While continuous electrocardiographic monitoring using an implantable loop recorder (ILR) resulted in a three-fold increase in atrial fibrillation (AFib) detection and anticoagulation initiation, it did not significantly reduce the risk of stroke or systemic arterial embolism, according findings from the LOOP study published in The Lancet and presented at ESC Congress 2021.

Researchers randomized 6,004 Danish patients (47.3% women) in a 1:3 ratio to ILR monitoring (n=1,501) or standard care (n=4,503). All patients were over the age of 70 years (median age of 74) and had at least one risk factor for stroke, including hypertension, diabetes, heart failure or previous stroke. Individuals with a cardiac implantable electronic device, any history of AFib, or who were using oral anticoagulation were excluded. The primary outcome was time to the combined endpoint of stroke or systemic arterial embolism.

Overall results found the primary outcome occurred in 318 participants, including 67 (4.5%) in the IRL monitoring group and 251 (5.6%) in the standard care group (1.09 events per 100 person-years; 95% CI 0.96–1.24). Additionally, cardiovascular death occurred in 43 participants (2.9%) in the IRL monitoring group compared with 157 (3.5%) in the standard care group, and death from any cause occurred in 168 participants (11.2%) in the IRL monitoring group compared with 507 (11.3%) in the standard care group.

Study investigators, however, did observe that individuals in the IRL monitoring group were more likely to have AFib detected and to start oral anticoagulation compared with those receiving standard care. AFib was diagnosed in 31.8% of participants in the IRL monitoring group (n=477) and 12.2% of patients in the standard care group (n=550). Similarly, oral anticoagulation was initiated in 29.7% of participants in the IRL monitoring group (n=445) compared with 13.1% of participants in the standard care group (n=591).

"In a population of high-risk patients, AFib was detected and treated much more often in those undergoing ECG monitoring," said principal investigator Jesper Hastrup Svendsen, MD, from Copenhagen, Denmark. "We found a non-significant 20% reduction in risk of stroke which was not accompanied by a similar reduction in cardiovascular mortality. More studies are needed but our findings may suggest that not all AFib is worth screening for, and not all screen-detected AFib merits anticoagulation."

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: ESC Congress, ESC21, Arrhythmias, Cardiac, Atrial Fibrillation, Stroke, ACC International

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