Adequacy of Anticoagulation in Patients with AF
Adequacy of Anticoagulation in Patients with AF
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.
Atrial fibrillation (AF) is a growing public health problem associated with significant morbidity and mortality. Patients with AF have an increased risk of embolic stroke; those with nonvalvular AF have at least a 5-fold increased risk, and those with valvular AF have an estimated 17-fold increased risk. The initial stroke is often a major infarct, resulting in severe disability or death. Numerous randomized, controlled trials conclusively showed that long-term warfarin therapy can reduce the risk of stroke by 68%/year in patients with nonvalvular AF and even more in those with valvular AF. Despite this robust evidence for efficacy, many patients may not realize the beneficial effects of warfarin because they are managed suboptimally.
Warfarin is most safe and efficacious when maintained within a narrow therapeutic range as measured by international normalized ratio (INR). In fact, the most powerful determinant of embolic stroke in patients treated with warfarin is the INR, with the risk of embolic events increasing steeply once the INR falls below 2.0. In contrast, the risk of hemorrhage with warfarin therapy rises sharply at INRs greater than 4.0-5.0. Maintaining patients within their target INR range is influenced by several factors, such as diet, concomitant drugs, diseases, and age. It has been said that nearly all the risk attributable to embolic events (specific to those with AF) appears to be eliminated by warfarin as long as patients are adequately anticoagulated. Therefore, we evaluated the adequacy of anticoagulation therapy in patients with AF coming to a hospital for any reason.
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.
Atrial fibrillation (AF) is a growing public health problem associated with significant morbidity and mortality. Patients with AF have an increased risk of embolic stroke; those with nonvalvular AF have at least a 5-fold increased risk, and those with valvular AF have an estimated 17-fold increased risk. The initial stroke is often a major infarct, resulting in severe disability or death. Numerous randomized, controlled trials conclusively showed that long-term warfarin therapy can reduce the risk of stroke by 68%/year in patients with nonvalvular AF and even more in those with valvular AF. Despite this robust evidence for efficacy, many patients may not realize the beneficial effects of warfarin because they are managed suboptimally.
Warfarin is most safe and efficacious when maintained within a narrow therapeutic range as measured by international normalized ratio (INR). In fact, the most powerful determinant of embolic stroke in patients treated with warfarin is the INR, with the risk of embolic events increasing steeply once the INR falls below 2.0. In contrast, the risk of hemorrhage with warfarin therapy rises sharply at INRs greater than 4.0-5.0. Maintaining patients within their target INR range is influenced by several factors, such as diet, concomitant drugs, diseases, and age. It has been said that nearly all the risk attributable to embolic events (specific to those with AF) appears to be eliminated by warfarin as long as patients are adequately anticoagulated. Therefore, we evaluated the adequacy of anticoagulation therapy in patients with AF coming to a hospital for any reason.
