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. 2023 Apr 1;8(4):326-334.
doi: 10.1001/jamacardio.2022.5526.

Prevalence and Prognostic Significance of Bradyarrhythmias in Patients Screened for Atrial Fibrillation vs Usual Care: Post Hoc Analysis of the LOOP Randomized Clinical Trial

Søren Zöga Diederichsen  1 , Lucas Yixi Xing  1 , Diana My Frodi  1 , Emilie Katrine Kongebro  1 , Ketil Jørgen Haugan  2 , Claus Graff  3 , Søren Højberg  4 , Derk Krieger  5 , Axel Brandes  6   7   8 , Lars Køber  1   9 , Jesper Hastrup Svendsen  1   9
Affiliations

Prevalence and Prognostic Significance of Bradyarrhythmias in Patients Screened for Atrial Fibrillation vs Usual Care: Post Hoc Analysis of the LOOP Randomized Clinical Trial

Søren Zöga Diederichsen et al. JAMA Cardiol. .

Abstract

Importance: There is increasing interest in heart rhythm monitoring and technologies to detect subclinical atrial fibrillation (AF), which may lead to incidental diagnosis of bradyarrhythmias.

Objective: To assess bradyarrhythmia prevalence and prognostic significance in persons screened for AF using implantable loop recorder (ILR) compared with unscreened persons.

Design, setting, and participants: This was a post hoc analysis of the Implantable Loop Recorder Detection of Atrial Fibrillation to Prevent Stroke (LOOP) randomized clinical trial, which took place in 4 sites in Denmark. Participants were 70 years or older without known AF but diagnosed with at least 1 of the following: hypertension, diabetes, heart failure, or prior stroke. Participants were recruited by letter invitation between January 31, 2014, and May 17, 2016. The median (IQR) follow-up period was 65 (59-70) months. Analysis took place between February and June 2022.

Interventions: ILR screening for AF with treatment of any bradyarrhythmia left to the discretion of the treating physician (ILR group) vs usual care (control group).

Main outcomes and measures: Adjudicated bradyarrhythmia episodes, pacemaker implantation, syncope, and sudden cardiovascular death.

Results: A total of 6004 participants were randomized (mean [SD] age, 75 [4.1] years; 2837 [47.3%] female; 5444 [90.7%] with hypertension; 1224 [20.4%] with prior syncope), 4503 to control and 1501 to ILR. Bradyarrhythmia was diagnosed in 172 participants (3.8%) in the control group vs 312 participants (20.8%) in the ILR group (hazard ratio [HR], 6.21 [95% CI, 5.15-7.48]; P < .001), and these were asymptomatic in 41 participants (23.8%) vs 249 participants (79.8%), respectively. The most common bradyarrhythmia was sinus node dysfunction followed by high-grade atrioventricular block. Risk factors for bradyarrhythmia included higher age, male sex, and prior syncope. A pacemaker was implanted in 132 participants (2.9%) vs 67 (4.5%) (HR, 1.53 [95% CI, 1.14-2.06]; P < .001), syncope occurred in 120 (2.7%) vs 33 (2.2%) (HR, 0.83 [95% CI, 0.56-1.22]; P = .34), and sudden cardiovascular death occurred in 49 (1.1%) vs 18 (1.2%) (HR, 1.11 [95% CI, 0.64-1.90]; P = .71) in the control and ILR groups, respectively. Bradyarrhythmias were associated with subsequent syncope, cardiovascular death, and all-cause death, with no interaction between bradyarrhythmia and randomization group.

Conclusions and relevance: More than 1 in 5 persons older than 70 years with cardiovascular risk factors can be diagnosed with bradyarrhythmias when long-term continous monitoring for AF is applied. In this study, ILR screening led to a 6-fold increase in bradyarrhythmia diagnoses and a significant increase in pacemaker implantations compared with usual care but no change in the risk of syncope or sudden death.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Diederichsen reported grants from the Innovation Fund Denmark, the Research Foundation for the Capital Region of Denmark, the Danish Heart Foundation, Aalborg University Talent Management Programme, Arvid Nilssons Fond, Skibsreder Per Henriksen, R. og Hustrus Fond, and Medtronic; nonfinancial support from Medtronic devices (Reveal LINQ); and grants from European Union Horizon 2020 during the conduct of the study as well as personal fees from Vital Beats and Bristol-Myers Squibb/Pfizer outside the submitted work. Dr Krieger is a Medtronic focus group member. Dr Brandes reported personal fees/speaker honoraria from Bayer, Boehringer Ingelheim, Bristol Myers Squibb and grants from Theravance, Region of Southern Denmark, and Zealand Region outside the submitted work. Dr Køber reported personal fees and speaker honorarium from Bayer, Boehringer, AstraZeneca, Orion Pharma, Novo Nordisk, Novartis, and Sanofi outside the submitted work. Dr Svendsen reported grants from the Innovation Fund Denmark, the Research Foundation for the Capital Region of Denmark, the Danish Heart Foundation, Aalborg University Talent Management Programme, Arvid Nilssons Fond, Skibsreder Per Henriksen, R. og Hustrus Fond, and Medtronic; is a member of Medtronic advisory boards; and has received speaker honoraria and research grants from Medtronic during the conduct of the study. No other disclosures were reported

Figures

Figure 1.
Figure 1.. Bradyarrhythmia Detection
Time to first event curves (with inset) for diagnosis of bradyarrhythmia by randomization group are displayed. ILR indicates implantable loop recorder.
Figure 2.
Figure 2.. Bradyarrhythmia Subtypes, Symptoms, and Treatment
Bradyarrhythmia diagnoses with symptom status (A) and treatment (B) by randomization group are displayed, counting the highest-grade event in participants diagnosed with more than 1 subtype (21 participants [0.5%] in the control group and 11 [0.7%] in the ILR group). Medical treatment includes drug dose adjustments or discontinuation or treatment of concomitant conditions. AVB indicates atrioventricular block; ILR, implantable loop recorder; SND, sinus node dysfunction.
Figure 3.
Figure 3.. Pacemaker Implantation and Syncope
Time to first event curves (with insets) for pacemaker implantation (A) and syncope (B) by randomization group. ILR indicates implantable loop recorder.
Figure 4.
Figure 4.. Symptoms in Participants Receiving Pacemaker
Symptoms according to indication in participants receiving pacemaker by randomization group are displayed. AVB indicates atrioventricular block; ILR, implantable loop recorder; SND, sinus node dysfunction.
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