Treatment patterns and real-world effectiveness of warfarin in nonvalvular atrial fibrillation within a managed care system

Abstract

Within usual clinical care for the managed care population examined, warfarin remains underused despite current guidelines recommending its use in nearly all patients with nonvalvular atrial fibrillation. Although utilization of anticoagulation clinics and INR values attained were unknown in this study, the observed risk reductions for ischemic stroke and thromboembolism were lower than those achieved in clinical trials, while no increased risk for hemorrhage was observed. These findings suggest that warfarin is used conservatively, and dosed cautiously, diminishing the full potential benefit of anticoagulant therapy in patients with nonvalvular atrial fibrillation.

Discontinuation/Interruption of Warfarin Therapy in Patients with Nonvalvular Atrial Fibrillation

“…1,7 Administration of anticoagulants such as warfarin is associated with notable reductions in the risk of thromboembolic events in patients with AF, as recommended by practice guidelines such as those by the American College of Cardiology, American Heart Association, and European Society of Cardiology. [1][2][3][4][8][9][10][11] Warfarin decreases the risk of stroke by 64% to 86% compared with placebo. [12][13][14][15][16] Warfarin has also been associated with decreased total health care costs among patients with AF in comparison with patients who were not taking warfarin.…”

Atrial Fibrillation and Stroke in the General Medicare Population

“…7,8 Others indicate increased incidence of bleeding complications from warfarin use in the community. 9,10 Recent studies using managed care system data indicate that real-world effectiveness in clinical practice results in relative risk reduction of only approximately 20%. 10 An integrated delivery system with 80% of patients managed by a coagulation service achieved a 50% relative risk reduction.…”

Cost Efficiency of Anticoagulation With Warfarin to Prevent Stroke in Medicare Beneficiaries With Nonvalvular Atrial Fibrillation

“…11 The stroke risk reduction in patients anticoagulated in ordinary clinical practice appears to be considerably lower, with risk reductions of 22% to 32%. 12,13 The reduced benefit of warfarin on the risk of stroke appears to be due, at least in part, to the low prevalence and quality of anticoagulation in ordinary clinical practices compared with controlled clinical trials. One likely reason for underuse of warfarin in clinical practice is overestimation of the risk of bleeding compared with the risk of stroke, especially in elderly patients.…”