Clinical utility of a novel wireless implantable loop recorder in the evaluation of patients with unexplained syncope

The implantable loop recorder (ILR) is particularly useful for monitoring patients with syncope, given the episodic nature and unpredictable pattern of recurrent episodes. Current practice guidelines advocate ILR implantation in select patients with unexplained syncope.

The purpose of this study was to evaluate the clinical utility and potential advantages of a novel wireless ILR in a consecutive cohort of patients with unexplained syncope.

Patients with unexplained syncope despite a comprehensive evaluation who underwent implantation of a Transoma Medical Sleuth ILR were examined. ILR implantation was considered in these patients if left ventricular function was ≥ 40% and if syncope was recurrent, associated with trauma, and/or associated with an abnormal ECG (e.g., bifascicular block).

The Sleuth ILR was implanted in 50 patients. During mean follow-up 293 ± 211 days, 16 (32%) patients had recurrent near-syncope or syncope. Only half of the patients self-activated the ILR; in the other half, a diagnosis was established based on autoactivation-initiated storage of a significant arrhythmia event. Overall, there were 5 patients with complete heart block, 3 with sinus node dysfunction, 3 with supraventricular tachycardia, 2 with neurally mediated syncope, and 3 with a nonarrhythmic cause of syncope. The median time from an event to physician notification was 150 minutes (interquartile range 99, 297 min). Median time from ILR implantation to final diagnosis was 71 days (interquartile range 24, 143 days; range 3-683 days).

A diagnosis of syncope was ultimately made in nearly one third of patients with unexplained syncope. Patients frequently did not activate their ILR at the time of recurrent syncope. However, the wireless ILR automatically transferred ECG data to a central monitoring station within minutes to hours of the arrhythmic event, virtually eliminating the possibility of data loss, thus greatly facilitating clinical decision making.