title: Clinical Predictors of Pacemaker Implantation in Patients with Syncope Receiving Implantable Loop Recorder with or without ECG Conduction Abnormalities.
abstract: BACKGROUND
  Implantable loop recorders (ILR) allow prolonged cardiac rhythm monitoring and improved diagnostic yield in syncope patients. Predictive factors for pacemaker (PM) implantation in the ILR population with unexplained syncope have not been adequately investigated. In this single center, retrospective, observational study we investigated factors that predict PM implantation in this population.
  
  
  METHODS
  We retrospectively analyzed our ILR database of patients aged over 18 years who underwent ILR implantation for unexplained syncope between January 2009 and June 2013. Patient case notes were examined for demographics, history, electrocardiogram (ECG) abnormalities, investigations, and events during follow-up. The primary end-point was the detection of a symptomatic or asymptomatic bradycardia requiring PM implantation.
  
  
  RESULTS
  During a period of 4.5 years, 200 patients were implanted with ILR for unexplained syncope, of who n = 33 (16.5%) had clinically significant bradycardia requiring PM implantation. After multivariable analysis, history of injury secondary to syncope was found to be the strongest independent predictor for PM implantation (odds ratio [OR]:9.1; P < 0.001; 95% confidence interval [CI]: (3.26-26.81). Other significant predictors included female sex, PR interval > 200msec, and age >75 years. In patients without conduction abnormalities on the ECG, history of injury secondary to syncope was found to be the strongest independent predictor for PM implantation (OR: 8.16; P = 0.00027; 95% [CI]: (2.67-26.27).
  
  
  CONCLUSIONS
  A history of injury secondary to syncope and female sex were independent predictive factors for bradycardia necessitating PM implantation in patients receiving an ILR for syncope with or without ECG conduction abnormalities.
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Nauman
authors.initials: N
authors.lastname: Ahmed
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Antonio
authors.initials: A
authors.lastname: Frontera
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Alexander
authors.initials: A
authors.lastname: Carpenter
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Stafenia
authors.initials: S
authors.lastname: Cataldo
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Georgia M
authors.initials: GM
authors.lastname: Connolly
authors.affiliation: University of Bath, Bath, United Kingdom.
authors.forename: Matteo
authors.initials: M
authors.lastname: Fasiolo
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Tim
authors.initials: T
authors.lastname: Cripps
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Glyn
authors.initials: G
authors.lastname: Thomas
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Ihab
authors.initials: I
authors.lastname: Diab
authors.affiliation: Bristol Heart Institute, University Bristol Hospitals NHS Foundation Trust, Bristol Royal Infirmary, Bristol, United Kingdom.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Duncan
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011379:Prognosis; D019919:Prosthesis Implantation; D012189:Retrospective Studies; D013575:Syncope / Q000150:complications / Q000503:physiopathology / Q000628:therapy*
keywords: implantable loop recorder; pacemaker; syncope