Patients with atrial fibrillation (AFib) who switch from warfarin to direct oral anticoagulants (DOAC) are often able to successfully make that transition, according to new data published in the Journal of the American Heart Association.

Much of the study's analysis focused on time in therapeutic range (TTR), a common quality measure for anticoagulation therapy with warfarin.

"TTR can affect the effectiveness and safety of warfarin, and previous studies have suggested that a TTR greater than 0.58 is needed for patients with AFib to benefit from warfarin therapy compared to aspirin alone," wrote lead author Krishna N. Pundi, MD, with the department of medicine at Stanford University School of Medicine, and colleagues. "In the United States and much of the world, excluding integrated health care systems in Europe, system‐wide TTRs are observed to be low, including in clinical trial settings. With DOACs demonstrated to be non‐inferior or superior to warfarin in preventing strokes with lower risk of major bleeding, the most recent combined American College of Cardiology/American Heart Association/Heart Rhythm Society and European Society of Cardiology guidelines recommend anticoagulating with a DOAC preferentially over warfarin in eligible patients, and use of a DOAC in patients who are unable to maintain a therapeutic international normalized ratio (INR) level."

In the study of 128,605 patients, 32,377 patients were moved from warfarin to a DOAC (switchers). The remaining patients, meanwhile, stayed on warfarin (non-switchers).

Data came from the Veterans Health Administration, and all patients were treated from 2009 to 2018. Ninety-eight percent of patients were men, and the median age was 72 years old.

For the study's primary outcome analysis, the necessary INR data needed to analyze the patient's TTR was available in 8,016 switchers.

Overall, patients with TTR less than 0.5 were more likely to be switched to DOAC. This was also true for patients with a TTR less than 0.6 or TTR less than 0.7.

The study's authors noted that proportion of days covered (PDC) greater than 0.8 was associated with was lower rates of stroke and mortality without an increase in bleeding events. That threshold was met by 76% of switchers after 365 days. Even patients with a TTR less than 0.5, the authors found, were able to hit that threshold 70% of the time.