Key result
Implantable loop recorders yield a ~34% diagnostic rate, led by evaluations for palpitations.
Why the study?
Implantable loop recorders are widely used to evaluate syncope, palpitations, and cryptogenic stroke, but real-world data on their diagnostic yield remain limited.
What is the diagnostic yield of implantable loop recorder monitoring in a real-world population evaluated for syncope, palpitations, and cryptogenic stroke?
Cohort (n=340)
No
What is the diagnostic yield of implantable loop recorder monitoring in a real-world population evaluated for syncope, palpitations, and cryptogenic stroke?
In routine clinical practice, implantable loop recorders provide an overall diagnostic yield of 34.1%—mostly within the first year of implantation—leading to targeted therapeutic interventions such as pacemaker or ICD implantation in a substantial proportion of diagnosed patients.
Background Implantable loop recorders (ILRs) are widely used in the evaluation of syncope, palpitations, and cryptogenic stroke, but real-world data on their diagnostic yield remains limited. Objective To evaluate the diagnostic yield of ILRs in a real-world population from a local health unit in Portugal. Methods Single-center retrospective cohort of patients (pts) who underwent ILR monitoring (Dec 2014-Dec 2024). Baseline clinical, electrocardiographic and echocardiographic variables and outcomes (all-cause mortality, cardiovascular (CV) mortality, heart failure (HF) hospitalization and urgent pacemaker (PM) implantation) were collected. Diagnostic findings included symptomatic sinus node disease (SND), atrioventricular (AV) node disease (high-grade AV block; complete AV block), new-onset atrial fibrillation (AF), slow AF (symptomatic ventricular pause >3s) and sustained supraventricular (SVT) or ventricular tachycardia (VT). Results A total of 340 ILRs were implanted. Annual implant numbers increased over time, peaking at 64 in 2023 (Figure 1A). Syncope was the main indication (n=274, 80.6%), followed by palpitations (n=35, 10.3%) and cryptogenic stroke (n=18, 5.3%). Patients were predominantly male (50.6%), with a mean age of 64.9±15.6 years. Baseline electrocardiograms revealed sinus rhythm in 65% and bundle branch block (BBB) in 12.8%. The median left ventricular ejection fraction was 60%. The overall diagnostic yield was 34.1%, with a median time to diagnosis of 6 months. Diagnostic yield declined markedly after the first year (Figure 1B). Among syncope pts, the diagnostic yield was 33.2%; 66 pts (72.5%) subsequently received a cardiac implantable electronic device - 64 pts received a pacemaker (16 for complete AV block, 35 for SND, 7 for high-grade AV block, 3 for bradycardia-tachycardia syndrome, 3 for slow AF) and 2 pts received an implantable cardioverter-defibrillator (ICD) for VT. Among pts monitored for cryptogenic stroke the yield was lower (16.7%), with the diagnosis of AF in 2 pts and sustained asymptomatic VT in another patient, although the findings led to therapeutic changes in 2/3 of cases. In the palpitation’s subgroup, the diagnostic yield was 48.6%, mainly SVT, with targeted treatment in 47% of diagnosed cases (Figure 2). Pts were followed for a median of 23 months [IQR 9-38]. During follow-up, 30 pts experienced adverse outcomes, including 11 urgent admissions for syncope requiring subsequent PM implantation and 3 hospitalizations for HF. Overall, 23 patients died (6.8%), of whom 3 CV deaths. Conclusion ILRs are a highly valuable diagnostic tool for the evaluation of syncope, cryptogenic stroke and palpitations. In this real-world cohort, ILRs demonstrated a good diagnostic performance, with a diagnostic yield of 34%, and most diagnoses occurring within the first year after implantation.Fig. 1:(A) Nr of ILR; (B) Time to diagnosisFig. 2:Diagnosis outcomes
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Vazao et al. (2026) conducted a cohort in Syncope, palpitations, and cryptogenic stroke (n=340). Implantable loop recorder (ILR) monitoring was evaluated on Overall diagnostic yield (symptomatic sinus node disease, AV node disease, new-onset AF, slow AF, and sustained SVT or VT). Implantable loop recorders achieved an overall diagnostic yield of 34.1% (median 6 months to diagnosis), including 33.2% in syncope, 48.6% in palpitations, and 16.7% in cryptogenic stroke.
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