ARTESIA
For the ARTESIA study, 4012 patients with device-detected AFib and other clinical risk factors for stroke were randomly assigned to treatment with apixaban (5 mg twice daily) or aspirin (81 mg daily).
After a mean follow-up of 3.5 years, the primary endpoint – stroke or systemic embolism – occurred in 55 patients in the apixaban group (0.78% per patient-year), compared with 86 patients in the aspirin group (1.24% per patient-year), giving a hazard ratio of 0.63 (95% confidence interval, 0.45-0.88; P = .007).
“The risk of stroke or systemic embolism was lower by 37% with apixaban than with aspirin, and the risk of disabling or fatal stroke was lower by 49%,” Dr. Healey reported.
In the “on-treatment” population, the rate of major bleeding was 1.71% per patient-year in the apixaban group and 0.94% per patient-year in the aspirin group (HR, 1.80; 95% CI, 1.26-2.57; P = .001).
Fatal bleeding occurred in five patients in the apixaban group and eight patients in the aspirin group. Symptomatic intracranial hemorrhage occurred in 12 patients with apixaban and 15 patients with aspirin.
One of the main findings of the trial is the lower-than-expected risk of ischemic stroke in this population – about 1% per year in the aspirin group, which was reduced to 0.64% per year in the apixaban group.
The authors noted that “simply counting strokes as compared with bleeding events might suggest a neutral overall effect. With apixaban as compared with aspirin, 31 fewer cases of stroke or systemic embolism were seen in the intention-to-treat analysis, as compared with 39 more major bleeding events in the on-treatment analysis.”
However, they pointed out that strokes involve permanent loss of brain tissue, whereas major bleeding is usually reversible, with most patients having complete recovery, which was the case in this study.
“Thus, on the basis of the considerably greater severity of the stroke events prevented than the bleeding events caused, we believe that these findings favor consideration of the use of oral anticoagulation for patients with risk factors for stroke in whom subclinical atrial fibrillation develops,” they concluded.
First well-powered trial addressing this question
Discussing the ARTESIA trial at an AHA press conference, Christine Albert, MD, Cedars-Sinai Medical Center, Los Angeles, said: “I want to emphasize how important this trial is.”
She explained that current guidelines do not recommend any treatment for patients with device-detected AFib that is not shown on ECG, even though it is known this confers some excess risk of stroke.
“ARTESIA is the first well-powered, long-term trial looking at this question,” she said. “It found a clear reduction in the risk of stroke/systemic embolism with apixaban vs aspirin, but there was also a significant amount of bleeding – about an 80% increase. The question is whether the benefit on stroke is worth it given the bleeding risk.”
Dr. Albert highlighted the low absolute risk of stroke in this study population of around 1.2%, pointing out that even with the 37% relative reduction with anticoagulation, stroke is only reduced in absolute terms by 0.4%.
“We are going to have to take this back to committees and guidelines and look at the balance between the benefit on stroke and the increase in bleeding,” she concluded.
Noting that observational studies have shown that the duration of AFib impacts the risk of stroke, Dr. Albert suggested that patients with longer-duration AFib may benefit from anticoagulation to a greater extent; and given that the bleeding seen in ARTESIA was mainly GI bleeding, it might be possible to screen out patients at high risk of GI bleeding.
She also pointed out that a lot of patients discontinued anticoagulation treatment in both ARTESIA and NOAH-AFNET 6, showing that this is not an easy strategy for elderly patients.
In an editorial accompanying publication of the ARTESIA trial, Emma Svennberg, MD, Karolinska Institute, Stockholm, also concluded that, “going forward, we must balance the increased bleeding risks with the risk for disabling strokes,” and that “future substudies and meta-analyses may provide further insights regarding treatment benefits in specific subgroups.”