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Direct oral anticoagulant use lower with higher CHA2DS2-VASc score

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CHICAGO — New data presented at the American Heart Association Scientific Sessions suggest that in a real-world setting, use of direct oral anticoagulants was lower than warfarin in patients with a high CHA₂DS₂-VASc score.

Warfarin was once the drug of choice for decreasing stroke risk in patients with atrial fibrillation, but in the last decade, newer drugs such as direct oral anticoagulants, including apixaban (Eliquis, Bristol-Myers Squibb/Pfizer), rivaroxaban (Xarelto, Bayer/Janssen) and dabigatran (Pradaxa, Boehringer Ingelheim), have been introduced, according to study researcher Ajoe John Kattoor, MD, from the University of Arkansas for Medical Sciences.

“People have been starting to use these direct oral anticoagulants instead of warfarin in patients with AF. They started to come onto the market around 2010 and, with the approval of apixaban in 2013, use has been increasing,” he told Cardiology Today.

Previous studies, Kattoor noted, are mainly from 2014 to 2015, not long after direct oral anticoagulants became available.

“We couldn’t actually capture how those drugs are doing in the real world. In our study, we wanted to see how anticoagulants — whether direct oral anticoagulants or warfarin — are being prescribed in the community, especially in light of the availability of these newer drugs. We also wanted to look at potential differences in outcomes in clinical trials vs. real-world practice,” he said.

Prescribing trends

Kattoor and colleagues evaluated anticoagulant use in 2,362 patients with newly diagnosed AF who were prescribed an anticoagulant from 2014 to 2017 in the University of Arkansas database system. Of these patients, 1,306 were on warfarin and 1,056 were on a direct oral anticoagulant.

Results showed that warfarin, compared with direct oral anticoagulants, was more likely to be prescribed for black patients (P < .001) and patients with hypertension (P = .025), diabetes (P < .001), congestive HF (P < .001), liver disease (P = .013) or renal failure (P < .001), according to Kattoor.

One of the reasons that patients with renal failure were prescribed direct oral anticoagulants less often, he said, may be due to the fact that the warfarin may be safer in patients with lower creatinine clearance.

About half of patients had a CHA₂DS₂-VASc score of 3 or less while the other half had a higher score. One interesting finding, Kattoor noted, is that patients with higher CHA₂DS₂-VASc scores were also more likely to be prescribed warfarin than those with lower scores (P < .001).

“It is not entirely clear why patients with higher CHA₂DS₂-VASc scores were given warfarin initially. One reason may be that these patients are also at a higher risk for bleeding because they have comorbidities that may increase bleeding risk and warfarin has a readily available reversal agent to stop bleeding. Also, patients with higher scores are usually older and, again, naturally have a higher risk for bleeding,” Kattoor said.

He added that these patients also usually have renal failure, which precludes the use of direct oral anticoagulants if their creatinine clearance is below a certain range.

“We also think that in some cases, insurers will only approve the use of direct oral anticoagulants if warfarin has been tried and the patient does not do well,” Kattoor said.

Differences in outcomes

In multivariate analysis of clinical outcomes with warfarin vs. direct oral anticoagulants, the researchers found that the risk for stroke (9.7% vs. 7.4%; OR = 0.77; 95% CI, 0.57-1.01) and the risk for gastrointestinal bleed (6% vs. 4.6%; OR = 0.91; 95% CI, 0.62-1.35) were similar between groups.

They noted a trend toward a lower incidence of intracranial hemorrhage in the direct oral anticoagulant group (3.5% vs. 2%; OR = 0.6; 95% CI, 0.32-1.01), but the difference was not significant because the sample size was not large, according to Kattoor. Other studies, for instance, have shown that the risk for intracranial hemorrhage actually is lower with direct oral anticoagulants, he noted.

“Further larger studies assessing the safety of direct oral anticoagulants in patients with high CHA₂DS₂-VASc score are needed,” the researchers wrote. – by Melissa Foster

Reference:

Kattoor AJ, et al. Poster Mo1296. Presented at: American Heart Association Scientific Sessions; Nov. 10-12, 2018; Chicago.

Disclosure: The authors report no relevant financial disclosures.