Loop monitoring detects bradyarrhythmia in 20% of high-risk patients with no prior AF
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Continuous monitoring via implantable loop recorder detected bradyarrhythmia in more than 20% of high-risk patients aged 70 years or older with no history of atrial fibrillation, researchers reported.
“This was a secondary analysis of our large randomized LOOP trial reported in Lancet in 2021. This trial found AF in more than 30% by screening, which was treated with anticoagulants, but no significant reduction in strokes. We now turned to look at other arrhythmias, because the implantable loop recorder has a good sensitivity for this. Arrhythmias were all adjudicated using ECG material,” Søren Zöga Diederichsen, MD, PhD, of the department of cardiology at Copenhagen University Hospital-Rigshospitalet, Denmark, told Healio. “The biggest takeaway is that more than 20% of these ordinary people have underlying, unknown bradyarrhythmias. Usual care diagnosed the same in less than 4%, about six times fewer. The added diagnoses were driven by asymptomatic cases, and the overdiagnosis lead to increased pacemaker implants with zero signal towards protective effect on syncope, sudden death or death, when compared with unscreened individuals.”
Data were derived from Diederichsen SZ, et al. JAMA Cardiol. 2023;doi:10.1001/jamacardio.2022.5526.
The LOOP trial enrolled 6,004 adults aged 70 years or older with hypertension, diabetes, HF or prior stroke and no history of AF (mean age, 75 years; 47% women), and was designed to assess whether an implantable loop recorder for unknown AF (Reveal LINQ, Medtronic) could prevent stroke in this high-risk population.
As Healio previously reported, in the main results of LOOP, continuous implantable loop monitoring increased AF detection threefold and subsequent anticoagulation initiation compared with usual care, but did not reduce risk for stroke or systemic embolism in adults aged 70 years or older with at least one stroke risk factor.
For the post hoc analysis, Diederichsen and colleagues evaluated the prevalence and prognosis associated with bradyarrhythmia detected during continuous loop recording in this high-risk population.
The post hoc analysis of LOOP was published in JAMA Cardiology.
Findings of the LOOP post hoc analysis
The median follow-up was 65 months and outcomes of interest included adjudicated bradyarrhythmia episodes, pacemaker implantation, syncope and sudden CV death.
The researchers reported that bradyarrhythmia was diagnosed in 3.8% of the control arm compared with 20.8% of the loop monitoring arm (HR = 6.21; 95% CI, 5.15-7.48; P < .001). Overall, 23.8% of bradyarrhythmia episodes detected in the control arm were asymptomatic compared with 79.8% in the loop monitoring arm.
The most common bradyarrhythmia was sinus node dysfunction followed by high-grade atrioventricular block, according to the study.
Individuals with detected bradyarrhythmia were more often older, were more often male and were more likely to have had prior syncope. Subsequently, bradyarrhythmias were associated with increased risk for syncope, CV death and all-cause death, with no interaction between bradyarrhythmia and randomization group, according to the study.
Loop monitoring also increased the likelihood of pacemaker implantation compared with usual care (HR = 1.53; 95% CI, 1.14-2.06; P < .001); however, researchers observed no difference in risk for syncope (P = .34) or sudden CV death (P = .71).
Establish ‘clear symptomatology before implanting pacemaker’
“As a minimum, the findings underline the requirement for a clear symptomatology before implanting pacemaker,” Diederichsen told Healio. “Some would say that the findings even push back towards implanting devices for bradyarrhythmia since the underlying prevalence was so extensive — ie, these arrhythmias are not diseases needing treatment; they are parts of normal physiology like aging.
“Despite the lack of clear clinical benefit of detecting and managing bradyarrhythmias, the trial showed that these subclinical bradyarrhytmias were strongly associated with downstream clinical outcomes,” Diederichsen said. “Importantly, the association between bradyarrhythmia and outcomes was statistically indifferent between the arms, even though the vast majority of bradyarrhythmia in the implantable loop recorder arm was treated conservatively. This again implies that one might as well await treating the bradyarrhythmia until it is at a stage where it would have been diagnosed by standard clinical work-up, without risking clinical deterioration. Still, the association with outcomes implies that clinical benefit could potentially arise from finding bradyarrhythmias and treating the underlying causes — in some individuals.”
For more information:
Søren Zöga Diederichsen, MD, PhD, can be reached at soeren.zoega.diederichsen@regionh.dk.
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