, 56.3% men) were eligible for further evaluation. Most had nonvalvular AF; in 44.5% the INR was subtherapeutic, in 36.5% it was therapeutic, and in 18.9% it was supratherapeutic. Patients admitted for any thromboembolic event and for ischemic stroke were significantly more likely to have subtherapeutic INRs. Conclusion. It is well documented in the literature that warfarin is underprescribed, but our results suggest that even in treated patients, about half are inadequately protected from thromboembolism.