One in four with AF stops warfarin within first year
MedWire News: Around one in four patients newly starting warfarin therapy for atrial fibrillation (AF) stops taking it in the first year, despite a low overall rate of hospitalizations for hemorrhage, a large community-based study in the USA shows.
Reporting their findings in the journal Circulation: Cardiovascular Quality and Outcomes, the authors suggest that difficulties in controlling therapy and concerns about bleeding risk are the likely causes for discontinuing therapy.
Margaret Fang (University of California, San Francisco) and colleagues followed patients newly diagnosed with nonvalvular AF who were enrolled in the Anticoagulation and Risk Factors in AF (ATRIA) study, to determine reasons for the high rates of warfarin nonuse that have been observed in multiple cross-sectional studies of AF patients. Whether such nonuse reflects a lack of warfarin initiation at the time of AF diagnosis or patients discontinuing therapy remains unclear, they note.
The researchers identified 1488 patients, aged an average of 71.8 years, who were newly started on warfarin and were followed-up for a median of 4.6 years.
They found that 26.3% of these patients discontinued warfarin within the first year of starting therapy. Hospitalization for hemorrhage meanwhile was relatively uncommon, at a rate of 2.3%, but led to discontinuation of warfarin therapy in 65% of cases.
Multivariable analysis excluding patients who were hospitalized for hemorrhage indicated that the lower patients' chance of benefiting from warfarin was, the less likely they were to remain on therapy.
Specifically, patients were at increased risk for prolonged (at least 180 consecutive days) warfarin discontinuation if they were younger (hazard ratio [HR]=1.33 for age <65 years vs ≥85 years), had worse anticoagulation control (HR=1.46 for every 10% decrease in therapeutic international normalized ratio range), and had a lower stroke risk (HR=2.54 for CHADS2 stroke risk index of 0 vs 4-6).
"Stroke prevention efforts should address the appropriate persistence of warfarin therapy in patients with AF," the authors conclude.
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