One-Third of AF Patients Cease Anticoagulation Treatment

Many patients undergoing warfarin therapy for atrial fibrillation (AF) discontinue it within the first year, according to a new study.

Researchers at Henry Ford Hospital, the University of Michigan Health System, and other institutions conducted a study involving 734 patients with non-valvular AF who participated in the Michigan anticoagulation quality improvement initiative experience; all of the patients started warfarin treatment between 2011 and 2013. The researchers explored treatment discontinuation rates, including in patients scheduled for electrical cardioversion (ECV) or radiofrequency ablation (RFA) procedures.

The results showed that within one year, nearly 37% of the patients stopped taking the anticoagulation drug. Among those that underwent ECV or RFA the discontinuation rate was even higher, with more than 54% off warfarin after one year. A second predictive factor for drug cessation was low time in the therapeutic range during the first year of therapy. Race and ethnicity were not predictive factors for treatment discontinuation. The study was published on January 4, 2017, in JAMA Cardiology.

“It's unclear why these patients stopped taking warfarin; the drug's side effects, such as bruising, may play a role. People taking warfarin must also undergo routine blood tests; some people may stop taking the drug to avoid having to do this,” said senior author cardiologist James Froehlich, MD, of U-M. “We need to understand why they are stopping warfarin and figure out what other medications might be better adhered to in order to prevent strokes.”

Warfarin, commercualy known as Coumadin, decreases blood coagulation by inhibiting vitamin K epoxide reductase, an enzyme that recycles oxidized vitamin K to its reduced form after it has participated in the carboxylation of several blood coagulation proteins, mainly prothrombin and factor VII. It was initially introduced in 1948 as a pesticide against vermin, and is still popular for this purpose. In the early 1950's warfarin was found to be effective and relatively safe for preventing thrombosis and embolism in many disorders. It is the most widely prescribed oral anticoagulant drug in North America.