Usefulness of last generation insertable cardiac monitors in the diagnosis of unexplained syncope

Aims: Guidelines recommend insertable cardiac monitor (ICM) in the early phases of the evaluation of unexplained syncope (US) syncope, when an arrhythmic etiology is suspected. We examined the diagnostic yield of the last generation ICM (LG-ICM) to establish the causes of US, by assessing in the clinical practice the incidence of: relevant arrhythmia diagnosis, syncope recurrences and CM-guided cardiac electronic device (CIED) implantation. We investigated also baseline patient characteristics associated to an increased risk of relevant arrhythmias and of syncope recurrence.

Methods: Data prospectively collected from consecutive patients receiving LG-ICM for investigation of US or presyncope in our institution between November 2020 and January 2023 were analyzed.

Results: A total of 109 patients (mean age 64.4 ± 16.1 years, 40.4% women) with US or pre-syncope episodes underwent implantation of the LG-ICM. During a mean follow-up of 11.7 ± 8.1 months, LG-ICM diagnostic yield was 42%. In particular, LG-ICM detected cardiac arrhythmias in 29 (27%) patients (in 6 out of them during a syncope recurrence) and to exclude the arrhythmic origin of the syncope in additional 19 (17%) patients. LG-ICM guided the implantation of a CIED in 16 (15%) US patients, due to the diagnosis of asystole or severe bradycardia. Age ≥ 65 years (p = 0.012) and atrial arrhythmia history (p = 0.004) are significant independent predictors of arrhythmic diagnoses performed by LG-ICM, while CAD is predictor of syncope recurrence (bordering on statistical significance, p = 0.056).

Conclusions: The diagnostic yield of LG-ICM in US syncope is comparable to those of ILR and previous generation ICM. The advantages of LG-ICM should be sought in lower hospital workload necessary to manage ICM data. Age ≥ 65 years and atrial arrhythmia history are independent predictors of significant ICM-detected arrhythmias.