Heart Failure Events After Long-term Continuous Screening for Atrial Fibrillation: Results From the Randomized LOOP Study.

Background: Mounting evidence indicates that even device-detected subclinical atrial fibrillation is associated with a higher risk of heart failure (HF). However, the potential impact of atrial fibrillation screening on HF remains unknown.
Methods: The LOOP Study (Atrial Fibrillation detected by Continuous ECG Monitoring using Implantable Loop Recorder to prevent Stroke in High-risk Individuals) evaluated the effects of atrial fibrillation screening on stroke prevention using an implantable loop recorder (ILR) versus usual care in older individuals with additional stroke risk factors. In this secondary analysis, we explored the following HF end points: (1) HF event or cardiovascular death; (2) HF event; (3) event with HF with reduced ejection fraction (HFrEF); and (4) HFrEF event or cardiovascular death. Outcomes were assessed in a Cox model both as time-to-first events and as total (first and recurrent) events analyzed using the Andersen-and-Gill method.
Results: Of 6004 participants (mean age 74.7 and 52.7% men), 1501 were randomized to ILR screening and 4503 to the control group. In total, 77 (5.1%) in the ILR group versus 295 (6.6%) in the control group experienced the primary outcome of an HF event or cardiovascular death. Compared with usual care, ILR screening was associated with a nonsignificant reduction in the primary outcome for the time-to-first event analysis (hazard ratio, 0.78 [95% CI, 0.61-1.01]) and the total event analysis (hazard ratio, 0.77 [95% CI, 0.59-1.01]). Similar results were obtained for the HF event. A significant risk reduction in total events was observed in the ILR group for the composite of HFrEF event or cardiovascular death and for HFrEF event (hazard ratio, 0.74 [95% CI, 0.56-0.98] and 0.65 [95% CI, 0.44-0.97], respectively).
Conclusions: In an older population with additional stroke risk factors, ILR screening for atrial fibrillation tended to be associated with a lower rate of total HF events and cardiovascular death, particularly those related to HFrEF. These findings should be considered hypothesis-generating and warrant further investigation.
Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02036450.
Competing Interests: Dr Krieger reports to be a Medtronic Focus Group member. Dr Healey reports research grants and speaking honoraria from Medtronic, Boston Scientific, Bristol-Myers Squibb/Pfizer, and Servier, and consulting fees from Boston Scientific and Bayer, not related to this work. Dr Branges reports research grants from The Region of Zealand, The Canadian Institutes of Health Research, The Danish Heart Foundation, and Theravance, and speaker honoraria from Boehringer Ingelheim and Bristol-Myers Squibb, not related to this work. Dr Køber reports speaker honoraria from Novo Nordisk, AstraZeneca, Novartis, and Boehringer, not related to this work. Dr Svendsen reports to be a member of VitalBeats and Medtronic advisory boards and to have received speaker honoraria and research grants from Medtronic in relation to this work and outside this work. Dr Diederichsen reports to be a part-time employee of VitalBeats and an advisor at Bristol-Myers Squibb/Pfizer, not related to this work. The other authors report no conflicts.