title: The diagnostic yield of implantable loop recorders in unexplained syncope: A systematic review and meta-analysis.
abstract: BACKGROUND
  Guidelines recommend that implantable loop recorders (ILRs) are used in the evaluation of people with recurrent unexplained syncope in the absence of high-risk criteria, and in high-risk patients after a negative evaluation. The aim of this systematic review was to analyze the diagnostic yield of ILRs in these patients.
  
  
  METHODS
  We performed a systematic search in order to retrieve studies enrolling adults undergoing ILR implantation for undetermined syncope. The primary outcome was the overall diagnostic yield, defined as the proportion of patients with syncope recurrence and an available ILR recording or an automatic detection of a significant arrhythmia. Secondary outcomes were the proportions of patients with the specific etiologic diagnoses on the total of subjects and the proportion of an analyzable ECG recording during symptoms. We used a random effects model for the meta-analyses.
  
  
  RESULTS
  Forty-nine studies, enrolling 4381 subjects, were included. The overall diagnostic yield was 43.9% (95% CI=40.2%, 47.6%; I2=79.8%). The proportions of subjects finally diagnosed with arrhythmic syncope, ventricular arrhythmias, supraventricular arrhythmias and bradyarrhythmias were 26.5%, 2.7%, 4.9% and 18.2%, respectively. The proportion of an analyzable ECG recording during symptoms was 89.5% (95% CI=86.1%, 92.1%; 1236 subjects; 36 studies; I2=44.9%). Median time to diagnosis was 134days. Heterogeneity is an important limitation to be acknowledged.
  
  
  CONCLUSIONS
  About a half of unexplained syncope subjects implanted with an ILR were diagnosed, and around 50% of them had an arrhythmia. Life-threatening arrhythmias as well as ILR complications and death due to arrhythmic events were very rare.
authors.affiliation: Dipartimento di Medicina Interna e Specializzazioni Mediche, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milano, Italy; Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, Milano, Italy. Electronic address: monica.solbiati@gmail.com.
authors.forename: Monica
authors.initials: M
authors.lastname: Solbiati
authors.affiliation: Dipartimento di Scienze Biomediche e Cliniche "L. Sacco", Università degli Studi di Milano, Milano, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Casazza
authors.affiliation: Department of Biomedical Sciences, Humanitas University-Humanitas Research Hospital, Rozzano, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Dipaola
authors.affiliation: Department of Biomedical Sciences, Humanitas University-Humanitas Research Hospital, Rozzano, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Barbic
authors.affiliation: Dipartimento di Anestesia, Rianimazione ed Emergenza Urgenza, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milano, Italy.
authors.forename: Maja
authors.initials: M
authors.lastname: Caldato
authors.affiliation: Dipartimento di Medicina Interna e Specializzazioni Mediche, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milano, Italy; Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano, Milano, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Montano
authors.affiliation: Department of Biomedical Sciences, Humanitas University-Humanitas Research Hospital, Rozzano, Italy.
authors.forename: Raffaello
authors.initials: R
authors.lastname: Furlan
authors.affiliation: Department of Cardiac Sciences, University of Calgary, Calgary, Canada.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sheldon
authors.affiliation: Dipartimento di Medicina Interna e Specializzazioni Mediche, Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico, Milano, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Costantino
mesh_terms: D003937:Diagnosis, Differential; D015716:Electrocardiography, Ambulatory / Q000295:instrumentation*; D004567:Electrodes, Implanted; D006801:Humans; D012008:Recurrence; D015203:Reproducibility of Results; D013575:Syncope / Q000175:diagnosis*
keywords: Arrhythmia; Diagnosis; Implantable loop recorders; Syncope; Systematic review