(Too) Many Patients With AF Stop Warfarin Within a Year

Larry Hand

January 04, 2017

ANN ARBOR, MI — A high rate of patients with atrial fibrillation discontinue warfarin therapy within a year, especially patients who have undergone electrical cardioversion (ECV) or radiofrequency ablation (RFA), according to new research published online January 4, 2017 in JAMA Cardiology[1].

"This study confirms what we've known, which is that patients who start warfarin to prevent stroke in atrial fibrillation are frequently discontinuing therapy. Over the course of a year we're seeing up to a third of these patients discontinuing," Dr Geoffrey D Barnes (University of Michigan Medical Health System) told heartwire from Medscape.

"What I think is really new about this study is we see a big difference based on whether or not patients have had a cardioversion or an ablation procedure," he continued. "The patients who are undergoing one of those two procedures have a much higher rate at which they're discontinuing therapy within the first year."

Barnes and colleagues analyzed data on a randomly selected sample of 734 patients initiating warfarin therapy for nonvalvular AF between August 2011 and December 2013 at six centers as part of the Michigan Anticoagulation Quality Improvement Initiative. Follow-up continued through June 2015.

They found that 270 (36.7%) patients discontinued warfarin therapy within a year. That included 118 of 218 (54.1%) patients who underwent ECV or RFA and 152 of 516 (29.5%) patients who did not (P<0.001).

In addition to having undergone ECV or RFA, predictors of discontinuing warfarin therapy included lower CHA2DS2-VASc score (mean score 3.0 vs 3.7; P<0.001) and lower time in the therapeutic range in the first year (mean 51.2% vs 65.5%; P<0.001).

Although guidelines recommend 4 to 8 weeks of anticoagulation therapy after an ECV, little research is available on the continuation of therapy, the researchers wrote.

"That raises concern because we don't know if either of those therapies is really effective at keeping people in a sinus rhythm and therefore removing their risk of stroke," Barnes told heartwire. "There's been some debate as to just how successful these are and whether the stroke risk persists after a cardioversion or after an ablation."

"In our study we just looked at patients on warfarin," he added. "What we also don't know is whether the same patterns exist in patients who are taking the newer direct oral anticoagulants or whether there might be a different pattern of treatment in those cases."

Barnes concluded, "Atrial fibrillation is a chronic disease, so preventing stroke requires chronic therapy, and we should really consider carefully whether or not stopping anticoagulation is appropriate even after a patient undergoes a cardioversion or an ablation procedure."

The Michigan Anticoagulation Quality Improvement Initiative is funded by Blue Cross Blue Shield of Michigan. Barnes reported receiving research support from Bristol-Myers Squibb and Pfizer and consulting fees from Portola. Disclosures for the coauthors are listed in the paper.

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