Implantable Loop Recorder Increases AFib Detection in Patients At Risk of Stroke


Data show oral anticoagulation following atrial fibrillation screening was initiated in 1036 participants, with 445 (29.7%) in the ILR group versus 591 (13.1%) in the control group.

Jesper H. Svendsen, MD

Jesper H. Svendsen, MD

Due to lack of evidence on the health benefit of screening for atrial fibrillation, a recent study examined if screening and the use of anticoagulants can prevent stroke in individuals at high-risk of atrial fibrillation.

A team of investigators, led by Jesper H. Svendsen, MD, Department of Cardiology, Copenhagen University Hospital, observed implantable loop recorder (ILR) screening showed a 3-time increase in atrial fibrillation detection and anticoagulation initiation, but data show no significant reduction in the risk for stroke or arterial embolism.

The study was presented online at the European Society of Cardiology (ESC) 2021 Congress.

The Methods

Investigators performed The Atrial Fibrillation Detected by Continuous ECG Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-RIsk Individuals (The LOOP study), as a randomized controlled trial at 4 centers in Denmark.

Eligibility for the trial included individuals aged 70-90 years with at least 1 of 4 conditions, including hypertension, diabetes, previous stroke, or heart failure. These patients did not have atrial fibrillation or a history of atrial fibrillation, or a pacemaker.

During an initial screening visit, investigators confirmed eligibility requirements and took a standard 12-lead ECG.

Patients were randomized at a 1:3 ratio to ILR monitoring or to the usual care group as control through an online system with a block size of 4 - 8 participants stratified by center.

At baseline, investigators assessed medical history, drug prescriptions, vital signs, and blood samples. All participants in the ILR group were followed up with continuous ECG monitoring. If investigators detected atrial fibrillation of ≥6 minutes in the ILR group, the participant was recommended initiation of oral anticoagulants.

The team noted the primary outcome was the combined endpoint of stroke or systemic arterial embolism. Secondary outcomes included the combined endpoint of ischemic stroke, transient ischemic attack, or systemic arterial embolism, the combined endpoint of stroke, systemic arterial embolism, or cardiovascular death, all-cause death, and cardiovascular death.

The Results

A total of 6205 individuals were screened for inclusion between January 2014 - May 2016, with 6004 of these patients included in the study.

Following inclusion, patients were randomized with 1501 patients (25.0%) assigned to the ILR group and 4503 (75.0%) to control. Data show the mean age of the participants was 74.7 years and 2837 patients (47.3%) were women. In addition, 5444 (90.7%) had hypertension.

A mean follow-up of 64.5 months (IQR 59.3 - 69.8) took place, with atrial fibrillation diagnosed in 477 participants (31.8%) of 1501 participants in the ILR group, compared to 550 participants (12.2%) of 4503 participants in the control group (hazard ratio HR 3.17; 95% CI, 2.81 - 3.59; P <.0001).

In addition, investigators initiated oral anticoagulation in 1036 participants, with 445 participants in the ILR group (29.7%) compared to 591 patients (13.1%) in the control group (HR 2.72; 95% CI, 2.41 - 3.08, P <.0001).

The team noted the primary outcome of stroke or systemic arterial embolism occurred in 318 participants, including 315 participants having stroke and 3 participants having systemic arterial embolism.

Data show it occurred in 67 patients (4.5%) in the ILR group versus 251 participants (5.6%) in the control group, showing 1.09 events per 100 person-years (95% CI, 0.96 - 1.24). They found no significant difference between the group (HR 0.80; 95% CI, 0.61 - 1.05, P = .11).

Further, the team found major bleeding occurred in 221 participants, including 65 (4.3%) in the ILR group compared to 156 (3.5%) in the control group (HR 1.26; 95% CI, 0.95 - 1.69, P = .11).


The team noted that despite limited evidence of hard outcomes, screening for atrial fibrillation is increasing in application, with new technologies showing feasibility as screening tools, including wearables.

“On the one hand, the findings of the current trial indicate that systematic, intensive screening might not decrease stroke rates, even in individuals at high risk, and not all screen-detected atrial fibrillation should merit anticoagulation,” investigators wrote. “On the other hand, the time-to-event curves for stroke overlapped during the first 2–3 years after which they appeared to diverge due to increasing event rates in the control group.”

The study, “Implantable loop recorder detection of atrial fibrillation to prevent stroke (The LOOP Study): a randomised controlled trial,” was published online in The Lancet.

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