Diagnostic yield of implantable loop recorders in routine clinical practice - a 10-year single-centre experience
A Fonseca Vazao, A Martins, M Amado, J R Pereira, C Esteves, M Baburko, J Carvalho, D Severino, H Martins, D DuraoAbstract
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