Accidental diagnosis of bradyarrhythmia in patients monitored for atrial fibrillation
Authors: Diederichsen SZ , Xing LY , Frodi DM , Kongebro EK , Haugan KJ , Graff C , Hoejberg S , Krieger D , Brandes A , Koeber L , Svendsen JH 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): The study was supported by The Innovation Fund Denmark [12-135225], The Research Foundation for the Capital Region of Denmark [no grant number], The Danish Heart Foundation [11-04-R83-A3363-22625], Aalborg University Talent Management Programme [no grant number], Arvid Nilssons Fond [no grant number], Skibsreder Per Henriksen, R. og Hustrus Fond [no grant number], Medtronic [no grant number], and the AFFECT-EU consortium which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 847770.

Background
The interest in heart rhythm monitoring and technologies to detect arrhythmia is increasing. The prevalence and prognostic significance of subclinical bradyarrhythmias is unknown.

Objectives
To assess the accidental diagnosis of bradyarrhythmia and its subsequent treatment and prognostic impact in persons screened for atrial fibrillation compared to unscreened persons.

Methods
We utilized a randomized trial of ≥70-year-olds with cardiovascular risk factors recruited outside the hospital setting to receive implantable loop recorder screening for atrial fibrillation (ILR group) vs. usual care (Control group). Time-to-event analyses were performed for bradyarrhythmia, pacemaker implantation, syncope, and sudden cardiovascular death.

Results
A total of 6004 participants were randomized (mean age 75 years, 47% women, 91% with hypertension, 20% with prior syncope), 4503 to Control and 1501 to ILR. The median follow-up period was 64.5 [59.3, 69.8] months. A total of 675 deaths occurred with an overall rate of 2.16 (2.00-2.33) per 100 person-years, and 67 sudden cardiovascular deaths occurred with a rate of 0.21 (0.15-0.28) for the Control group and 0.23 (0.14-0.37) for the ILR group (hazard ratio (HR) 1.11 (0.64-1.90), p=0.71)).
The overall rate of incident bradyarrhythmia was 1.63 (1.49-1.79) per 100 person-years, and bradyarrhythmia was diagnosed in 172 (3.82%) and 312 (20.8%) participants in the Control and ILR group, respectively (HR 6.21 (5.15-7.48), p&lt;0.0001) (Figure 1). The most common bradyarrhythmia was sinus node dysfunction (SND) which was diagnosed in 68 participants in the Control group (1.51%) and 214 in the ILR group (14.26%). In the Control group, 57.35% of diagnoses of sinus node dysfunction resulted in pacemaker implantation, compared to 12.15% in the ILR group where the majority was treated conservatively (Figure 2). The second-most common type of bradyarrhythmia was high-grade atrioventricular block (AVB) which was diagnosed in 86 participants in the Control group (1.91%) and 54 in the ILR group (3.60%). In both groups, the majority of high-grade AVB was treated with pacemaker, although 29.63% in the ILR group were treated conservatively. Risk factors for bradyarrhythmia included higher age, male sex, and prior syncope.
Overall, a pacemaker was implanted in 132 (2.93%) and 66 (4.40%) participants (HR 1.53 (1.14-2.06), p&lt;0.0001), syncope occurred in 120 (2.66%) and 33 (2.20%) participants (HR 0.83 (0.56-1.22), p=0.34), and sudden cardiovascular death occurred in 49 (1.09%) and 18 (1.20%) participants (HR 1.11 (0.64-1.90), p=0.71) in the Control and ILR group, respectively.

Conclusions
Bradyarrhythmias are highly common in ≥70-year-olds with cardiovascular risk factors. Compared to Control, ILR monitoring led to a six-fold increase in diagnosis of bradyarrhythmia and a significant increase in pacemaker implantations, but no change in the risk of syncope or sudden death.