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.