Israel Medical Association Journal

Background: The implantable loop recorder (ILR) is an important tool for the evaluation of unexplained syncope, particularly in cases of rarely occurring arrhythmia.

Objectives: To review the clinical experience of two Israeli medical centers with the ILR. Methods: We reviewed the medical records of patients with unexplained syncope evaluated with the ILR at Rabin Medical Center (2006–2010) and Wolfson Medical Center (2000–2009).

Results: The study group included 75 patients (44 males) followed for 11.9 ± 9.5 months after ILR implantation. Patients’ mean age was 64 ± 20 years. The ILR identified an arrhythmic mechanism of syncope in 20 patients (17 bradyarrhythmias, 3 tachyarrhythmias) and excluded arrhythmias in 12, for a diagnostic yield of 42.7%. It was not diagnostic in 17 patients (22.7%) at the time of explant 26 patients (34.7%) were still in follow-up. In two patients ILR results that were initially negative were reversed by later ILR tracings. The patients with bradyarrhythmias included 9 of 16 (56.3%) with surface electrocardiogram conduction disturbances and 2 of 12 (16.7%) with negative findings on carotid sinus massage. All bradyarrhythmic patients received pacemakers the seven patients for whom post-intervention data were available had no or mild symptoms.

Conclusions: The ILR has a high diagnostic yield. Pre-ILR findings correlating with the ILR results are conduction disturbances (positive predictor of arrhythmia) and negative carotid sinus massage results (negative predictor of arrhythmia). Proper patient instruction is necessary to obtain accurate results. Caution is advised when excluding an arrhythmia on the basis of ILR tracings, and long-term follow-up is warranted.