Systolic Blood Pressure and Effects of Screening for Atrial Fibrillation With Long-Term Continuous Monitoring (a LOOP Substudy)

Abstract

Background: Hypertension is a well-known risk factor for atrial fibrillation (AF) and stoke, but data on the interaction between systolic blood pressure (SBP) and effects of AF screening are lacking. Methods: The LOOP Study randomized AF-naïve individuals aged 70 to 90 years with additional stroke risk factors to either screening with implantable loop recorder (ILR) and anticoagulation initiation upon detection of AF episodes ≥6 minutes, or usual care. In total, 5997 participants with available baseline SBP measurements were included in this substudy. Outcomes were analyzed according to the time-to-first-event principle using cause-specific Cox models. Results: The hazard ratio of stroke or systemic arterial embolism for ILR versus control decreased with increasing SBP. ILR screening yielded a 44% risk reduction of stroke or systemic arterial embolism among participants with SBP ≥150 mm Hg (adjusted hazard ratio, 0.56 [0.37-0.83]). Within the ILR group, SBP≥150 mm Hg was associated with a higher incidence of AF episodes ≥24 hours than lower SBP (adjusted hazard ratio, 1.70 [1.08-2.69]) but not with the overall occurrence of AF (adjusted P>0.05). Conclusions: The impact of AF screening on thromboembolic events increased with increasing blood pressure. SBP≥150 mm Hg was associated with a >1.5-fold increased risk of AF episodes ≥24 hours, along with an almost 50% risk reduction of stroke or systemic arterial embolism by ILR screening compared to lower blood pressure. These findings should be considered hypothesis-generating and warrant further study. Registration: URL: https://www.clinicaltrials.gov; Unique Identifier: NCT02036450.