Appropriate Use of Antithrombotic Medication in Canadian Patients With Nonvalvular Atrial Fibrillation

This national chart audit of 7,019 patients with nonvalvular atrial fibrillation (AF) from 735 primary care physician practices sought to examine the management of Canadian patients with AF through an evidence-based, guideline-recommended approach. The appropriate use of oral anticoagulants (OACs) in this patient population and the potential factors guiding OAC choice were examined. Suboptimal dosing was seen. In patients on warfarin, 30.9% had not achieved a time in therapeutic range (TTR) in excess of 65% and, despite current Canadian guideline recommendations, were continued on warfarin rather than one of the novel OACs. In patients who received no antithrombotic therapy, 65.5% met criteria for treatment with an OAC. In addition, 62.8% of patients who were treated with acetylsalicylic acid monotherapy met guideline criteria for the use of an OAC. In those patients treated with an OAC, 24.8% were not on the recommended dose based on the product monograph or, if on warfarin, had a TTR <65%. Of the patients on novel OACs (NOACs), 7.4% of patients were underdosed, whereas overdosing was seen in 4.3%. Factors that may have contributed to dosing outside recommendations included underestimation of stroke risk, overestimation of bleed risk, compliance concerns, and lack of provincial reimbursement. In conclusion, significant correctable gaps remain in optimal treatment for stroke prevention in AF.