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Predictors for discontinuation of warfarin therapy identified
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The occurrence of electrical cardioversion or radiofrequency ablation, increased risk factors and low time spent in therapeutic range were all predictors of discontinuation of warfarin therapy for patients with atrial fibrillation at risk for stroke, according to new data.
Within the Michigan Anticoagulation Quality Improvement Initiative, Geoffrey D. Barnes, MD, MSc, of the Frankel Cardiovascular Center at the University of Michigan Health System, Ann Arbor, and colleagues explored predictors for the discontinuation of warfarin therapy in randomly sampled unselected patients with AF across six sites in Michigan.
The researchers collected data on therapeutic time in range and calculated a CHA2DS2-VASc score for each patient.
Participants began warfarin therapy from August 2011 to December 2013 and were followed up through June 2015.
Of the patients initiating warfarin therapy in the study period (n = 734), 36.8% discontinued therapy within the first year (n = 270). Of those who had undergone electrical cardioversion (ECV) or radiofrequency ablation (RFA), 54.1% had discontinued warfarin therapy (n = 118) compared to 29.5% of participants without ECV or RFA (n = 152; P < .001).
Patients who discontinued warfarin therapy within the first year of treatment were more likely to have undergone ECV or RFA (43.7%), have a lower CHA2DS2-VASc score (mean, 3) and have less time in therapeutic range during the first year (mean, 51.2%) vs. those who continued warfarin therapy (21.6%, 3.7 and 65.5%, respectively) (all P < .001), the researchers wrote.
Undergoing ECV or RFA (HR = 1.86; 95% CI, 1.32-2.61), a participant’s CHA2DS2-VASc score group (HR for score of 0 vs. score of 2 to 9 = 3.89; 95% CI, 2.05-7.36) and low time in range (HR = 1.45, 95% CI, 1.33-1.58) were all predictors of discontinuation of warfarin therapy; however, race or ethnicity was not.
“The association of ECV or RFA with discontinuation of warfarin therapy is an important consideration given the lack of consensus around long-term stroke risk following ECV or RFA,” the researchers wrote. “Guidelines suggest at least 4 to 8 weeks of anticoagulation following ECV but do not specify if stopping anticoagulation is appropriate after that initial period. Conclusive data are needed regarding the efficacy of extended prophylaxis with warfarin beyond 4 to 8 weeks after a successful ECV or RFA.” – by Cassie Homer
Disclosure: Barnes reports receiving research support from Bristol-Myers Squibb/Pfizer and consultant fees from Aralez and Portola. Please see the full study for the other researchers’ relevant financial disclosures.
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