Anticoagulant therapy is recommended for several conditions, including atrial fibrillation (AF), venous thromboembolism, and after heart valve replacement. While warfarin is commonly used to prevent ischemic stroke in patients with AF, direct oral anticoagulants (DOACs) and nonpharmacologic therapies may be equally or more effective than traditional warfarin.^, In addition, warfarin has a narrow therapeutic index and can interact with many drugs and foods, which poses a challenge to using it.

A key strategy for reducing the risk of stroke or bleeding associated with warfarin is to maintain an optimal time in therapeutic range (TTR). TTR refers to the length of time a patient’s international normalized ratio (INR) remains between 2 and 3, which is a widely accepted measure of effective warfarin management. While there is no universally accepted safe range for TTR, patients whose INR is in the therapeutic range more than 70% of the time have better outcomes in terms of stroke prevention. In addition, those with INR control greater than 40% of the time have improved survival.

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