Additional Diagnostic Value of Very Prolonged Observation by Implantable Loop Recorder in Patients with Unexplained Syncope

Abstract

In the literature, the average diagnostic yield of the implantable loop recorder (ILR) is reported to be 35% over an observation period generally less than 18 months. The aim of this study was to evaluate the diagnostic value of ILR during very prolonged observation. Consecutive patients who had received one or more (in the case of battery exhaustion before diagnosis) ILR (Reveal/plus/DX, Medtronic Inc.) from 2001 to 2010 were included. The diagnostic ECG was classified according to the ISSUE classification. We analyzed 157 patients (87 males, 69 ± 14 years): 70 of these were followed up for ≥18 months. The estimated cumulative diagnostic rates were 30%, 43%, 52%, and 80% at 1, 2, 3, and 4 years, respectively; 26% of diagnoses were made after 18 months. The diagnostic yield was independent of structural heart disease, bundle branch block, number of syncopes, age, and gender; the median time to diagnosis of ISSUE type 1 patients was shorter than that of the others (4 [2;10] vs. 16 [6;23] months; P = 0.003). During the observation period, 3 patients (1.9%) died and none suffered arrhythmic death. Prolonging observation up to 4 years increased the diagnostic value of ILR in syncopal patients and was safe. A quarter of patients diagnosed needed more than 18 months of follow-up. As consequence, when a strategy of prolonging monitoring is chosen, monitoring should be maintained even for several years until diagnosis is established.