title: Time relation between a syncopal event and documentation of atrioventricular block in patients with bifascicular block: clinical implications.
abstract: BACKGROUND
  Transient high-degree atrioventricular (AV) block is a common cause of syncope in patients with bifascicular block (BFB) but the intermittent nature of AV block makes ECG documentation a challenge. A sensitive and safe tool to investigate BFB patients with syncope would be a bradycardia-detecting pacemaker, which provides a possibility of studying the time relation between the index syncopal episode and the development of high-degree AV block.
  
  
  METHODS
  Twenty-seven patients with BFB and syncope were studied prospectively. All patients received a single-chamber ventricular-based pacemaker with bradycardia-detecting ability. A bradycardia episode was defined as a heart rate of < 30 beats/min lasting > or = 6 s.
  
  
  RESULTS
  During a median follow-up of 60 months, a bradycardia event was detected in 14 patients (52%), of whom 13 also had documented high-degree AV block on ECG. The median time between the syncopal episode and the first pacemaker-detected bradycardia event was 5 months and after an additional median time of 6 months, high-degree AV block was documented on the ECG. In 10 of 13 patients (77%) high-degree AV block was documented within 24 months of the syncopal episode corresponding to an annual incidence of 19% during the first 2 years of follow-up in the study population.
  
  
  CONCLUSIONS
  In this group of BFB patients a syncopal episode was highly predictive of the development of high-degree AV block within 24 months, justifying pacemaker therapy without prior ECG verification.
authors.affiliation: Department of Cardiology, Karolinska Institute, South Hospital, Stockholm, Sweden. fariborz.tabrizi@karolinska.se
authors.forename: Fariborz
authors.initials: F
authors.lastname: Tabrizi
authors.forename: Mårten
authors.initials: M
authors.lastname: Rosenqvist
authors.forename: Lennart
authors.initials: L
authors.lastname: Bergfeldt
authors.forename: Anders
authors.initials: A
authors.lastname: Englund
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001919:Bradycardia / Q000175:diagnosis / Q000209:etiology*; D002037:Bundle-Branch Block / Q000150:complications; D016757:Death, Sudden, Cardiac / Q000209:etiology; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000150:complications* / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011446:Prospective Studies; D013575:Syncope / Q000209:etiology*; D013997:Time Factors