IMPORTANCE Atrial fibrillation (AF) screening trials have failed to demonstrate a significant reduction in stroke risk. The impact on stroke severity and the importance of prior strokes are unknown.OBJECTIVE To assess stroke characteristics in patients undergoing implantable loop recorder (ILR) screening for AF vs usual care and assess the importance of prior stroke. DESIGN, SETTING, AND PARTICIPANTSThis was a post hoc analysis of the Atrial Fibrillation Detected by Continuous Electrocardiogram Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-Risk Individuals (LOOP) randomized clinical trial. Persons 70 years or older without known AF but diagnosed with 1 or more of the following, hypertension, diabetes, heart failure, or prior stroke, were screened for inclusion. Four sites in Denmark recruited participants by letter between January 31, 2014, and May 17, 2016. The median (IQR) follow-up period was 65 (59-70) months. Data were analyzed from April 1 to May 31, 2022. INTERVENTIONS ILR screening for AF and anticoagulation initiation if AF duration of 6 minutes or longer was detected (ILR group) vs usual care (control group). MAIN OUTCOMES AND MEASURES Adjudicated stroke, classified according to the modified Rankin Scale (mRS) using a score of 3 or more as a cutoff for severe (disabling or lethal) stroke, and according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification for ischemic strokes. RESULTS A total of 6205 individuals were screened for inclusion, and 6004 were randomized and included in the analysis; 4503 participants (75%; mean [SD] age, 74.7 [4.1] years; 2375 male [52.7%]) were assigned to the control group and 1501 participants (25%; mean [SD] age, 74.7 [4.1] years; 792 male [52.8%]) were assigned to the ILR group. A total of 794 of 4503 participants (17.6%) in the control group had a history of prior stroke compared with 262 of 1501 participants (17.5%) in the ILR group. During follow-up, AF was diagnosed in 1027 participants (control group, 550 [12%] vs ILR group, 477 [32%]), and anticoagulation was initiated in 89% of these (910). A total of 315 participants (5.2%) had a stroke (control group, 249 [5.5%] vs ILR group, 66 [4.4%]), and the median (IQR) mRS score was 2 (1-3) with no difference across the groups. A total of 272 participants (4.5%) had ischemic stroke (control group, 217 [4.8%] vs ILR group, 55 [3.7%]), and 123 (2.0%) had severe stroke (control group, 100 [2.2%] vs ILR group, 23 [1.5%]), and the hazard ratios comparing the control and ILR groups were 0.76 (95% CI, 0.57-1.03; P = .07) and 0.69 (95% CI, 0.44-1.09; P = .11), respectively. For participants without prior stroke, the hazard ratios were 0.68 (95% CI, 0.48-0.97; P = .04) and 0.54 (95% CI, 0.30-0.97; P = .04), respectively. CONCLUSIONS AND RELEVANCEThis post hoc analysis of the LOOP randomized clinical trial found that ILR screening for AF did not result in a significant decrease in ischemic or severe strokes compared with usual care. Exploratory subgroup analyses indicated a possible red...
Background: Research suggests N-terminal pro-B-type natriuretic peptide (NT-proBNP) to be a strong predictor of incident atrial fibrillation (AF) and stroke. However, its utility in AF screening remains unknown. This study aimed to investigate NT-proBNP as a potential marker for screening efficacy with respect to AF yield and stroke prevention. Methods: In the LOOP Study, 6004 AF-naïve individuals aged 70-90 years with additional stroke risk factors were randomized 1:3 to either continuous screening with implantable loop recorder (ILR) and anticoagulation initiation upon detection of AF episodes ≥6 minutes, or usual care (Control). This post-hoc analysis included the study participants with available NT-proBNP measurement at baseline. Results: A total of 5819 participants were included (mean age 74.7 years (standard deviation, 4.1), 47.5%females). The median NT-proBNP level was 15 pmol/L [interquartile range: 9-28], corresponding to 125 pg/mL [interquartile range: 76-233]. NT-proBNP above median was associated with an increased risk of AF diagnosis both in the ILR group (hazard ratio (HR) 1.84 [95% confidence interval (CI): 1.51-2.25]) and the Control group (HR 2.79 [95% CI: 2.30-3.40]). Participants with NT-proBNP above median were also at higher risk of clinical events compared with those having lower levels (HR 1.21 [95% CI: 0.96-1.54] for stroke or systemic embolism (SE), 1.60 [95% CI: 1.32-1.95] for stroke/SE/cardiovascular death, and 1.91 [95% CI: 1.61-2.26] for all-cause death). Compared with usual care, ILR screening was associated with significant reductions in stroke/SE and stroke/SE/cardiovascular death among participants with NT-proBNP above median (HR 0.60 [95% CI: 0.40-0.90] and 0.70 [95% CI: 0.53-0.94], respectively), but not among those with lower levels (p interaction =0.029 for stroke/SE and 0.045 for stroke/SE/cardiovascular death). No risk reduction in all-cause death was observed in either NT-proBNP subgroup for ILR versus Control (p interaction =0.68). Analyzing NT-proBNP as a continuous variable yielded similar findings. Conclusions: In an elderly population with additional stroke risk factors, ILR screening for AF was associated with a significant reduction in stroke risk among individuals with higher NT-proBNP levels, but not among those with lower levels. These findings should be considered hypothesis-generating and warrant further study before clinical implementation.
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