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

Screening for atrial fibrillation: the role of CHA2DS2-VASc and atrial fibrillation burden

Individuals with subclinical atrial fibrillation (AF) face an increased risk of thromboembolic events, which may potentially be mitigated through AF screening and subsequent anticoagulation. However, data from randomized clinical trials (RCTs) indicate a lower stroke risk in subclinical AF compared with the clinical phenotype. This-along with the inherent bleeding risk related to anticoagulation-seems to render the net clinical benefit of AF screening less evident. Further, current guidelines recommend consideration of CHA2DS2-VASc score and AF episode duration to guide screening and treatment. These recommendations, in general, lack support and seem questionable in view of the limited RCT data. More evidence is warranted to provide insights into the potential benefits of screening and treatment of screen-detected AF in specific population subgroups and AF phenotypes.

Effects of Atrial Fibrillation Screening According to N-Terminal Pro-B-Type Natriuretic Peptide: A Secondary Analysis of the Randomized LOOP Study

BACKGROUND

Research suggests NT-proBNP (N-terminal pro-B-type natriuretic peptide) to be a strong predictor of incident atrial fibrillation (AF) and stroke. However, its utility in AF screening remains unknown. The aim of this study was to investigate NT-proBNP as a potential marker for screening efficacy with respect to AF yield and stroke prevention.

METHODS

In the LOOP Study (Atrial Fibrillation Detected by Continuous ECG Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-Risk Individuals), 6004 AF-naïve individuals at least 70 years old and with additional stroke risk factors were randomized 1:3 to either screening with an implantable loop recorder (ILR) and initiation of anticoagulation upon detection of AF episodes lasting ≥6 minutes or usual care (control). This post hoc analysis included study participants with available NT-proBNP measurement at baseline.

RESULTS

A total of 5819 participants (96.9% of the trial population) were included. The mean age was 74.7 years (SD, 4.1 years) and 47.5% were female. The median NT-proBNP level was 15 pmol/L (interquartile range, 9-28 pmol/L) corresponding to 125 pg/mL (interquartile range, 76-233 pg/mL). NT-proBNP above median was associated with an increased risk of AF diagnosis both in the ILR group (hazard ratio, 1.84 [95% CI, 1.51-2.25]) and the control group (hazard ratio, 2.79 [95% CI, 2.30-3.40]). Participants with NT-proBNP above the median were also at higher risk of clinical events compared with those having lower levels (hazard ratio, 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 (hazard ratio, 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 (Pinteraction=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 (Pinteraction=0.68). Analyzing NT-proBNP as a continuous variable yielded similar findings.

CONCLUSIONS

In an older 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.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT02036450.

Atrial Fibrillation Detection and Management in Hypertension

Hypertension is prevalent in >70% of atrial fibrillation patients. In turn, hypertensive patients have up to 73% greater likelihood of atrial fibrillation. Current guidelines recommend that a systematic atrial fibrillation screening may be justified in all patients aged ≥65 years with at least 1 cardiovascular disease, including hypertension. Although most blood pressure monitors include algorithms to detect atrial fibrillation with a high sensitivity of 96 [92-98]% and specificity of 94 [91-96]%, an electrocardiography confirmation is necessary to establish a diagnosis of atrial fibrillation. Early detection and diagnosis of atrial fibrillation is important to allow initiation of atrial fibrillation management. In the Early Treatment of Atrial Fibrillation for Stroke Prevention Trial (EAST-AFNET 4), hypertension was present in 88% of participants, and early rhythm control therapy lowered the risk of adverse cardiovascular outcomes in patients with early atrial fibrillation aged >75 or with CHA₂DS₂-VASc score ≥2 (Congestive heart failure, Hypertension, Age ≥75 (doubled), Diabetes, Stroke (doubled), Vascular disease, Age 65-74, Sex category [female]) and cardiovascular condition. Strategies for early atrial fibrillation detection should always be linked to a comprehensive atrial fibrillation work-up infrastructure organized within an integrated ABC pathway (Anticoagulation/Avoid stroke; Better symptom control; Cardiovascular and Comorbidity optimization). For secondary prophylaxis, blood pressure control should be embedded in a combined risk factor management program. In hypertensive patients where no atrial fibrillation is detected, intensive blood pressure lowering therapy for primary prophylaxis should be initiated to reduce the risk of developing atrial fibrillation and other cardiovascular complications in the future. The aim of the article is to review the current literature on atrial fibrillation detection and management in hypertensive patients.

Screening for atrial fibrillation to prevent stroke in elderly individuals with or without preexisting cardiovascular disease: A post hoc analysis of the randomized LOOP Study

BACKGROUND

An evidence-based approach for risk stratification of subclinical atrial fibrillation (AF) and hereby AF screening is lacking. This study aimed to investigate whether established cardiovascular diseases (CVD) could help to identify the population more likely to benefit from AF screening.

METHODS

The LOOP Study randomized AF-naïve individuals aged ≥70 years and with additional stroke risk factors to either screening with implantable loop recorder (ILR) and subsequent anticoagulation upon detection of new-onset AF episodes ≥6 min, or usual care. In this sub-study, all participants were divided into two risk groups according to the presence/absence of CVD (defined as ischemic heart disease, heart failure, previous stroke, valvular heart disease, or peripheral artery disease).

RESULTS

A total of 1997 (33.3%) had CVD at baseline and experienced higher incidences of stroke or systemic arterial embolism (SAE), ischemic stroke, stroke/SAE/cardiovascular death, and all-cause death (adjusted HR 1.34 [1.06-1.69], 1.31 [1.02-1.69], 1.49 [1.23-1.79], and 1.59 [1.36-1.85], respectively) than those without. For ILR screening versus usual care, there was no decrease in stroke/SAE, ischemic stroke, or stroke/SAE/cardiovascular death among participants with CVD (adjusted p-values >0.05), whereas significant reductions in these outcomes were obtained by screening among those without CVD (adjusted HR 0.64 [0.44-0.93], 0.54 [0.35-0.82], 0.64 [0.46-0.87], respectively); adjusted p-values for interaction ≤0.05.

CONCLUSIONS

In an elderly, at-risk population, ILR screening did not prevent stroke significantly in individuals with CVD, whereas screening was associated with approximately 40% stroke risk reduction among those without CVD. However, these findings should be considered as hypothesis-generating and warrant further study.

Severity and Etiology of Incident Stroke in Patients Screened for Atrial Fibrillation vs Usual Care and the Impact of Prior Stroke: A Post Hoc Analysis of the LOOP Randomized Clinical Trial

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 Participants

This 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 Relevance

This 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 reduction of these outcomes among participants without prior stroke.

Trial Registration

ClinicalTrials.gov Identifier: NCT02036450.