Time to manual activation of implantable loop recorders--implications for programming recording period: a 10-year...

A new generation of commercially available implantable loop recorders (ILRs) has improved arrhythmia detection algorithms but reduced manually activated ECG storage duration. We investigated the effect that this would have had on symptom-arrhythmia correlation in a retrospective patient cohort.

Retrospective review of all patients receiving a Medtronic Reveal 9525/9526 for the investigation of unexplained syncope or pre-syncope in our centre between 1998 and 2008. All ILRs were programmed for a single manual activation with 40 min retrospective ECG recording. We identified all patients who subsequently underwent permanent pacemaker implantation and analysed the time delay between bradycardia onset and manual ILR activation. Five hundred and sixty-four patients underwent implantation of an ILR during the study period. Of these, 57 (10%) subsequently underwent the implantation of a pacemaker (31 male, median age 66 years, range 9-86 years). In this group, 35 of 57 (61%) bradycardia diagnoses were made in patients (18 male, median age 65 years, range 9-86 years) after manual activation of the ILR. The median time from bradycardia onset to ILR activation was 136 s (0-488 s). Nineteen recordings showed high-grade atrio-ventricular block and 16 sinus node disease.

Ten-year experience with the ILR confirms its utility in establishing a pacemaker indication as the cause for syncope or pre-syncope in 6% (34 of 564) of recipients following manual activation. This requires a recording loop of sufficient duration to reliably include both symptoms and activation.