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Published on: July 20, 2022
Effects of Atrial Fibrillation Screening According to Echocardiographic Measures of Cardiac Structure and Function: A
Flemming Javier Olsen1,2, Søren Zöga Diederichsen3, Peter Godsk Jørgensen1
1Department of Cardiology Copenhagen University Hospital-Herlev and Gentofte Hellerup Denmark.
Insights
Screening for subclinical atrial fibrillation (SCAF) with an implantable loop recorder (ILR) reduced stroke risk, particularly in individuals with reduced left atrial contraction strain. This finding highlights a potential personalized approach to stroke prevention in high-risk populations.
Area of Science:
- Cardiology
- Preventive Medicine
- Medical Devices
Background:
- Subclinical atrial fibrillation (SCAF) increases stroke risk, but its treatment with oral anticoagulation remains uncertain.
- Investigating SCAF screening's impact on stroke prevention is crucial for high-risk individuals.
Purpose of the Study:
- To evaluate the treatment effect of SCAF screening using an implantable loop recorder (ILR) on stroke prevention.
- To determine if cardiac structure and function measures modify the treatment effect of SCAF screening.
Main Methods:
- An echocardiographic substudy of the LOOP trial, randomizing older adults to ILR monitoring or usual care.
- Echocardiography assessed left ventricular size/function, left atrial volume/strain, and valvular pathology.
- Primary outcome: composite of stroke or systemic embolism.
Main Results:
- No conventional echocardiographic measures modified the treatment effect of ILR screening.
- Left atrial contraction strain significantly modified the treatment effect (Pinteraction=0.003).
- Reduced stroke risk was observed with ILR in participants with lower left atrial contraction strain (<16.5%).
Conclusions:
- Conventional echocardiographic measures did not alter the stroke prevention benefit of SCAF screening.
- Reduced left atrial contraction strain identified a subgroup benefiting significantly from ILR-guided SCAF screening and anticoagulation.
Background:
Subclinical atrial fibrillation (SCAF) poses an increased stroke risk, but whether oral anticoagulation for SCAF prevents stroke is unclear. We sought to investigate the treatment effect of SCAF screening according to measures of cardiac structure and function.
Methods:
This was an echocardiographic substudy of the LOOP (Atrial Fibrillation Detected by Continuous ECG Monitoring) study, which randomized older people at risk of stroke to usual care or an implantable loop recorder (ILR) with monitoring for SCAF and subsequent oral anticoagulation. A subset (24% of trial population) underwent echocardiography to measure left ventricular size and function, left atrial volume and strain, and valvular pathology. The primary outcome was a composite of stroke or systemic embolism.
Results:
The study included 1422 participants (ILR: n=1001; control: n=421; mean age: 74 years; men: 54%). During follow-up, 354 (25%) were diagnosed with AF (ILR versus control: 30% versus 12%). During a median follow-up of 5.5 years (interquartile range, 4.9-5.9 years), 55 (4%) developed the primary outcome (ILR versus control: 3.9% versus 3.8%). No conventional measure of cardiac structure and function modified the treatment effect from randomization. However, left atrial contraction strain significantly modified the treatment effect (Pinteraction=0.003), such that a lower risk of the primary outcome was noted from ILR with lower left atrial contraction strain values (hazard ratio [HR], 0.38 [95% CI, 0.16-0.87], for participants with contraction strain<16.5%).
Conclusion:
In a post hoc analysis of the LOOP study, conventional echocardiographic measures did not modify the effect of SCAF screening for stroke prevention. However, a significant stroke risk reduction was observed from ILR randomization among participants with reduced left atrial contraction strain.
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