Subclinical atrial fibrillation: Who benefits from oral anticoagulation?

The value of anticoagulation to prevent embolic stroke in subclinical atrial fibrillation detected by implantable cardiac devices has not been established. Recently, two randomized controlled studies scrutinized whether such patients benefit from oral anticoagulation to prevent embolic strokes. These two studies were the NOAH-AFNET-6 (anticoagulation with edoxaban in patients with atrial highrate episodes) trial and the ARTESiA (Apixaban for stroke prevention in subclinical atrial fibrillation) study, but they came to different conclusions using different primary endpoints. While the investigators of NOAH-AFNET-6, based on a composite primary endpoint, concluded that no patient with device-detected AF should be anticoagulated, the ARTESiA investigators demonstrated the overall value of anticoagulation based on stroke/systemic embolism as the sole endpoint. However, the main question for subclinical atrial fibrillation patients is to which extent stroke and thromboembolism can be prevented by anticoagulation and weighing such a benefit to the risk of major bleeding. After initial confusion a meta-analysis of both studies focusing on the endpoints "ischemic stroke" and "all-cause stroke" showed an overall superiority of anticoagulation against placebo/aspirin therapy. The combined evidence demonstrated to the cardiovascular community the superiority of anticoagulation but confined to those with high risk, i.e., CHA₂DS₂-VASc score > 4, particularly in those with any type of vascular disease. The meta-analysis also showed that no anticoagulation is indicated in patients with CHA₂DS₂-VASc score < 4, and with shared decision-making recommended for those with CHA₂DS₂-VASc score of 4. It is reassuring that despite the first impression of diverging results in the two major trials, a meta-analysis helped to clarify the uniformity and consistency of the results across the studies, which will help physicians and nurses in their daily care of patients with implantable devices.