LOOP
(2021)Objective
Assess whether screening for atrial fibrillation using an implantable loop recorder (ILR) followed by anticoagulation in detected cases reduces the risk of stroke or systemic embolism in high-risk older adults.
Study Summary
• In high-risk individuals without known atrial fibrillation, ILR screening tripled the detection rate of atrial fibrillation and increased oral anticoagulation initiation. However, this did not result in a statistically significant reduction in stroke or systemic embolism compared to usual care. These findings suggest that widespread screening and treatment of short-duration subclinical atrial fibrillation may not meaningfully lower stroke risk.
Intervention
Randomized controlled trial in Denmark across four centers. N=6004 adults aged 70–90 years with ≥1 stroke risk factor (hypertension, diabetes, heart failure, or prior stroke) randomized in a 1:3 ratio to: • ILR monitoring (n=1501): anticoagulation recommended for AF episodes ≥6 min • Usual care (n=4503) Median follow-up: 64.5 months.
Study Design
Arms: Array
Outcome
• Atrial fibrillation diagnosis: 31.8% (ILR) vs. 12.2% (control); HR 3.17; p<0.0001
• Anticoagulation initiation: 29.7% (ILR) vs. 13.1% (control); HR 2.72; p<0.0001
• Stroke or systemic embolism: 4.5% (ILR) vs. 5.6% (control); HR 0.80; 95% CI 0.61–1.05; p=0.11
• Major bleeding: 4.3% (ILR) vs. 3.5% (control); HR 1.26; p=0.11
• No participants were lost to follow-up; overall event rates were lower than expected
• Anticoagulation initiation: 29.7% (ILR) vs. 13.1% (control); HR 2.72; p<0.0001
• Stroke or systemic embolism: 4.5% (ILR) vs. 5.6% (control); HR 0.80; 95% CI 0.61–1.05; p=0.11
• Major bleeding: 4.3% (ILR) vs. 3.5% (control); HR 1.26; p=0.11
• No participants were lost to follow-up; overall event rates were lower than expected