Women With A-fib Less Likely to Get Oral Anticoagulants Regardless of Risk

Women with nonvalvular atrial fibrillation (A-fib) were less likely to receive oral anticoagulation (OAC) compared with men despite the recent introduction of non-vitamin K oral anticoagulants (NOAC) and the incorporation of female sex as an independent risk factor for thromboembolic events into the CHA2DS2-VASc score, a new analysis suggests.

“This shows us that clinicians need to be taking the time to evaluate each patient’s thromboembolic and bleeding risk,” Lauren E. Thompson, MD, MSCS (University of Colorado School of Medicine, Aurora, CO), told TCTMD. “We also need to go beyond that to identify the barriers that limit women from being able to get on medication—whether it is at a provider level or a patient preference.”

According to Thompson, historically there has been a perception that women have a higher risk of bleeding on warfarin and, because of more intensive monitoring requirements, that women were less likely to be agreeable to taking warfarin, suggesting that warfarin may have been the component driving gender differences in OAC use.

With this study, Thompson and colleagues wanted to evaluate if the advent of NOACs and the incorporation of female sex in to CHA2DS2-VASc score lessened sex differences seen in the use of OACs. To do so, Thompson and colleagues used data from the PINNACLE National Cardiovascular Data Registry from 2008 to 2014 to compare the association of sex with OAC use overall and by CHA2DS2-VASc score.

The results were published online in the Journal of the American Heart Association.

Of the 691,906 patients with A-fib included, 48.5% were women. Overall, roughly 60% of patients in the study with an indication for an OAC were actually prescribed the treatment. Women were significantly less likely to use an OAC overall compared with men (56.7% vs. 61.3%; P < 0.001). When stratified by CHA2DS2-VASc score, women had significantly lower rates of OAC use compared with men at every level (P <0.001 for all).

During the study period, rates of OAC use increased for both men and women, but use remained higher in men over all. Following 2010, when the first NOACs received regulatory approval, use of NOACs in women increased at a slightly higher rate compared with men (56.2% per year vs. 53.6% per year). But despite these increases, women remained significantly less likely to receive any OAC compared with men at any study time point (P < 0.001).

Appropriate OAC for All

Thompson and colleagues point out in the paper their results do not necessarily reflect those from other registries, a fact confirmed by the primary investigator of ORBIT-AF, who commented on Thompson et al’s paper for TCTMD. “In the ORBIT-AF registry we did not find a significant difference in women and men receiving oral anticoagulation,” Jonathan P. Piccini, MD (Duke University Medical Center, Durham, NC) told TCTMD.

However, Thompson and colleagues noted that registries like ORBIT-AF prospectively enrolled patients based on inclusion and exclusion criteria, which could introduce selection bias.

“Our study looked at outpatient clinical practices in the U.S., not patients enrolled in clinical trial sites,” Thompson said. “This is the first real world trial looking at what is being done and it suggests that even though we are making changes to try to increase awareness of women’s increased thrombotic risk, there is still room for improvement.”

According to Piccini, Thompson et al’s paper should highlight not who is less likely to receive OAC therapy, but rather underscore the fact that not all patients who should be receiving OAC are getting them, keeping in mind that women appear to be at elevated risk.

“The main take away from this analysis and similar analyses are that, based upon what we know, women probably are at increased risk for stroke and systemic embolism with AF,” Piccini said. “Like any patient who has risk factors, we need to make sure they are receiving treatment if appropriate, meaning they don’t have an absolute contraindication to receiving these treatments.”