Challenges in Screening
There are many uncertainties regarding our current approaches to AF screening. Remaining questions include which subgroup of patients to screen, the best modality to use for screening and the subset of subclinical AF (SCAF) cases likely to benefit from oral anticoagulants (OAC). Two recently published large screening studies have produced somewhat contradictory results but provide important new insights about such questions.
In the ‘clinical outcomes in systematic screening for atrial fibrillation’ (STROKESTOP)38 trial, population aged 75 to 76 years without an earlier diagnosis of AF were screened using intermittent ECG recordings over 2 weeks yielded 3% detection of new AF cases with 90% patients eventually put on OAC.39 AF detection rate was only 0.5% from the first ECG used to screen.39 This highlights the low yield of using a single ECG for screening even in elderly population because of a paroxysmal nature of the arrhythmia. With further continuation of this study (median follow up 6.9 years), screening resulted in a slight benefit in outcomes (i.e., stroke, emboli and bleeding) compared to standard of care.38 These results suggest that screening is safe and beneficial in elderly population.38
In contrast, the ‘implantable loop recorder detection of atrial fibrillation to prevent stroke’ (LOOP)40 trial screened patients aged 70-90 years, with at least one additional stroke risk factor.40 In the intervention group, implantable loop recorders were used for prolonged monitoring to detect AF and started on OAC if AF lasted more than 6 minutes. Results showed 3 times increase in AF detection and OAC initiation however, it did not result in better outcomes (stroke and emboli prevention) compared to the control group. Different results from this study have been attributed to detection of very short episodes of AF with loop recorder which might not benefit from anticoagulation.40
The best approach to population wide screening also remains unresolved. Systematic screening using (pulse palpation alongside an ECG) has not been shown to be superior to opportunistic screening (pulse palpation followed by ECG if the former is positive) in various clinical trials.29,41,42