Experiences with implantable loop recorders in syncope patients

Introduction

Implantable loop recorders (ILRs) provide continuous rhythm surveillance and are recommended by recent ESC guidelines for patients with unexplained syncope. Recent advances include incorporating AI alongside traditional algorithms to detect diagnostic recordings. However, many recordings remain still false positives, increasing workload.

Purpose

The purpose of the study was to evaluate all patients who received an ILR for unexplained syncope and to explore how symptom-based scheduled monitoring (SBSM) functions in patients with a high volume of false positive alerts.

Methods

This retrospective study reviewed data of 204 ILR-monitored patients (2021–2025); 176 met the syncope indication criteria. Key data elements included diagnoses, monitoring duration, and healthcare use. A Symptom based scheduled monitoring (SBSM) approach was assessed for patients with frequent false positives. Figure 1 shows the transition pathway to SBSM, in which alerts are disabled and evaluated quarterly, or earlier if the patient experiences symptoms occur.

Results

The Median age of 176 patients (99 female, 56.3%) was 63.0 years (IQR 49.5-74.5). Mean durations of follow-up were 171 days (SD 240) for the diagnosed group and 695 days (SD 348) for the undiagnosed group (p < 0.01).

During follow-up, 60 patients (34%) received a diagnosis, with a median time of 84 days (IQR 18-216 days). The diagnoses were as follows: the predominant diagnosis was SSS with 30 patients (50%), followed by AV block with 20 (33.3%) and atrial fibrillation with 4 (5.7%), while the remaining 6 patients (10%) had other specified diagnoses. Median time between diagnosis and pacemaker implantation was 15 days (IQR 3-29) for 51 patients.

Most patients received their diagnosis early on: 25% within 18 days, 50% within 90 days, 66.7% within 180 days, 81.7% within 270 days, and 85% within the first year. Figure 2 shows the diminishing benefits of prolonged active monitoring via the Kaplan–Meier curve.

SBSM was initiated in 31 patients a median of 206 days after implantation (IQR 96–456) and lasted a median of 410 days (IQR 203–685). The median number of alert episodes was 1123 (IQR 17–1521) compared with 1 (IQR 0–13) during active monitoring and SBSM, respectively. Emergency visits and hospitalisations did not differ between the active monitoring and SBSM groups.

Conclusions

This study confirms that ILRs are effective in the diagnostic work-up of unexplained syncope, yielding diagnoses in over 30% of cases. Because most diagnoses occur soon after implantation, prolonged follow-up mainly produces false positive alerts that increase device clinic workload. In selected patients, this alert burden can be managed by disabling automatic alerts and reviewing ILR data quarterly instead.Picture 2Picture 1